DOCUMENT RESUME Aviation Machinist's Mate Phase II, 2

DOCUMENT RESUME

ED 223 900 CE 034 540

TITLE Aviation Machinist's Mate Phase II, 2-6. Military Curriculum Materials for Vocational and Technical Education. INSTITUTION Coast Guard, Elizabeth City, NC. AircraftRepair and Supply Center.; Ohio State Univ., Columbus.National Center for Research in Vocational Education. SPONS AGENCY Office of Education (DREW), Washington, D.C. PUB DATE 78 NOTE 261p.; For related document, see CE 034 539. PUB TYPE Guides - Classroom Use - Materials (For Learner) (051) -- Guides - Classroom Use Guides (For Teachers) (052)

EDRS PRICE MF01/PC11 Plus Postage. DESCRIPTORS *Aerospace Education; *Air Transportation;*Aviation Mechanics; Behavioral Objectives; Curriculum Guides; *Maintenance; Postsecondary Education; Secondary Education; *Technical Education; Textbooks IDENTIFIERS Military Curriculum Project

ABSTRACT These teacher and student materials, the second section of a two phase secondary/postsecondary-level course on aviation machinists, make up one of a number ofmilitary-developed curriculum packages selected for adaptation tovocational instruction and curriculum development in a civiliansetting. The purpose of the course is to train students tomaintain aircraft engines, perform intermediate and major inspections on engines andtheir related systems, field test and adjust componentsof engines, and replace compressor turbine blades andcombustion chamber liners. This phase, Fixed Wing Aircraft, contains 7 weeks ofinstruction totaling 189 hours on: Reciprocating Engines (10 lessons,27 hours); Fuels and Ignition (12 lessons, 27 hours); Starts, Stops, and Runups(4 lessons, 27 hours); and Troubleshooting(12 lessons, 27 hours). Instructor materials include a curriculumoutline containing a weekly breakdown of lessons, topic objectives,equipment and furniture requirements, training aids and devices needed, andpublications used as texts or references. Thestudent materials consist of 10 chapters from the Navy training manual,"Aviation Machinist's Mate R 3 & 2, NAVPERS 10342-A." (YLB)

*********************************************************************** Reproductions supplied by EARS are the best that can bemade from the original document. *********************************************************************** mTTJTARY CURRICULUM MATERIALS

The military-developedcurriculum materials in this course package were selected by theNational Center for Research in Vbcational Education MilitaryCtrriculum Project for dissemr ination to the six regionalCurriculum Coordination Centers and other instructional materialsagencies.The purpose of disseminating these courses was tomake curriculum materials developed by the military moreaccessible to vocational educators in the civilian setting.

The course materials wereaoquired, evaluated by project staff and practitioners in the field,and prepared for the ailitary dissemination.Materials which were specific to omitted or appro- were deleted,copyrighted materials were either val for their use was obtained.These course packages contain curriculum resource materialswhich can be adapted to support vocational instruction and curriculumdevelopment. Military Curriculum Materials for The National Center Vocational and Mission Statement Technical Education

FT-we ww--i:www-wr ,70177:::rwry-v71

w w ww - I

The National Center for Research in Information and Field Vocational Education's mission is to increase Divif;ion the ability of diverse agencies, institutions, and organizations to solve educational problems relating to individual career planning, preparation, and, progression. The National The Hationr11 Center for Research Center fulfills its mission by: in VocrItional Education

Generating knowledge through research

Developing educational programs and products

Evaluating individual program needs A) and outcomes

Installing educational programs and products \ip1.1," 14). Operating information systems and services

Conducting leadership development and !:',i1 training programs 1 l' 1

h 'r E; FOR FURTHER INFORMATION ABOUT 0,° Military Curriculum Materials '''", WRITE OR CALL Program Information Office '`.4t t'+1 "% The National Center for Research in Vocational f I''Vr Education f;.''.:.':'' The Ohio State University r 64.:./i .;11ttl'iti,i,i,i.' .''' 1960 Kenny Road, Columbus, Ohio 43210 141 '4.'''t' :TIt.,:y,itill;',41k Telephone: 614/486.3655 or Toll Free 800/ ' ' ,,';''.F:11' 848.4815 within the continental U.S. :''.! .\12' (except Ohio) I Military Curriculum Materials What Materials How Can These Materials Be Obtained? Dissemination Is. Are Available?

Center accessibility of One hundred twenty courses on microfiche Contact the Curriculum Coordination an activity to increase the in your region for information onobtaining military developed curriculum materials to (thirteen in paper form) and descriptions of each have been provided to the vocational materials (e.g., availability and cost). They vocational and technical educators. refer Curriculum Coordination Centers and other will respond to your request directly or materials agency This project, funded by the U.S. Of fice of instructional materials agencies for dissemi- you to an instructional Education, includes the identification and nation. closer to you. acquisition of curriculum materials in print Coursematerialsinclude programmed form from the Coast Guard, Air Force, CUlifilCULM COOl MINA 110:1 Ct:h1 I EHS Army, Marine Corps and Navy. instruction, curriculum outlines, instiuctor guides, student workbooks apd technical NORTHWEST manuals. EAST CENTRAL Access to military curriculum materials is William Daniels provided through a "Joint Memorandum of Rebecca S. Douglass Director Understanding" between the U.S. Office of The 120 courses represent the following Dit ector 100 North First Street Building 17 Education and the Department of Defense. sixteen vocational subject areas: Spring( iekl, IL 62777 Airdustrial Park Olympia, WA 98504 Agriculture Food Service 217/782-Q759 The acquired materials are reviewed by staff 206/753.0879 and subject matter specialists, and courses Aviation Health Building & Heating & Air deemed applicable to vocational and tech- SOUTHEAST Construction Conditioning MIDWEST nical education are selected for dissemination. James F. Shill, Ph.D. Trades Machine Shop Robert Patton Director Clerical Management & Director The National Center for Research in Mississippi State University Occupations Supervision 1515 West Sixth Ave. Vocational Education is the U.S. Office of Drawer DX Conimunica(ions Meteorology & Stillwater, OK 74704 Education's designated representativeto Mississippi State, MS 39762 1)1 al ling Navigatioir 405/377 2000 nquire the materials and conduct the project 601/325.2510 activit ies. Electronics Photography Engine Mechanics Public Service NORTHEAST WESTERN Project Staff: Lawrence F. H. Zane, Ph.D. The number of courses and the subject areas Joseph F. Kelly, Ph.D. Wesley E. Budke, Ph.D., Director represented will expand as additional mate- Director Director National Center Clearinghouse rials with application to vocational and 225 West State Street 1776 University Ave. Trenton, NJ 08625 Honolulu,111 96822 Shirley A. Chase, Ph.D. technical education-are identified and selected 609/292.6562 808/948.7834 Project Director for dissemination.

t.) Classroom Course 2-6

AVIATION MACHINIST'S MATE, PHASE II

Table of Contents

Course Description Page 1

Curriculum Outline Page 3

Tools & Hardware Page 41

Reciprocating Engine Familiarzation Page 72

Reciprocating Engine Fuel Systems Page 95

Reciprocating_Engine Lubricating Systems Page 118

Reciprocating Engine Ignition Systems Page 141

Reciprocating Engine Accessories Page 171

Reciprocating Engine Repair Page 185

Propeller Operation and Maintenance Page 201

Ground Handling Equipment and Procedures Page 223

Line Operations and Maintenance Page 236 AVIATION MACHINIST'S MATE, PHASE II Classroom Course 2-6 /

Developed by: D.O.T. No.: 639.281 United States Coast Guard Occupational Area: rlavalnpmant and Aviation Review Dates Target Audiancn: March 19, 1975 Grades 11-adult

Print Pages. 249 Cost:

Availability: Military Curriculum Project, The Center for Vocational Education, 1960 Kenny Rd., Columbus, OH 43210

g 1 vi E i.; ..:, ;.: C .9 n.2 o E E2 5 0, =ti c o 11. .0 8u 46 = ... -e. t 2. 0 0 I; itrt 11 1 7"iii 1 t . 6 Contents: a.. ,I; 1 g m 4 cr. 8 I.- trw ai. I>- Phase II Fixed Wing Aircraft -' R aciprocating Engines (General) o

Fuels and ignition

Hydraulic3

Propellers ',

Line Safety and Inspections

Starts, Stops, and Run-Ups

Troublashooting

Expires July 1, 1978 (::)0.1,,,, 0 NTIR ROI VOCATIONAL MATO ...)sai I NNW'. V A .c9._

Course Description

This IS the seeonJ section oi a two-phase cous se tot Aviation Machinists. Students completing the enure Louise will be able to maintain anciatt engaics. perform intermediate and major inspections un engines and their related systems, field test and adjust components of engines including fuel pumps, vJIN/C5, reguiooms, magnetos, and tepiace compiessur turbine blades and cumbustiun chamber liners. A tha d phase dedling with spew ic mtai y ail ft wds deleted. Students shuuid compete Aviation Machmisei Mate, Phase I (2.51 before beginning this second phase uf the LOW Se.

Pnase II Fixed Wing Aircraft contains seven "weeks" of instruction totaling 189 hours. Each "week" of instruction cont.iiii.> ,us.eral lessoi-i

Week 7 Rec,procating Engines (Generall (ten lessons, 27 hours) Week 8 Fuels and Ignition (twelve lessons, 27 hours) Week 9 Hydraulics (twelve lessons, 27 hours) Week 10 Propellers (sixteen lessons, 27 hours) Week 11 Line Safety and Inspections (twelve lessons, 27 hours) Week 12 Starts, Stops, and Runups (four lessons, 27 hours) Week 13 Troubleshooting (twelve lessons, 27 hours)

This section ol Jse two-pnase course contains both teacher and student materials. Printed instructor materials inciude a cut i icuium outline con taming a weekly breakdown ut iessons, topic objectives, equipment and furniture requirements, training aids and devices needed, publications used as texts o ieterences, and space requirements. The student 'miter iefs consist of ten chapters from the Navy training manual, Awath,n Machinest"4 Mate R 3 & 2. NAVPERS 10342-A.

Several additional military manuals and commercial texts were recommended for use as texts and references, but they are nut pi ovided. N. 5pec.fit. audiovisuals were recommended. These materiais can be adapted for individualized instruction or used as remedial or independent study In alrcraf t maintenance courses.

CliDeCIKTIA FOR WOMPIAL 0.031011 '...>(,, VAT( +NNERS,,, 1 u ,. . p,,r- " i. " 3 CURRICULUMOUTLINE

FOR

CLASS "A" ADSCHOOL doiaL

A 21 WEEKCOURSE oa-6

CLASSIFICATION: UNCLASSIFIED

PREPAREDBY

USCG AIRCRAFT REPAIR AND SUPPLY CENTER

ELIZABETH CITY, N.C.

Reviewed BY S:tE: J. ROY,. C.:IPT(USCG (CQMDT.(G.-.EAE)

e/ Approved By: F-./7. ":".r" tducuLion )lyision

1 TABLE OF CONTENTS

PHASE I AIRMAN PREPARATORY PAGE 1 WEEK 1 INDOCTRINATION & MATH PAGE 1 WEEK 2 PHYSICS PAGE 2 WEEK 3 BASIC ELECTRICITY BALANCE, AND INSTRUMENTS PAGE 2 WEEK 4 AERODYNAMICS, WEIGHT & PAGE 3 WEEK 5 HARDWARE & HANDTOOLS PAGE 3 WEEK 6 PUBLICATIONS PHASE II (FIXED WINGAIRCRAFT) PAGE 3 WEEK 7 RECIPROCATING ENGINES(GENERAL) PAGE 4 WEEK 8 FUELS & IGNITION PAGE 4 WEEK 9 HYDRAULICS PAGE 5 WEEK 10 PROPELLERS PAGE 6 vaK 11 LINE SAFETY &INSPECTIONS PAGE 6 WEEK 12 STARTS, STOPS &RUN-UPS PAGE 6 WEEK 13 TROUBLESHOOTING PHASE III (ROTARYWING AIRCRAFT) PAGE 7 HH52A HELICOPTER WEEK 14 INTRODUCTION TO THE PAGE 7 HH52A HELICOPTER(CONT) WEEK 15 INTRODUCTION TO THE PAGE 7 ENGINE WEEK 16 INTRODUCTION TO THE T-58 PAGE.8 T-58 ENGINE PRACTICAL WEEK 17 INTRODUCTION TO TEE PAGE 8 WEEK 18T-58 ENGINE PRACTICAL PAGE 9 WEEK 19 HH52A PRACTICAL PAGE 9 WEEK 20 HH52A LINE SERVICING& MAINTENANCE PAGE 9 WEEK 21 SURVIVAL PAGE 10 THRU 29 TOPIC OBJECTIVES SECTION IV APPENDICES ,3 MATE (AD) 1. MISSION: TO PROVIDE AVIATION MACHTNIST'S CANDIDATES WITH THE CLASS "A"LEVEL TRAINING NECESSARY TO FULFILL THE REQUIREMENTSFOR ADVANCEMENT TO AD3AS SET FORTH IN THE CG-311, ENLISTEDRATINGS QUALIFICATION MANUAL.

2. SCOPE: AVIATION MACHINIST'S MATESMAINTAIN AIRCRAFT ENTMS, TURBINE AND RECIPROCATING, ANDTHEIR RELATED SYSTEMS INCLUDING THE INDUCTION,COOLING, FUEL, OIL, COMPRESSION, COMBUSTION, TURBINE,IGNITION, PROPELLER AND EXHAUST SYSTEMS; PREFLIGHTAIRCRAFT; PERFORM INTERMEDIATE AND MAJOR INSPECTIONSON ENGINES AND THEIR RELATED SYSTEMS; FIELD TEST ANDADJUST COMPONENTS OF ENGINES INCLUDING FUEL PUMPS, VALVES.,REGULATORS, MAGNETOS AND OTHER COMPONENTS OFTHE ENGINES AND ENGINE RELATED SYSTEMS; REMOVE, REPAIR ANDREPLACE COMPRESSOR TURBINE BLADES AND COMBUSTIONCHAMBER LINERS; MAINTAIN AND ADJUST HELICOPTER DRIVESHAFTING, POWER TRANSMISSIONS, GEAR BOXES AND CLUTCH ASSEMBLIES;PRESERVE AND DEPRESERVE ENGINES, ENGINE ACCESSORIES ANDCOMPONENTS; AND SUPERVISE ENGINE SHOPS. PRACTICAL FACTORS FOR THE AVIATION MACHINIST'S MATE RATING ARE APPLICABLETO THE AIRCRAFT AND EQUIPMENT ASSIGNED OR AVAILABLE.

3. OBJECTIVES:

A. UPON COMPLETION OF THIS COURSE,THE TRAINEE WILL: TECHNICAL REQUIREMENTS FOR (1) BE ABLE TO FULFILL THE AVIATION MACHINIST'S MATE, THIRDCLASS, AS ESTAB- LISHED BY CG-311, ENLISTED RATINGSQUALIFICATIONS MANUAL.

(2) HAVE DEMONSTRATED THE QUALITIESEXPECTED OF A COAST GUARD PETTY OFFICER.

B. IN ORDER TO ACHIEVE THESEOBJECTIVES, THE TRAINEE MUST SATISFACTORILY COMPLETE THE CURRICULUMAS LISTED IN THE FOLLOWING PAGES, AND IN A MANNERCONSISTENT WITH AR&SC TRAINING DIVISION POLICIES.

13 819 Hours Length of Course ...... 21 Weeks

Based on a 39.0 hour week.

A training hour represents approximately sixtyminutes of actual instruction. There are six such training hours in eachday, with each separated by a ten minute break.

Military requirements are met by a fifteen minuteperiod each morning prior to commencement of classes and onehour each Friday afternoon. This ±ncludes musters, marching, and classroom instruction.

BREAKDOWN OF TRAINING

1. Technical Training 409.0 Hours Classroom a. 158.0 Hours b. Line or practical

2. Supplementary Training 52.5 Hours a. Military 31.5 Hours b, Physical 168.0 Hours 3. Miscellaneous AVERAGE WORK WEEK 27.0 Hours 1. Technical Training 2.5 Hours 2. Military Training 1.5 Hours 3. Physical Training 8,0 Hours 4, Miscellaneous

a. Reviewing (Friday afternoon)

b. Testing

c. Cleanup

d. Coffee Breaks PHASE I (AIRMAN PREPARATORY)

Week 1 AD(A) School Indoctrination &Mathematics 4.0 AD(A) School Indoctrination 2.0 1-1 Introduction to Mathematics 3.0 1-2 Fractions 2.0 1-3 Decimals 2.0 1-4 Percentages 1.0 1-5 Positive and Negative Numbers 2.0 1-6 Ratio and Proportion 2.0 1-7 Formulas 2.0 1-8 Angles 2.0 1-9 Triangles 5.0 1-10 Areas and Volumes 27.0

Week 2 Physics 3.0 Math Review 2.0 2-1 Matter and ElectronTheory .2.0 2-2 Force and Pressure 2.0 2-3 Pascal's Law 4.0 2-4 Mechanics of Gases 4.0 2-5 Mechanics of Heat introduction to Diaphragmand Fluid Type 2-6 2.0 instruments 2.0 2-7 Force and Motion 2.0 2-8 Work and Power 2.0 2-9 Principles of Machine:- 1.0 2-10 Introduction to Gears Gyro Instruments 1.0 2-11 Introduction to 27.0

(1) 10 Basic Electricity

3-1 Introduction to Static Electricity 2.0

3-2 introduction to Dynamic Electricity 2.0

3-3 Introduction to Ohm's Law and the Rheostat 2.0

3-4 Introduction to Series Circuits 3.0

3-5 Introduction to Parallel Circuits 3.0

3-6 Introduction to Magnetic Theory & Electromagnetism 3.0

3-7 Introduction to Electrical Components 4.0

3-8 Introduction to Safety Devices and Controls 4,0

Voltage Regulators

Reverse Current Relays

Circuit Breakers

"' 0 1-9 introduction to Basic Aircraft Electrical Systems J.

3.10 The Simpson Multimeter 1.0

Week 4 Aerodynamics/Weight & Balance/Instruments

4-1 Introduction to Aircraft 6.0

4-2 Fundamental Rotation and Stresses 2.5

4-3 Aircraft Controls & Systems 3.5

4-4 Atmospheric Effects on Aircraft 1.5

4-5 introduction to Aerodynamics 4.5

4-6 Rotary Wing Aerodynamics 3.0

4-7 introduction to Weight & Balance 6.0 27.0

(2) lb ii.,5!ek 5 Hardware & Handtools 4.0 1 5-1 Introduction to Hardware & Materials

5-2 introduction to Common liandtools 6.5

5-3 Nuts, Bolts, Screws, Fa5teners and Special.Aircraft Hardware 6.5

5-4 SafteyDevices & Safety Wiring Practical 10.0 27.0

Week 6 Publications

6-1 Introduction to the Naval Aeronautical Publication index, 01, 02 and 03 Series of Publications 4.0

6-2 Introduction to the Federal Supply System 4.0

6-3 Bulletins and Changes (Navy) 1.0 1.0 6-4 CG ATN, ATO, AMB, and AMC's

6-5 CG Directives, Publications, and Reports index - CG-236 1.0

6-6Flight Record Form C0-4377 1.5

6-7 UR Form, CG-4010 1.0

6-8 Aircraft Records 6.0

6-9 Aircraft Material Stocking List,CG-298 1.5 6-10 Introduction to Air Force Technical OrderSystem 3.0

6-11 Introduction to Coast Guard TechnicalOrder System 1.0

Practical 2.0 27.0

EHASE II (Fixed Wing Aircraft)

Week 7 Reciprocating Engines (General)

7-1 Introduction to Power Plants 2.0 1.0 7-2 Radial Engine Breakdown

7-3 Principals of Engine Operation 4.0

7-4 Cylinders, Valves, and Valve Operating Mech. 3.0

If (3) 'Auk" Reciprocating Engines(Continued) 2.0 7-5 Power Transmission Mechanisms 2.0 7-6 Superchargers 1.0 7-7 Cooling and Exhaust System 2.0 7-8 Introduction to Lubrication System 2.0 7-9 Introduction to Aviation Lubricants 8.0 7-10 Introduction to Carburetion 27.0

Week 8 Fuels & Ignition 1.5 8-1 Aviation Fuels 1.0 8-2 Introduction to Aviation Fluids 1.5 8-3 Introduction to Aircraft FuelSystems .5 8-4 Fuel - Air Ratios Engine Ignition Sys. 1.0 8-5 Introduction to Reciprocating 1.0 8-6 Types of Magnetos 2.0 8-7 Circuits & Components of theS9LU Mag. 1.0 8-8 Mechanical Operation of theS9LU Mag. 2.0 8-9 Electrical Operation of thesgla Mag. 1.0 8-10 Description & Operationof the Induction Vib. 1.0 8-11 Introduction to Spark Plugs 13.5 8-12 Timing the S9LU Magneto(Practical) 27.0

Week 9 Hydraulics 3.0 9-1 Basic Principle and Theoryof Hydraulics .5 9-2 Operation of a Basic AircraftHydraulics System 1.0 9-3 Hydraulic Sealing Devices andHydraulic Fluids 3.0 9-4 HU-16E Hydraulic System(General) Week 9 Hydraulics (Continued) I/

9-5 HU-16E Main Hydraulic System 5.0

9-6 HU-16E Sub. System 5.0

9-7 HU-16E Hand Pump System 3.0

9-8 Shock Struts 1.0

9-9 The Nose Wheel Shimmy Damper 1.0

9-10 The Variable Delivery Pump 3.0

9-11 The independent Brake Master Cylinder .5

9-12 The Disc Type Brake 1.0 27.0

Week 10 Propellers

10-1 Introduction to Prope/ler Theory & Types 4.0

10-2 Introduction to the 43D50 Prop. 1.0

10-3 Introduction to the 43D50 Prop. Blade Assy. 1.0

10-4 Introduction to the 43D50 Hub Assy. 1.0

10-5 Introduction to the 43D50 Oil Trans. HousingAssy. 1.0

10-6 introduction to the 43D50 Prop. Dome Assy. 2.0

10-7 Introduction to the Low Pitch Stop Lever Assy. 1.0

10-8 Introduction to the Control Slip Ring Assy. Including the Brush Pad Bracket Assy. 1.0

10-9 Introduction to the Double-Acting Gov. Assy. 1.0 10-10 introduction to the StepMotor ElectricHead Assy. 2.0

10-11 Introduction to the Integral OilControl Pump Housing 3.0

10-12 Introduction to the Aux. Oil Supply System 1.0

10-13 introduction to the Prop Electrical Circuit 2.0

10-14 Procedures for Propeller Servicing 1.0

LO-15 Introduction to the 43D50 Prop Deicing System 1.0

10-16 Prop. Removal & Installation (Practical) 4.0 27.0 (5) 19 IIAek 11 Line Safety & Inspections 1.0 11-1 introduction to Tow Vehicles 2.0 11-2 introduction to Mobile Elect. Power Plants g 11-3 High & Low Pressure Air, Uses & Characteristics .cl 2.0 11-4 Safety in Maintenance 2.0 11-5 Line Safety

11-6 Introduction to Maintenance Stands & Equipment :5 2.0 11-7 Aircraft Servicing & Ground Handling 2.0 11-8 Introduction to Periodic Inspection 1.5 11-9 Introduction to the HU-16E Work CardSystem 11-10 Introduction to Phased Inspection 1.0

11-11 Introduction to AircraftCorrosion 2.0 Practical Application ---2-410 11-12 Periodic Inspection, 27,0

Week 12 Starts, Stoos, & Runups 2.0 12-1 Aux. Power Plant 2.0 12-2 Introduction to Start & Stop theHU-16E Engine 4.5 12-3 Operational Runup of HU16E 18.5 Practical Application 12-4 27.0

Week13 Troubleshootiu 1.0 13-1 Introduction to Trouble Shooting .5 13-2 Universal Prop. Protractor .5 13-3 Introduction to the Dial Indicator Introduction to the Piston PositionIndicator 13-4 1.0 (Time Rite) 1.0 13-5 Introduction to the Magneto TimingLight 1.0 15-6 introduction to the Cold Cylinderindicator Introduction to the S-1 Type Diff.Comp. Tester 1.0 13-7 ,U /3 112ek 13 ricubleShooting (Continued) 1.0 13-8 Introduction to the High Volt.Insulation Tester 1.0 13-9 Trouble Shooting AircraftSystems 3.0 13-10 Trouble Shooting theR-1820-76 Engine 1.5 13-11 Line Maintenanceof HU-16 Engine 14.5 13-12 Practical Application 27.0

PHASE III (Rotary Wing Aircraft)

Week 14 Intro to the 1-iH52A Helicopter 3.0 14-1 Development & Theory of RotaryWing Flight 2.0 14-2 HH52A Airframe 4.0 14-3 HH52A Electrical System 4.0 14-4 HH52A Fuel System Shafts 5.0 14-5HH52A Gear Boxes and Drive 6.0 14-6 HH52A Rotor Head and Blades Systems 3.0 14-7 HH52A Flight Control 27.0

Week 15 Intro to the HH52AHelicooter (Continued) 6.5 15-1 HH52A Hydraulic System 6.5 15-2 HH52A Landing Gear System 3.0 15-3 HH52A Heater System 2.0 15-4 HH52A Hoist System 2.5 15-5 HH52A Fire Detector &Extinguishing Systems Procedures, Safety Wiringand 15-6 Review of Torquing 6.5 Hardware & Publications 27.0

Week 16 Intro to the T-58 Engine 4.0 16-1 Jet Engine Theory 2.0 16-2 T-58 Engine 3.0 16-3 Compressor & Accessory Sectionof the T-58 Engine

171 21. /4

-1.72k 16 Intcoto the T-i8 Engine, 1.0 Combustion Section of the T-58Engine 2.0 16-5 Gas Generator Section of theT-58 Engine 1.0 16-6 Power Turbine Section of theT-58 Engine 2.0 16-7 Airflow of the T-58 Engine

16-8 Lubrication System of the T-58Engine 6.0 16-9 Fuel System of the T-58Engine 16-10 Electrical and Stator VaneActuating Systems 3.0 of the T-58 Engine Control 1.0 16-11 Introduction to'HH52 Corrosion 27.0

Week 17 Intro to the T- 8 En inePractical 2.0 17-1Jet Engine Preservation 1.0 17-2 T-58 Engine Removal

1.0 . 17-3 Preparation of the T-58 Enginefor Shipment from the Shipping Container 1.0 11-4 Removal of the T-58 Engine 2.0 17-5 T-58 Engine InspectionProcedures 6.0 17-6T-58 Engine Accessory Removal 14.0 17-7 T-58 Engine Power TurbineRemoval

MIND 17-8 T-58 Engine Gas GeneratorTurbine Removal

17-9 T-58 Engine CombustionSection Removal and Compressor Section Splitting 27.0

Week 18 T-58 Practical (Continued) 5.0 18-1 installation of CompressorStator & CombustionSection 5.0 18-2 installation of Gas Generator& Power Turbine Sections Lines, Leads, and Fittings 6.0 18-3 Installation of Accessories, 5.0 18-4 Installation of T-58 ReadyEngine Kit Components Head Assy. 1.0 18-3 Introduction to Removal ofthe HH52A Main Rotor Main Transmission ofthe HH52A 5.0 18-6 Removal of Rotor Head & 27.0 24 (R1 /5-

Vet* 19 HH52A Practical 11 Maintenance of the HH52A Main RotorHead & Gearbox Assemblies (2 Hours Class, 10 HoursPractical) 12.0 3.0 19-2 Installation of the Main Rotor Head &Star Assembly Installation of Main Gear Box QuickChange Unit Practical 12.0 19-3 27.0

'Week 20 HH52A Line Servicing & Maintenance Engine installation &Depreservation 1.5 20-1 5.5 Engine Installation Practical for the HH52A 2.0 20-2 Preflight & Servicing Requirements 4.0 Preflight Practical 2.0 20-3 Rescue Hoist & PlatformRecovery Procedures Check Out 2.0 Rescue Hoist Operational Supervision) 3.0 Aircraft Hoisting Exercise(Live Hoisting Under 1.5 20-4 Aircraft Ground Handling Practical 2.0 - Aircraft Ground Handling 1.0 20-5 Aircraft Taxi Signals. 2.5 Practical Aircraft Taxi Signals 27.0

PHASE I (AIRMAN PREPARATORYCONTINUED)

Week 21 Militar, CG-333 - Survival Officer Specialties & 21-1 Introduction to USCG Warrant 1.0 Uniform Identification 2.5 21-2 Air Station Organization 1.5 21-3 Introduction to Air StationWatch Lists .5 21-4 introduction to ShipboardArmament 1.5 21-5 NBC Warfare 4.o 21-6 Survival 8.0 21-7 Survival Equipment 2.0 Practical 3.0 Flight Physiology & WaterSurvival Training 21-8 3.0 Practical (Conducted at Navy Norfolk on afacility availablebasis) 27.0 2

/ n \ /f

WEEK 1

TITLE Introduction to Mathematics

TOPIC OBJECTIVE student with generalmathematics, fractions, To familiarize the ratio decimals, percentages, positiveand negative numbers, and volumes, and proportion, introductionto angles, area's and triangles. The student will be ableto: mathematical terms used. (a) Name and explain the utilizing the terms andformulas (b) Correctly solve problems discussed. / 7

WEEK 2

TITLE Introduction to physics

TOPIC OBJECTIVE To familiarize the student with matter, electron theory, force and pressure, Pascal's Law, heat, force and motion, work and power, principles of machines, and gears. The student will be able to:

(a) Define the physics terms discussed in this week.

(b) List and explain the laws dealing with physics.

20 WEEK 3

TITLE

Introduction to 5asic Electricity

TOPIC OBJECTIVE

To introduce the student to the theory of basic electricitY2 electrical components, safety devices, basic DC aircraft electrical systems and the Simpson Multimeter. The student will be able to:

(a) Define and explain the followini:

(1) Static Electricity.

(2) Dynamic Electricity.

(3) Ohm's Law and the Rheostat.

(4) Series Circuit.

(5) Parallel Circuits.

(6) Magnetic Theory and Electromagnetism.

(7) Electrical Components.

(8) Safety Devices and Controls.

(9) Basic DC Aircraft Electrical System.

(10) Simpson Multimeter.

(b) Describe safety precautions to be observed when dealing with electricity and electrical components.

(d) Explain current flow and resistance. 191

WEEK 4

TITLE Introduction to Aerodynamics

TOPIC OBJECTIVE To familiarize the student with types and classes ofaircraft, rotational axis and stresses encountered in flight,aircraft control systems, atmospheric effects on aircraft, aerodynamics, rotary wing aerodynamics, weight and balance,electrical and remote reading instruments, and navigation instruments. The student will be able to:

(a) Explain safety precautions outlined in CG ATN-4-7l tobe observed when maintenance is performed on an aircraft control system.

(b) Define the terms, laws, and principles utilized in aerodynamics.

(c) Solve problems in weight and balance utilizingthe terms, formulas and load adjuster. Describe the purpose of electrical and navigationinstruments.

2 (13) 02O

WEEKS_

TITLE Hardware and Handtools

TOPIC OBJECTIVE the AtAidenrt-with the selectioh-andproper use of To familiaftze the in- hardware and handtoolsassociated with aviation, more common torque wrenches etc:.-- cluding certain specialtools, ie. micrometers, Also introduces hlm tothe correct safetyprocedures associated.with able to: hardware and handtaols,She student will be .of-metals, metal-characteristics, (a) List and exp.lain properties forms, shapeSIand alUysutiliied. tubing used in aircraft,explain the (b) List the two types of and list and color coding used toidentify tubihe systems explain installationprocedures a6q:precautions. list Imes of selected commonhandtools (c) Identify, describe and including Vernier Micrometers-and dial indicators. list uses of the morecommon hardware Identify, describe and rods, and rod Ihcluding control cables,turnbuckles, control ends. Describe the use of atensiometer. and safety precautionsinvolved with (e) Identify, explain uses of, cotter pins. Satisfactorly demonstrate different safety wire.and sample safety wire his knowledge andability by completing a and cotter pin boardin one hours time. WEEK 6

TITLE

Publications

TOPIC OBJECTIVE student with thevarious forms,publications, To familiarize the The student logs and records associatedwith Coast GuardAviation. will be able to: and describe the purposeof the Naval (a) Name the five parts Index. Explain the Navypublications Aeronautical Publications between a manualand numbering system. Explain the difference Describe the purposeof the a letter typepublication. Explain maintenance manual andthe illustrated partsbreakdown. "a-marnral or lettertype the sequence ofevents for locating publication. three parts of afederal stock number. (b) Name and describe the Explain the sequence Identify by name theCRL2N, CRL2N, andNMDL. of issue, description, of events fordetermining the FSN, unit and price of anitem beginning with apart number. purpose of andthe three catagoriesof (0 Name and explain the changes and bulletins(Navy). of AMB's, AMC's,ATN's and ATO's. (d) Name and explain the purpose and the purpose of thedirectives, Publications (e) Name and describe CG-236. Describe the securityclassification Reports Index, and the method of system, its purposeand identifing code, numbering and filingdirectives. record form,CG-4377 and Identify by numberthe aircraft flight (f) the method ofnumbering and explain the purposeof each part, and filing the aircraftflight record. explain the purpose,importance, and the (g) Identify by number and CG-4010. desired results ofthe unsatisfactoryreport form, explain the purposeof the aircraftlog and (h) Name, describe, and record. the purpose ofOPNAV 4790/35, Maintenance (i) Identify and explain Instruction. the aircraftmaterial Identify and explainthe objectiyes of (.i) the three categoriesof stocking list. List and describe material as listedtherein. 2 'VJEEK 6 (Cont'a)

(k) Name and explain NI&RF and list of applicable publication systems. Describe the AFTO system and its purpose. Explain the AFTO numbering system.

(1) Describe the Coast Guard technical order system and its purpose.

( 16 ) 2.3

WEEK 7

TITLE Reciprocating Engines (General)

TOPIC OBJECTIVE

To familiarize the studentwith various types ofreciprocating engines, engine construction,engine components andengine operation. The student will ba ableto: cooling and exhaust systems. (a) Explain the purpose of the components used in abasic (b) Name and describe various lubrication system. of oil flow through a (c) List the components in sequence dry sump system. system of Aviationlubricants (d) Explain the classification and the importance of properhandling and storage. designation of andoperation of (e) Describe the units, the the pressure carburetor% 24

WEEIC 8

Title

Fuels and Ignition

Topic Objective

To familiarize the student with basic requirements of aviation fuels, octane rating and performance numbers; how they are established and identified, an safetyprecautions to be observed while handling. The student will be able to:

(a) Explain the requirements of a basic aircraft fuel system and functions of various compOnents that comprise a basic aircraft fuel system.

(b) Explain the path of fuel flow on the HU-16E, theimportance of fuel air ratios and their effects on engineoperation, to indentify by name various indications of improperfuel air mixtures.

(c) State the purpose of an engine ignitionsystem and list the major components which make up an engineignition system, state their purpose and location on theengine or aircraft, define terms applicable to aircraft magnetos andinterpret each character of the designation S9LU-3.

(d) List the three (3) circuits of the S9LU-3 anddescribe their purpose and construction features.

(e) Describe the mechanical operation of magnetos,draw the complete magnetic and electrical circuitsof the S9LU-3 and explain current flow.

(f) Describe the types of spark plugs used inCoast Guard aircraft; how they are constructed andprecautions to be used while handling.

(g) Demonstrate the ability to bench time the S9LU-3,and time a magneto to an R-1820 engine in thetime alloted. WEEK 9

Title

Hydraulics

TODie Objective

To familiarize the studentwith a basic understandingof a hydraulic system including components,types of' fluid, operation and minor maintenance. At the completion of this week the student will be ableto: and esadvantlages of a (a) Name and describe the advantages hydraulic system. practical (b) Name and describe theessential.componehts hydrauAic system (11ydraulicja,c1c), Ana explain how force is tx*Tsmitted Ito= inputto-o4tbUt. =.1itmatica l. probleffsillustrating (c) Solve correctly simple the mechanicaladvantage-444evd in hydraulics. component in a basichydraulic (d) Explain the purpase of each system. used in (e) Name and describe thevarious sealing devices aircraft hydraulic systems. of the different (f) Explain the application and purpose design hydraulic sealingdevices. bf hydraialic%Ifluids andtheir (g) Name and describe the types characteristics. types of hydraulic systemsused in (h) Name and describe the the HU-16E. components that are commonto both (i) Name and describe the power operated systems. and volumes of the components (j) List the pressure limits that are common to both poweroperated systems.

k) Perform minor maintenance onthe system.

(19 ) c26

WEEK 10

Title

Propellers

Topic Objective To familiarize the student with basic propeller types, propeller theory, operation, removal, installation, servicing and safety. The student will be able to:

(a) Explain the forces created by a rotating propeller, how the propeller produces thrust, and safety rules to be observed in the area of propeller rotational plane.

(b) Explain the. meaning of various letters and numbers in the propeller hub assembly model designation and identify the seven (7) components that make up the43D50 propeller.

(c) List and describe the major parts of the propeller hub assembly; state the location, purpose and the flow ofoil through the hub, explain the proper procedure forsecuring and locking the hub assembly to the propeller shaft.

(d) List and describe the major parts of the propellerblade and state the location of each. Explain the purpose of each major part of the assembly.

(e) List and describe the purpose, major parts, locationand functions of the dome assembly.

(f) State the location and purpose of the slip ring andbrush pad and how they are mounted.

(g) State the location, purpose and operation ofthe governor stepmotor head and integral oil system.

(h) State the purpose of the aux oil system. List and describe the components and operation of the aux oilsystem.

(i) List and describe the major components ofthepropeller electrical circuit and explain its operation.

List the proper oil acceptable for use inthe43D50 propeller and correct procedures for servicing.

(k) Name and identify components of the deicingsystem and explain its operation.

(1) Explain the proper procedure forremoval and installation of the 43D50 propeller assembly. 3 q a7

WEEK 11

Title

Line Safety and Inspections

Topic ObSective

To familiarize the student with general ground support equipment, operating procedures and safety precautions. The student will be introduced to:

(a) General ground support equipment, including demonstraticns.

(b) Aircraft servicing and ground handling.

(d) Aircraft corrosion and corrosion control practices.

(e) HU-16E periodic inspections.

1 30

(211 WEEK 12

Title

Starts, Stops and Run-ups

Topic Objective

To familiarize the student with the correct procedures for inspection and operation of the APU and the R1820 Engine. The student will be able to:

(a) Demonstrate the purpose, application and use of the V-32D-2 APU.

(b) Perform pre-flight and post-flight inspections of the HU-16E aircraft.

(c) Perform starts, run-ups and stops of the APU and Main engines of the HU-16E, in compliance with the NATOPS , Manual 01-85-AC1 and the Standardization Manual, CG-372.

( 2 2 1 WEEK /3

Title

Trouble Shooting

ToRie Objective

To familiarize the student with the correct methods, tools and procedures for effective trouble shooting and minor discrepancy repairs. The student will be able to:

(a) Explain the reason for trouble shooting, where to locate information concerning the trouble and the use of the four step and V.I.C.E. method used in trouble shooting.

(b) Demonstrate the ability to correctly use and the purpose of the following items:

universal propeller protractor dial indicator piston position indicator magneto timing light cold cylinder indicator S1 type differential compression tester high voltage tester

(c) Demonstrate the ability to make idle mixture and idle speed adjustments; fuel and oil adjustments; remove, inspect and install spark plugs; clean reciprocating engines.

(23) 3/ j

MODIFICATIONS

67,6 0244-o21 of this publication has (have) been deleted in

adapting this material for indlusion in the "Trial Implementation of a

Model System to Provide Military Curriculum Materials for Use in Vocational

and Technical Education."Deleted material involves extensive use of

military forms, procedures, systems, etc. and was not considered appropr3ate

for use in vocational and technical education. 3/ APPENDICES

SECTION A EQUIPMENT AND FURNITURE REQUIREMENTS PAGE Al

SECTION B TRAINING AIDS AND DEVICES PAGE Bl THRU B2

SECTION C PUBLICATIONS USED AS TEXTS OR PAGE Cl THRU G6 REFERENCES

SECTION D SPACE REQUIREMENTS PAGE Dl

SECTION E STAFFING REQUIREMENT BY GRADE AND PAGE El THRU E3 RATE WITH ORGANIZATION 3.2

NumberpC 341 item ingersol rand 1. Hanger air compressors, 1 Handsaw, do-all 65 Bookcase, section, metal 17 Bookcase, base, metal 6 Buffer, floor Cabinet, duplicator 1 letter size 7 Cabinet,.file, metal, 25 Cabinet, storage 1800 1 Calculator, Viotor 1 Calculator, Friden 23 Chairs, swivel, desk Chairs, student 159 board 1 Chalk & bulletin 1 Charger, battery 1 Cleaner, steam 8 Coat racks 1 Floor Jack 1 Cutter, Paper Desk, metal, dOublepedestai 7 '.iedestal 13 Desk, metal, single, Drill, electric,hand 3 :land 1 Drill, Pneumatic, 1 Drill press 6 Fan, pedestal 8 1C 5,card 1 S-16E Cabinet, 2 Grinder, bench 1 Lathe, metal turning Lockers, metalsingle 13 ditto 1 Machine, duplicating, 1 Reel, air hose disc 1 Sander, belt & 1 Saw, electriccircular 1 Saw, recipricating 1 Saw, miter box 1 Refrigerator 1 Sander, orbital I Saw, horizontalband 8 Stand, office machine 4 Stools, draftsman 114 Table, student Tap & die set 2 Electric 4 Typewriter, office, 1 Vacuum cleaner Water cooler 2 Burner/welderoxy/acetylene 1 Welder, electric, 1 ea (Student lounge) 2 Couches 4 Lounge chairs (Student Lounge) TRAINING ArbesANDoEvICES

Atrtber of each item

2 HU16E Aircraft (1 operational) 3 HH52A Helicopter 1 Applicator, Water 1 Applicator, rust lick 1 Auxiliary Power Unit 2 Borescopes Chalk Boards 5 castors 8 Carts, 3 Shelves with 2 Cnmpression Tester image 1 Copy maker, Thermal 1 Compressor, air, Cornelius 1 Electronic Stensil Cutter 1 Gantry, 3 Ton Capacity 350 16mm movies 1 Hydraulic Power Unit 1 Grease Gun, LincolnPneumatic 1 Hoist, electric 1 Indicator, dial Jack, AC 3 Ton 3 1 Jet Cal. Tester 1 Kit, T58, specialtools 3 Multimeters 1 Micrometer, set Micrometer, depth 1 Portable, 28 VDC 1 Power supply,+ engine 1 Preservation unit, 2 Projector, opaque Projector, 16mm 5 Slide 1 Projector, Sound on 7 Projector, overhead Protractor, propellop 6 bearing/bushing 1 Puller Kit, mechanical, Rectifier, 28 VDC 1 portable 2 Screen, slide & movie, 1 S.V.A. Ind, KitT58 1 Tester, Delta P 1 Tester, Torque Wrench 1 Tool Box, Roll Around 1 Tractor, Towing 1 Vacublast machine 6 Vise, bench 8 Wrench, torque 2 T58 engines 1820 QEC's 2 mock-up 1 HU16E Hydraulic system 1 HU16E Fuel System mock-up

B-1 2 NU16E Propeller system modk-up 1 HU16E Propeller cut away 3 HH52A Maintenance stands 2 Universal tow bars 1 HU16E Heater system mock-up 1 HH52A Heater system mock-up 1 HU16E Electrical system mock-up 1 HH52A Electrical System mock-up 1 HU16E Engine instruement system mock-up 1 HU16E Auto Pilot system mock-up 1 HU16E Fuel Indication system mock-up 1 Radial engine ignition siming & valve mock-up 3 T-58 Engine carts 1 T-58 Engine cans 1 1820 Engine cut-away 1 HH52A Transmission & rotor head cut-away 3 HH52A Rotor blades & stand 2 HU16E Oil Tank cut.-away 1 43D50 Propeller. & Stand 1 Propeller bench 1 Hydraulic testing unit ALL 43D50 Propeller special tools ALL T-58 Engine special tools ALL- HH52A special tools Z T-58 Engine nose stands 2. T-58 Engine power turbin stands 1 Waukeshaw portable power unit 2 Aero stands 4 HU16E Maintenance stands ALL 1820 special tools 35-

PUBLICATIONS USED AS TEXTS OR REFERENCES

:EEK 1 A. Math Study Guide CNATT-P-630 B. Basic Mathematics, Vol. 1

iEEK 2 - A. Aviation Physics Study Guide and Workbook, CNATT-F-40 B. Powerplants for Aerospace Vehicles, CH-10, page 200- 201 (Third Edition) C. Basic Electricity, NAVPERS 10086A D. Airman Manual NAVPERS 10307A E. Aviation Electricians Mate 3&2 NAVPERS 10348-B F. The New American Machinist's Handbook, by Rupert Legrand

EEK 3 A. Basic Electricity, NAVPERS 10086A B. Aviation Physics Workbook CNATT-P-40 C. USCG pamphlet 210 D. AE 3&2 Manual NAVPERS 10348-8 E. Powerplants for Aerospace Vehicles

/EEK 4 - A. NIT Basic Science, chapter 8 (Third Edition) B. BUWEPS INST 13100.7 C. Airman Manual NAVPERS 10307A D. CG ATN 4-71 E. Sikorsky Theory of Flight F. Helicopter History and Aerodynamics Manual NAVAIR 00-80T-88 G. DD form 365 A, 8, C, & F H. Aviation Electricians Mate 3&2 NAVPERS 10348-B

4EEK 5 - A. FAA Airframe and Powerplant Mechanics Manual(AC65-15) B. Airman Manual NAVPERS 10307 C. AMS 3&2 NAVAER 10308 D. NIT Basic Science Aerospace Vehicles (Third Edition) E. Military Standards MS 33540

::EEK 6 - A. Maintenance Instructions Manual NAVWEPS 01-85AB-2 B. Illustrated Parts Breakdown NAVWEPS 01-85AB-4 C. CRL1N, CRL2N, NM0L, C0006 D. ATN 5-60 E. CG-199-1, CG-236 F. Commandant Instruction 13090.2A G. ATN 5-70 H. Commandant Instruction 13090.1A I. OPNAVINST 4790.2, Vol. II J. CG-298 A/C Material Stocking List K. AFTO 00-5-1, 00-5-2, NI&RT 0-1-01

C-1. 3 G

?UBLICATIONS USED AS TEXTS ORREFERENCES

WEEK - 7 A. NAVPERS #10343A B. FAA Powerplant ManualAC65-12 C. NIT Powerplants for AerospaceVehicles D. NAVPERS #10342A E. NAVWEPS #00-80T-42 F. NAVAIR 02A-35GH-502 G. Hya R1820-76 Engine H. NAVWEPS 03-108A-101 PD12K-10 CarbManual

WEEK - 8 A. Powerplants for Aerospace vehicles3rd Ed Nit B. NAVPERS 10342 C. Aviation fuels NAVAER06-5-501 D. NAVAIR 01-85AB-2 HU16-E.E&MManual E. NAVPERS 10335A F. FAA Airframe and PowerplantsManual AC65-12 CH.4 G. COMDT INST 13000 series,GREB3B H. Time-rite piston positioninstruetion book I. NAVAIR 02A-35GH-502

WEEK - 9 A. NAVPERS # 10310A B. Basic.science for AeroipaceVehicles C. NAVWEPS 01-85AC-1,NW01-85AB-2 Vehicles 3rd ED. N.I.T. WEEK -10 A. Powerplants for Aerospace B. Hamilton Standard's Prop toPilot C. NW 03-20CC-38 D. NW 03-20CC-39 E. NW 03-20CC-40 F. NA 01-85AB-2

WEEK -11 A. NAVPERS 10342-A (ADR3&2) B. NAVAIR 19-45-10 C. NAVPERS 10307-C (AIRMAN) D. USCG Institute course forAD2 E. NAVWEPS 00-80T-96 F. NAVPERS 1037-B G. NA 01-85AB-2 H. NA01-85AC-1 I. ATN 1-71 & 1-71D J. Maintenance & repair of aero space K. Vehicles N.I.T. L. HU16 Aircraft ModelBulletin 145 M. ATN 4-71 N. NA 01-1A-509 0. ATN 1-68

WEEK -12 A. NA 01-AC-1 B. NA 01-AB-2 C. NA 01-85AC-1 31

PUBLICATZONS USED AS TEXTS OR REFERENCES

D. NA01-85AB-2 E. CG372 F. NA02A-35GH-502

WEEK -43 A. NAVAIR 01-85A3-2 B. NAVWEPS 10085-A C. NAVAIR 02A-35GH-502 D. CG 372 E. NAVWEPS 01-1A-506

WEEK -14 A. NW 00-80T-88 B. Sikorsky Tbeory ofFlight C. CGTO 1H-52A-1 D. CGTO 1H-52A-2 E. Sikorsky Service SchoolManual

WEEK -15 A. CGTO 1H-52A-1, HH52AFlight Handbook Maintenance Manual B. CGTO 1H-52A-2, H152A C. CGTO 1H-52A-4, HH52AI.P.B. D. NA 02B-105AHB-2 vehicles 3rd ED(NIT) WEEK -16 A. Powerplants for Aerospace Systems 3rd ED(NIT) B. Jet Aircraft Power C. T-58 Engine TrainingGuide NA 02B-105AHB-2 D. Maintenance Manual E. T58-G#-88 Intermediate

WEEK -17 A. NAO2B-105AHB-2 B. NA 15-02-500 C. CGTO 1H-52A-2 D. CGTO 1H-52A-6 E. CGTO T58-8B-6EM Serieswork cards F. CGTO 1H-52A-6FI workcards G. ATN 1-71

WEEK -18 A. CGTO T58-8B-6EM B. NA 02B-105AHB-2 C. CGTO 1H-52A-2

WEEK -19 A. CGTO 1H-52A-2

WEEK -20 A. CGTO 1H-52A-2 B. NA 0213-105AH13-2 C. CGTO 1H-52A-6 D. ATN NO. 1-71 E. HH52A Bulletin No.40 F. CGTO 1H-52A-1 G. NAVPERS 10307-6

WEEK -21 A. USCG Pamphlet No.159 B. Coast GuardsmanManual C. CG 333 D. CG 294 E. CG Bihphlet No.108, 109 4 5 3E,

PUBLICATIONS VSED AS1SX1:5 OR REFtRaCES

F. NAVWEPS 00-80T-56 ,NAVAIR 13-1-6.2 G. NAVPERS 10087, NAVAIR00-80-T-52 H. CG Pamphlet No .458

C-14 21 SPACE REQUIREMENTS

Office Spaces Space Required

Chief, AD Training Branch Office 151 sq ft

Asst Chief, AD Training Branch Office 144 sq ft

Testing and Files Office 300 sq ft

Instructors Offices 1475 sq ft

Conference Room 475 sq ft

Student Lounge 448 sq ft

Classrooms for AD(A) School-3 each with minimum of475 sq ft

HU-16E (C) School Classroom 1000 sq ft

HH-52A (C) School Classroom 875 sq ft

T-58 Engine and Propeller Shop 2000 sq ft

Shop (Training Aids Maintenance) 616 sq ft

Training Aids Storage 744 sq ft

Special Tool Storage 250 sq ft

Store Room 150.sq ft

Head, Student's and Staff 322 sq ft

Furnace Room 112 sq ft

Total Floor Space including Hangar 25,690 sq ft

D1 4 i MODIFICATIONS

../eVi.b-xs. 45 of this publication has (have) been deleted in

adapting this material for inclusion in the "Trial Implementation of a

Model System to Provide Military Curriculum Materials for Use in Vocational

and Technical Education."Deleted material involves extensive use of military forms, procedures, systems, etc. and was not considered appropriate

for use in vocational and technical education.

40 023da-- AVIA6.Y1aiehl.1/14 )9??Ie- N AV RZe_.6 )031/ a- 4

CHAPTER 5

TOOLS ANDHARDWARE

TOOLS The ADR3 and ADR2 must have awell rounded knowledge of many differenttypes of tools and the purpose for whichthey are designed. One of the most importantattributes thata mechanic can haveis the ability to use the tools that he will needfor the everyday performance of his job, whether itbe a simple and minor adjustment of acomponent or a major job such as an engine change. A mechanic is known by the toolshe keeps. The use of tools may vary, butsafety, good AM.14 of tools never care, and the proper stowage Figure 5-1.-Standard Navytoolbox. vary. Some ofthevarious tools (including selection, use, and care) that the ADRmight his duties are assigned tasks. Thetools should be organized useinthe performance of in the box by type andsize, and those needed described in the following paragraphs. often placed where they canbe reached without NOTE: Two Rate TrainingManuals-Basic contents of the box. Airman, Nav- digging through the entire Handtools, NavPers 10085-A, and Tools should be maintainedin an orderly Pers 10307-B-also contain a descriptionof most aircraft parts, pieces with detailed fashion, and extras such as tools used by the ADR, together the box. instructions for using them. Thematerial cov- of "junk," etc., kept out of ered in this chapter is intended tosupplement, rather than repeat, the informationgiven in Diagonal Pliers be studied these training manuals and should Diagonal cutting pliers (fig.5-2) are used in conjunction with them. for cutting small, light material,such as wire HANDTOOLS and cotter pins in areas which areinaccessible When an ADR reports to anactivity, it is to the larger cutting tools. toolbox As the cutting edges arediagonally offset highly probable that he will be issued a pliers are or toolkit. The size ofthe toolbox or toolkit approximately 15 degrees, diagonal to which he is adapted to cutting smallobjects flush with a will depend on the work center is a diagonal assigned. It could be a small toolkitissued to surface. The inner jaw surface Diagonalpliersare planecaptains, a medium sized toolboxfor straight cutting edge. toolbox damaged easily and should not beused in place troubleshooters, or the standard Navy cutting tools desiFned used by most powerplantcheck crews. (See of tin snips or other metal for heavier work. Diagonalpliers should nt. ier fig. 5-1.) be used to hold objects, becausethey exert a The toolbox will most likelycontain only than other types of those tools neededoftenin performing the greater shearing force

73 AVIATION MACHINIST'S MATE R 3 & 2

The handle drive is usually square. In the other endofthe socket is a 6-point or 12-point opening very much like the opening in the box end wrench. The 12-point socket needs to be swung only half as far as the 6-point socket before it has to be lifted and fitted on the nut for a new grip.Itcan therefore be used in closer quarters where there is less room to move the handle. Most sockets have 12-points. However, the 6-point socket has its use with AM.15 nuts made of stainless steel, which are made Figure 5-2Diagonal cutting pliers. of harder metal than that of the wrench. Ex- tensive use of a 12-point socket on such nuts pliersof a similar size. The sizes of the or bolts would cause excessive wear on the diagonal cutting pliers are designated by the 12-points so that the socket might fail to hold. overall length of the pliers. By contrast, because of the greater holding Socket Wrench surface, a 6-point socket holds the stainless steel nut better, offering less chance for wear The socket wrench is one of the most of the wrench. versatile wrenches in the toolbox. Basically, Sockets are classified for size according to itconsistsofa handle and a socket type two factors. One is the drive siie or square wrench which can be attached to that handle. opening which fits on the square drive of the A complete socket wrench setconsists of handle. The other is the size of the opening several types of handles along with bar exten- in the opposite end, which fits the nut or bolt. sions, universals, adapters, and a variety of The standard aircraft mechanic toolbox is us- sockets. (See fig. 5-3.) ually outfitted with sockets having 1/4-, 3/8-, SOCKETS.A socket has an opening cut in and 1/2-inch-square drives. The openings that one end to fit a drive on a detachable handle. fit onto the bolt or nut are graduated in 1/16-

SLIDING T-BAR HANDLE RATCHET HANDLE Vi,...... ,,Za > tEXTENSION (ifiZm..d...... m.aaa BARS

~14 6 POINT 12 POINT SOCKET SOCKET FLEXIBLE EXTENSION MALE FEMALE ADAPTER ADAPTER DEEP SOCKET UNIVERSAL UNIVERSAL SOCKET JOINT

AM.18 Figure 5-3.Typiral socket wrench set.

74 Chapter 5TOOLS AND HARDWARE V3 inch sizes. Sockets are also made in deep lengths the wrench handle at an angle. A universal to fit over spark plugs and long bolt ends. socket is also available; and universal socket There are four types of handles used with joints, bar extensions, and universal sockets these sockets. (See fig. 5-3.) Each type has in combination with appropriate handles make special advantages, and the good mechanic it possible to form a variety of tools that will chooses the one best suited to the job at hand. reach otherwise inaccessible nuts and bolts. The square driving lug on the socket wrench Another accessory item which comes in handles has a spring-loaded ball that fits into handy sometimes is an adapter which allows a recess in the socket receptacle and holds the the ADR to use a handle having one size of drive assembly together.This mated ball-recess with a socket having a different size of drive. feature prevents the parts of the wrench from For example, a 3/8- by 1/4-inch adapter would falling apart during normal usage, but a slight make it possible to turn all 1/4-inch-square pull disassembles any wrench connection. drive sockets with any 3/8-inch square drive RATCHET HANDLE.This handle has a handle. reversing lever which operates a pawl (or dog) There are special sockets which are used inside the head of the tool. Pulling the handle to adapt various types of screwdriver bits to a in one direction causes the pawl to engage in speed handle (fig. 5-4). This socket type screw- the ratchet teeth and to turn the socket. Moving driver is used to remove recessed head screws in the opposite direction causes the pawl to from access panels on aircraft. slide over the teeth, permitting the handle to back up without moving the socket. This allows Combination Wrench rapid turning of the nut or bolt after each partial turn of the handle. With the reversing TheADR'stoolboxshouldcontaina lever in one position, the handle can be used complete set of combination wrenches. The com- for tightening. In the other position, it can be bination wrench(fig.5-5) has an open-end used for loosening. wrench on one end and a box-end (of the same HINGED HANDLE.The hinged handle is size) on the other end. For speed and light also very convenient. To loosen a tight nut, stress operations, use the open-end; then switch swing the handle at right angles to the socket. to the box-end for safety under stress. For ease This gives the greatest possible leverage. After of explanation, each end of the wrench will be loosening the nut to the point where it turns discussed separately. easily, move the handle into the vertical position The box-end fits completely around the nut and then turn the handle with the fingers. or bolthead. The box-end is usually constructed SLIDING T-BAR HANDLE.While using the sliding bar on T-hanclle, the head can be PHILLIPS REED positioned at either the end or the center of the a sliding bar. Select the position which is needed PRINCE for the job at hand. SPEED HANDLE.Thespeed handleis worked like the woodworker's brace. After the nuts are first loosened with the sliding bar handle or the ratchet handle, the speed handle will help remove the nuts in a hurry. In many instances the speed handle is not strong enough to be used for breaking loose or tightening. The speed socket wrench should be used carefully, to avoid damaging the nut threads. ACCESSORIES.To completethesocket wrench set, there are several accessory items. Extension bars of different lengths are made to extend the handles to any length needed. A AM.19 universal joint allows the nut to be turned with Figure 5-4.Screwdriver adapter.

75 -1/ AVIATION MACHINIST'S MATE R 3 & 2

using any open end type wrench, always insure that the wrench fits the nut or bolthead, and pullon the wrench-never push.Rushing a wrench is dangerous. The threads could break loose unexpectedly and cause damage to adja- 15* OFFSET ALLOWS CLEARANCE 1 cent equipment or injury to the person using 1° the wrench. III UM AIIIItill Adjustable Wrenches AM.20 Figure 5-5.-Combination wrench. Adjustable wrenches are not intended to replace open end wrenches, but they are useful with 12 points. The advantage of the 12-point in working in restricted areas. In addition, construction is that the wrench will operate they can be adjusted to fit odd size nuts. between obstructions where space for the handle However, adjustable wrenches are not intended to swing is limited. A very short swing of the for standard use but rather for emergency use. handle will turn the nut far enought to allow the They were notbuiltfor use on extremely wrench to be lifted and the next set of points hard-to-turn items. As shown in figure 5-6, to be fitted to the corners of the nut. It is adjustable wrenches have a fixed jaw (A) and possible to use this wrench in places where an adjustable jaw (B) which is adjusted by a the swing angle is limited to as little as 30 thumbscrew (C). By turning the thumbscrew, degrees. the jaw opening may be adjusted to fit various The box-end portion of the wrench is de- sizes of nuts. The size of the wrenches ranges signed with an offset in the handle. Notice in from 4 to 18 inches. The maximum jaw openings figure 5-5 how the 15 degrees offset will allow vary in direct proportion to the length of the clearance over nearby parts. One of the best handle. features of the box-end is that there is little Adjustablewrenchesareoftencalled or no chance of a wrench slipping off the nut "knuckle busters" because mechanics frequently or bolt. However, there is the disadvantage of suffer the consequences of improper usage of slow work with the box-end of the combination these tools. wrench. Each time the wrench is backed off, the wrench has to be lifted up and refitted to the head of the work. Therefore, to save time, use the nonslip box-end of the wrench to break loose tight bolts or to snug up work after the bolt has been seated with a faster type wrench which might slip under stress. The jaws of the open end portion -of the combination wrench are machined at 15 degrees from parallel in respect to the centerline of the handle. This permits the use of the wrench in places where there is room to make only a part of a complete turn of a nut or bolt. If the wrench is turned over after the first swing, it will fit on the same flats and turn the nut farther. After two swings on the wrench, the nut is turned far enough sothata new setof flats are in position for the wrench. The open end of the combination wrench may be used on tubing nuts and in cramped places too small for a socket or box-end to AM.21 be slipped over the nut or bolthead. When Figure 5-6.-Adjustable wrenches.

- Chapter 5TOOLS ANDHARDWARE

There are four simple stepsto follow in choose one of the using these wrenches. First, HEAVY DUTY correct size;thatis, do not pick a large SQUARE 12-inch wrench and adjust thejaw for use on SHANK a 3/8-inch nut.This could result in a broken lt and a bloody hand.Second, be sure the size wrench are adjusted SCREW HOLDING jaws of the correct DRIVER to fitsnugly on the nut. Third,position the wrench around the nut untilthe nut is all the COMPRESSION OF SPRING way into the throat ofthe jaws. If not used in HOLDS SCREW FIRMLY this mariner, the result is aptto be as bloody AGAINST TIP OF DRIVER as before. Fourth,pull the handle toward the side having the adjustable jaw.This will prevent the adjustable jaw fromspringing open and REED AND PRINCE slipping off the nut. If the locationof the work DRIVER will not allow all four steps tobe followed when using an adjustable wrench, thenselect another type of wrench for the job. Adjustable wrenches should becleaned in a solvent, and a light oil appliedto the thumbscrew and the sides of theadjustable jaw. They should also be inspected oftenfor cracks which might result in failure of thewrench. Screwdrivers Two basic screwdriverblade types are usedthe common blade for use onconventional slotted screws and a crosspointblade for use RATCHET AND SPIRAL DRIVER on the recessed headPhillips or Reed and AD.14 of screwdrivers Prince type screws. Both types Figure 5-7.Typical screwdrivers. are illustrated infigure 5-7. The commonand crosspoint blade types are usedin the design wheel; check of various special screwdrivers,some of which 2. Square off the end with the for squareness by resting the tip onthe handle are also shown infigure 5-7. shank of the COMMON SCREWDRIVERS.Thecombined of a trysquare, and move the identifies the size screwdriver close to the blade ofthe trysquare. length of the shank and blade and shank are of common screwdrivers.They vary from If the blade of the trysquare 2 1/2 to 12 inches. Thediameter of the shank parallel, the tip is square. and the width and thicknessof the blade tip CROSSPOINT SCREWDRIVERS.There are which fits the screw slot arein proportion to two types of crosspoint screwdriversin common the length of the shank. Theblade is hardened usethe Reed and Prince, andthe Phillips. to prevent it from beingdamaged when it is The Reed and Prince screwdriversand Phillips interchangeable; used on screws.Itcan easily bechipped or screwdrivers are NOT The therefore, always use a Reed andPrince screw- blunted when used for other purposes. and a blade of a poor quality screwdriverwill some- driverwith Reed and Prince screws when being used Phillips screwdriver with Phillips screws.The times become damaged even screwdriver will result in properly. use of the wrong A damaged common screwdrivermay be mutilation of the screwhead. if done correctly. OFFSET SCREWDRIVERS.An offset repaired by dressing the blade where there This can be done by thefollowing instructions: screwdriver (fig. 5-7) may be used wheel so is not sufficient vertical spacefor a standard 1. Dress the sides with an emery are con- that the blade is symmetricalin shape. screwdriver. Offsetscrewdrivers

77 AVIATION MACHINIST'S MATE R 3 & 2

structed with one blade forged in line and another blade forgedatrightanglesto the shank handle. Both blades are bent 90 degrees to the shank handle.. By alternating ends, most screws can be seated or loosened even when the swinging space is very restricted. Offset screwdrivers are made for both standad and rec essed head screws. BALL PEEN HAMMER CAUTION: When using any type of screwdriver, do not hold the work in the hand. If the point slips,it can cause a bad cut. The AIn will always be safe when'followi.Ng this rule: Never get any part of the body in :ront of the screwdriver point. This is a good safety rule for any sharp-pointed tool. When removing a screw from an assembly that is not stationary, hold the work on a solid surface, in a vise, or PLASTIC HAMMER with some other holding tool.

Hammers PLASTIC FACE Generally speaking, this group is composed of various types of hammers, all of which are used to apply a striking force where the force AM.23 of the hand alone is insufficient. Each of these Figure 5-8.Hammers. hammers is composed of a head and a handle, even though these parts differ greatly from ADR's toolbox. The weight of the plastic head hammer to hammer. So that the ADR may have may range from a few ounces to a few pounds. a better idea of their differences and uses, The plastic mallet may be used for straighten-. let's consider the types of hammers used most ing thin sheet ducting or when installing clamps. frequently. (See fig. 5-8.) SAFETY PRECAUTIONS.Hammers are BALL-PEEN HAMMER.The ball-peen dangerous tools when used carelessly and with- hammer is sometimes referred to as a machin- out consideration. Practice will help the ADR ist's hammer. It is a hard faced hammer made to learn to use a hammer prop6Tly. Some of forged tool steel. important things to remember when using a The flat end of the head is called the face. hammer or mallet are as follows: This end is used for most hammering jobs. Hold thehandle near the end with the The other end of the hammer is called the peen. fingers underneath and the thumb along the The peen end is smaller in diameter than the side or on top of the handle. The thumb should face and is therefore useful for striking areas restonthehandle and never overlap the that are too small for the face to enter. fingers.Oil on the face of the hammer will Ball-peen hammers are made in different cause it to glance off the work; therefore, wipe weights, usually 4, 6, 8, and 12 ounces and 1, theoil off with a rag then rub the face with 1 1/2, and 2 pounds. For most work, a 1 1/2- coarse sandpaper or emery cloth. Never use pound and a 12-ounce hammer will suffice. a hammer which has a loose head or cracked MALLETS.Amalletisasoft faced handle.Itis dangerous to personnel and to hammer. Mallets are constructed with heads property. Most hammer accidents are causedby made of brass, lead, tightly rolled strips of a loose head or a slippery handle, so remember rawhide, and plastic or plastic with a lead core this when using any kind of strikingtool. Tighten for added weight. the loose hammerhead by driving a wedge in Plastic mallets similar to the one shown in the end of the handle. This spreads the handle figure 5-8 are the type normally found in the tightly inside the head. Do not strike a hardened

78 5 4 Chapter 5TOOLS AND HARDWARE steelsurface withasteel hammer. Small pieces of steel may break and injure someone or damage the work. Use a soft hammer in striking hardened steel or highly polished stock. If a soft hammer is not available, use a piece of copper, brass, lead, or wood to protect the hardened steel. However, it is permissible to strikea punch orchisel directly with the ball-peen hammer because the steel in the AM.25 heads of punches and chisels is slightly softer Figure 5-10.-Channel-lock pliers. than that of the hammerhead. channel locks are less likely to slip from the Vise Grip Pliers adjustment setting when gripping an object. The channel-lock pliers will only be used where it The ADR uses this tool a number of ways. is impossible to use a more adapted wrench or These pliers can be adjusted to various jaw holding device. Many nuts and bolts and sur- openings by turning the knurled adjusting screw rounding parts have been damaged by improper at the end of the handle. Vise grips can be use of channel-lock pliers. clamped and locked in position by pulling the lever toward the handle. The vise grip pliers Duckbill Pliers are shown in figure 5-9. They may be used as a clamp, speed wrench, portable vise, and Duckbill pliers(A,fig. 5-11) have long for many other uses where a locking, plier wide jaws and slender handles. Duckbills are type jaw may be employed. used in confined areas where the fingers cannot CAUTION: Vice grip pliers should be used be used. The jaw faces of the pliers are scored with care since the teeth in the jaws tend to to aid in holding an item securely. Duckbills are damage the object on which they are clamped. ideal for twisting the safety wire used in securing They should not be used on nuts, bolts, tube bolts, nuts, and screws. fittings, or other objects which must be reused. Needle-Nose Pliers Channel-Lock Pliers Needle-nose pliers (B, fig. 5-11) are used Channel-lock pliers (fig. 5-10) can be easily in the same manner as duckbill pliers. However, identified by the extra-long handles, which make there is a difference in the design of the jaws. them a very powerful gripping tool. The inner Needle-nose jaws are tapered to a point which surfaces of the jaws consist of a series of makes them adapted to .nstalling and removing coarse teeth formed by deep grooves, a surface small cotter pins. They have serrations at the adapted to grasping cylindrical objects. Channel nose end and asidecutter near the throat. locks have grooves on one jaw and lands on the Needle-nose pliers may be used to hold small other. The adjustment is effected by changing items steady, to cut and bend safety wire, or to thepositionof the grooves and lands. The do numerous other jobs which are too intricate or too difficult to be done by hand alone. NOTE: Duckbill and needle-nose pliers are especially delicate. Care should be exercised when using these pliers to prevent springing, breaking,or chipping the jaws. Once these pliers are damaged, they are practically useless. Wire-Twister Pliers

AM.24 Wire-twister pliers (C, fig. 5-11) are three- Figure 5-9.-Vise grip pliers. way pliers, which hold, twist, and cut. They are

79 AVIATION MACHINIST'S MATE R 3 & 2

(A) DUCX BILL

FLEXIBLE TYPE

(Et) NEEDLE NOSE

AM.26 ).? Figure 5-11.Pliers. (A) Duckbill; (B) needle nose; and (C) wire twister. designed to reduce the time used in twisting EXTENDED POSITION RETRACTED POSITION safety wire on nuts and bolts. To operate, (A) (8) grasp the wire between the two diagonal jaws, and the thumb will bring the locking sleeve into place. A pull on the knob twirls the twister, making uniform twists in the wire. The spiral rod may be pushed back into the twister without unlocking it, and another pull on the knob will give a tighter twist to the wire. A squeeze on the handle unlocks the twister, and the wire can be cut to the desired length with the side cutter. The spiral of the twister should be lubricated occasionally. Mechanical Fingers Small articles which have fallen into places where they cannot be reached by hand may be AM.27 retrieved with the mechanical fingers. This Figure 5-12.Mechanical fingers. tool is also used when starting nuts or bolts indifficultareas. The mechanical fingers, to the top plate to compress the spring, the shown in figure 5-12, have a tube containing tool fingers extend from the tube in a grasping flat springs which extend from the end of the position. When the thumb pressure is released, tube to form clawlike fingers, much like the the tool fingers retract into the tube as far as screw holder. The springs are attached to a the object they hold will allow. Thus, enough rod that extend., from the outer end of the tube. pressure is applied on the object to hold it A plate is attached to the end of the tube, and a securely. Some mechanicalfingershave a similar plate to ue pressed by the thumb is flexible end on the tube to permit their use in attached to the end of the rod. A coil spring close quarters or around obstructions. placed around the rod between the two plates NOTE: Mechanical fingers should not be holds them apart and retracts the fingers into used as a substitute for wrenches or pliers. the tube. With the bottom plate grasped between The fingers are made of thin sheet metal and the fingers and enough thumb pressure applied can be easily damaged by overloading.

5 Chapter 5TOOLS AND HARDWARE

not in good repair. A tool thatis broken or in Flashlight poor condition is the surest wayto ruin the Each toolbox should have a standardNavy equipment to be repaired. Althoughthe ADR flashlight will be assigned to a particular workcenter, his vaporproof two-cell flashlight. The such as is used constantlyduring all phases of main- work area could be numerous places tenance. Installed in both ends of theflashlight the line, high power turnup area,hangar deck, are rubber seals whichkeep out all vapors. flight deck, etc. Therefore, the properselection, The flashlight should be inspectedperiodically use, and care of handtoolscould mean a con- for the installation of these seals, the spare siderable savings in manhours andmaterials. bulb, and colored filters which are contained The selection and use of the righttools are the in the end cap. NOTE: Do not throw awaythe mark of a good mechanic. night The care of handtools shouldfollow the filters; they will be necessary during articles; that is, operations, especially carrier operations. same pattern as for personal always keep handtools clean and freefrom dirt, After use, return Inspection Mirror grease, and foreign matter. tools promptly to their properplace in the broken or There are several typesofinspection toolbox. Whenever tools become mirrors available for use in aircraftmainte- damaged, they should be repaired orreplaced. nance. The mirror isissued in a variety of Any spare time between workassignments sizes and may be round orrectangular. The should be utilized for tool repairs andcleaning. mirror is connected to the end of arod and may be fixed or adjustable.(See fig. 5-13.) Responsibility The inspection mirror aids inmaking de- cannot Most handtools are not feasiblyrepairable. tailed inspection where the human eye original low cost directly see the inspection area. Byangling the Due to this fact and their it (compared to power and special tools),they are mirror, and with the aid of a flashlight, the activity is possible to inspect most required areas. classed as consumable. However, must pay for replacements.Therefore, it is help eliminate Selection, Use, and Care the duty of each individual to the need forreplacements.One method of inventory In the selection of handtoolsalways use the accomplishing this is by carrying an proper tool for the job. Never usewrenches or of tools in each toolbox so that uponcompletion bars, of a job all tools can be accountedfor. A tool pliers as hammers, screwdrivers for pry waste of funds; etc. Never use makeshift tools ortools that are that has been lost represents a

AM.29 Figure 5-13.-Typical inspection mirror.

5( AVIATION MACHINIST'S MATE R 3 & 2 in addition,it is a definite liability. If it has using tools whose casings were not properly been left loose in an aircraft, it can become a grounded. Electric tools used in the Navy must dangerous missile when the aircraft is launched have a three-prong plug, the third prong being or when theaircraft is performing violent the ground. maneuvers. Pneumatic tools are driven by compressed Frequently a squadron tool crib has the air. When it is necessary to use power tools responsibility for all tools in the squadron. This inside or on an aircraft, pneumatic tools are includes issuance, inventory of toolboxes, and preferred over electric tools, because an elec- ordering new tools for replacement of broken tric spark might start a fire. In an area where or lost tools. gasoline fumes may besuspected, electric tools are prohibited. Inventory Requirements Pneumatic toolsthat are equipped with torque devices should not be used for the final The basic objective of an inventory is to torquing of nuts or studs. The torque of the insure a proper balance between the supply of, pneumatic tool or nut runner, as it is commonly and the demand for, those tools required for called, should be set at a lower torque value the efficient operation and maintenance of a than specified for the nut or bolt, and then a squadron or maintenance activity. To accom- hand torque wrench should be used for the final plish this objective it is necessary that tools be torque. identified and cataloged to provide accurate Hydraulic powered wrenches are used when knowledge of the tools being used. Each item high torque values are required, such as 2,000 should be accounted for every 30 to 90 days in or 3,000 foot-pounds. These wrenches have a accordance with squadron instructions. The hand pump for building up pressure to turn number of handtools on hand in relation to the the nut and a pressure gage, usually calibrated number required by theactivity should be infoot-pounds, for indicating the amount of indicated by the inventory. torque applied. When using any type of hydraulic power tool,be sure that the work is held Reordering securely and that the tool fits the nut properly.

Tools are reordered as the inventory re- SPECIAL TOOLS quirements dictate. Usually the senior petty officer or his delegate reorders all tools, both This category of tools is not part of the work centertoolsand those for individual individual toolbox. Special tools are normally toolboxes, as they are needed. However, squad- maintained in a central toolroom and signed ron or maintenance activity policy is followed out when needed. A tool falls into the special in all cases. category for the following five main reasons: It is unwise to wait until the number of tools 1.It is an item of Special Support Equip- needed is too large, as itis easier for thement that was designed,manufactured, pro- supply department to fill a small order rather cured, stocked, and issued for the purpose of than a large one. maintaining one model of aircraft, engine, or a particular piece of equipment. POWER TOOLS 2.It is a seldom used tool, and the majority of time it would merely take up room in Power tools may be divided into two general the toolboxes. However, when needed, its use classeselectric and pneumatic. In aviation, a is essential in aircraft maintenance. third type will be used occasionallyhydraulic 3.Itis a high cost item, and to insure power tools. better utilization of each of this kind, fewer Navy safety regulations require that the are available. casingsofallelectrically driven tools be 4. The awkward size and the shape of grounded. This regulation is for the protection thetool make itextremely difficult,if not oftheoperator.People have actually been impossible, to issue one to each ADR to carry electrocuted by ordinary house current when around in his toolbox.

50 Chapter 5TOOLS AND HARDWARE

5.Itis an instrument type of toolthat of the engine and then reassembling it to the depends upon precise calibration for its use- specified limits. This job is best accomplished fulness. It could be knocked out Of adjustment whenever the special tool designed for this if subjected to the normal handling of an ADR purposeisused. The strainer assembly is toolbox. placed within the tool and pressure is then Of course, a special tool may be covered used to compress the strainer sufficiently to under more than one or even all of the fore- enable you to use the special pliers to remove going categories. the lockring that holds the strainer assembly Special tools are listed in Allowance Lists together. After the strainer screens are cleaned published by the Naval Air Systems Command, .and the strainer itself is ready to be assembled, and their use is explainediithe Technical the toolis again used to complete the final Manuals covering the particular aircraft, engine, assembly. (See figs. 5-15 (A) and 5-15 (B).) or piece of equipment for which they were WORK CENTER TOOLS designed. AND TOOL CRIBS Work center tools are the larger, low- Sweeney Powerwrench usage, and special tools for use on special The Sweeney Powerwrench is used in the (A) removal and installation of propellers. It has a number of adapters that will adaptthe wrench to any size propeller shaft and propeller re- tainingnut.This wrench is a double gear reduction wrench with which it is possilale to torque the retaining nut to the exact amount of required torque.It is used in conjunction with the standard 3/4-inch drive torque wrench. Care must bemaintained to adhere to the torque values thatarelistedon the plate adjacent to the handle. This wrench can also be used to loosen or tighten the engine thrust bearing nut. (See fig. 5-14.) Main Oil Strainer Assembly and Disassembly Tool An ADR will often have the job of disassembling and cleaning the main oil strainer

AD.13 Figure 5-15.--(A) Main oil strainer assembly and disassembly tool; (B) main oil AD.12 strainer assembly in the tool show- Figure 5-14.Powerwrench. ing removal of lockring.

83 AVIATION MACHINIST'S MATE R 3 tz 2 S'? equipments. A work center tool crib is normally steady motion. (A fast or jerky motion will utilized to make available those special tools result in an improperly torqued unit.) When needed to perform various phases of work center the torque applied reaches the torque value maintenance. However, work center tools also which isindicated on the handle setting, the include any handtools required to perform more handle will automatically release or "break" extensive maintenance than canbe accomplished and move freely for a short distance. The from a toolbox. The work center tools are release and free travel is easily felt, so there determined by the size and type of the activity is no doubt about when the torquing process and by the allowance set forth in the Section G is complete. Allowance List. To assure getting the correct amount of Tools used in an aircraft maintenance activ- torqueonthe fasteners,all torque handles ity are determined by the mission of the activity must be tested at least once a month or more and the type of aircraft to be maintained. In often if usage indicates it is necessary. view of this, there is no hard and fast rule as The following precautions should be ob- to the type and/or number of tools that may be served when using torque wrenches: supplied in the different toolboxes and tool cribs. 1. Do notuse the torque wrench as a A squadron (or activity) tool crib is often hammer. established under theresponsibilityofthe 2. When using the Micrometer Setting type, maintenance department. Its purpose is for the do not move the setting handle below the lowest stowage and issue of low-usage handtools and torque setting. However,it should be placed those tools which are common to more than one at its lowest settingprior to returning to storage. work center. Many special tools which are 3. Do not use the torque wrench to apply provided by the aircraft manufacturer are also greater amounts of torque than its rated capacity. stowed in the tool crib. A complete list of 4. Do not use the torque wrench to break these special tools can be found, in the Mainte- loose bolts which have been previously tightened. nance Instructions Manual, section one, for each 5. Never store a torque wrench in a toolbox type aircraft and engine. or in an area where it may be damaged.

TORQUE WRENCHES TORQUE VALUES There are times when, for engineering Torquing can be described a:3 the twisting reasons, a definite pressure must be applied stress that is applied to the fasteners to secure to a nut. In such cases a torque wrench must components together. These fasteners can be be used. The torque Tirench is a precision nuts, bolts, studs, clamps, etc. Torque values tool consistmg of a torque-indicating handle for these fasteners are expressed in inch-pounds and appropriate adapter or attachments. It is or foot-pounds. Unless otherwise stated,all used to measure the amount of turning or torque valvesshould beobtained with the twisting force applied to a nut, bolt, or screw. manufacturer's recommended thread lubricant The three most commonly used torque applied to the threads. wrenches are the Deflecting Beam, Dial In- Torque valves are usually found in the table dicating,and Micrometer Setting types (fig. of limits section of the Service Instructions 5-16). When using the Deflecting Beam and the Manuals. This one section contains most of Dial Indicating torque wrenches, the torque is the torque value information needed for the read visually on a dial or scale mounted on repair of the engine and should be referred to the handle of the wrench. when any torque values are needed. However, To use the Micrometer Setting type, unlock in case there is no torque specified, the torque the grip and adjust the handle to the desired values in table 5-1 can be used as a guide in setting onthe micrometer type scale, then tightening nuts, bolts, and screws. Using the relock the grip.Install the required socket proper torque allows the structure to developits or adapter to the square drive of the handle. designed strength and greatly reduces the pos- Place the wrench assembly on the nut or bolt sibility of failure due to fatigue. One word of and pull in a clockwise direction with a smooth, cautionnever rely on memory for torque infor-

6 ti 53 Chapter 5TOOLS AND HARDWARE

MICROMETER SETTING

DIAL INDICATING

EXTENSION TORQUE WRENCH S TYPICAL EXTENSION ATTACHED (CENTER LINES CONNECTING) DEFLECTING BEAM_ E + L

S TYPICAL EXTENSION ATTACHED (CENTER UNES BISECTING) AD.15 Figure 5-16.Torque wrenches. mation, but look up the correct torque value Such unequal distribution of force may cause each time it is needed. A nut or bolt that is not shearing or snapping of the bolts. torqued to the proper torque value may cause Torque wrench size must be considered the loss of an engine or aircraft. when torquing. The torque wrenches are listed The proper procedure is to tighten at a according to size and should be used within this uniformly increasing rateuntil the desired recommended range. Use of larger wrenches torqueisobtained.In some cases, where which have too great a tolerance results in gaskets or other parts cause a slow permanent inaccuracies. Wnen an offset extension wrench set, the torque must be held at the desired (crowf3ot) is used with a torque wrench, the value until material is seated. When applying effective length of the torque wrench is changed. torque to a series of bolts on a flange or in an The torque wrench is so calibrated that when area, select a median value. If some bolts in a an extension is used, the indicated torque (the series are torqued to a minimum value and torque which appears on a dial or gage on the others to a maximum, force is concentrated on torque wrench) may be different from the actual the tighter bolts and is not distributed evenly. torque that is applied to the nut or bolt. There-

6.1.

....., AVIATION MACHINIST'S MATE R 3 & 2 CV

Table 5-1.Torque value in inch-pounds for standard nuts, bolts, and screws.

Standard nuts, bolts, and screws Shear type nuts Wrench size Bolt, stud, or Tension type nuts screw size AN310 and AN365 AN320 and AN364 1/4 4-48 4-5. 5 2. 5-3. 5 5/16 6-40 7. 5-11 4. 5-6. 5 11/32 8-36 12-15 7-9 3/8 10-32 20-25 12-15 7/16 1/4-28 50-70 30-40 1/2 5/16-24 100-140 60-85 9/16 3/8-24 160-190 95-110 5/8 7/16-20 450-500 270-300 3/4 1/2-20 480-690 290-410 7/8 9/16-18 800-1, 000 480-600 15/16 5/8-18 1, 100-1,300 660-780 1 1/16 3/4-16 2,300-2,500 1,300-1, 500 1 1/4 7/8-14 2, 500-3, 000 1, 500-1, 800 1 7/16 1-14 3, 700-5, 500 2,200-3,300

NOTE: AN specification numbers may be superseded by MS specification numbers. fore, the wrench must be present to compensate L=Length of torque wrench (distance between for the increase when an offsetextension center of drive and center of griO. wrenchisused-the torque ordecrease in E=Length of extension of adapter (distance actualtorqueascompared toindicated between center of drive and center of torque. broached opening measured in the same Occasionally,itisnecessary to use a place as L). special extension or adapter wrench together EXAMPLE: Recommended torque is100 with a standard torque wrench.In order to inch-pounds. Using a torque wrench and a 6-inch arrive at the resultant required torque limits, adapter, determine reading on torque wrench. the following formula should be used: 1200 S -100 x 12 - 66.6 inch-pounds (6 + 12)-18 S -T x L (E + L ) Figure 5-16 shows some torque wrenches and an example of the measuring for the above Where: formula. When the estension is pointed back toward the handle of the torque wrench, subtract S=Reading of setting on torque wrench. the effective length of the torque wrench. If the T=Recommended torque on part. extension is pointed at a right angle to the

86 Chapter 5TOOLS AND HARDWARE torque wrench, then the actual value does not factured from aluminum alloy. However, exchange. posed lines and lines subject to abrasion or It is not advisable to use a handle extension intense heat are made of stainless steel. There- on a deflecting beam type torque wrench at fore, the ADR will be concerned more with any time. A handle extension alone has no stainless steel lines. When an engine fuel line effect on the reading of the other types. The requires replacement, the normal procedure is use of a drive and extension on any type of to draw a preformed line, with fittings attached torque wrench makes the use of the formula to replace the defective line.If a line must be mandatory. When applying the formula, force manufactured locally and installed on an engine must be applied to the handle of the torque or component, the following procedures should wrench at the point from which the measure- be followed: ments were taken. If this is not done, the torque Lines should normally be kept as short and obtained will be in error. free of bends as possible. However, tubing should not be assembled in a straight line, because a SELECTION AND USE OF AIRCRAFT bend tends to eliminate strain by absorbing HARDWARE vibration and compensates for thermal expan- sionandcontraction. Bends are preferred to Aircraft hardwareis the term used in elbows, because bends cause less of a power reference to a great many items used in air- loss. A few of the correct and incorrect methods craft and powerplants construction. These in- of installing tubing are illustrated in figure 5-17. clude fasteners, couplings, clamps, brackets, Hose is used in aircraft where there is a fittings, bolts, nuts, washers, wire and cables, necessity for flexibility, such as connections to and related hardware. units that move while in operation, or to units Because of the small size of most hardware attached to a hinged portion of the equipment. items, their importance is often overlooked; It is also used in locations that are subjected however, the safe and efficient operation of any to severe vibration. The following steps are aircraftisgreatly dependent upon correct general procedures for installing flexible hose. selection and use of aircraft hardware. This Figure 5-18 shows the correct and incorrect section discusses these various items, and installation of flexible hose. providesinformation which willaid in the 1. Do not use oil on any self-sealing hose selection and correct use of aircraft hardware. to aid in installation. Oil or water may be used on all other types of fuel, oil, and coolant TUBING hose during the installation procedure; however, watershouldnotbe used wheninstalling Since weight elimination is vital in aircraft hydraulic or pneumatic tyre hose. design, the majority of rigid tubing used for 2.Install the hose so that it will not be hydraulic and pneumatic systems ismanu- subject to twisting under any operating condition.

RIGHT

-00

WRONG WRONG WRONG AD.34 Figure 5-17.Correct and incorrect methods of installing tubing.

87 AVIATION MACHINIST'S MATE R 3 & 2

the rigid connecting points. Flexible hoseshould IC:=1:::=E:03 12:3:2203 allowed to have RIGHT WRONG never be rigidly supported or too much excessive motion. 6.Eliminate all chafing points by using suitable type supports and insuring adequate clearance. 7.Protect all flexible hoses from excessive temperaturesbyeitherinstallingshrouds around them or relocating the lines sothat they will not be affected. Use flame-resistanthose forward of the firewall as directed by applicable instructions. 8. Where hose connections are made to the various engine driven accessories,install the hose so that there is an adequate amountof slack in the hose to prevent the possibilityof the hose being pulled off the nipple of the fitting to which it is attached. 9. Whenever a length of hose is connected to the engine with a hose clamp, firmlysupport the hose in a manner that will prevent vibrational and torsional strain on the hose connection.If possible, place the Support approximately 3 inches from the engine connection. 10.If possible, install the hose or hose assembly so that the markings on thehose AD.33 are visible. Figure 5-18.Correct and incorrect Hose and hose assemblies should bechecked installation of flexible hose. ateach inspection period for deterioration. Leakage, separation of the cover or braid from lack of This in itself will be a deterrent to preventthe theinner tube,cracks,hardening, fittings from loosening. When replacing any flexibility, and excessive cold flow are apparent hose in the oil, fuel, hydraulic, alcohol, water signs of deterioration and reason forreplace- injection, and pneumatic systems, the hose that ment. Cold flow is indicated by deep,permanent is installed should be the exact duplicate ofthe impressions and cracksinthe hose cove . hose thathas been removed as to length, produced by the pressure of the hoseclamps outside diameter, inside diameter, material, or supports. type, and contour unless otherwise directed. 3. When it is necessary to create bends in IDENTIFICATION OF FLUID LINES the hose to pass around objects, always be certain that the minimum radii permitted are Fluid lines in aircraft are identified by not exceeded. Bend radii tables for all typesof markers made up of color codes, words, and geometric symbols. These markersidentify installations are contained in Aircraft Structural primary Hardware, NA 01-1A-8. each line as to its function, content, 4. Do not use clamps or supporting clips hazard, and directionof flow. Figure 5-19 that are smaller than the outside diameter of lists the various types of fluid lines andindi- the hose. If smaller clamps are used, it may cates the color code and symbol for eachline. restrict the flow of the fluid through the hose Figure 5-20 illustrates the markers as used and damage may occur. for fuel lines. 5. Support the hose at least every 24 inches. In most instances, lines are markedby the (Closer supports are preferred.) Support the useof 1-inch tape or decals, as shownin hose so that it will not cause any deflectionof figure 5-20 (A). On lines 4 inches andlarger

88 Chapter 5TOOLS AND HARDWARE

FUNCTION COLOR SYMBOL

Fuel Red + Green, Gray Rocket Oxidizer 7.)

Rocket Fuel Red, Gray .4) Water Injection Red, Gray, Red Y a Yellow Lubrication . a

, Blue Yellow Hydraulic ) Blue Brown Solvent ) Orange, Blue Pneumatic lit Orange, Gray Instrument air 1.54

Coolant Blue 04110 Breathing Oxygen Green NM . .., Air Conditioning Brown, Gray 0. Monopropellant Yellow, Orange V' Fire Protection Brown 4> A DeIcing Gray AL Yellow, Green Rocket Catalyst ill Compressed gas Orange AiOr

Electrical Conduit Brown, Orange 41_1_ Inerting Orange, Green 1r

AM.67 Figure 5-19.Fluid line color codesand symbols.

6 6 AVIATION MACHINIST'S MATE Ft3 & 2

-..u. , ?at) . LPG FLAN 27 PGi .....( as oxygen, nitrogen, Freon, etc., are marked L PG FLAM 27 PSI PHDAN; and anesthetics and certainother LPG ....\ FLAN harmful materials are marked AAHM. LPG 27PS The aircraft and engine manufacturers (A) are responsible for the original installation of identification markers, and maintenanceper- sonnel are responsible for replacement when it becomes necessary. As a general rule, tapes and decalsare placed on both ends of a line and at least once in each compartment through which the line runs. In addition, identification markers are placed immediately adjacent to each valve, regulator,filter,or other accessory within a line. Where tags or paints are used, location requirements are thesame as for tapes (B) and decals. Complete instructions for installing fluid lineidentification markers are contained in MIL-STD-1247.

COUPLINGS

AD.21 The purpose of the coupling is to couple Figure 5-20.Fluid line identification group. or connect the ends of adjacent parts or lines. (A) Using tape and decals; (B) using The coupling also allows for slight misalign- metal tags; (C) using paints. ment ofthe two parts to be connected.It in diameter, lines in an oily environment, hot acts, to a slight degree, as a universal joint. lines, and on some cold lines, steel tags may There are several different types of coupling be used in place of tape or decals. (See fig. installations on aircraft engines, andone of 5-20 (B).) On lines, in engine compartments, the most common is shown in figure 5-21. where there is the possibility of tapes, decals, This is a flexible line installation andcare or tags being drawn into the engine induction should be exercised when working with this system,paintisused. (See fig. 5-20(C).) coupling. As can be seen in figure 5-20(A), reading The ADR must use the proper type span- from left to right, the line function is indi- ner wrench when removal or installation pro- cated by color code (red), name (fuel), and cedures areinvolved.Care should also be symbol (4-pointed star). Content of the line exercised with the working parts of the coupling is indicated by the name (LPG (liquid petroleum gas)); the primary hazard is indicated COUPLING NUT RETAINER HALVES COUPLINGaoor by the word FLAM; pressureisindicated in pounds per square inch (27 psi); and the direction of flow is indicated by arrows. (Two- headed arrows are used to indicate reversible flow where applicable.) In addition to the above mentioned markings,certainlines may be further identified as to specific function within a system; for example, DRAIN, VENT, PRES- SPLIT WASHER SPLIT WASHER SURE, RETURN, etc., as the case may be. (1- O-RING Lines containingtoxic materials are marked TOXIC in place of FLAM; lines con- AD.16 taining physically dangerous materials such Figure 5-21.Flexible line coupling.

90 Chapter 5TOOLSAND HARDWARE 59 such as the 0-ring, splitwasher, and retainer halves. Insure that a new0-ring is used on installation and thatithas been lubricated properly. The partsshould be installed as shown in figure 5-21.Then the coupling nut and the couplingbody should be slidtogether over the retaiiferhalves. The threadsshould then be engaged and theunit turned down by hand untiltight.The coupling shouldthen be tightened to the propertorque value and lockwired. The flexiblehalf coupling is shownin figure 5-22.It is similar to theflexible line coupling except for the useof a split washer on either side ofttie 0-ring seal.

CLAMPS

The clamps found onaircraft are used AD.19 from chafing on parts Zor preventing lines Figure 5-23.Clamps. oragainstother linesand to connect two lines or pieces of material. One type of clamp andits use in sup- choose one that is the lines can be seention, the ADR should porting flexible and rigid proper size and ingood material condition. in figure 5-23. Theseclamps should be checked type clamp used to prevent Figure 5-24 shows the for deteriorationof the rubber to secure the distributorcover to thedis- the metal partofthe clamp fromcutting similar is used the hose itis sup- tributor base. A clamp very into the outside wall of to secure the magnetogenerator cover. porting. In selecting aclamp for an installa- Another type of clamp thatthe ADR may be using is the Idealhose clamp. Thisclamp may be used on anytype of clamp installation on the aircraft.It is consideredtwo-blocked if the tips come closerthan three-sixteenths of an inch. Wheninstalling this type clamp, the excess strap shouldbe cut off to prevent possible breakage due tovibration. COUPLING The radial hose clampisa stainless SPLIT NUT steel strip spotwelded onthe saddle of the WASHERS 22 to Idealhose clamp.It comes in sizes 82 inclusive and it maybe used on fuel and oil lines. The larger sizes arenot to be used on fuel and oillines, but they maybe used on other installations. When installing hose clamps,always allow a minimumdistance of one-fourth of aninch aftof the bead on theline or fitting. The minimum amount of hoseextending past the THREADED 0-RING last clamp is one-fourthof an inch. Minimum FITTING distance between clampsis three-eights of an required on each side AD.17 inch if two clamps are Figure 5-22.Flexiblehalf coupling. of the connection.

6( 6 6 AVIATION MACHINIST'S MATE R3 & 2

just a few of the types that are used tosecure inspection plates, doors, and other removable panels on the aircraft or engine nacelle. These turnlock fastenersare also referred to by such terms asquick-opening,quick-acting, and stress panel fasteners. The most desirable feature of these fasteners is that they permit quick and easy removal ofaccess panels and doors for inspection and servicing. Camloc Fasteners Camloc fasteners are made in a variety of sizes and shapes. They are carried ina numbered series in the regular line, and also in the stressed-panel fastener in the heavy- duty line (SPF). The latter fastener is used DISTRIBUTOR in stressed panels that carry heavy structural loads. A quarter turnof the stud (clockwise) locks the fastener. The fastenermay be unlocked only by turning the stud counterclockwise. (See fig.5-25.) CLAMPING RING Dzus Fasteners

The Dzus fastener consists ofa rotatable stud, which may have a slot fcr a screwdriver, oritmay have a winged fitting onit for opening and closing without a tool.Italso has a permanently mounted spring anda grommet. The stud and grommet are mounted in the door or other removable part, and the spring is riveted to the frame of theaccess AD,27 on which the door fits, Figure 5-24.Distributor cover clamp. Cams on the stud engage with the spring to lock the fastener in the engaged position. When hose clamps are installed, they should The purpose of the grommet is to retain the be tightened to the torque value specified inthe stud in the access door. In some installations, appropriate Service Instructions Manual, Us- the grommet is not used as ually a retainer; the the torque on self-sealing hose is15 stud is secured to the access door bya snap- inch-pounds with a torque wrenchor finger ring, cup washer, or by dimpling of the metal tight plus2 1/2turns without a torque wrench. around the stud. Hoses should be braced or supported at least A quarter turn of the stud ina clockwise every 24 inches. . directionwilllockitinto position.It may be opened by turning counterclockwise. TUR.NLOCK FASTENERS This type of fastener may be opened and closed with a screwdriver, but it hasa special There are several different types of turn- tool called a Dzus key, designed for theopening lock fasteners with which the ADR willcome and closing process. See figure5-26for an in contact. The Camloc, Dzus, and Airlocare illustration of the Dzus fastener.

6 Chapter 5TOOLS AND HARDWARE b(

AM.39 1. Tension spring. 6.Receptacle attaching rivits. 2. Stud assembly 7.Outer skin. 3.Bushing. 8. Inner skin. 4. Retaining ring. 9. Insert. 5. Receptacle assembly. 10. Cover. Figure 5-25.--Camloc fastener. Airloc Fasteners weight. An example of a bracket is shown in figure 5-28(A). This type of bracket is used The Airloc fastener consists of a stud, to support a line, usually metal tubing, and stud cross pin, and a receptable. (See fig. 5-27.) theliaeis either brazed or welded to the The stud is attached to the access cover and bracket.Figure5-28(B) shows another line is held in place by the cross pin. The receptable mounting bracket; however, on this type bracket is riveted to the access cover fra,ae. A quarter the elbow that mounts the line swivels to allow turn of the stud (clockwise) locks the fastener for various types of installations. Figure 5-28(C) in place; counterclockwise unlocks it. shows a straight type line mounting bracket. Another type of bracket is the mounting bracket shown in figure 5-29. This installation BRACKETS is used to provide a mount for a component. When making an installation of this type, care The bracket is used to mount a part or must be exercised to insure that all nuts, urut to a structure or other body to support bolts, and other parts of the bracket do not

6 j AVIATION MACHLNIST'S MATE R 3 & 2

DETACHABLE ,3ART STUD ASSEMBLY

GROMMET

CUT-AWAY VIEW OF COMPLETE 4FATI DZUS ASSEMBLY

SPRING AND SPRING ASSEMBLY

gcg2 RIVETS

AD.22 Figure 5-26.Dzus fastener. rub or restrict the action of other structural members.

ADAPTERS

FIXED TYPE FLOATING TYPE (A) The word "adapter". is usually defined I 8 I as a device for connecting two pieces of apparatus or lines of two different sizes. Figure RECEPTACLE CROSS PIN 5-30 shows adapters being used to connect hydraulic ground test lines into the aircraft.

nvr THREADED FASTENERS At Many parts of the aircraft engine require

011111!IP.os / i frequent dismantling or replacement when the engine is being inspected. This makes it prac- ;EPP- i tical to use some type of threaded fastener, i_tzgrowfvgt enabling the mecnanic to complete the job in a reasonable amount of tiMe. This problem is PANEL STUD solved by the manufacturer through the use of various types of screws, nuts, and bolts. AMAO Bolts and screws are similar because both Figure 5-27.Airloc fastener. have a head at one end and a screw thread at

94 Chapter 5TOOLS AND HARDWARE

AFTERBURNER FUEL-OIL COOLER

(A) AD.24 Figure 5-28.(A) Line mounting bracket, rigid angle. the other. However, there are severaldiffer- ences between them. The threadedend of a bolt is always blunt while that of a screw may be either blunt or pointed. The threaded end of a bolt must be screwed into a nut,but the threaded end of a screw may fit into a nut or

INTERNAL 0-RING LINE MOWING BRACKET

GASKET 'Figata.CaZSZad AD.25 fUEL-OIL COOLER Figure 5-29.Mounting bracket.

other typeof female arrangement, or may fit directly into the material being secured. Classification of Threads Threads on aircraft bolts and screws are of the American NationalStandard type. This standard contains two series of threadsnational course (NC) series and national fine(NF) series. Most aircraft threads are of the NF series. (8) AD.24 Threads are also produced in right-hand Figure 5-28.(B) Line mounting and left-handtypes.The rigat-hand thread . bracket, swivel angle. patternisthe one which you will come in

71. il AVIATION MACHINIST'S MATE R 3 & 2

Table 5-2.Threads per inch on commonly used bolt sizes.

Threads per inch

Bolt diameter Coarse Fine

1/4 20 5/16 18 24 3/8 16 24 7/16 14 20 1/2 13 20 5/8 11 18 AD.26 Figure 5-30.Hydraulic ground test adapter. contact with most frequently when maintaining they are ordered. They also may be identified aircraft engines. bycolor,weight,type of construction, and thread size. Identification of Threads Except for a few very special types, nearly all the nuts used in maintaining aircraft and Threads are designated by the diameter, engines are Air Force-Navy Standard. In the number of threads per inch, thread series, stocklists,the part numbers will designate and classinparts catalogs, on blueprints, the type of nut. The common types and the and on repair diagrams. respective part numbers are: Plain, AN315 For example, No. 8-36NF-3 indicates a and AN334; Castle, AN310; Plain Check, AN316; No.8size diameter, 36 threads per inch, Light Hex, AN340 and AN345; Castellated Shear, nationalfine series, and a class 3thread. AN320; and Wing Nut, AN350. Also 1/4-20NC-3indicates a 1/4-inch, 20 The patented self-locking types are assigned threads per inch, national coarse series, and part numbers ranging from AN363 through a class 3 thread. A left-hand thread is indicated AN367. The BOOTS, FLEXLOC, FIBER LOCK- by the letters LH following the class of thread. NUT, ELASTIC STOPNUT, and the STEEL Table 5-2 shows the number of threads per SELF-LOCKING belong tothis group. Part inch on the most commonly used bolt sizes. number AN350 isassigned to the wingnut. Letters and digits following the part number Nuts indicate such items as material, size, threads per inch, and whether the thread is right-hand The types of nuts used in the engine and or left-hand. The letter B following the part aircraft structure are plain nuts, castle nuts, number indicates the nut material to be brass, checknuts, plate nuts, channel nuts, barrel nuts, a D indicates it to be 2017 aluminum alloy, a internal-wrenching nuts,external-wrencaing DD indicates it to be 2024 aluminum alloy, a C nuts, shear nuts, sheet spring nuts, and wing- indicates it to be stainless steel, and a dash in nuts. Many of these nuts are available in either place of a letter indicates the material to be self-locking or nonself-locking style. They are cadmium plated carbon steel. made of cadmium-plated carbon steel, The digit (or two digits) following the dash corrosion-resistant steel, brass, and anodized or the material code letter is the DASH NUM- aluminum alloy. BER of the nut and indicates the size of the Nuts are ordered separately from bolts shank and threads per inch of the bolt on which and one means of identifying them is through it will fit. The dash number corresponds to the the stock number in the catalog from which first figure appearing in the part number coding

21 Chapter 5-TOOLS AND HARDWARE &5 of general purpose bolts. A dash number 3,for example, indicates that the nut will fit anAN3 bolt (10-32), a 4 means it will fit an AN4bolt (1/4-28), a 5 indicates an AN5 bolt (5/16-24), and so on. Unless otherwise stated,threads per inch are given in national fine(NF) readings. The code, numbers for self-locking nuts end in three- or four-digit numbers. Thelast two digits refer to threads per inch and the one or two digits preceding these stand for the nut size in sixteenths of an inch. In stocklists, the full code number is given CASTLE NUT PLAIN NUT for each nut and the corresponding boltand thread size is also given in another column. If the description may be doubtful, an illustration is included. This arrangement makes the stock- list description quite complete and prevents errors when ordering nuts and bolts. The nuts that are used on aircraftand engines can hedividedinto two general categories-NONSELF-LOCKING NUTS and SELF-LOCKING NUTS. Nonself-locking nuts are those which must be safetied through the use of cotter pins, safety wire, lockwashers, or ILITU-114 locknuts. Self-locking nuts carry the locking ..= -... feature as an internal part of the nut. CASTELLATED WING NUT NONSELF-LOCKING NUTS.-Most ofthe SHEAR NUT familiar types of nuts, including the plainnut, the castlenut,castellated shear nut, plain AM.42 hex nut, and the plain checknut are of the nonself- Figure 5-31.-Nonself-locking nuts. locking type.Figure 5-31illustrates these various types of nonself-locking nuts. The CASTLE NUT is used in conjunction The LIGHT HEX NUT is a much lighter with drilled-shank AN hex-head bolts, eyebolts, nut than the plain hex nut and must be locked drilled head bolts, or studs. It is fairlyrugged by an auxiliary device.Itis used primarily and can withstand large tensional loads. Slots for light, miscellaneous requirements. (called castellations) in the nut are designed The PLAIN CHECKNUT is employed as to accommodate a cotter pin or lock wirefor a locking device for plain nuts,setscrews, safetying purposes. threaded rod ends, and other devices. The CASTELLATED SHEAR NUT is de- WINGNUTS are used and intended only for signed for use with such devices as drilledplaces where the desired tightness can be ob- clews bolts and threaded taper pins, which tained with the fingers and where the part or are normally subjected toshearing stresses parts are often removed for checking, such as only. Like the castle nut, it is castellated for fuel strainers. Wingnuts are secured by lock- safetying, but is not as deep nor as strong wiring. as the castle nut. SELF-LOCKING NUTS.-There aretwo The PLAIN HEX NUT is of rugged con- general types of self-locking nuts used currently struction. This makes it suitable for carrying in the maintenance of aircraft and engines-the large tensional loads. However, since it requires ALL-METAL type and the NONMETTALIC IN- an auxiliary safetying device,such as a checknut SERT type. The BOOTS and the FLEXLOC are or lockwasher, its use onaircraft and engine examples of the all metal type; the ELASTIC structures is very limited. STOP is an example of the nonmetallic insert

7,1 61b AVIATION MACHINIST'S MATE R 3 & 2 type. Figure 5-32 shows several examples of ofthe locking section properly. Thus, the self-locking nuts. spring, through the medium of the lockiw sec- The BOOTS self-locking nut is of one-piece tion, exerts a constant locking force on the bolt all-metal construction, designed to hold tight in in the same direction as a force that would spite of extreme vibration. It has two sections tighten the nut. The nut can be removed and and is essentially two nuts in one-a locking nut used again without impairing its efficiency. All and a load-carrying nut. The two sections are metal self-locking nuts ar e designed to withstand connected by a spring which is an integral part temperatures up to 500°F, but no higher. of the nut. The spring keeps the locking and The ELASTIC STOPNUT is designed with a load-carrying sections such a distance apart nonmetallic insert within it which locks the nut that the two sets of threads are out of phase; in place. When a bolt is run through the nut the that is, so spaced that a bolt which has been bolt threads cut threads in the insert. There screwed through the load-carrying section must are two types of inserts presently inuse-the push the locking section outward against the NYLON insert and the FIBER insert. Both of force of the spring in order to engage the threads these types of nuts are tough and durable.

1 1 BOOTS AIRCRAFT NWT, FLEXLOC NUT ...... 1104,..

NON-METALLIC ELASTIC ELASTIC TWO-LUG INSERT STOP NUT ANCHOR NUT LOCK NUT

BOOTS AIRCRAFT CHANNEL ASSEMBLY

ELASTIC STOP NUT CHANNEL ASSEMBLY AM.44 Figure 5-32.-Self-locking nuts.

7LI Chapter 5TOOLS AND HARDWARE 61

of But,a nutof this type must be discarded Head markings indicate the material whenever the insert loses its ability to lock which standard bolts are made andwhether or the nut in place. This type of nut should never not the boltis classed as a close-tolerance be used on any exhaust system components or bolt. (See fig. 5-33.) Additionalinformation, in any place where the nut will besubjected such as bolt diameter, bolt length,and grip to extreme temperatures. length, may be obtained from the boltpart The ANCHOR NUT (or PLATE NUT) is a number. self-locking type nut with lugs for fastening it In the bolt part number, AN3DD6A,for ex- tothestructureof the aircraft or engine, ample, the AN designates that it is an AirForce- usually by riveting. Both types of self-locking Navy Standard bolt, the 3 indicates thediameter nuts mentioned in the preceding paragraphs in sixteenths of an inch (3/16), the DDindicates are available in installations where it isfeasible the material is 2024 aluminum alloy, the6 indi- to use an ANCHOR NUT. This type of nut will cates the grip and length (as taken fromspecial not be found in general use on the aircraft engine tables), and the A indicates that the shank is itself, but will be found in and around the cowling. not drilled for cotter pin safetying.Absence of There are certain precautions that must be the letter A indicates the shank is drilled. taken in the care and use of the self-locking nut. The letter C in place of the DDindicates Bolts, studs, and screws with damaged threads corrosion-resisting steel, and the absence of or rough ends should not be used, as this will a letter indicates,cadmium-plated steel. The tend to damage the insert and render it in- letter H preceding the 6 indicates thehead is effective. Do not use self-locking nuts on bolts, drilled for safetying with wire. studs, or screws that are less than one-fourth inch in diameter and have cotter pin holes. Washers The nuts should not be overtightened. Torque values should be observed at all times, and the Washers used in aircraft and engines may bolt must be of sufficient length to protrude be grouped into three generalclassesPLAIN through the nut and have at least one full thread washers, LOCKWASHERS, and SPECIAL visible to the eye. washers. Figure 5-34 shows someof the most commonly used washers. Bolts PLAIN washers are widely used underAN Most bolts used in aircraft structures and hex nuts to provide a smooth bearingsurface to engines are either general-purpose, internal- act as a shim in obtaining the correctrelation- wrenching, or close-tolerance AN (Air Force- ship between the threads of the bolt andthe nut, Navy), NAS (National Aircraft Standard), or MS and to adjust the position ofcastellated nuts (Military Standard) bolts.In many cases the with respect to drilled cotter pinholes in the aircraft or engine manufacturer is required to bolts.Plain washers are also used under make bolts of different dimensions and greater lockwashers to prevent damage to thesurface strength than the standard type of bolt. Such of soft materials. bolts are made for a particular application and LOCKWASHERS are used whenever the self- used. itis of extreme importance to use the exact locking or castellated type nut is not replacement when necessary. If such bolts are Sufficient friction is provided by thespring not available, but can be manufactured locally, action of the washer to preventloosening of the identical material and heat treatment that the nut from vibration. Lockwashers arenot are specified in the applicabledrawings must be used as part of a fastener forprimary or used. Such special bolts are usually identified secondary structures or in any place onthe en- by an S stamped on the head. gine where vibration may tend to loosen apart. AN bolts come in three head styleshex- SPECIAL washers such as ball-socketand head,clevis,and eyebolt.(Seefig. 5-33.) seat washers, taper pin washers, andwashers NAS bolts are available in hex-head, internal- for internal-wrenching nuts and bolts arede- wrenching, and countersunk-head styles. MS signed for special purposes. bolts come in hex-head and internal-wrenching The ball socket and seat washers areused head styles. in applications where the bolt maybe installed

7i) AVIATION MACHINIST'S MATE R 3 & 2

TYPE OF BOLTS

COUNTERSUNK HEAD BOLT

INTERNAL WRENCHING BOLT DRILLED HEX HEAD DOLT

CID EYEBOLT CLEVIS BOLT

HEAD MARKINGS

CLOSE ALUMINUM CORROSION STEEL (160,000 TOLERANCE STEEL ALLOY RESISTANT TO 180,000 (STEEL OR STEEL (125,000 ALUMINUM (62,000 P S I) ALLOY) P S i) (125,000 P S I ) P S I) AD.29 Figure 5-33.Types of bolts and bolt-head markings. at an angle to the surface or where perfect Installation of Nuts, alignment with the surface is required at all Bolts and Washers times,such as cylinder holddown bolts and engine mount bolts. When any part of an aircraft or engine is The taperpin washersareused with about to be installed, it should be ascertained threaded taper pins, and are installed under that the correct number and type of nuts, bolts, thenut to effect adjustment where aplain and washers are used in the installation process. washer would distort. Always examine the markings on the head of the Washersthatareused forinternal- bolt to determine that it is the right type of wrenching nuts and bolts are used in conjunction material to be used for the job at hand. with NAS internal-wrenching bolts. The washer Be sure that washers are used both under used under the head is countersunk to seat the head of the bolt and under the nut whenever the bolt-head shank radius. A plain type washer it is specified. A washer guards against damage is used under the nut. to the material being bolted andprevents corro-

100 70 Chapter 5TOOLS AND HARDWARE C-r

Afire

LOCK WASHERS BOLT GRIP LENGTH CORRECT

I 11.1MITP'

I -Am- -11 PLAIN BAIL SOCKET 1APER PIN " SPECIAL WASHE,I15 Am.45 BOLT GRIP LENGTH TOO SHORT Figure 5-34.Various types of washers. sion of the structural members. AnALUMINUM ALLOY washer should be used underthe head and nut of a steel bolt securingALUMINUM ALLOY or MAGNESIUM ALLOYMEMBERS. Any corrosion that occurs will thenattack the washers rather than the members.Steel washers should be used whereboth the material being fastened and the bolts are madeof steel. DO NOT use washers made ofALUMINUM BOLT GRIP LENGTH TOO LONG metal on ALLOY or of any other type of soft AM.46 any part or portion of the exhaustsystem. incorrect When installing nuts, bolts, andwashers, Figure 5-35.Correct and elways be certain to install the boltwith its bolt length. head in the direction of flight or whenever possible, install it with the head UP. This way,if is screw) in an oversized or elongated(out-of- thenut has been improperly secured or load until shaken loose by vibration and falls off,the bolt round) hole will carry none of its shear will remain within the part and continueto retain the parts have yielded ordeformed enough to oversized hole its holding capability althoughthe nutis missing. allow the bearing surface of the grip to come in contact with the bolt.Tolerances on GRIP LENGTH.Be certain that the specified, as are length of the bolt is correct. TheGRIP LENGTH drilled holes, unless otherwise IS THE LENGTH OF THE UNTHREADEDPOR- follows: TION OF THE BOLT SHANK. Generallyspeak- ing, the grip length should equal thethickness of Nominal drill the material.which is being boltedtogether. Not diameter Hole tolerance more than ONE threadshould bear on the material, and the threaded portion of theshank 0.040 to should be showing through the nut.(See fig. 5-35.) 0.1285 plus 0.002 minus 0.001 BOLT FIT.In fitting bolts, all boIthoIes 0.136 to must present a good mechanical fit.A bolt (or c 0.228 plus 0.003 minus 0.001

101

7 r AVIATION MACHINIST'S MATE R 3 & 2 74

Nominal drill tions. All nuts except the self-lockingtypes must diameter Hole tolerance be safetied; the method used depending upon the particular installation. Figure 5-37 illustrates 0.234 to the correct methods of installing safety wire. 1/2 plus 0.004 minus 0.001 The following general rules apply to safety 33/64 to wiring: 3/4 plus 0.005 minus 0.001 1.All safety wires must be tight after in- 49/64 stallation, but not under so much tension that to 1 plus 0.007 minus 0.001 normal handling or vibration will break the wire. 1 1/64 2. The wire must be applied so that all to 2 plus 0.010 minus 0.001 pull exerted by the wire tends to tighten the nut. 3. Twists should be tight and even and the COTTER PINS wire between nuts as taut as possible without overtwisting.Wire between nuts should be Cotterpinsare used to secure bolts, twisted with the hands. The use of pliers will screws, nuts, and pins. Some cotter pins are damage the wire. Pliers may be used only for made of low-carbon steel, while others consist final end twist prior to cutting off excess wire. of stainless steel and thus are more resistant Annealed copper safety wire is used for to corrosion. In addition, stainless steel cot- sealing firstaid kits, portable fireexting- ter pins may be used inlocations where nonmagnetic material is required. Regardless of shape or material, all cotter pins are used for the same general purposesafetying. Figure BOLT HEADS 5-36 shows three types of cotter pins and how their size is determined. NOTE: Whenever uneven prong cotter pins are used, the length measurement is to the end of the shortest prong. (ill SAFETY WIRE CASTLE NUT \\\z Safety wire comes in many types and sizes. One must first select the correct type and size of wire for the job. Annealed corrosion-resisting SAFETY METHODS SHOWN ARE FOR wire is used in high-temperature, electrical- RIGHT HAND THREADS. LEFT HAND OPPOSITE. equipment,and aircraft-instrument applica- Jr,

1.---LENGTH

DIAMETER SAFETY WIRE OVER HEAD

UNEVEN PRONGS OPTIONAL

SAFETY WIRE AROUND HEAD

AD.28 AM.331 Figure 5-36.Types of cotter pins. Figure 5-37.Safety wire installation.

102

7 Chapter 5TOOLS AND HARDWARE /7/

valves, chemicals should be wiped up promptly,and all uishers, oxygen regulator emergency disposed of in covered and other valves and levers usedfor emer- rags used should be gency operation of aircraftequipment. This metal containers. in case of an Handtools should be in good shape,of the wire can be broken by hand proper type, and used onlyfor the purpose for emergency. which they were designed. Equipment must be operated only byquali- SAFETY PRECAUTIONS fied personnel, and all safety devicesand guards condition. The Most accidents which occur innoncombat must be installed and in good equipment should also be inspected forbroken operations can be prevented if thefull cooper- Check to see that ation of personnel is gained andvigilance is or damaged components. The ADR periodic maintenance, servicing,and/or call- exercised to eliminate unsafe acts. equipments should diligently inspect his work areas,tools, bration are up to date for those and equipment to detect potentiallyhazardous requiring it. appropriate cor- NOTE: The safety precautions presented and unsafe conditions and take in nature rective action. in the above paragraphs are general problem. and should be observed at all times.For addi- Fire hazards present a serious precautions "No Smoking" rules should bestrictly enforced. tional information concerningsafety air- for portable tools refer to chapter14, Depart- Ground wires should be installed on every for Shore craft during maintenance toelinate dangerous ment of the Navy Safety Precautions static electrical buildup. Spilledoil, grease, and Activities, NAVSO P-2455.

103

73 CHAPTER 6

RECIPROCATING ENGINE FAMILIARIZATION

The reciprocating engine has been the prime to the spark plugs at the proper time in all kinds source of power for aircraft since the beginning of weather and under other adverse conditions'. of aviation. Although the turbojet engine (due to Carburetors are needed that will deliver fuel in its light weight, ease of maintenance, and relia- the correct proportion to the air ingested to the bility) has made steady gains in replacing the cylinders regardless of the attitude, altitude,or reciprocating engine in most naval aircraft, type of weather in which the engine is operated. many aircraft still use reciprocating engines. The engine needs a type of oil system that de- Therefore,the need stillexistsfor well- livers oil under the proper pressure to all of the trained mechanics to maintain these engines. operating parts of the engine at all times it is The fundamental requirements of aircraft running. And, it must have a system of dampening reciprocating engines, the theory of operation, units to dampen out the vibrations of the engine and engine construction are discussed in this thatare developed whenever theengine is chapter. In the succeeding chapters the various operating. systems of the reciprocating engine and their All of the above requirements dictate the use interrelationships are discussed separately. of dual ignition, dry sump lubrication in large engines, special carburetor designs, vibration FUNDAMENTAL REQUIREMENTS dampening devices, special engine mounts, and many other special features, all of which are All engines must meet certain general re- relatively less important in powerplants for quirements of efficiency, economy, and reli- marine and automobile use. ability.In addition,the duty for which an aircraftengineisdesigned imposes other requirements that are almost as important. Be- EFFICIENCY sides being economical in fuel consumption,an aircraft engine must be economical in the cost The reciprocating aircraft engine must have of original procurement and maintenance, and high thermal and mechanical efficiency. Thermal must meet exacting requirements of efficiency efficiency is the ratio between the number of and low weight per horsepower.It must be heat units in the fuel that are converted into capable of sustained high-power output with no useful power at the propeller shaft and the total sacrifice in reliability; it must also have the number of heat units in the fuel that are con- durability to operate for long periods of time sumed. The mechanical efficiency is measured between overhauls. It needs to be as compact by the ratio of the shaft output or brake horse- as possible, yet have easy accessibility for power to the indicated horsepower developed in maintenance. It is required to be as vibration the cylinders. free as possible and be able to covera wide It includes power losses due to friction and range of power output at various speeds and other sources in the engine and its accessories. altitudes. It is obvious then, that whenever the heat and These requirements dictate the use of igni- power losses of the engine can be reduced, its tion systems that will deliver the firing impulse efficiency can be increased. The efficiency of

104 Chapter 6RECIPROCATING ENGINEFAMILIARIZATION 73 gains in reducing the engine can also be increasedin other ways its performance. Tremendous following paragraphs. the weight of the aircraftengine through im- and these are seen in the provement in design andmetallurgy have re- sulted in engines now producingapproximately ECONOMY 1 horsepower for each pound ofweight. Fuel economy is practicallyanother way of saying high thermal efficiency,which was de- SUSTAINED HIGH-POWER OUTPUT In the early fined in the preceding paragraph. the aircraft aircraft engines, fuel economy wasnot too im- Unlike the automobile engine, of short duration engine must operate at arelatively high per- portant as most flights were output throughout and military loads weresmall. But, since the centage of its maximum power engine and its service life. The aircraftengine is at full development of the high compression takeoff is made. It may the increased cost of modern dayfuels, economy power output whenever a operation has become an itemof prime or may not hold this powerfor periods of time of up to the limits thathave been set by the manu- consideration. facturer. Very seldom is maximumpower held on the engine for morethan 2 minutes and RELIABILITY usually not that long. Within a fewseconds after engines is of lift-off, the power is reduced to a powerthat is The reliability of aircraft be maintained prime importance. Enginefailure of a carrier used for climbing and which can reduces the fighting for longer periods of time.After climbout to based aircraft not only accomplished, the effectiveness of the carrier butalso results in cruising altitude has been cases, highly power of the engine(s)is further reduced to a the loss of material and in many maintained for the trained pilots and crewmen ifthe aircraft is cruise power which can be lost at sea. The enginemanufacturer insures duration of the flight. the reliability of his productby spending thousands of dollars and manhoursin design, re- DURABILITY search,and testing. Close controlof every is main- In a well-designed aircraftengine, the cost manufacturing and assembly procedure the durability of the tained, and each engine isthoroughly tested of operation is reduced by An additional insur- engine, which materiallyextends the periods before it leaves the factory. between necessary overhauls. Earlyaircraft ance factor is thatthe Navy requires that every after compara- engine coming from thefactory must pass a engines required overhauling is finally accepted. tively few hours of operation.Today,for certain Navy acceptance test before it aviation, opera- Reliability is thus built intothe engine by types of engines used in naval continued reliability tion for periods in excess of1,500 hours between the manufacturer, but the designers have of the engine is determinedby the maintenance, overhauls is authorized. Engine Careful mainte- devoted much thought and considerationto the overhaul, and flying personnel. metallurgists also nance and overhaulmethods, thorough periodic requirement of durability; of the oper- have made major contributionsto increased inspections, and strict observation of stronger and ating limits established bythe engine manufac- durability by the development engine failure a tougher metals. The durabilitybuilt into the turer and the Navy will make adherence rare occurrence. engine must be safeguarded by strict to good maintenance andoperating procedures. WEIGHT ACCESSIBILITY brake horse- If the weight of an engine per For purposes of inspection,repair, or re- power (called the specific weightof the engine) adjustments to aircraft placement of parts and making is decreased, the useful load that an various units of the engine, it is necessarythat can carry and theperformance of the aircraft and its accessories itself obviously are increased.Every excess all sections of the engine pound of weight carried by an aircraftreduces should be as accessible as possible.

105

8 1 AVIATION MACHLNIST'S MATE R 3 & 2 7/ PARTS INTERCHANGEABILITY In the first place, internal combustion is the process by which a mixture of air and fuel is The various parts of an aircraft engine are burned in a chamber from which power may be made with such precision that it is possible to taken directly. The word engine means a ma- exchange parts without the necessity of extensive chine in which heat energy released by the proc- hand fitting. The interchangeability of parts be- ess of combustion is converted into mechanical tween engine models of like horsepower sim- energy. Reciprocating means motion back and plifies the stockkeeping problems of the avia- forth, in the case of engines, the motion of the tion supply system and reduces the number of piston within the cylinder. Therefore, in the spare parts required for emergency situations. reciprocating eraine, gasoline is vaporized and mixed with air, 2:, then forced or drawn into a COMPACTNESS cylinder, compressed by a piston, and then ignited by an electric spark. The conversion of the In order to effect proper streamlining and resultant heat energy into mechanical energy and balancing of an aircraft, the shape and size of then into work is accomplished in the cylinder. the engine must be as compact as possible. In (See fig. 6-1.). single-engine aircraft, the shape and size of the The operating cycle of internal-combustion engine also affect the view of the pilot, making reciprocating engine may bedefined as the a smaller engine better from this standpoint in seriesof events requiredtoinduce, com- addition to reducing the drag created by a large press,ignite, burn, and expand the air/fuel frontal area. chargein the cylinder, and to scavenge or Weight limitations, naturally, are closely exhaust the products of the combustionprocess. related to the compactness requirement. The When thecompressed mixture is ignited, more difficult it becomes to keep the specific the resultant gases of combustion expand very weight within the allowable limits. The radial engine, due toits compact arrangement, has INTAKE SPARK PLUG EXHAUST the advantage over the inline type in keeping VALVE ALVE its weight within allowable limits in proportion to the horsepower developed. To enable the inline engine to develop power comparable to the radial engine, its weight and length would have to be increased proportionately. COMBUSTION T D C CHAMBER OPERATING FLEXIBILITY PISTON STROKE Operating flexibilityis the ability of an engine to run smoothly and give desired per- CONNECTING ROD formance at all speeds from the idling range to 13 D C CYLINDER FLANGE maximum power allowable. In addition to the -...... requirement of unfailing reliability, the engine may be operated in widely varying positions and _ inextreme weather conditions. Driving the modern day propeller has put a demand on the TOP CENTER--"'"'7-'4../ \ engine to produce a wide range of operating I 1 speeds that the engine of yesterday did not have CRANK SHAFT i to meet. 1 II I / \ t \ i'"N / THEORY OF OPERATION BOTTOM CENTER .-...... 1....1,- %., ....// Before discussing the theory of operation of the internal-combustion reciprocating engine, AD.30 it must be clear how it derives its name. Figure 6-1.Reciprocating engine cylinder.

106 Chapter 6RECIPROCATING ENGINEFAMILIARIZATION largely in powering rapidly and force the piston to moveaway from naval aviation. It was used motion of the auxiliary power units to furnishpowerfor start- the cylinder head. This downward to the aircraft piston, acting on the crankshaftthrough the ing aircraft and to supply power circular or for checking electrical unitsaboard. As the name connecting rod, is converted to a require only rotary motion by thecrankshaft, and thus implies, two-stroke cycle engines system drives the one up and one downstroke of the piston to com- through a reduction gearing plete the required series of eventsin the cylin- propeller shaft. the cylinder der. Thus the enginecompletes the operating A valve in the top or head of crankshaft as shown opens to allow the burned gasesto escape, and cycle in one revolution of the and the pro- in figure 6-2. the momentum of the crankshaft engines in pres- peller forces the piston back up inthe cylinder All aircraft reciprocating in the cycle. ent use in naval aviationoperate on the four- where it is ready for the next event calledthe OTTO Another valve in the cylinder headthen opens strokecycle,sometimes CYCLE after its originator, aGerman physicist. to let in a fresh charge of theair/fuel mixture. has many ad- The valve allowing for the escapeof the The four-stroke cycle engine vantages for use in aircraft.One is that this burning exhaust gases is calledthe EXHAUST readily to high per- VALVE, and the valve which letsin the fresh type of engine lends itself charge of the air/fuel mixtureis called the formance through supercharging. opened and In this type of engine, fourstrokes are re- INTAKE VALVE. These valves are series of events closed mechanically at the propertimes by the quired to complete the required or operating cycleof each cylinder, as shown valve operating mechanism. revolutions of the in describing engine in figure 6-3. Two complete Other terms used crankshaft are required for thefour strokes; operation are as follows: thus, each cylinder in an engineof this type 1. BORE and STROKE. TheBORE is the of the internal diameter of the cylinder.The STROKE firesoncein every two revolutions is the distance that the pistontravels from the top crankshaft. to the bottom, or fromthe bottom to the top, of the cylinder. For eachrevolution of the crank- FOUR-STROKE CYCLE shaft there are two strokes of thepiston, one up ENGINE OPERATION and one down. An engine cycle is the seriesof operations 2. TOP DEAD CENTER(TDC). Top cleric] piston assumes when or events which aninternal combustion engine center is the position that a must perform to operatecontinuously and de- it reaches its maximumdistance from the cen- timed (made to terline of the crankshaft. Thisposition may also liver power. These events are be referred to as "the topof the stroke." occur in a certainsequence) by the construction 3. BOTTOM DEAD CENTER(BDC).Bot- of the engine. that the piston Inside a 9-cylinder four-cycleengine op- tom dead center is the position minute (RPM), assumes when it reaches itsminimum distance erating at 2,000 revolutions per This posi- a seriesofeventsis being repeated very from the centerline of the crankshaft. rapidly. In 1 minute, 9 pistonsstart and stop tion is also known as "the bottomof the stroke," jump across the and it is at the opposite endof the cylinder from 4,000 times; 18,000 sparks points of 18 spark plugs; 9intake and 9 exhaust the top dead center position. valves open and close 1,000times. Despite this 4. COMPRESSION RATIO.The volume of operation, only 5 dif- the space in a cylinder abovethe piston at top apparent complexity of volume. The ratio ferent events (induction,compression, ignition, dead center is the clearance expansion, and exhaust) aretaking place, but between the total volume of thecylinder with these events very the piston at bottom deadcenter, to the clear- each cylinder is repeating rapidly. These 5 eventscomprise the cycle of ance volume, is calledthe compression ratio. (fig. 6-3)are discussed This is expressed 7:1, 9:1, etc. operation. These cycles There are two operating cyclesin general in the following paragraphs. NOTE: In the following discussionof the usethe two-stroke cycleand the four-stroke it should be cycle. The two-stroke hasdisappeared from four-stroke cycle engine operation,

107 AVIATION MACHINIST'S MATE R 3 & 2 74

CYLINDER COMPRESSION AND CRANKCASE INTAKE STROKE

CYLINDER POWER AND CRANK- CASE COMPRESSION STROKE

CYLINDER INTAKE AND EXHAUST STROKE

AD.31 Figure 6-2.Two-stroke cycle. realized that the timing of the ignition and the It can be noted in the following paragraphs valve events will vary considerably in different that the timing of each event is specifiedin engines. Many factors influence the timing of terms of degrees of crankshaft travel on the a specific engine, and it is most important that stroke during which the event occurs. It should the engine manufacturer's recommendations in be remembered that a certain amount of crank- this respect be followed by service personnel in shaft travel is required to open a valve fully; maintenance and overhaul. The timing of the therefore, the specified timing represents the valve and ignition events is always specified in startofopening rather than the full-open degrees of crankshaft travel. position of the valve.

108 77 Chapter6RECIPROCATING ENGINE FAMILIARIZATION

VALVES CLOSED EXHAUST OPEN INTAKE OPEN VALVES CLOSED

17/ 4 g 4 EXHAUST INTAKE COMPRESSION POWER STROKE STROKE STROKE STROKE 1 4 I

(A) ( 8 ) (c) (0) AD.32 Figure 6-3.Four-stroke cycle. cool incoming air/fuel mixture, toincrease the Intake Stroke amount of the air/fuel mixtureinduced into the the products During the intake stroke, the pistonis pulled cylinder, and to aid in scavenging rotation of the of combustion. downward in the cylinder by the about 50° crankshaft. This reduces the pressurein the The intake valve is timed to close to 75° past bottom dead center on the compres- cylinder and causesair under atmospheric specific engine, pressure to flow throughthe carburetor, which sion stroke, depending upon the The air/fuel to allow the momentum of theincoming gases to meters the correct amount of fuel. completely. Because mixture is compressed by theimpeller and then charge the cylinder more pipes and intake valves of the comparatively largevolume of the cylinder passes through the intake bottom into the cylinders. The quantity.orweight of the above the piston when the piston is near charge depends upon the degree of dead center, the slight upwardtravel of the air/fuel piston during this time does nothave a great throttle opening. effect on the incoming flow of gases.This late The intake valve is openedconsiderably the gases before the piston reaches top dead center onthe timing can be carried too far because in order to induce a greater may be forced backthrough the intake valve exhaust stroke, late closing. quantity of the air/fuel charge intothe cylinder and defeat the purpose of the and thus increase the horsepower.The distance the valve may be opened before topdead center, Compression Stroke such as however, is limited by several factors, closed,the the possibility that hot gasesremaining in the Aftertheintakevalveis cylinder from the previous cycle mayflash continued upward travelof the piston com- the intake pipe and the induction presses the air/fuelmixture in order to obtain back into and expansion char- system. thedesiredburning acteristics. In all high-power aircraft engines,both the electric intake and the exhaust valves areoff the valve The charge is fired by means of an spark as the piston approaches topdead center. seats at top dead center at the startof the intake from 20° to 35° stroke. As mentioned above, theintake valve The time of ignition will vary the exhaust before top dead center, depending uponthe re- opens before top dead center on in order to stroke (valve lead), and the closing of theexhaust quirements of the specific engine, the piston insure complete combustion of thecharge by valve is delayed considerably after the top dead has passed top dead center andhas started the the time the piston is slightly past intake stroke (valve lag). This timingis called center position. aid in Many factors affect ignition timing,and the VALVE OVERLAP and is designed to considerable cooling the cylinder internally bycirculating the engine manufacturer has expended

109

80 AVIATION MACHINIST'S MATE R 3 & 2 zif time in research and testing to determine the begin to push the burned exhaust gases out the best setting. All engines incorporate devices for exhaust port. The speed of the exhaust gases adjusting the ignition timing, and it is most leaving the cylinder creates a low pressure in important that the ignition system be timed the cylinder. This low or reduced pressure is according to the engine manufacturer's recom- used to speed the flow of the fresh air/fuel mendations. charge into the cylinder as the intake valve is beginning to open. The intake valve opening is Power Stroke timed- to occur at 8° to 55° before top dead center on the exhaust stroke on various engines. As the piston moves through the top dead NOTE: The preceding description of the center position at the end of the compression operating cycles and of the four-stroke cycle stroke and starts downward on the power stroke, operation is of a general nature and should not it is pushed by the rapid expansion of the burning be used for any specific model engine. For gases in the cylinder head with a force that can specific instructions always refer to the appli- be greater than 15 tons at the maximum power cable publications for each individual engine. output of the engine. The temperature of these burning gases may be between 3,000° and HORSEPOWER 4,000° F. As the piston is forced downward during The common unit of mechanical power is the the power stroke by the pressure of the burning horsepower(hp).Latein the 18th century, gases exerted upon it, the downward movement James Watt, the inventor of the steam engine, of the articulating (connecting) rod is changed found that an English workhorse could work at to rotary movement by the crankshaft. Then the the rate of 550 ft-lb per second, or 33,000 ft-lb movement is transmitted to the propeller shaft per minute, for a reasonable length of time. to drive the propeller. As the burning gases are From his observations came the HORSEPOWER, expanded, the temperature drops to within safe which is the standard unit of power in the limits before the exhaust gases pass out through English system of measurement. the exhaust valve. As stated above, work is the product of The. timing of the exhaust valve is deter- force and distance, and power is work per unit mined by, among otherconsiderations, the of time. Consequently, if a 33,000-pound weight desirability of using as much of the expansive is lifted through a vertical distance of 1 foot in force as possible and of scavenging the cylinder 1 minute, the power expended is 33,000 ft-lb as completely and rapidly as possible. The valve per minute, or exactly 1 horsepower. isopened considerably before bottom dead Work is performed not only when a force center on the power stroke (on some engines at is applied for lifting; force may be applied in any 50° to 75 ° before bottom dead center) while there direction. If a 100-pound weight is dragged along isstill some pressure in the cylinder. This the ground, a force isstill being applied to timing is used so that the pressure can force perform work, although the direction of the the gases out of the exhaust port as soon as resulting motion is approximately horizontal. possible. This process frees the cylinder of The amount of this force would depend upon the waste heat after the desired expansion has been roughness of the ground. obtained and avoids overheating the cylinder If the weight were attached to a spring scale and the piston. Thorough scavenging is very graduated in pounds, then dragged by pulling on important, because any exhaust products re- the scale handle, the amount of force required maining in the cylinder will dilute the incoming could be measur?d. Assume that the force air,"fuel charge at the start of the next cycle. requiredis90 pounds, and the 100-pound weight is dragged 660 feet in 2 minutes. The Exhaust Stroke amount of work performed in the 2 minutes will be 59,400 ft-lb, or 29,700 ft-lb per minute. As the piston travels through bottom dead Since 1 horsepower is 33,000 ft-lb per minute, center at the completion of the power stroke the horsepower expended in this case will be and starts upward on the exhaust stroke, it will 29,700 divided by 33,000, or 0.9 horsepower.

110 -77% Chapter 6-R ECIPROCATING ENGINE FAMILIARIZATION

Indicated Horsepower frictionof moving parts,drawinginfuel, expelling exhaust, driving oil and fuel pumps, The INDICATED HORSEPOWER (ihp) pro- and the like. On modern aircraft enginesthis duced by an engine is the horsepower calculated power loss through friction may be ashigh as from the indicated mean effective pressure and 10 to 15 percent of the indicated horsepower. the other factors which affect the power output of an engine. Indicated horsepower may be said Brake Horsepower to be the power developed in the combustion chambers without reference to friction losses The actual horsepower that is delivered to within the engine. The ihp for a four-cycle engine the propeller shaft is called brake horsepower. can be calculated from thefollowing formula, It is the indicated horsepower minus the friction in which the letter symbols inthe numerator are horsepower and is that part of the total horse- arranged to spell the word "plank' to assist in power developed that canactually be used to memorizing the formula: do work.

PLANK Thrust Horsepower 33,000 Thrust horsepower can be considered as the where: end result of the engine and the propeller working together. If a propeller could be designed P = Indicatedmeaneffectivepressure to be 100 percent efficient, the thrust horsepower (imep) in pounds per square inch. and the brake horsepower would be the same. L = Length ofthestroke in feet or in However, the efficiency of the propeller varies fractions of a foot. with the engine speed, attitude, altitude, temper- A = Area ofthe piston head or cross ature,airspeed, and while taxiing; thus the sectional area of the cylinder, in square ratio of the thrust horsepower and thebrake inches. horsepower delivered to the propeller shaft will N = Number of power strokes per minute, never beequal. For example,if an engine rpm. develops 1,000 brake horsepower and is used 2 with a propeller having 85 percent efficiency, K = Number of cylinders. the thrust horsepower of that engine-propeller In the formula above, the areaof the piston combination is 85 percent of 1,000, or 850 thrust times the imep gives the force acting on the horsepower. Of the four types of horsepower piston in pounds. This force multiplied bythe discussed,itis the thrust horsepower that length of the stroke in feet gives the WORK determines the performance of the engine- performed in one power stroke, which, multi- propeller combination. plied bythe number of power strokes per minute, gives the number of ft-lb per minute ENGINE TYPES AND DESIGNATIONS of work produced by one cylinder. Multiplying this result by the number of cylinders in the Although aircraft engines of many different engine gives the amount of work performed,in designs have been constructed and used in naval ft-lb, by the engine. Since horsepower is defined aircraft, the only types of engines in use today as work done at the rate of33,000 ft-lb per are the inline and radial.The difference in minute,thetotal number offt-lb of work these two types of engines, as discussed in performed by the engine is divided by 33,000 the following paragraphs, is the types of crank- to find the indicated horsepower. shaft and cylinder arrangement. (See fig. 6-4.) Friction Horsepower INLINE Friction horsepower is the indicated horse- Inline engines have the cylinders arranged power minus brake horsepower. It is thehorse- in one or more straight lines,parallel to the power used by an engine inovercoming the crankshaft. Inline engines may bevertical,

111 V AVIATION MACHINIST'S MATE R 3 & 2 Navy, the radial is considered the basic aircraft engine andis used for discussion in this training manual. RADIAL Radial engines are built with the cylinders arranged around the crankcase. The 18-cylinder radial engine shown in figure 6-4 illustrates how the cylinders radiate from the crankcase similar to the spokes in a wheel. Modern radial engines have the cylinders arranged in one or two rows and are accordingly termed single- row and double-row. Present single-row engines have 7 or 9 cylinders, while the double-row engines have 14 cylinders in two rows of 7, or OPPOSED 18 cylinders in two rows of 9. The largest radial engine used by the Navy was the R-4360 which had 28 cylinders composed of four iows of 7 cylinders each. DESIGNATIONS A system of engine designation has been developed and is currently being used by the Navy and Air Force.Itutilizes standard symbols to represent the type and model of the various engines currently being used in military aircraft and missiles. The standard designation system classifies aircraftreciprocating engines accordingto cylinder arrangement (0-opposing and R-radial) and the size of the engine in terms of total piston displacement to the nearest 5 cubic inches (area of the piston head in square inches times the lengthofthestrokeininchestimesthe numberofcylinders).In addition, a model number is assigned to each new model of the basic engine. Figure 6-5 illustrates the designation symbols for a widely used radial engine and should be referred to during the following discussion. RADIAL

AD.33 R 3 3 5 0 .. 3 6 W A Figure 6-4.-Types of reciprocating engines. --r 1 Ta...... SUFFIX L....a.... WATER INJECTION EQUIPPED opposed, or V: these type names are derived ...... MODEL INDICATOR MODEL NUMBER from the cylinder arrangement. These engines 1 TYPE NUMERALS can be air cooled or liquid cooled.The only 1 TYPE INDICATOR type of inline engine used in naval aircraft is the air-cooled opposed type. AD.34 NOTE: Although a limited number of op- Figure 6-5.-Reciprocating engine posed type inline engines are in use in the designation symbols.

112 7,- b0 Chapter 6RECIPROCATING ENGINE FAMILIARIZATION Fi/ in a 1. Type indicator. The first partof the terchangeability of the complete engine specific airplane. In general, suffixletters are designation consists of a letterindicating the the letters type of engine. (Rradial.) added consecutively starting with numerals con- A, B, C, etc., except for theletter "W" which 2. Type numerals. The type equipped with sist of a dash and a numberrepresenting piston is reserved to indicate engines inches. water injection. When so used, thesuffix letter displacement to the nearest 5 cubic suffix letter (3,350-cubic inches displacement.) "W" always precedes any other indicator included in the model indicator.(Wwater in- 3. Model indicator. The model change.) consists of a dash and a modelnumber or a jectionequipped.) (Aminor design dash and a model number with asuffix letter. a. Model number. Themodel number RECIPROCATING ENGINE is a numeral(s) which is assignedto identify a CONSTRUCTION specific configuration within theengine type. type of For a thorough knowledge ofaircraft re- Air Force model numbers for each that the Avia- engine begin with -1 and continue with consec- ciprocating engines, it is essential begin tion Machinist's Mate R know howthey are con- utive ODD numbers. Navy model numbers the engine with -2 and continue with consecutiveEVEN structed. First, he should learn that isconstructedinseveral distinct sections. numbers. (36Navy developed.) 6-6, NOTE: If the Air Force or Navyprocures an Engine sections, as illustrated in figure for the other serve as housings for thecrankshaft, reduction engine model originally developed assemblies of the engine. They service, the type number does notchange. gears, and drive The suffix letter affordrigidity to the entire enginestructure b. Suffix letter(s). which the en- indicates a minor design change whichaffects and serve as the base or bed on performance, flight safety, installation, orin- gine is built.

CYLINDER

SUPERCHARGER PISTON HOUSING

CRANKCASE CRANKCASE FRONT MAIN REAR MAIN FRONT RE AR SECTION SECTION

IMPELL ER SUPERCHARGER PROPELLER CONNECTING DIF FUSER CAM REAR HOUSING REDUCTION ROD CRANKSHAFT PLATE DRUM COVER GEARS ASSEMBLY V A CCESSORIES NOSE POWER SUPERCHARGER SECTION SECTION SECTION SECTION AD. 35 Figure 6-6.Engine sections.

113 AVIATION MACHINIST'S MATE R 3 & 2 g'o2

Engine sections support the cylinders and siderably. An exploded view of the R-3350 engine the crankshaft, and provide the means of attach- is shown in figure 6-7. ing the engine to the engine mount and to the aircraft structure. Front Section

CRANKCASE SECTIONS The crankcase front section supports the propeller shaft bearings, thrust nut, propeller The engine shown in figure 6-6 is a single- reductiongearing,propeller governor, dis- row, nine-cylinder, radial engine of relatively tributors, front oil sump and scavenge pump, simple construction, having a one-piece nose and torque cell, torquemeter boost pump, and the a two-section main crankcase. The larger ignition harness. The front cam and tappet twin-row engines are of slightly more complex assembly, which opens and closes the valves construction. For example, the crankcase of the in the front row of cylinders, is also located Wright R-3350-32W engine is composed of the in this section. crankcase front section, four crankcase main sections (the front main, the front center, the Crankcase Main Sections rear center, and the rear main sections) the rear cam and tappet housing, the supercharger The crankcase main sections (the front front housing, the supercharger rear housing, main, front center, rear center, and the rear and the supercharger rear housing cover. Pratt main) house the main bearings, which support and Whitney engines of comparable size incor- the crankshaft. This portion of the engine is porate the same basic sections, although the often referred to as the power section, for it construction and the nomenclature differ con- is here that the reciprocating motion of the

SUPERCHARGER REAR CAM a FRONT HOUSING TAPPET HOUSING CRANKCASE SUPERCHARGER CRANKCASE MAIN SECTIONS REAR HOUSING FRONT SECTION

REAR MAIN REAR CENTER FRONT MAIN SUPERCHARGER FRONT CENTER REAR HOUSING COVER

AD.36 Figure 6-7.R-3350 engine.

114

-7 o

Chapter 6RECEPROCATING ENGINE FAMILIARIZATION engine is converted to the rotary motion of the used in single-row and twin-rowengines are crankshaft. The cylinders are mounted on these usually built up from two or three sections.The of three sections. crankshaft of the R-3350 engine consists sections; the crankshaft front, center,and the Rear Cam and Tappet Housing rear section and permitsthe use of solid master rods. Other engines may use asingle piece The rear cam and tappet assembly,which crankshaft in which all the journals andcrank- actuates the valves of the rear row of cylinders, pins are machined as a single unit.It is neces- master rod with such ishoused in this section of the crankcase.sary to use a split type units. Supercharger Front Housing Two general methods are used in the construction of built-up crankshafts. Thecrankshaft The supercharger front housing provides shown in figure 6-9 employs thesplit-clamp outlets from the supercharger, through which method; other crankshafts use the split-spline the air/fuel mixture is directed (through the method. intake pipes) to the cylinders. Mounting pads In all crankshafts used in navalaircraft are provided for attaching theengine to the engines,the journals and crankpins are of engine mount. The power recovery turbines hollow construction to allow for theminimum are mounted on the frontsupercharger housing. weightwith the maximum bearingsurface. Supercharger Rear Housing Crankshaft Balancing Together with the supercharger front hous- The counterweights shown in thecrankshaft ing, the supercharger rear housing containsthe illustration serve two functions. First, the coun- supercharger and the supercharger drive mech- terweights balance the rotating andrecipro- anism. It also provides a mounting place forthe cating masses of the crankpin and theconnecting aircraft engines carburetor(or mastercontrol), direct fuel rods. Secondly, in all modern injection pumps, the engine-driven fuel pump, the counterweights serve to dampen theseparate the tachometer generator, the synchronizing power impulses and thusdampen the torsional or twisting vibrationsimpoded on the crankshaft generator for the engine analyzer, and the rear propeller oil sump. The supercharger fronthousing and insuring the even flow of power to the the supercharger rear housing areshown in shaft. This latter operation isperformed by suspending the counterweights from thecrank- figure 6-8. cheeks. (See fig. 6-9.) The slightmovement allowed the counterweights tendstooffset CRANKSHAFT the power impulses and provides forsmoother The crankshaft of the engine receivesthe operation. power developed in the cylindersand delivers it to the propeller. In other words,it converts ARTICULATING RODS rotary the power strokes of the pistons into the cylin- motion which turns the propeller. In a radial engine the piston in one Crankshafts are termed single-throw and der in each row is connected tothe crank- two-throw and are used in single-row and twin- shaft by a master rod. All otherpistons in row radial engines respectively.The terms the row are connected to the masterrod by an "single piece" and "built-up" may also be articulatingrod.In the case of the R-3350 applied to crankshafts according to the methodengine, which has 2 rows of cylinders,there of construction employed. are 2 master rods and16 articulating rods. Atengine assembly, the entire masterand articulating rod assembly is built upand then Crankshaft Construction installed on the crankpin as a unit. Atypical Crankshafts are machined from solid steel radial engine master rod arrangement isshown forgings of nickel alloy steel. The crankshafts in figure 6-10.

115 AVIATION MACHINIST'S MATE R 3 & 2 gi(

AD.37 Figure 6-8.Supercharger front and rear housings.

The articulating rods are constructedof MASTER ROD(S) forged steel alloy in either the I- or H-shape, denoting thecrosssectional shape. Bronze The master rod serves as the connect- bushingsare pressed into the bores in each ing link between the piston pin and the crank- end of the rod to provide knuckle pin and piston pin;italso provides for the attachment of pin bearings. In the R-3350 engine, the knuckle the articulating rods. The master rod is usu- pin bushing is lined with lead-tin on the inner ally shaped like a banjo. The crankpin end diameter. orthe"big end"contains the crankpin or NOTE: In the inline engine, the pistons master rod bearing; flanges around the big are connected directly tothe cran.kshaft by end provide for the attachment of the artic- connecting rods. The typical inline engine will ulatingrods. The articulating rods are at- have connecting rods that have been constructed tached to the master rod by the knuckle pins, in the same manner as the articulating rods. which are pressed into holes in the master However, the crankshaft end will be lai.'Wand rod flangesatassembly. A plain bearing, will have a replaceable bearing insert. usuallycalledapiston pin bushing,isin-

116

94 Chapter 6RECIPROCATLNG ENGINE FAMILIARIZATION

144110;

7 4.a" 10

AD.38 Front main bearing. 9.Rear counterweight assembly. 1. Crankshaft rear section. 2.Crankcheek clamp, screw, and washer. 10. Crankshaft front section. 11.Counter weight stop. 3. Accessory drive and starter shaft. 4.Center main bearing. 12. 13.Rear main bearing. 5.Crankpin plug. Crankshaft center section. 14.Oil retainer bolt. 6. Front counterweight 7.Center bearing support. 15. 8.Center section oil retainer. assembly. Figure 6-9.Two-throw crankshaft(R-3350 engine). master rod piece type of crankshaft, thebig end of the stalled in the piston end of the as is the crankpin or to receive the piston pin. master rod is split, The master rod piston is moreheavily master rod bearing. The main partof the master row rod is installed on the crankpin;then the bear- loaded than the other pistons in the same master because this piston restrains themaster rod ing cap is set in place and bolted to the from turning around the crankpinunder power rod. impulses from the other pistons. When a crankshaft of thesplit-spline or Knuckle Pins split-clamp typeisemployed,aone-piece and the articu- master rod is used. The master construction lating rods are assembled and theninstalled on The knuckle pins are of solid sections are then except for the oil passages drilled in thepins, the crankpin; the crankshaft These joined together. In engines that usethe one- which lubricate the Imuckle pin bushings.

117 AVIATION MACHINIST'S MATE R 3 & 2 8(6

SOLID TYPE MASTER ROD SPLIT TYPE MASTER ROD

ARTICULATING ROD

KNUCKLE PIN LOCK PLATE

KNUCKLE PIN

AD.39 Figure 6-10.Articulating rod assembly. pins are pressed into holes in the master rod PISTONS flanges and retained hi position by spider- shaped lock plates bolted to the flanges. The piston acts as a moving wall in the combustion chamber. After the air/fuel mix- Lock Plates ture has been admitted to the cylinder, the pistoncompressesthemixture,whichis The lock plates have two additional functions ignited by the spark plug at the proper time. besides the one of retaining the knuckle pins in The, piston then transmits the work accom- the master rod. They also hold the crankpin or plished by the combustion of the mixture, and master rod bearings in place and transmit lubri- theresulting expansion of gases forces the cating oil from the crankpin bearing to the piston downward. This force is transmitted knuckle pins. to the crankshaft through the articulating rod

118 9,1 Chapter 6RECIPROCATING ENGINEFAMCMIARIZATION (or master rod), and then on the return up- portions of the piston walls that liebetween ward stroke forces the exhaust gasesfrom each pair of ring grooves are called theRING LANDS. the cylinder. In addition to acting as a guide for thepiston head, the piston skirt incorporates thepiston Construction pin bosses. The piston pin bosses areof heavy construction to enable the heavyload on the The majority of aircraft enginepistons are piston head to be transferred tothe piston pin. machinpdfromaluminumalloyforgings. Grooves are machined in the outsidediameter Piston Pin of the piston to receive the pistonrings, and cooling fins are provided on the insideof the engine The piston pin joins the piston tothearticu- piston for greater heat transfer to the machined in the oil. lating rod or master rod. It is Pistons may be either the trunk type or the form of a tube from a nickel steelalloy forging, casehardened and ground. The pistonpin is slipper type, both shown in figure 6-11. Thetop of the face of the piston, or head, may beeither flat, sometimes called a wristpin because be machined similarity between the relative motionsof the convex, or concave. Recesses may that of the in the piston head to preventinterference with piston and the articulating rod and human arm. the valves. aircraft en- As many as six grooves may bemachined The piston pin used in modern compres- gines is the full-floating type, socalled because around the piston to accommodate the the piston and sion rings and oil rings. Thecompression rings the pin is free to rotate in both are installed in the threeuppermost grooves; in the articulating rod piston pinbearing. immediately The piston pin must be held inplaceto pre- the oil control rings are installed the cylinder abovethe piston pin. The piston isusually vent the pin ends from scoring surplus walls.In earlier engines, springcoils were drilled at the oil control rings to allow pin bores at oil scraped from the cylinder wallstopass back installed in grooves in the piston ring is either end of the pin. The modernpractice is to into the crankcase. An oil scraper aluminum in one installed at the base of the piston wall orskirt install a plug of relatively soft consumption. These or both of the pin ends toprovide a good bearing to prevent excessive oil surface against the cylinder wall.

COMPRESSION RINGS Piston Rings OIL CONTROL RINGS The piston rings prevent leakageof gas Pis TON PISTON PIN BOSS PIN chamber and ALUMINUM pressure from the combustion PLUG reduce to a minimum the seepage of oilinto the combustion chamber. The rings fit intothe piston

011.. SUPPER RING grooves but spring out to pressagainst the cyl- CS;) PISTON inder walls; when properly lubricated,the rings SUPPER TYPE form an effective gas seal. Most piston rings are made of high grade cast iron. After the rings are made,they are ground to the cross section desired.They are then _split so that they may be slipped overthe outside of the piston and into the ring grooves DOME HEAD FLAT HEAD RECESSED HEAD CONCAVE HEAD which are machined into the pistonwall. Since AD.40 their purpose is to seal the clearancebetween the piston and the cylinder wall, theymust fit the Figure 6-11.Piston assembly gas- and types of pistons. cylinder wall snugly enough to provide a

119

9 0 AVIATION MACHINIST'S MATE R 3 & 2 tightfit;they must exert equal pressure at ring retains the surplus oil above the ring on all points on the cylinder wall; and they must the upward piston stroke, and this oil is re- make a gastight fit agaMst the sides of the turned to the crankcase by the oil control rings ring grooves. on the downward stroke. Gray cast iron is most generally used in making piston rings. However, many other mate- CYLINDERS rials have been tried. In some engines, chrome- plated mild steel piston rings are used in the The portion of the engine in which the power top compression ring groove because these is developed is called the cylinder. The functions rings can better withstandthe high temperatures of the cylinder are to provide a combustion present at this point. chamber where the burning and expansion of COMPRESSION RING.-The purpose of the gases take place, and to house the piston and the compression rings is to prevent the escaping articulating rod (or master rod). of gas past the piston during engine operation. There are four major factors that need to be They are placed in the ring grooves immediately considered in the design and construction of the below the piston head. The number of compres- cylinder assembly. These are asfollows: sion rings used in the engine on each piston 1.Itmust be strong enough to withstand is determined by the type of engine and its the internal pressures that are developed during design, although most aircraft engines use two engine operation. compression rings plus one or more oil control 2.It must be constructed with alightweigut rings. metal that will reduce the total engine weight. The cross section of the ring may be rec- 3.It must have good heat conducting prop- tangular or wedge shaped with a tapered face. erties so thatit can obtain efficient cooling. The tapered face presents a narrow bearing 4.It must be comparatively easy and in- edge to the cylinder wall which helps to reduce expensive to ;manufacture, inspect, and maintain. friction and provide better sealing. The cylinder that is used in the air-cooled OIL CONTROL RINGS.Oil control rings radial engine is the overhead valve type shown are placed in the grooves immediately belowthe in figure 6-12. Each cylinder is an assembly of compression rings and above the piston pin two major parts: The cylinder head and the cyl- bores. There may be one or more oil control inder barrel. At assembly, the cylinder head is rings per piston; two rings may be installed expanded by heating and then screwed down on in the same groove, or they may be installed in the cylinder barrel, which has been chilled; thus, separate grooves. Oil control rings control the when the head cools and contracts, and the bar- thickness of the oil film on the cylinder wall. If rel warms up and expands, a gastight joint too much oil enters the combustion chamber, it results. will burn and leave a thick coating of carbon on the combustion chamber walls, the piston Cylinder Heads head, and the valve heads. This carbon can cause The purpose of the cylinder head is to pro- the valves and piston rings to stick if it enters vide a place for combustion of the air/fuel the ring grooves or valve guides. In addition, the mixture and to give the cylinder more heat con- carbon may cause detonation, preignition, or ductivityfor adequate cooling. The air/fuel excessive oil consumption. To allow the surplus mixture is ignited by the spark in the combustion oil to return tu the crankcase, holes are drilled chamber and commences burning as the piston_ in the piston ring grooves or in the lands next to travels towards top dead center on the compres= these grooves. sion stroke. The ignited charge is rapidly ex- OIL SCRAPER RING.-The oil scraper ring panding at this time and pressure is increasing usually has a beveled face and is installed in the so that as the pislon travels through the TDC groove at the bottom of the piston skirt. The positionitis driven downward on the power ring may be installed with the scraping edge stroke. The intake and exhaust valve ports are away from the piston head or in the reverse located in the cylinder head along with thespark position, depending upon cylinder position and plugs and the intake and exhaust valve actuating the engine series. In the latter case, the scraper mechanisms.

120

9 b Chapter 6RECLPR0CATING ENGINE FAMILIARIZATION

The cylinder barrel is made of a steel alloy CAST ALUMINUM forging with the inner surface hardenedto resist INTAKE HEAD EXHAUST wear of the piston and the pistonrings which VALVE I VALVE bear against it. This hardening is usually done by exposing the steel to ammonia or cyanide gas while the steel is very hot. Thesteel soaks up nitrogen from the gas whichforms iron nitrides on the exposed surface. As a result of this process, the metal is said to be nitrided. The barrel will have threads on the outside diameter at one end so that it may be screwed into the cylinder head. Most air-cooled cylinder barrels have replaceable aluminum cooling fins COMBUSTION-L*1 attached to them, although some may have the CHAMBER cooling fins machined as an integral part of the barrel.

ARTICULATING VALVES =#'Er (CONNECTING) R 0 D Valves are the means with which the air/fuel mixture is permitted to enter the cylinders and the burned gases are expelled. The FORGED STEEL valves that are used in aircraft engines are of BARREL the conventional poppet type; they are called AD.41 this because of the popping action that takes Figure 6-12.Cutaway view of a place when they are lifted off of the valve seats. and cylinder -assembly. The valves are also typed.as to their shape are called either MUSHROOM orTULIP because The cylinder head is usually madefrom of their resemblance to these plants.Figure aluminum alloy because of its light weight andits 6-13 illustrates the various shapes and types excellent heat conductivity. WheneVer greater of these valves. strengthis desired, the cylinder heads are forged but they are usually made by the casting Construction process. After casting, the sparkplugbushings, valve guides, rocker arm bushings,and the The valves in the cylinders of an aircraft valve seats are installed in the cylinderhead. engine are subjected to high temperatures, cor- The valve seats are circular rings ofhardened rosion, and operating stresses that require a metal which protect the relatively soft metalof metal alloy that is able to resist all ofthese the cylinder head from wear of thehammering factors. The valves of the R-3350 engine are action of the valves and from the hotexhaust constructed of forged steel, having a cobalt tip. gases. Notice the extralarge cooling fin area The intake valve has a stellite face andthe in the vicinity of the exhaust valve infigure exhaust valve has a nichrome face. The head of the valve is that part which 6-12. serves to open and close thecylinder ports. Cylinder Barrels The head has a ground face, which forms aseal In general, the cylinder barrel in which the against the ground valve seat in the cylinder piston operates must be made of a high-strength head when the valve is in the closed position. material, usually steel. It must be as light as The valve stern acts as a pilot for the valve head cyl- possible. It must have the proper characteristics and rides in the valve guide installed in the for operating under high temperatures. Itmust inder head for this purpose. The neck isthe it must part that forms the junction between thehead be made of a good bearing material and hardened have high tensile strength. and the stem. The tip of the valve is

121

9 AVIATION MACHINIST'S MATE Ft 3 & 2 vicinity. Do not maltreat this typevalve or attempt to break or cut it open. LARGE STEM SODIUM CHAMRER HARDENED TIP In some engines, the intake valve may beof the tulip type and have a smaller stem thanthe SMALL STEM exhaust valve, or it may be similar in appearance to the exhaust valve buthave a solid stem and head. However, present practice inhigh- powered engines is to use the same typeof valve NECK in both the intake and exhaust. VALVE-OPERATING MECHANISM FACE HOLLOW-HEAD MUSHROOM The valve-operating mechanism consistsof MUSHROOM TYPE TYPE HEAD those components necessary to openand close the valves at the correct points in theoperating cycle. In a radial engine, the major components of the valve-operating mechanism arethe cam ring, the cam followers or tappets, thepush rods, the rocker arms, and the valve springs. These parts are shown diagrammaticallyin figure 6-14. Cam Ring TULIP TYPE SEMI-TULIP TYPE TULIP TYPE In a single-row radial engine, the camring AD.42 is located between the propeller reduction gear- section. In a Figure 6-13.Valve types. ing and the front end of the power twin-row radial engine, a second camfor the is to withstand the hammering of the valverocker operationof the valves in the rear row arm as it opens the valve. installed between the rear end of the power section and the supercharger section. Both valves used in the R-3350 engine are with of the mushroom type, are the sameweight, are The cam ring is mounted concentrically partially filled with sodium, but are not inter- the crankshaft and is driven by thecrankshaft changeable. The faces of the valves, asnoted at a reduced rate of speed throughthe cam above, are not constructed of the samematerial. intermediate drive gear assembly. The cam The valves may be identified in this manner; ring has two parallel sets of lobesspaced the around the outer diameter, one set(cam track) the intake valve will have a flat milled on the ex- tip to identify it. for the intake valves and the other for valve haust valves. The cam rings used in anR-3350 Both the intake valve and the exhaust and the are partially filled withmetallic sodium. This engine have four lobes on both the intake material is an excellent heat conductorand is exhaust tracks, and the timing of thevalve placed in the valve for this purpose. Thesodium events is determined by the spacing of these will melt at approximately 208°F and therecip- lobes and the speed at which the cam rings are rocating motion of the valve circulatesthe driven in relation to the speed of the crankshaft. liquid sodium and enables it to carry awayheat The valve lift (distance that the valveis lifted from the valve head to the valve stem,where off of its seat) and the valve duration(length of it is dissipated through the valve guide tothe time the valve is held open) are bothdeter- cylinder head and the cooling fins. Thus the mined by the shape of the cam lobes. operating temperatureof the valve may be Tappet Assembly reduced 300° to 400°F. NOTE: Exposure of the sodium contained in The tappet assembly consists of a cylindri- these valves to the outside air will resultin cally shaped tappet, which slides in andout in a fire, explosion, and injury to personnelin the tappet guide installed in one of thecrankcase

122 90 qy Chapter 6RECIPROCATING ENGINE FAMILIARIZATION

ROCKER ARM SPLIT KEY ADJUSTING SCREW VALVE SPRING ASSEMBLY

POSH ROD TAPPET. VALVE GUIDE BALL SOCK2T SPRING CRANKCASE, ....ilk,.

CAM LOBE VALVE ---TAPPET TAPPET ROLLER

CAM RING

CAM REDUCTION GEAR CRANKSHAFT CAM DRIVE GEAR

CRANKSHAFT

AD.43 Figure 6-14.Valve-operating mechanism (radial engine). sections over the cam ring; a cam follower or rod transmits motion from the tappet assembly tappet roller, which follows the contour of the to the rocker arm; it is enclosed in a tubular cam ring and lobes; a tappet ball socket or push housing that extends from the crankcase to the rod socket; and a tappet spring. The function of cylinder head. the tappet assembly is to convert the rotational movement of the cam lobe into reciprocating motion and to transmit this motion to the push Rocker Arm rod, rocker arm, and then to the valve tip, opening the valve at the proper time. The pur- The rocker arm, mounted in the rocker arm poseof the tappet spring is to take up the housing or rocker box in the cylinder head, clearance between the rocker arm and the valve transmits the motion of the push rod to the valve. tip in order to reduce the shock load when the This arm is provided with an adjusting screw valve is opened.. which provides for the adjusting of the clearance at the valve stem tip. The screw is always ad- Push Rod justed to give a slight clearance at the valve The push rod is constructed of hollow steel stem tip to make sure that the valve closes tubing with hardened ball-shaped ends. The push fully.

123

9d AVIATION MACHINIST'S MATE R 3tv. 2 9c2 transmit propeller thrust to the engine nose Springs section. Two or more concentric valve springs are used for each valve in the majority ofaircraft Roller Bearings by split engines. The springs are held in place and locks installed in the recess of the valvespring Roller bearings ax-: made in many types groove shapes, but the two types generally usedin the upper retainer or washer, and engage a roller and the machined into the valve stem. The functionsof aircraft engine are the straight the valve springs are to close the valveand to tapered roller bearings. Straight rollerbearings hold the valve securely on the valve seat. are used where thebearing is subjected to radial loads only. In tapered roller bearings,the inner- are cone BEARINGS andouter-race bearing surfaces shaped. Such bearings will withstandboth radial There are three types of bearings in use in and thrust loads. Straight rollerbearings are the radial engine-plain, roller, and ball. Balland used in the R-1820 and theR-3350 engines for roller bearings are used in the engine wherever the crankshaft main bearings. possible. PROPELLER REDUCTION GEARING Plain Bearings The increased brake horsepowerdeveloped Plain bearings are generally used for the by modern aircraft engines resultspartly from crankpin, cam ring, knuckle pin, piston pin,and increased crankshaft speeds. Itis therefore the accessory drive shaft bearings. Thevalve necessary to drive the propellerthrough a sys- guides and the tappet guides are alsoplain tem of reduction gearing in order toreduce the bearings. However, the motion of the parts of speed of propeller rotation toenable the pro- instead peller to operate efficiently. Wheneverthe speed which they support is reciprocating speed of sound of rotary. or the blade tips approach the theefficiencyof the propeller deteriorates Plain bearings are usually made of non- to ferrous (having no iron) metals, such asbronze, rapidly. Another reason that it is necessary aluminum, and various alloys of copper,tin, reduce the propeller rpm is that ahigher horse- bearings in power can be developed inthe engine and con- and lead. Master rod or crankpin be obtained some engines, such as theR-3350, are thin shells sequently a greater power output can of steel, plated with silver on both theinside than would be possibleif the propeller was and the outside surfaces and withlead-tinplated directly driven by the crankshaft. diameter only. The reduction gearing in the radialengines over the silver on the inside type. It is Smaller bearings, such as those used to support used by the Navy is of the planetary various shafts in the accessory section, are called planetary because in thissystem small widely pinion gears rotate about an inner gear, asthe called bushings. Porous bushings are of used in this instance. They are ()Hitebushings. planetsrotate about the sun. Two types They are impregnated with oil so that theheat planetary gear systems are used:The bevel of friction brings the oil to thebearing surface planetary gear and the spur planetary gear. during engine operation. Both types are shown in figure 6-15.

Ball Bearings Spur Planetary Type A ball bearing assembly consists of grooved The R-3350 engine,which has a spur inner and outar races, one or more sets ofballs, planetary type reduction system, has adriving and, in bearings designed for disassembly, a gear splined to the frontsection of the crank- bearing retainer. They are used for super- shaft, a stationary gear secured to the nose section, and 20 pinion gears rotatingin a pinion charger impeller shaft bearings and rocker arm propeller bearings in some engines. Special deep groove carrier assembly that is bolted to the ball bearings are used in aircraftengines to shaft.

124

I Uti Chapter 6RECIPROCATING ENGINE FAMILIARIZATION 93

BELL GEAR

1600 SUN GEAR 2400 RPM RPM PINION

SPUR-- REDUCTION 3:2

1600 2400 RPM RPM

SEVEL-- REDUCTION 3:2 Figure 6-15.Planetary reduction gears. AD.44

As the.driving gear is turned by the crank- driving gear and walk around the stationary shaft, the planetary pinions are rotated around bevel gear, which is bolted to the nose section their own axes. The teeth of the planetary gears, of the crankcase. however, are in mesh with the stationary gear. The propeller reduction gear ratio, that is, As they revolve they also walk around the sta- the ratio between the speed of the crankshaft and tionary gear. Since the pinions are mounted on the speed of the propeller shaft, varies in dif- a carrier assembly which isbolted to the ferent engines according to the type of propeller prop shaft,it also rotates. This system pro- used as well as other considerations. Obviously, vides a propeller shaft to crankshaft ratioof a propeller having two blades would have to be 0.4375:1. driven at a higher rotational speed than a pro- In the other type of spur planetary gear- peller having three or four blades. ing,the position of the gears is reversed; the inner (sun) gear is secured to the crankcase front section and forms thefixed gear, PROPELLER SHAFTS while the outer (bell) gear is splined to the crankshaft. The operating principle, however, Except for a difference in the pinion flange is the same. and in the size of the shaft, the propeller shafts used in all modern high-power engines are similar. The shaft is threaded at the forward Bevel Planetary Type end for the propeller attaching nut. Splineslo- cated to the rear of these threads engage simi- The bevel type of planetary gearing operates lar splines in the propeller hub. A shoulder on the same principle asthe spur planetary towards the rear of the propeller shaft provides type. The driving gear is machined withexternal a seat for the inner race of thepropeller thrust beveled gear teeth and is attached to the crank- bearing. The shaft is threaded forward ofthe shaft. A set of mating bevel pinion gearsis thrust bearing seat for the installation of the mounted in a cage which is attached to the pro- thrust bearing nut which retains the bearing in peller shaft. The pinion gears are driven bythe place. The shaft is generally hollow throughout

125

101 AVIATION MACHINIST'S MATE R 3 & 2 W its length and carries the oil passage required SUPERCHARGER REAR HOUSING for the operation of hydraulically controlled AND ACCESSORY DRIVES propellers. Located aft of the front supercharger housing is the rear supercharger housing and cover. POWER RECOVERY The supercharger rear housing provides a mounting pad for the carburetor (or master Recovery ofpowerthatis usually control if it is a direct fuel injection engine), lostthroughtheexhaustsystem is ac- a mounting pad on either side of the carbure- complishedthrough the use of three blow- tor for mounting the direct fuel injection pumps, down type turbines (power recovery turbines), and also mounting pads for the engine driven whichhave the exhaustgases from thefuel pump, tachometer generator, synchroniz- cylinders ported through them. Each turbineing generator, and the rear engine main oil receivestheexhaustgasesfrom six cy- pump and sump. linders,threefrontandthree rear. The The rear cover provides for the mounting of gasesentertheturbine at the nozzle andthe various accessories neededfor the operation causetheturbine wheel to spin at a highof the engine and the aircraft. All of these ac- rateofspeed.The turbine wheel is con- cessories are driven at various speeds through nectedtotheengine through a system ofgear takeoffs from the accessory drive and gearingandshaftinganda fluid couplingstarter shaft. The type of accessories that are whichallows theenergy developed to be mounted here will depend largely upon the returnedto the crankshaft. The power that mission of the aircraft, but will usually include may be recoveredwillapproximate 450the following: AC and DC generators, a vacuum brakehorsepoweratthe maximum power pump,hydraulic pump, starter, magneto or output of the engine. magneto generator, etc.

126 CHAPTER 7

RECIPROCATING ENGINE FUEL SYSTEMS

In general, the reciprocating engine fuel ditions. There is no such thing as the perfect systems found to be most satisfactory may be fuel, since a fuel which is suitable for a combat divided into two parts: aircraft piston engine will not work satisfactorily 1. The airframe system. This system con- in a diesel engine and vice versa. sists of fuel tanks, with their connecting lines; While the fuel must be suitable for the en- fuel transfer valves; selector and shutoff valves gine, the engine must also be suitable for the to establish an emergency system; and fuel fuel. Making the engine suitable for the fuel is tank boost pumps. necessary to insure that adequate supplies are 2. The engine system, This system in- available for the intended use. cludes filters, engine-driven fuel pumps, car- Liquid fuels are in many respects ideal fuels buretor, etc. for use in internal-combustion engines. For Both the airframe fuel system and engine convenience, liquid fuels are classified as either fuel system are discussed in this chapter. NONVOLATILE or VOLATILE. The former are Operation and maintenance of fuel systems are used in diesel engines. The volatile class in- also included. cludes those fuels which are used commonly with NOTE: To help the ADR to understand the a carburetor .and are carried into the engine fuel systems for reciprocating engine aircraft, cylinder in an evaporated or partially evaporated the type, designation, and requirements of the state.Among these are alcohol, benzol, and fuel used by the reciprocating engine are also gasoline. Gasoline is almost universally used in covered. aircraft reciprocating engines. Gasoline is a blend of liquid hydrocarbons AVIATION GASOLINE (compounds containing only hydrogen and carbon) ranging in boiling points from approximately Aviation fuel is a liquid containing hidden 900 to 425°F. These hydrocarbons are present energy, which by the process of cumbustion is in varying quantities, depending on the source released as heat and is turned into mechanical and purpose of the gasoline. The specifications energy in the engine. This mechanical energy for gasoline are very detailed and exacting to is then used to produce thrust, which propels insure that fuel has the desired characteristics. the aircraft. The basic requirement of furnish- A number of tests are required to determine the ing energy is, however, qualified by a number of suitability of the fuel for a particular engine. other requirements which are almost as basic, However, you, as an Aviation Machinist's Mate since there are many liquids whose potential R, will be primarily interested in the FUEL energy cannot be utilized to produce mechanical GRADE, which is the octane rating and/or the energy in aircraft engines. performance number of the fuel and the fuel An engine fuel must be made to suit the .en- purity. gines in which it is to be used. In the case of In selecting a fuel, there are several factors the aircraft engine, the fuel must also be suitable that must be considered. As one fuel cannot for use under a wide variety of operating con- have all the requirements to the greatest degree,

127

U AVIATION MACHINIST'S MATE R 3 & 2 the fuel selected must be a compromise of vari- blended in a manner to give a very high anti- ous factors. The most importantfactors in- knock value. volved in the choice of a fuel are as follows: 1.Heat energy content. Octane Rating 2. Volatility. 3. Antiknock value. Iso-octane is a reference fuel havinga very 4. Storage stability. high antiknock value. Normal heptane is a ref- 5. Purity. erence fuel having a very lowantiknock (high The meaning and importance of these factors detonation) value. A mixture of the two wil have are discussed in the following sections. an antiknock value somewherebetween these two extremes. The antiknock value of themixture will vary with the proportions of the mix- HEAT ENERGY CONTENT ture. Increasing the percentage ofiso-octane in the mixture (decreasing the proportionof A fuel satisfactory for aircraft engines must normal heptane) increases the antiknock(octane have a high potential heat energy content per unit number) value of the mixture. The octane num- weight. By having this high energy content, the ber (antiknock value) of a fuel is equalto the weight of fuel to be carried is lower than if a percentage of iso-octane in the mixture having low energy content fuel is used, so that more the same knock characteristics as the fuelin of the load carrying capacity is available for the question. payload. To perform the test for octane rating, a single-cylinder knock test engine is utilized. the VOLATILITY Two float chambers are incorporated in carburetor so -that the fuel being tested canbe Volatility is defined as the vapor-forming fed from one chamber and theiso-octane characteristicsof a substance. Since liquid heptane mixture from the other. The engine, fuels must be in a vaporous state to burn, under load conditions which will produceslight volatilityis an important property to bede- detonation, is operated alternately on the fuel termined in choosing a suitable fuel for an air- to be tested and the known test mixture. Atest craft engine. The volatility of the fuel has an of a mixture of iso-octane and heptane is found effect on its starting, accelerating, vapor lock- which exactly matches the antiknock valueof ing, and distribution characteristics. Gasoline the fuel under test in the opposite float chamber. is a very satisfactory fuel in this respect,since Thus, for example,if the fuel under test is it can be blended during refining to give thede- equal in antiknock characteristics to a mixture sired characteristics. of 70-percent iso-octane and 30-percentnormal heptane, the rating given the fuel is 70 octane. not ANTIKNOCK VALUE It is readily apparent that octane ratings may exceed 100 percent. The method of ratingfuels The antiknock value of a fuel (its ability to with an antiknock value greater than iso-octane resist detonation) is of great importance in air- is discussed in the following paragraphs. craft reciprocating engines. Due to thehigh compression pressures in the engine, brought Performance Numbers about either by high compression ratios, a high degree al supercharging, or both, some fuels As previously explained, if a fuel has an have a tendency to increase their rate of burning antiknock value greater than iso-octane,it during the combustion process, causing an ex- must be rated on a different scale. This scale plisive combustion called detonation. Detona- is called performance number and isobtained tion causes a loss of power and engine damage. by adding tetraethyl lead (ethyl) to isa-octane By use of a fuel of a high antiknock value, it is for a new reference fuel. possible to reduce detonation tendencies and When rating fuels for performance number, increase the power output and theefficiency of their antiknock characteristics are compared to an engine. Gasoline can bemanufactured and this new reference fuel. Thus, for example,if

128 .. Chapter 7RECIPROCATDIG ENGINE FUEL SYSTEMS 7

the fuel to be rated equals the antiknock char- driven fuel pumps, a maximum of seven electric acteristics for iso-octane plus 3 cm3 (cubic auxiliarybooster and transfer pumps, fuel centimeters) of lead per gallon, this fuel would quantity gages, and all necessary plumbing and be rated as having a performance number of 146. controls. This indicates than an engine operating on this Under normal conditions, fuel inthe wingtip fuel would be able to develop46percent more tanks, bomb bay tahks, and center section tanks power than if it were operating on straight iso- is transferred to the main tanks (outer wing octane. panel tanks) before being supplied to the engines. Fuel in the bomb bay tanks is first transferred Fuel Grades to the center section tanks before being transferred to the main tanks. Float valves in the When the fuel grade includes a number of 100 center section and main tanks, together with or less, this number indxcates the octane number, the transfer boost pumps, automatically ac- If the number is above 100, it is known as the complish fuel transfer, provided the fuel con- performance number. When the grade includes trol panel is placed in normal. two numbers such as grade 100/130 or grade 91/96,the first number indicates the rating at OPERATION lean mixture conditions and the second indicates the rating at rich mixture. Thus, grade 100/130 Control of the fuel system is accomplished indicates a lean mixture rating of 100 per- from the pilot's overhead control panel. Con- formance number (also 100 octane number) and trol knobs on the panel actuate electric motors, that the rich mixture performance number is 130. accessible within the fuselage, which in turn are The addition of tetraethyl lead to any fuel will cable-connected to the individual fuel selector increase its antiknock value in both lean and and crossfeed valves, located aft of each engine rich mixtures, but not to the same degree. The nacelle. The individual actuators, which position first and second figures in grade91/96both the fuel valves, can also be positioned manually refertooctane numbers of fuel containing in case of electrical failure. tetraethyl lead. In normal use, the fuel is supplied to the engines from the outer wing tanks. As the outer AIRFRAME FUEL SYSTEM wing tank fuel level drops, float valves automatically allow transfer of fuel in sequence The airframe fuel system provides a con- from the wingtip tanks, the center section tank, trolled means of receiving fuel from external and the bomb bay tank. In case of an emer- sources and supplying fuel from tanks and cells gency, fuel can be transferred from the center within the aircraft to the engines. The airframe section tanks to the engines. fuel system is made up of the main fuel system and the auxiliary fuel system. The main fuel Fuel Transfer system consists of fuel tanks, cells, and plumbing permanently mounted in the aircraft fuselage Normal fuel transfer is accomplished in and wings. The auxiliary fuel system consists the following sequence: of drop tanks mounted on pylongs under the 1. When the fuel level in the main tank wings or attached to the wingtips. drops to 3,600 pounds(600gallons), the float NOTE: Some of the larger aircraft have an valvein the number 3 cell opens, allowing internal auxiliary fuel system. The SP-2H, for fuel in the wingtip tank to be transferred to instance, utilizes two lightweight self-sealing the main tank. fuel cells that can be mounted side by side in the 2. When the fuel level in the main tank bomb bay. drops to2,880pounds(480gallons), the float The SP-2H fuel system includes six outer valvein the number 1cell opens, allowing wing panel cells and eight center sectioncells. fuel in the center section tank to be transferred Also included are two bomb bay and two wingtip to the main tank. tanks which are optional loading. Control of the 3. When the fuel level in the center section fuel system is accomplished by two engine- tank drops to 3,600 pounds (600 gallons), the - 129

1 00 AVIATION MACHINIST'S MATE R 3 & 2 float valve in the number 1 cell opens, allowing main tanks, center section tanks, wingtip tanks, fuel in the bomb bay tank to be transferred to and the bomb bay tanks. the center section tank. NOTE: Although the aircraft is normally NOTE: The fuel control panel incorporates equipped with circular 200 U.S. gallon wingtip a fuel flow diagram. By positioning the tank tanks, the elliptical 350 U.S. gallon wingtip tanks selector valvecontrols and fuel flow valve are interchangeable. If the aircraft is equipped controls to obtain unbroken lines, the course with the elliptical tanks, fuel loading must be of the fuel flow obtained under various selector limited to 180 U.S. gallons in each tank. valve settings is clearly indicates. Defueling Auxiliary Fuel TranSfer The SP-2H is defueled through the defuel In the event that fuel fails to transfer from valves(fueldrain Valves). The valves are the center section tanks to the main tanks, fuel mounted over the landing gear trunnion, just remaining in the center section tanks can be forward of the bulkhead, below the rear beam on obtained by selecting the center section tanks the inboard side of the nacelles, and at the aft as the engine feed tanks. end of the lower electronic compartment. The Fuel in tanks on one side of the airplane defuel valves are two-position valves which can can be transferred through the crossfeed line be operated only at the valves. When the valves to tanks on the opposite side, according to the are opened, fuel drains from the systemthrough settings of the fuel tanks selector valves. The the drain port in the valve. transfer-boost pump in the tank receiving fuel must be OFF, the transfer-boost pump in the FUEL CELLS AND TANKS (SP-2H) tank yielding fuel ON, and the boost pump high- low selector switch in the HIGH position. The aircraft fuel system consists of the following fuel cells and tanksouter wing tanks, Engine Supply center section tanks, wingtip tanks, and bomb bay tanks. Fuel from either outer wing tank or center The outer wing tanks include three fuel section tank can feed directly to one or both tanks installed in each outer wing panel between engines. In normal use, however, fuel is sup- wing stations 204 and 420. (Each tank is complied only through the outer wing tanks. The posed of two interlaced cells.) The cells are transferboost pumps ineitherthe center constructed oflightweight, bladdertype, section tanks or the outer wing panel tanks are nonself-sealing,orsemirigid,self-sealing capable of maintaining fuel pressure to an en- cells, depending on the manufacture date of the gine in case the engine-driven fuel pump fails aircraft. (provided the jet engines are not operating). The center section fuel cells are lightweight Fuel crossfeed is available in the SP-2H and is bladder type cells and are not of self-sealing used when an engine failure occurs or when construction. They consist of eight cells in- necessary to equalize fuel levels in the left and stalled in line in the wing center section, four on right wing tanks. each side of the centerline of the fuselage. The four cells on the left are interconnected and act Refueling as a single tank, and the four on the right are similarly interconnected. Although normal refueling of most models of The wingtip tanks are an integral part of the SP-2H aircraft is by gravity fueling through the center-mounted, circular nacells installed at thefiller units located in each tank, some models each wingtip. Each tip tank is a self-contained are refueled by connecting an outside fuel supply unit; the filler neck, drain valve, and transfer to the aircraft pressure fueling receptacle lo- pump are all easily accessible, and do not re- cated in the tip of the engine nacelle, mounted quire removal of any other structure. Quick- on the aft side of the rear main spar. The air- ;elease plumbing and electrical fittings make it craft should be fueled in the followingsequence plssible to jettison the tanks if desired.

130 l Ub .'9 Chapter 7RECIPROCATLNG ENGINE FUEL SYSTEMS

Provisions are incorporated in the bomb bay it not only prevents foreign matter fromenter- for two lightweight s311-sealing cells. The cells ing the carburetor, but also becauseof its loca- occupy the full length of the bomb bay and are tion at the low point of the fuel system,traps mounted side by side. When both cells are used, any small amount of waterthat is present in the they are plumbed together to act as one bomb bay system.Inmultiengineaircraft,one main tank. The cells may be jettisoned, if desired, as straineris usually installed in each engine all connections are of the quick-release type. nacelle. . In the strainer shown in figure '7-1,the fuel STRAINERS enters at the side, passes through the screen, and leaves at the top. While thefuel is passing Strainers are installed in the tank outlets, through the strainer body, all dirt orsediment and frequently in the tank filler necks. These are settles to the bottom, where it can beremoved of fairly coarse mesh and prevent only the larger by opening the drain cock. The draincock is particles from entering the fuel system. Other usually connected by a drain line to anoverboard strainers are provided in the carburetor fuel drain connection. inlets and in the fuel lines themselves. The The strainer should be drainedbefore each latter are fine mesh strainers. flight, and the screen removed andcleaned at The main fuel strainer shown in figure 7-1 periodic inspections, with extreme care exer- is provided with a fine mesh screen and is in- cised to prevent damage to the screen. stalled at the lowest point in the fuel system. The function of the main strainer is important; PUMPS

All aircraft used by the Navy areequipped with pressure feed fuel systems.The basic source for this pressure isthe engine-driven fuel pump, but auxiliary fuel pumps orbooster pumps are required in every pressurefeed system for several purposes: tosupply fuel pressure for starting the engine,to supply fuel to the primer system, and for use as an emergency pump in case of failure of theengine-driven unit. The type of pump widely used untilrecent years is the hand-operated wobble pump, nowrapidly being superseded in Navy aircraftby an electrically driven pump. Thiselectrically driven auxiliary pump may be of the sametype as the engine-drivenvpump or may be of the submerged type, called a submerged tank boosterpump.

Engine-Driven Fuel Pump

The purpose of the engine-driven fuel pump is to deliver a continuous supplyof fuel at the proper pressure at all timesduring engine operation. The type of pump in universal useat the present time is the positivedisplacement rotary vane type pump. A typical engine-driven pump of this typeand AD.45 a diagram showing the operationof the unit are Figure 7-1.Main fuel strainer. shown in figure 7-2.

131

1 U t . AVIATION MACHINIST'S MATE R 3 E.: 2 /a

Fuel pumps vary in design. Regardless of sary to incorporate a bypass valve in theengine-. variations in design, the principle of operation driven pump. Both the fuel pressure relief valve of all vane type fuel pumps is the same. and the bypass valve may be contained in the Since the engine-driven fuel pump is turned same mechanism. by a gear train in the accessory section of the engine,it is necessary to provide, within the Auxiliary Fuel Pumps pump itself, a means of varying the amount of fuel (under constant pressure) delivered to the An auxiliary fuel pump is provided in fuel carburetor to meet the varying demands of dif- systems in order to deliver fuel under pressure ferent engine power outputs. Constant pressure to the carburetor as required whenever the is maintained by a spring-loaded pressure relief engine-driven fuel pump is not operating; for valve. Figure 7-2 shows the pressure relief valve example, during starting or in case of failure of in operation, bypassing excess fuel back to the the engine-driven fuel pump. inlet side of the pump. Auxiliary fuel pumps are used during start- Before starting the engine, when the engine- ing to pump fuel to the carburetor and priming driven fuel pump is not turning, the auxiliary system, and may be used as an emergency source fuel booster pump is used for priming and to of pressure in the case of failure of the engine- deliver fuel under pressure to the carburetor. driven pump. The electrically driven booster In order that fuel pumped by the booster pump pump is also turned on for takeoff andclimb as will pass through the stationary engine-driven a standby pressure source and alsofor high pump on its way to the carburetor, it is neces- altitude flight, the latter to pressurize the fuel

RELIEF VALVE BYPASS PORTS THROUGH ADJUSTMENT FACE OF RELIEF VALVE RELIEF VALVE ADJUSTMENT RELIEF VALVE

DIAPHRAGM

BYPASS VALVE

SLIDING VANE

AD.46 Figure 7-2.Engine-driven, rotary vane type pump.

132

1U0 /0/ Chapter 7RECIPROCATING ENGINEFUEL SYSTEMS supply to the engine-driven pump in order to driven, are given in the appropriatetechnical guard against the possibility of vapor lock. publications for a particular aircraft orengine. The type of electrically driven pump that is General instructions are given here. submerged in the tank, and which serves to pres- When working on fuel systems, keep inmind surize the entire system between thetank and the potential danger in gasoline. Allsafety pre- thecarburetor operateson thecentrifugal cautions must be rigidly enforced. principle. These pumps are driven by4aplosion- Before removing a fuel pump, have a suitable container available for catching anyfuel proof motors and the design of tne impeller is sub- such that it allows only vapor-free hquid_fuel to which may be in the lines or pump. If the be pumped through the system. This type of merged type pump is to be removed, itwill be submerged pump is shown in figure 7-3. necessary to defuel the tank, or totransfer the In some of the later service type aircraft, fuel to other tanks of the system. electrically driven centrifugal pumps are used The fuel lines should be disconnectedfrom which have two pumping speeds providing for the pump before removing the holddownnuts. high-pressure and low-pressure outputs as se- The pump should be pulled straight awayfrom lected by the pilot. The low-speed position of the its mounting flange. It is usually necessaryto pump switch is selected by the pilot forlow- transfer the fuel line fittings from the old pump and medium-altitude cruise. The pilot selects to the pump to be installed. Comparethe new the high-speed position for takeoff, high-power pump with the old one toascertain that the pumping direction is the same. INLET andOUT- outputs, and high-altitude flight. The In addition to the purposes outlined above, an LET are marked on the head of the pump. auxiliary electrically driven fuel pump of the bypass valve must be installed on theoutlet side submerged type may be used to transfer fuel of the pump. from one tank to another through a crossfeed A new gasket should be used when installing line incorporated in the fuel system. the new pump. The holddown nutsshould be tightened to the proper torque with atorque Removal and Installation wrench. The nuts should be safetied as soon Specific instructions for the removal and in- as possible after beingtightened to the proper stallation of fuel pumps, both auxiliary and engine torque to eliminate the possibility of an over- sight. Carefully inspect the fuel lines and hose clamps, and replace them with newparts if necessary. Install the lines onthe fittings and tighten the hose clamps to the propertorque. Carefully inspect for fuel leaks under pressure.

FUEL SELECTOR VALVES One or more selector valves are providedin FUEL IN the system to accomplish the following: CELL 1. Selection of the tanks from which fuelis to be drawn. 2.Selection of the engine or engines to which the fuel is to go. 3.Selection of the tank to receive fuel in tank-to-tank transfer. IMPELLER 4. Routing fuel during refueling operations. ELECTRICAL 5. Stopping fuel flow. LEAD The size and number of ports, or openings, AD.47 in selector valves vary with the typeof instal- Figure 7-3.Submerged boost pump. lation. For example, a single-engine aircraft

133

1 U / AVIATION MACHLNIST'S MATE R 3 & 2 with two fuel tanks and a reserve supply re- Fuel Pressure Gage quires a valve with four portsthree inlets ' from the tanks and a common outlet. The valve The fuel pressure gage indicates the pres- must accommodate the fuel flow capacity of the sure of the fuel entering the carburetor. This fuel line, must not leak, and must operate easily gage may be included with the oil pressure gage with a definite "feel" or "click" when it is in and the cylinder head temperature gage in one the correct position. Selector valves may be casing, called the ENGINE GAGE UNIT. Most operated either mechanically or electrically. aircraft today have separate gages for each of these functions. They are mounted on the in- FUEL DRAINS strument panel of the cockpit, or at the flight engineer's panel, so that the pilot or the engi- One or more accessible drains are provided neer can read all of them at a moment's glance. at low points in the fuel system so that all fuel In multiengine aircraft, there is an individual may be completely drained, as necessary, to ef- gage for each function of the engine. fect repairs of the system. Drains are usually provided at the main strainer and at the bottom Fuel Flowmeter of each tank. It is normal practice to drain a small amount of fuel from aircraft before flight The fuel flowmeter is normally used only in to remove any water which may have accumu- multiengine aircraft.It indicates to the pilot lated within the fuel system due to condensation, (or to the flight engineer) the amount of fuel that or which may have been introduced into the tanks is being supplied to the carburetor, and for all with the fuel. practical purposes, the amount of fuel being consumed by the engine. A fuel flowmeter, FUEL GAGES usually calibrated in pounds per hour, is furnished for each engine of multiengine aircraft. The most commonly used instruments which furnish the necessary information concerning CARBURETORS the fuel system to the pilot are the fuel quantity gage, the fuel pressuregage, and the fuel flow- The objective of the carburetor is to mix meter. with the air going into the engine the proper weightof fuelfor all,operating conditions Fuel Quantity Gages in accordance with a predetermined mixture formula. The basic requirements of a carburetor Fuel quantity gages are mounted on the in- are the same, regardless of the type of carbu- strument panel in the cockpit, or on the flight retor employer or the model engine on which it engineer's panel in some multiengine aircraft. is installed. Therefore, in the following para- They indicate, either in pounds or gallons, the graphs the model 58-CPB11 carburetor and the total remaining fuel in each individual fuel tank. model PR-5852 master control are covered as On some aircraft,one fuel gage, called a typicalcontrols, and the model PR58T1 in- TOTALIZER, indicates the total amount of fuel jection carburetor is covered for comparison. remaining in all of the fuel tanks. Older type aircraft use a float system to determine the amount of fuel remaining in the TYPES fuel tank(s). This type of system is being replaced by the capacitance type system. The There are two types of carburetors in com- capacitance type system of measuringfuel mon use on naval aircraft todaythe float type quantity is more accurate in measuring the fuel and the pressure injection type. Of the two types, level, as it measures the fuel by weight instead the pressure injection carburetor is the most of in gallons. Fuel volume will vary with tem- widely used. perature (a gallon of gasoline weighs more when it is cold than when it is hot); thus, if it is meas- DESIGN AT IONS ured in pounds instead of gallons, the measure- Each carburetor used on Navy aircraft has a ment will be more accurate. model designation to identify the individual type. 134 Chapter 7-RECIPROCATING ENGINE FUEL SYSTEMS /a3

In the following paragraphs the meaning of each area of the enginemounting flange in square letter and number in the model designations is inches. MODEL LETTER.-The letter followingthe explained. Stromberg types are discussed first, major design followed by the Chandler-Evans. size number is used to indicate a change which distinguishes a newmodel from Stromberg preceding ones. The first part of the Stromberg designator is MODEL MODIFICATIONNUMBER.-The a prefix, consisting of a letter or seriesof let- number following the model letterindicates that ters and indicating the type of carburetor. there are only slight differencesbetween similar models. For example,PD12H1,PD12H2, and Stromberg types in common use are as follows: for minor NA-Natural atomization (commonly called PD12H3 carburetors are alike except the float type). differences, P-Pressure type with regulator valve at Chandler-Evans the fuel inlet. Another letter, which indicates the type of An example of a Chandler-Evansdesigna- barrel, always follows the prefix. The letters tion is 58-CPB11. It is interpreted asfollows: and their meanings on NA type carburetors are 58-Number of square inches opening atthe as follows: muunting flange. R-Single barrel, single float. CP-Constantpressure,directmetering 13-Double barrel, single float in chamber type. to the rear. B-Model change. An example is NA R9C2, and is interpret- 11-Model modification. The serial number of theChandler-Evans ed as follows: that is NA-Natural atomization. carburetor also contains information R-Single float. pertinent: 9-Barrel size. 1.First two numbers-year ofmanufacture. 2. Third numeral and letter. C-Major modification. indicates the 2-Minor modification. a. Designator number, basic parts list setting number of thecarburetor. The letters for the Stromberg P series basic are as follows: b. At.the present there are three R-Rectangular barrel. parts list setting numbers in use,13,000, 14,600, 13-Double barrel. and 49,300. An example is PD12K10, and is interpreted (1) 5B-Designator number for the 13,000 parts list number. as follows: (2) 5F)Designator number for the 12-Barrel size. 14,600 and 49,300 parts list number. K-Major modification. serial num- 10-Minor modification. 3. Remaining numerals in the SIZE NUMBER.-The number following the bercontain theshipping sequence number. type letter indicates the size of thecarburetor An example is 555F159, and isexplained as barrel. For a carburetor with cylindrical bar- follows: rels, each unit increase in size number, above 55-Shipped in 1955. the numeral 1, indicates an increase of one- SF-Parts list group 14,600. , -7 fourth inch in the barrel diameter. The basic 159-159th unit shipped in 1955. number (1) has a value of 1 inch in the NA series, The parts list number which isalsolocated and 1-3/16 inch in the P series. Eachadditional on the nameplate containsthe following informa- number above the basic number indicates a1/4- tion: inch increase in barrel diameter. The designa- 1. Numbers in front of the dashindicate the tion PD 12 would indicate a barrel diameter of basic parts group list. 3-15/16 inches, and NAR 9 would indicate a bar- 2. Alphabetical/numerical sufficfollowing rel diameter of 3 inches. the dash- For carburetors with rectangular bar- a.Indicatesdesignchangeswhich rels,the size number indicatesthe inside affect interchangeability of detail parts.

135

11, AVIATION MACHINIST'S MATE R 3 & 2 /cY

b. Carburetors having the same suffix stant and, therefore, any change in airflow to are interchangeable as to functional parts and the engine will result in a proportionate change installation. in fuel flow. c.Suffic numbers should be checked To compensate for the decrease in density against the section B allowance list or engine of the air as the altitude and/or air temperature logbook before installation of the carburetor. are increased, an automatic mixture control is provided. This consists of an altitude valve, OPERATING PRINCIPLES controlled by an oil and nitrogen filled bellows, placed in series with the boost venturi. A de- Although all carburetors are designed to crease in air density causes the bellows to ex- deliver the desired fuel/air mixture for all pand, moving the altitude control valve further engine operating conditions, they accomplish into its seat, thereby restricting the airflow this in different ways. Therefore, the operating through the boost venturi. principles of the 58-CPB11 and Stromberg carb- Five jets and a diaphragm-actuated "B" uretors are discussed separately in the follow- valve are provided in the carburetor to take care ing paragraphs. of varying mixture ratios called for by changing engine operating conditions. A sixth jet and six 58-CPB11 bleeds are utilized for flow limiting purposes. Under engine idling conditions, the desired Themodel 58-CPB11 carburetorisa mixture varies from that controlled by the air direct-metering pressure type carburetor that metering system. A throttle-operated idle valve delivers fuelto the spinner injection valve in the fuel discharge passage provides for con- in the correct proportion to the weight of the trol of the mixture. An adjustment on the linkage air passing through the throttle valves. The between the throttle and the idle valve provides carburetor meters fuel in the desired air/fuel a means for obtaining the correct idling mixture. ratioto meet the many differing conditions To compensate for slow reaction of the fuel under which the engine may be operated. It metering system at rapid acceleration of the maintains these _Air/fuel ratios automatically engine, a piston is provided at the rear end of throughout the operating range of the engine re- the idle valve. Sudden throttle opening will force gardless of the temperature or density of the a fuel charge into the discharge pressurebalance surrounding air or the altitude at which the line, raising the pressure on the balance dia- engine is operated up to its service ceiling. phragm of the regulator valve to provide im- Airflow to the engine is controlled by the mediate additional fuel necessary for rapid ac- throttle valve opening and is measured by the celeration of the engine. venturi. A boost venturi is used in the carburetor to amplify the measurement of the air- Stromberg flow. The air passing through the boost venturi is in proportion to the amount being consumed The Stromberg injection carburetor is a hy- by the engine. dromechanical device 'employing a closed feed The airflow, as indicated by venturi suction, system from the fuel pump to the discharge is used to control fuel flow to the engine through nozzle. It meters fuel through fixed orifices ac- the action of the pressure regulator assembly, cording to the mass airflow through the throttle which consists of a pressure regulator valve body and discharges it under a positive pressure. and three diaphragms in series. As the throttles The carburetor is an assembly of the fol- are opened, the venturi suction increases, caus- lowing units: throttle body, automatic mixture ingthe pressure regulatorto move open. control, regulator unit, fuel control unit, and This permits more fuel to enter the metering some have adapters. chamber until the fuel pressure against the fuel THROTTLE BODY.-The purpose of the diaphragm balances the metered suction dif- throttle body is to measure and control the air- ferential on the air diaphragm andthe discharge flow;all air entering the engine must flow fuel pressure on the fuel balance diaphragm. The through the throttle body. This airflow is meas- ratio of fuel forces to air forces remains con- ured, both by volume and by weight, in order that

136 Chapter 7RECIPROCATING ENGINEFUEL SYSTEMS id5--- the proper amount of fuel can be addedto meet to the idle valve and to thepilot's "throttle" control in the cockpit. theenginedemandsunderallconditions. travel of the Bernoulli's principle, which states that anin- The throttle stop limits the crease in velocity will cause adecrease in throttle valve and has an adjustmentwhich sets pressure is applied to the.boostventuri in order engine idle speed. of volume The main venturi increases theefficiency of togetan accurate measurement setting up the airflow to the engine. This low-pressure meas- the boost venturi by aiding in urement is vented tc chamber "B"(or low- low-pressure area. pressure side of the airdiaphragm), while a The impact tubes take asample car- sample of the carburetor inlet air isbeing buretor inlet air and direct it to theAMC and picked up by the impact tubes anddirected to then on to chamber "A." the automatic mixture control (AMC),which AUTOMATIC MIXT UR E CONTR OLThe directed on to purposeof the AMC isto compenssate for measures the air density and is due to chamber "A" (or the high-pressure sideof changes in air density and temperature the air diaphragm). The pressure differential altitude changes. The AMC is a sealedmetallic bellows. Inside the bellows are nitrogenand oil. ofthetwo chambers acting upontheair diaphragm is known as the air metering force, The nitrogen compensates forchanges in air (See density and temperature. The oil isused to which tends to open the poppet valve. Nitrogen is fig. 7-4.) dampen the effect of engine vibration. it is used, rather than some other gas,because it As air flows through the boost venturi, the same measured in accordance with Bernoulli'sprin- is chemically stable, or it remains when exposed to other materials. ciple.It is by measuring this low pressure that to re- we can calculate the airflow.At the same time, One end of the 1,allows is recessed this low pressure is used to operate theair ceive the needle, which in turn, issecured to the bellows by a snapring. Thereis also a spring diaphragm and establish the air meteringforce. needle at the point The throttle body controls the airflowwith that extends up against the be where it is attached to the bellows.The purpose the throttle valves. The throttle valves may the AMC is to either rectangular or disk shaped, depending on of the needle valve spring in valves are stabilize the movement of thebellows-operated the design of the carburetor. The needle, thereby preventing the size of theneedle mounted on a shaft which is connected bylinkage - valve seat restriction from beingchanged due [WARE MR to engine-vibration. The AMC is sealed at 28 inches of mercury absolute pressure; therefore, anychange in the existing atmospheric pressure will cause are- action of the bellows. As the AMCis taken to higher altitude, where it is exposedto a gradual but definite change in existingatmospheric pressure, the bellows will expandand tend to equal the outside pressure. This action ofthe bellows will cause the needle to move. Then, asthe AMC is brought back towards sealevel and the pressure on the outside becomesgreater, the bellows will contract. The AMC is located on thethrottle body and is so situated that the needle protrudesinto the passage through whichthe impact pressure passes to "A" chamber.(See fig. 7-4.) At altitudes, then, the expansion of thebellows will cause the needle to restrictthe flow of air to - auto- "A" chamber, causing a drop in"A" chamber Figure 7-4.Throttle body and of the pressure dif- matic mixture control(AMC). AD. 48 pressure and a lowering

137

11d AVIATION MACHINIST'S MATE R 3 & 2 / 06 ferentialbetween chambers "A" and "B." This At this point, a spring in the regulator unit will cause the fuel metering force to close the takes over the control of the valve. This spring poppet valve until the fuel metering force equals is known as the idle spring. It holds the poppet the air metering force. The AMC can be cleaned valve open in the idle range. The pressure regu- in the field, provided the lead seal at the point lated by the poppet valve is used to set up a of adjustment is not disturbed. "fuel metering force." The fuel metering force REGULATOR UNIT.The purpose of the will always oppose the air metering force, and regulator unit is to regulate the fuel pressure the two forces must always be equal, except in to the inlet side of the metering jets of the fuel the idle range, when the fuel metering force control unit. The regulator unit, then, is a "pres- overcomes the air metering force and the idle sure regulator." (See fig. 7-5.) The unit has spring comes in to aid the air metering force. at its disposal the pressure maintained by the The fuel metering force is set up across a fuel pump. This pressure is automaticallyregu- diaphragm. On one side of the fuel diaphragm, lated by the regulator unit accordingto themass there is metered fuel pressure, which is regu- airflow. The throttle body sets up a pressure lated by the discharge nozzle. On the opposite differential which, through passages, is vented side of the fuel diaphragm, there is unmetered to opposite sides of the air diaphragm. This is fuel pressure, which is regulated by the opening known as the air meteringforce. Attached to this of the poppet valve. The air metering force will diaphragm is a stem which has a poppet valve then regulate the fuel metering force in pi opor- on the other end. The poppet valve is arranged tion to the mass airflow through the throttle body. so thatit opens as the airflow through the The airdiaphragm separates chambers throttle body increases and tends to close as "A" and "B." The air metering force is set up the airflow decreases. As the throttle closes, across this diaphragm. there is a point at which the air metering force The fuel diaphragm separates chambers is no longer strong enough to open the poppet "C" and "D." The fuel metering force is set up valve. across this diaphragm.

VENT CHAMBER IDLE SPRING

SEAUNG DIAPHRAGM VAPOR SEPARATOR

BALANCE DIAPHRAGM

POPPET VALVE AIR DIAPHRAGM B DIAPHRAGM

'1 FuEL STRAINER MIXTURE CONTROL BLEEDS FUEL PRESSURE FUEL DIAPHRAGM GAGE CONNECTiON FUEL INLET

AD.49 Figure 7-5.Regulator unit.

138 114 /57 Chapter 7-RECIPROCATING ENGINE FUELSYSTEMS

Chambers "A" through "E": unit and the outlet pressure is controlledby the impact pres- discharge nozzle. 1. Chamber "A" is regulated the sure. The jets in the basic fuel control unit are 2. Chamber "B" is boost venturi pres-auto lean jet, the auto rich jet, andthe power the fuel sure. enrichment jet. The basic fuel supply is required to run the engine with a lean mixtureand 3. Chamber "C" is meteredfuelpressure, rich jet controlled by the discharge nozzle. is metered by the auto lean jet. The auto 4. Chamber "D" is unmetered fuelpres=adds enough fuel to the basicflow to give a sure, controlled by the openingof the poppet slightly richer than BEST POWERmixture when RICH valve. the manual mixture control is the AUTO 5. Chamber "E" is fuel pump pressure,position. The power enrichment jetlimits the controlled by the pressure relief valve onthe amount of fuel that can be added to theauto lean fuel pumP. jet in the late power range. The poppet valve is attached by its stem to The four valves in the basic fuel controlunit both the fuel and air diaphragms. A sealingare the idle valve, the powerenrichment valve, diaphragm, is located between "B" and "C"the regulator fill valve, and the manualmixture chambers to seal metered fuel pressurefrom control. These valves and their functions areas boost venturi suction. follows: the 1. The idle valve is a round, contoured The balance diaphragm balances out placed in action of the sealing diaphragm. needle valveor a cylinder valve The single faced poppet valve has a dia- series with all other metering devicesof the phragm to balance out fuel drag on the poppet basic fuel control unit. It is connectedby linkage that itwill valve. to the throttle shaft in such a way The vapor separator located in "D" andrestrict the fuel flowing at low-powersettings "E" chambers are float and needlevalve ar-(idle range). The idle valve metersthe fuel angements which permit vapor formedin the in the idle range only. carburetor to return to the fuel tank. 2. The manual mixture control is arotary The mixture control bleeds are in a passage disk valve consisting of a round stationarydisc between chambers "A" and "B," andthey pro-with ports leading from the auto leanjet, the cham- auto rich jet, and two smaller ventholes.Another vide for a circulation of air tbroughthese is held bers to make the AMC unit effective. rotating port, resembling a cloverleaf, The carburetor fuel strainer is a finemesh against the stationary disc by springtension screen located in theinlet to "E" chamberand rotated over the ports inthat disc by the through which all the fuel must pass as itenters manual mixture control lever. Allports and removedvents are closed in the IDLE CUTOFFposition. "D" chamber. The strainer must be the auto and cleaned on all periodic inspections. In auto lean position, the ports from FUEL CONTROL UNIT.-The purpose of the lean jet and the two ventholes are open.The fuel control unit is to meter and controlthe fuel port from the auto rich jet remainsclosed in flow to the discharge nozzle. Thebasic unit this position. In the auto rich position,all ports consists of three jets and four valvesthat are are open. From this it canbe seen that there arranged in series, parallel-, andseries-parallel are-three positions of the manual mixturecontrol hookups. (See fig. 7-6.) These jets andvalves lever which enable the pilot to select alean receive fuel under pressure fromthe regulatormixture or a rich mixture, or to stopfuel flow unit and then meter the fuel as it goesto the entirely. The idle cutoff position is used onlyfor discharge nozzle. The manual mixturecontrolstarting or stopping the engine. Fuel forstarting valve controls the fuel flow. By the use of proper is supplied by the primer. size jets and regulating the pressuredifferential 3. The regulator fill valve is a small poppet across the jets, the right amountof fuel is de- type valve located in a fuel passagewhich sup- livered to the discharge nozzle,giving the de- plies chamber "C" of the regulatorunit with sired air-fuel ratio in the various powerset-metered fuel pressure. In idle cutoff,the flat inletportion of the cam lines up with thevalve stem tings.It should be remembered that the provides a pressure to the jets is regulatedby the regulator and a spring closes the valve. This

139

11 AVIATION MACHEslIST'S MATE R 3 & 2

POWER ENRICHMENT VA LVE MANUAL MIXTUR E CONTROL

AUTO LEAN JET REGULATOR FILL VALVE .

AUTO RICH JET

i POWER ENRICHMENT JET IOLE VALVE Ab.50 Figure 7-6.Fuel control unit. means of shutting off the fuel flow to chamber the metering and will meter fuel on through the "C" and thereby provides for a positive idle late power range. cutoff. 5. Carburetors equipped for water injection 4. The power enrichment valve is another are modified by the addition of a derichment poppet type valve. It is in parallel with the auto valve and a dericnment jet. lean and auto rich jets, but it is in series with The derichment valve and derichment jet the power enrichment jet. This valve starts to are in senes with each other and parallel with open at the beginning of the early power range. the power enrichment jet.In the late power Itis opened by the unmetered fuel pressure range, the derichment jet and the power enrich- overcoming metered fuel pressure and spring ment jet deliver the same quantity of fuel as tension. The power enrichment valve continues the power enrichment jet installed in the basic to open wider and wider through the power range carburetor. until the combined flow of the valve and the auto ADAPTER.The purpose of the adapter is to rich jet exceeds that of the power enrichment jet. adapt the carburetor to the engine. This unit At this point the power enrichment jet takes over may also contain the discharge nozzle and the

140 LI 0 Chapter 7RECIPROCATING ENGINE FUELSYSTEMS

engines which is on the air side ofthe diaphragm. The I. accelerating pump. (See fig. 7-7.) On attached valve, using fuel feed valves, however, thedischarge diaphragm then rises, lifting the feed valve and the fuel is sprayed outthe nozzle. Secured nozzle is eliminated, since the fuel which is designed to serves the same purposeand is built into the to the nozzle is a diffuser discharge improve distribution andatomization of the fuel engine. Where a spinner injection three types of dif- valve is used in place of the dischargenozzle, into the airstream. There are the fusers used in adapter-mounteddischarge noz- the accelerating pump is usually housed on the bow tie. Two side of the throttle body, and the adapteris then zlesthe rake, the bar, and working other diffusers built into someengines are the nothing more than a spacer and has no fuel feed valve and parts. slinger ring used with the The discharge nozzle is a spring-loaded the spinner ring used withthe spinner injection valve which maintains metered fuel pressure. discharge valve. The acceleration pump isused to compen- Before fuel can pass through the discharge noz- fuel flow during rapid zle, enough pressure must be built up againstthe sate for the inherent lag in diaphragm to overcome the tension of the spring acceleration of the engine.

ACCELERATING PUMP

DISCHARGENOZZLE

AD.51 Figure 7-7.Adapter.

141

.1 1 AVIATION MACHINIST'S MATE R 3 & 2

CARBURETOR REMOVAL into the impeller, remove the carburetor. Install a protective cover on the carburetor mounting The removal procedures will vary with both flange of the engine immediately, to prevent the type of carburetor concerned and the type of small parts of foreign material from fallLg engine on which it is used. The ADR must al- into the supercharger passages. ways refer to the applicable technical instructions concerning the installation on which he is CARBURETOR INSTALLATION working. The general procedures will be much the same, regardless of the type of carburetor The procedures discussed in this section concerned. Some general precautions are listed are based on a typical pressure injection car- below. buretor. Make sure the fuel shutoff (or selector) Remove the pipe plugs from the bottom of valve is in the closed position. Disconnect the the carburetor and allow the flushing oil, if pres- throttle and mixture control linkages, lockwire ent, to drain from the carburetor. The draining the throttle valve in the closed position; discon- may be hastened by removing the fuel strainer nect the fuel inlet line and all vapor return, gage, and the plug in the fuel inlet. Also, remove the and primer lines.Figure 7-8 illustrates the plug in the vapor vent outlet. When all oil has installation connection points on a typical car- drained from the carburetor, replace the fuel buretor. strainer and plugs. If the same carburetor is to be reinstalled, Place the manual mixture control lever in do not alter the rigging of the throttle and mix- the AUTO RICH position and the throttle lever in ture controls. Disconnect the airscoop, or air- the OPEN position. scoop adapter, at the carburetor top deck. Re- Fill the carburetor with fuel of the type to be move the air screens and gaskets from the top used in service operation. This can be ac- of the carburetor. Remove the nuts and washers complished by injecting the fuel through the regu- securing the carburetor to the engine. Using lar carburetor fuel inlet, continuing the flow extreme care to insure that nothing is dropped until oil-free fuel flows from the discharge

VAPOR TRAP FUEL INLET OUTLETS VENT LINE PORT CONNECTION

MIXTURE CONTROL LEVER

PRIMER FUEL THROTTLE CONNECTION LEVER ---

FUEL INLET PRESSURE CONNECTION AD.52 Figure 7-8.Carburetor connecting points.

142

11 Chapter 7RECIPROCATING ENGINE FUEL SYSTEMS /// nozzle or from the fuel outlet on the fuelcontrol The carburetor is equipped with a derich- fuel unit,if the fuel transfer tube is not installed at ment valve, which reduces the amount of this time. During the flushing procedure, actuate being furnished by the carburetor to the engine. the throttle valve and the mixture controllever. The derichment valve, when actuated by the Turn off the fuel flow, plug the fuel inlet and water pressure, shuts off the fuel being de- vapor vent outlet, and then allow thecarburetor, livered through the derichment jet, eliminating FILLED WITH FUEL, to stand for a minimum of the extra fuel normally used for cooling.At 8 hours before being used on an engine. This is the same time the water-alcohol mixture is de- necessary in order to soak the diaphragms andlivered downstream of the carburetor in the render them pliable to the degree they were when blower throat and mixed with the air/fuel mix- the unit was originally calibrated. ture. The addition of the water-alcohol intothe Check the carburetor for proper lockwiring induction system and the vaporization of the before installation on an engine. fluid then supplies the cooling formerly pro- Remove the protective cover from the car- vided by the excess fuel. buretor mounting flange on the engine. Place the Water injection produces its effects by cool- carburetor mounting flange gasket in position. On ing the air/fuel charge, thus increasing the some engines, bleed passages areincorporated charge density; by direct cooling of the piston and in the mounting pad. The gasket mustbe installed cylinder, permitting the use of higher BMEP so that the bleed hole in the gasket isalined with without the danger of detonation; and by per- the passage in the mounting flange. Be certain the mitting the use of leaner, best power mixtures. opening to the metered fuel passage isfree of The water injection system of the SP-2H foreign matter and a new fuel seal gasket is in- aircraft is composed of the following compo- stalled. nents. The engines are equippedwith an individ- Inspect the induction passages for the pres-ual system of a water tank, strainer, tank drain ence of any foreign materialbefore installing valve, water pump (similar to the engine-driven the carburetor. Install the carburetor on the fuel pump but have carbon vanes instead of steel mounting pad and gasket; install the attaching vanes), power control unit, control switch, and capscrews and tighten them to the propertorque a circuit breaker. value; then secure the screws with lockwire. WARNING: The water injection fluid is com- Place the carburetor air screen lower gas- posed of distilled water and METHYL ALCO- ket, the air screen, and the air screen upper HOL. The FLUID IS A DEADLY POISON, for gasket in position on the top face of the car-which there is no known antidote. The vapors of buretor. Mount the carburetor header, or thethe fluid, if inhaled in sufficient quantities, will carburetor airscoop adapter, on the carburetor. have the same effect as if the fluid were taken Reinstall the fuel transfer tube, if used, andinternally. attach all lines, electrical cables, and control linkages. DIRECT FUEL INJECTION WATER INJECTION In the direct fuel injection system, air alone, Some aircraft, such as the SP-2H, haverather than a fuel/air mixture, enters the cyl- engines that are equipped with waterinjection inder through the intake port. The liquid fuel is systems. injected directly into tile combustion chamber. The water injection system enables thepilot The direct fuel injection system has many to obtain more power from the engine,at takeoff advantages over the carburetor system. When or during emergencysituations in the air, than the fuel is discharged directly into the cylinder, is possible under normal operatingconditions. the engine starts more readily. With air, instead The carburetor, under normal operating con- of an explosive mixture, in the induction system, ditions at high-power settings, delivers morebackfiring is practically impossible. In a direct fuel to the engine than the engine actuallyneeds. injection system, there is less danger of induc- This excess fuel is used to carry off heat thatistion system icing, since the drop in temperature developed in the cylinders during the combustioncaused by vaporization of the fuel takesplace process and is scavenged with theexhaust gases.within the cylinder. Acceleration is improved

143 AVIATION MACHINIST'S MATE R 3 & 2

also because of the positive action of the in- are timed to the engine crankshaft, so that jection equipment. In addition, direct fuel injec- the cylinder receives the fuel charge at the tion improves fuel distribution and reduces the correct moment in relation to piston position overheating of individual cylinders often caused and the ignition event. by variation in mixture strength due to uneven fuel distribution. The fuel injection system also Fuel Injection Nozzles gives better fuel economy than a system in which the mixture flowing to the majority of cylinders must be made richer than necessary in order A fuel injection nozzle (fig. 7-9) is mounted that the leanest cylinder will receive a suf- in the front of each cylinder. The nozzle is com- ficiently rich mixture. posed of the following partsbody, valve, valve The direct fuel injection system of the spring and seat, an adjusting nut, and a packing R-3350-34 and -42 engine consists of a master seal. When the pressure in the fuel injection line control (carburetor) for metering the fuel; a fuel reaches approximately 500 psi, the valve within flow divider; two engine-driven injectionpumps, the injection nozzle is unseated and the fuel is which divide and distribute the metered fuel, forced into the cylinder. The valve stem within distribution lines; and an injection nozzle in each the nozzle incorporates an augerlike section cylinder. which causes the fuel to swirl as it leaves the nozzle. This is to aid the atomization of the fuel Master Control as it enters the cylinder.

The master control is mounted on the engine in the position otherwise occupied by the carburetor. This unit measures the airflow and meters the corresponding volume of fuel to the injection pumps. The master control is essentially the same as the injection carburetor except that the metered fuel is directed to the injection pumps instead of being discharged into the induction system.

Pumps The two injection pumps are mounted on pads on each side of the supercharger rear housing, just below the master control. The pump on the right side serves the front row of cylinders; the pump on the left side serves the rear row of cylinders. Each pump contains nine plungers, which divide and distribute the fuel (metered by the master control) to the combustion chambers of the engine cylinders. Each plunger feeds one cylinder exclusively. Metered fuel from the master control is directed through a fuel flow divider to the two injection pumps. Each of the pumps receiveS an equal amount of the fuel from the master control. An adapter which is timed to the engine provides for the mounting of each pump. The splined drive shaft of the pump has a master spline, so that the pump can be mounted on the AD.53 adapter in only one position. The pump adapters Figure 7-9.Fuel injection nozzle.

144 Chapter 7RECIPROCATING ENGINE FUELSYSTEMS

No repairs of the nozzle or adjustments are coloration appears after a reasonablewaiting permitted in the field. If malfunctions occurin period, repeat the process on other tankunits the operation of a nozzle, it must be replaced until the leak is located. The dye willleave a with a new or overhauled nozzle andthe defec- stain which can be traced back to the sourceof tive one must be turned in to be overhauled or the leak even after the tank unit has beenemptied scrapped. and the drippage has ceased. NOTE: Do not return the coloredfuel tobulk FUEL SYSTEM MAINTENANCE storage tanks or trucks, as there Issufficient dye in a 2-ounce can to color 10,000gallons of Maintenance of the aircraft and engine fuel fuel. system is the responsibility of the ADR. This in- The colored fuel is suitable for use in air- cludes the entire system except repairs to blad- craft engines inasmuch as the dye doesnot have der and sell-sealing cells and integral fueltanks, a harmful effect on theusefulness of the fuel. which are the responsibility of personnel-of the If it is not necessary to empty theaircraft fuel be AM rating. tank to repair the leak, the dyed fuel may Location of fuel system leaks along with burned in the engine. Fuel from tanks testedwith general maintenance procedures and the rigging dye will remain colored until the tanks havebeen and adjusting of the various fuel systemcontrols filled and emptied several times. Stains onthe are discussed in the followingparagraphs. aircraft structure or clothing can be removed NOTE: Safety around fuels cannot be over- with aircraft fuel or an approveddrycleaning emphasized. Therefore, when any maintenance solvent. is performed on or around aircraft fuel systems, NOTE: When this method of leak detectionis all safety precautions must be strictly complied used,an entryis required in the Aircraft will be with. Logbook so that the user of the aircraft aware that the fuel color resultsfrom the use of daily fuel LOCATION OF LEAKS the dye and should be disregarded in analysis. The use of internal lines, fittings, andfuel activating devices in aircraft fuel systems pre- Pumps sents a problem in determining the locationof Check boost pumps for proper operationand fuel leaks. The most practical method consists andfor of adding a concentrated solution of afuel soluble correct pressure output. Check for leaks red dye to the aircraft fuel tank andwaiting for condition of fuel and electrical connections.Be the dye to appear in leaking fuel. sure that the drain lines arefree of traps, bends, A liquid red dye is available which can be and restrictions. Check the motorbrushes for added directly to the aircraft fuel tank.(Before wear. the dye is used to determine the source offuel leaks, any visible fuel leaks in the tanksand MAIN-LINE STRAINER plumbing must be eliminated.) If it is necessary to use dye to locate a hidden leak, select a Drain water and sediment from the main- method for filling the fuel tanks that will allow line strainer at each preflight inspection.Re- the testing of only one questionable tank at a move and clean the screen atthe periods speci- timc. Add the liquid red dye to thesuspected fied in the applicable technical publications. tank when it is one-quarter full, using afull Examine the sediment removed from thehous- 2-ounce can of red dye for each 100 gallons of ing. Particles of rubber are often earlywarnings tank capacity; rinse the can with fuel. of deterioration of hose or self-sealingtanks. NOTE: Never use more than one 2-ounce Check for leaks and damaged gaskets. can of red dye for each100 gallons of fuel. Completely fill the tank with fuel after FUEL LINES AND FITTINGS adding the dye and wait for signs of coloration from the leaking fuel. Avery smallleak may re- Be sure that the lines are properly sup- quire an hour or more for colorto appear. If no ported and that the nuts and clamps aresecurely

145

121 AVIATION MACHINIST'S MATE R 3 & 2 tightened. To tighten hose clamps to the proper gaskets and seals with new components, check torque, use a hose-clamp torque wrench. If this the new gaskets and seals for cleanliness, and wrench is not available, tighten the clamp finger- integrity, and insure that it is the right part for tight plus the number of turns specified for the the job. Mating surfaces should be perfectly flat hose and clamp. Tighten clamps only when the so that the gasket can do the job for which it is engine is cold.If the clamps do not give a designed. Screws, nuts, and bolts that retain seal at the specified toi que, replace the clamps, units together should be evenly tightened or the hose, or both. After installing new hose, torqued to prevent leakage past the gasket or seal check the hose clamps daily andtighten if neces- in the unit. sary. When this daily check indicates that cold flow has ceased (cold flow is the flowing of the RIGGING AND ADJUSTING rubber from the clamping area), inspect the clamps throughout the system. Replace the hose This section covers some of the basic pro- if the plies have separated, if there is excessive cedures and inspections to be used in the rigging cold flow, if there are signs of chafing, or if the and adjusting of throttles, mixture controls, fuel hose is hard and inflexible. Permanent impres- selectors, firewall shutoff valves, fuel pres- sions from the clamps and cracks in the tube or sure, idle mixture, and idle rpm. Adjustmentsof cover stock indicate excessive cold flow. Re- the idle mixture, fuel pressure, and idle rpm are place hose which has collapsed at the bends or general in nature and are discussed first. The as a result of misaligned fittings or lines if there EC-121K is used as a typical aircraft for the is any doubt of its serviceability. Some hose purpose of rigging and adjusting throttles, mix- tends to flare at the ends beyond the clamps. ture controls, fuel selectors, and firewall shutoff This is not an unsatisfactory condition and does valves. These procedures are given only to not indicate leakage. Inspect all hose connections acquaint the ADR with the rigging and adjusting forward of the firewall at each engine change, procedures and should not be used for actually and replace all defective hose. rigging the controls on the aircraft.

SELECTOR VALVES FUEL PRESSURE Rotate selector valves and check for free In order to maintain the 'correct fuel pres- operation,excessive backlash, and accurate sure delivery to the carburetor or master con- pointer indication. If the backlash is excessive, trol, the engine-driven fuel pump has a relief check the entire operating mechanism for worn valve screw which can be adjusted to the proper joints, loose pins, and broken drive lugs. Replace amount of pressure. This screw sets the spring any defective parts in the operating mechanism. tension on the relief valve to relieve the pres- Inspect cable control systems for worn or frayed sure on the "out" side of the pump whenever the cables,damagedpulleys,and wornpully pump output exceeds the amount needed by the bearings. carburetor. (See fig. 7-2.) The excess fuel is thus bypassed back to the inlet side of the pump. REPLACEMENT OF GASKETS, The pump also contains a bypass valve that SEALS, AND PACKINGS allows fuel under pressure from an auxiliary pump to pass through the engine-driven pump In order to prevent leakage of fuel, it is of when itis not operating.If the pressure at utmost importance that all gaskets, seals, and the discharge side of the pump exceeds that for packings be properly installed. Listed below are which the relief valve is set, the valve is raised some of the general precautions which should from the valve seat against the pressure of the always be observed. relief valve spring. Fuel then passes through When replacing units of the fuel system, it the opening thus made and back to the inlet side is necessary to check each part for cleanliness, of the pump. insure that all of the old gasket material is re- The bypass valve is held closed by pressure moved, and insure that none of the old seal re- of the fuel and a small spring when the engine- mains in the groove seat. Always replace old driven pump is in operation. When the engine-

146 124 Chapter 7RECIPROCATING ENGENIE FUEL SYSTEMS driven pump is inoperative, and fuel is forced cation is obtained. The adjustment is shownin through the pump by an auxiliary pump, the fuel figure 7-10. enters the pump at the usual inlet, but is pre- After the desired rich indication is ob- vented from passing directly to the outlet port tained, lean the mixture, one notch at a time, until by the stationary vanes, and therefore goes a point is reached where the manifold pressure through the bypass valve to the outlet port and rises directly from its stabilized value. This is to the carburetor. the rich best-power setting. Allow the engine to operate at idling speed for several minutes until the cylinder head IDLE MDCTURE temperature stabilizes at the minimumvalue. Reset the idle speed stops for the desired idling If,in making the idle mixture check, the speed. manifold pressurerisesdirectly from the Itis possible that the knurled adjusting stabilized value, the idle mixture is not exces- screw will not provide a sufficient rangeof sively rich,but may be richer than a "rich adjuStmenttopermit obtaining the desired best-power"setting.In this case, turn the idlemixturesetting. In this case, the idle knurled mixture-adjusting screw, located on the link must be disconnected and the screw eye left side of the carburetor, about four notches screwedin Or out of the threaded bush- CLOCKWISE toward RICH. Repeat the mixture ing. Screw it IN to lean the mixture and OUT check with the control lever. If the manifold to enrich the mixture. One revolution of the pressure does not now indicate an excessively screw is equivalent to approximately13notches rich mixture, enrich the mixture until thisindi- ofadjustingscrewrotation on Stromberg

.:UTDMATIC MIXTURE CONTROL UNIT ADJUSTMENT THROTTLE BODY AUTOMATIC MIXTURE REGULATOR UNIT CONTROL UNIT VAPOR VENT CDNNECTION MANUAL MIXTURE AND NEEDLE SEAT CONTROL LEVER IDLE SPRING ADJUSTmENT EMERGENCY FULL RICH VALVE

VApoR VENT FLOAT FULCRUM SCREW

POPPET VALVE COVER THROTTLE LEVER STRAINER COVER

IDLE SPEED ADJUST6ENT

FUEL INLET CONNECTION ADAPTER FUEL PRESSURE CONNECTION IDLE LINK

IDLE LINK BDLT FUEL CONTROL UNIT IDLE MIXTURE ADJUSTMENT

IDLE ADJUSTMENT LOCK SCREW FUEL LINE FROM FUEL CONTROL UNIT TO SPRAY NOZZLE AD.54 Figure 7-10,Pressure injection carburetor nomenclatureand adjustments.

147

.12,3 //6 AVIATION MACHINIST'S MATE R 3 & 2

view NOTE: As previously stated,the EC-121K carburetors and master controls. A cutaway for the following of this linkage is shown in figure 7-11. is used as a typical installation discussion. Prior to attempting torig or adjust IDLE RPM any controls, the followinginspection should be throttle at the accomplished. If the rpm obtained with the rod bear- idle position differs from the idle rpmspecified Inspect all bellcranks, cables, and (usually 600 ings for looseness,cracks,and corrosion. in the Service Instructions Manual Particular attention should be giventhe rod and rpm on an engine equipped withexhaust stacks collector bellcranks where the bearing isstaked. This and 450 rpm on an engine equipped with cracking and corro- rings), reset the idle rpm stop. The engine must area is subject to stress for igni- sion. The adjustable rod endsshould be in- be warmed up thoroughly and checked the number tion system malfunctioning, asdescribed pre- spected for damaged threads and of threads remaining afterfinal adjustment. viously. Throughout any carburetor adjustment for wear, and procedure, run the engine up periodically to The drums should be inspected the cable guards should bechecked for proper approximately half of normal rated speed to loosened, the clear the engine. position. If the cables have been With the engine idling, turn the eccentric tension must be set. screw in either direction from thelowest setting to increase rpm. Adjust theeccentric screw THROTTLE as required to increase ordecrease rpm. Open the throttle to clear out the engine;close the The throttles are actuatedby cable systems throttle, and wait for the rpm to stabilize. Re- to the fire- peat this operation until the desiredidling speed which extend from the flight station wall in each nacelle. Leversfor each throttle is obtained. system are located on the pilot'scontrol stand and the flight engineer's controlstand. The con- IDLE LINK trols that are forward of thefirewall consist of a pulley mounted in aswinging bracket sup- WAVE WASHER ported by the nacelle structure,and two paraDel rods extending from the pulleyto a double- BUSHING armed bellcrank on the mastercontrol throttle shaft. The swinging bracket willcompensate for WASHER engine vibration and movement sothat the throttle settings will not be affected.To rig the CASTLE NUT throttle control, proceed as follows: ; %/"ZA :AD 1. Install a rigging pin in thefirewall pulley BOLT jI w and its bracket. 2. Adjust the push-pull rodsbetween the COTTER PIN s firewall pulley and the mastercontrol so that he throttle shaft is restingfirmly against the SCREW EYE meas. adsed stops and the pulley shaftcenter on the swinging bracket is the correctnumber of inches THREADED BUSHING IN:17: from the firewall. 3. Then adjust the cabletension inthe sys- HEX LOCK SCREW , that the pilot's k.....;;a01'..nn. tern to the proper tension so of cushion IDLE LEVER throttle lever has the correct amount in the closed position. mol position of the INDICATOR 4. While maintaining the pilot's lever, adjust the turnbucklesat the flight AD.55 engineer's control stand so thatthe flight en- amount of Figure 7-11.Idle mixture gineer's lever will have the correct adjustment linkage. cushion.

148 7/7 Chapter 7RECIPROCATING ENGINE FUELSYSTEMS rigthem, proceed 5. Recheck the cable tension,the throttle control stand. To as follows: shaft position, and the positionof both throttle control lev- levers in the cockpit. 1. Place the flight engineer's and check ers in the CLOSEDposition for the valves to 6. Then remove the rigging pin selector valve the throttle lever from both positionsin the cock- Nos. 1, 4, and 5. The three-way that there is a full control levers are to be placedin the midtravel pit several times to ascertain No. 3 positions, freedom of movement. position, or in the No. 2 and respectively. MIXTURE CONTROL LINKAGE 2. Adjust the cable tension tothe proper control is amount so that the controllevers to Nos. 1, The mixture control on the master amount of cushion cable operated from the flightengineer's control 4, and 5 have the proper swinging bracket in the CLOSED position.Remove the rigging stand to a pulley mounted on a amount of cush- on the overhead of the nacellestructure forward pin and check for the proper the mixture ion when the levers aremoved to the OPEN po- of the firewall. The bellcrank on selector valve control rod is connected to thispulleyby a push- sition.While the three-way assembly per- controlleversareinthe MIDposition, pull rod. The swinging bracket of tension on the forms the same function here as theswinging check for the proper amount throttle. cables. bracket assembly performs for the should The rigging of the mixturecontrol is as NOTE: All cable tension adjustments follows: be made in relation to temperature. rigging pin in the firewall 3. Recheck allcable tensions, position 1.Installa andtheposition pulley and bracket. ofthecontrollevers, onthe master ofthevalve actuating levers.Also check 2. The mixture control lever throughout control is to be placed in theIDLE CUTOFF forsmoothness of operation position. the operating range. 3. The push-pull rod betweenthe master control and the swinging bracket onthe firewall FIREWALL SHUTOFF VALVES should be adjusted until the swingingbracket is the proper distance from thefirewall. When this The four emergency fuel shutoffvalves are is done, slip the bellcrank ontothe mixture con- These are trol and then tighten it down againstthe serra- located upstream from the engines. manually operated two-way valvesand operate tions. air, oil, and hydrau- NOTE: Observe the precautions of adjusting in conjunction with the blast lic emergency shutoff valves.They are con- the rod end assembly so that it hassufficient panel in the thread engagement. trolled from the overhead control 4. Adjust the cable portion of thelinkage flightstation.The rigging procedure is as follows: so that the control lever inthe cockpit is in the hole. IDLE CUTOFF position. Then tighten thecables 1.Insert pin in the pulley rigging 2. Place valve lever in the OPENposition. to the proper tension. shut- 5. Remove the rigging pin and then operate 3. Place the flight station emergency travel sev- off lever in the OPEN position. the system through the full range of the proper eral times to insure that the mixturecontrol 4. Adjust the push-pull rod to to length and install on the valvelever. Make final plates are in the proper position in relation for the prop- the lever at the flight engineer's panel. adjustment as necessary to the rod er alignment of thelevers. FUEL SELECTOR 5.Operate the flight station leverto the check the The fuel tank selector and shutoffvalves OPEN and the CLOSED position to are cable operated from theflight engineer's proper operation of thevalve.

149 CHAPTER 8

RECIPROCATING ENGINE LUBRICATINGSYSTEMS

The ADR must be familiar with the lubri- degree of cohesien (sticking together) between cating system of aircraft engines, including oil the molecules of an oil determines its viscosity. tanks,oil coolers, temperature controls, and (Molecules are the smallest units of matter that strainers. He should know the operating char-retain chemical identity with the substance in acteristics of the system, particularly the oil mass.) Thus, the molecules of the more viscous flow and the oil temperature. This knowledge (high viscosity) oils bind themselves together will aid in obtaining the optimum performance, with far greater force than that existing in in terms of reliability and durability, from thelower viscosity oils where the bond of force engine. between molecules is much weaker. AVIATION LUBRICATING OIL Antifriction Oil is the lifeblood of the aircraft engine. If the oil supply to the bearings should cease, The lubricant should have highantifriction within a matter of seconds the lubricating films characteristicsto reduce the frictional re- would break down and cause scoring, seizing, sistance of the moving parts when separated and burning of the vital moving parts. Fortu- only by thin oil films. An ideal fluidlubricant nately, the engine oil pump and oil system are provides a strong oil film to prevent metal-to- dependable and, like the heart and circulatory metal contact and to create a minimum amount system of the human body, quietly perform their of oil friction or oil drag. function so well that their importance is often Lubricants should have the property of forgotten. resisting the wiping action that occurswherever microscopic films are used to preventmetallic OIL QUALITY REQUIREMENTS contact. The theory of fluid lubrication isbased on the actual separation of the metallicsurfaces For properlubricationoftheaircraft by means of an oil film. As long as the oil film engine, the lubricating oil must meet several isnot broken, the internal friction, or fluid very important requirements. friction, of the lubricant takes the place of the The conditions in both reciprocating and metallic sliding friction which otherwise would turbojet engines are so varied that one lubricant exist between the parts. could scarcely -be expected to produce ideal Chemical Stability lubrication conditions on all bearing surfaces. However, satisfactory results are obtained in a A lubricant shouldofferthe maximum well-designed engine with a lubricating oil having resistance to the formation of harmful deposits all the desirable properties in varying degree. on the metal parts. It should notattack or injure metals in the lubricated parts. Viscosity Cooling The internalfriction of the oil, or its One reason for using liquid lubricants is resistance to flow, is known as viscosity. The that they can be readily pumped or sprayed.

150

126 I/9 Chapter 8RECIPROCATING ENGINE LUBRICATING SYSTEMS

Regardless of the method of application, the oil Sealing absorbs the heat and later dissipates it through cooling devices. Many engine parts, especially The oil film on the various surfaces also those carrying heavy loads at high rubbing veloc- acts as an effective pressure seal particularly ities, are lubricated by oil under direct pressure. between piston, piston rings, and cylinder wall. Where direct pressure lubrication is not prac- The oil film also aids in sealing the various tical, a spray or mist of oil provides the required parting surfaces between various sections of prot ection. the engine. Corrosion Preventive FUNDAMENTALS OF LUBRICATING OIL A film of oil over the metal surfaces isolates the surfaces from the atmosphe-9 and combus- Lubrication in its various forms serves tion fumes, and aids in corrosion prevention. five purposes. They are as follows: 1. Reducing friction. Cleaning 2.Cooling the engine. As the oil is pumped through the bearings 3. Sealing various clearances in the engine. and flows over the various engine parts, it picks 4. Preventing corrosion. up various impurities and carries them through 5.Cleaning the engine. the oil system to the strainer where they are filtered from the oil stream. The impurities Friction Reduction may include the following: Lead and carbon particles produced by combustion, water, dust Friction (resistance to relative motion be- from the atmosphere, and metal particles from tween two bodies) produces heat. In aircraft worn or defective engine parts. engines, it is imperative that this friction and TYPES OF LUBRICANTS heat be kept to a minimum. The presence of a lubricating film between moving parts serves Lubricants may be classifiedby types this purpose. Due to its adhesive qualities, the according to their source or origin. ANIMAL lubricant sticks to the moving solids. The force OILS are not suitable lubricants for internal- which tends to hold the lubricant particles to- combustion engines, because they form fatty gether is known as cohesive quality. The lubri- acids, which will cause corrosion when exposed cant tends to separate into layers in such a to high temperatures. VEGETABLE OILS have manner that the resultant friction is that pro- good lubricating qualities, but break down (i.e., duced between the layers of lubricant rather change in chemical structure) when subjected than between the two solids. to longperiodsofoperationininternal- combustion engines. MINERAL-BASED LUBRI- Cooling CANTS are usually divided into three groups: Solids, semisolids, and liquids: As the oil is circulatedthrough the bearings Solids and splashed or sprayed on the various engine parts, it absorbs a great amount of heat. The Solidsincludemica,soapstone, and heat produced by friction and by the combustion graphite.Graphite, when in powdered form, process must be reduced and controlled. Thus, serves to fill the low spots in bearing surfaces oil cooling is an important factor in keeping the to form a smoother antifriction surface. Solid engine temperature within the proper limits lubricants do not dissipate heat rapidly conse- and is particularly important in cooling the quently,theiruseisrestrictedtolow- pistons and cylinders of reciprocating engines. temperatur e conditions. As the oil is pumped through the engine, the Semisolids temperature of the oil is greatly increased by absorbing heat from the engine. The oil then Semisolids are greases of the type used for carries the heat off to the oil coolers where steelbearings. They give excellent service it is dissipated. provided they are changed periodically.

151

12r AVIATION MACHINIST'S MATE R 3 & 2

oil. Operating an engine for anextended period Liquids of time below 60° C (140° F) mayresult in a oil, which Liquids are used as lubricants for internal-. buildup of a water emulsion in the combustion engines. They may be pumped or can contribute tothe precipitation of sludge that would normally be held insuspension by the sprayed, they provide good cushioning, they are oil. All effective in absorbing and dissipating heat, and dispersant additives in MIL-L-22851 engine turnups should be performedlong enough they remain chemically stable overlongperiods stabilize at the level of time under normal operating conditions. for the oil temperature to specified in the applicableAircraft NATOPS Flight Manual and for at least10 additional CLASSIFICATION OF water that LUBRICATING OILS minutes in order to boil off any may have condensed inthe oil. MIL-L- Aircraft enginelubricatingoilsare The dispersant oil, specification 22851, is basically a grade 1100oil, as men- classified as listed in table 8-1. dispersant type NOTE: All Navy and Marine Corps recip- tioned before. The commercial oils, which are essentially equivalentto MIL-L- rocating engines use,a single grade of ashless identified as dispersant type oil purchased under Specifica- 22851 oils, are available and are tion MIL-L-22851, Type II. This is basically a AeroShell oil W-100 or W-120 andHumble/Esso grade 1100 oil with additives to improveoxida- oil E-100 or E-120. tion resistance, to hold in suspension sludge and varnish forming particles, and to reduce foaming FACTORS AFFECTING TRANS- tendencies. The additives do not form ash when MISSION OF LUBRICANTS burned and therefore will not contribute to that greatly spark plug fouling deposits. Standard oildilution There are several factors affect the efficiency of transmittingpressure procedures can be used with this type oil during These are cold weather operations without hazard of exces- oil through the lubrication system. sive sludge breaking loose in the engine,which discussed in the following paragraphs. can occur when using anonadditive type oil. Cold weather operation often causes engine Foaming oil-inlet temperature to drop below the minimum alllubricat- required for evaporation of the productsof Foaming is a basic problem in fuel) ing systems. It is created byspraying oil from combustion (water and partially burned couplings and also by which blow past the piston and condense incold jets to the bearings and

Table 8-1.Classification oflubricating oils. Use NATO number MIL spec & grade Early turbine engine lube oil. 0-133 MIL-0-6081 Gr. 1010 fuel system preservative andoil. 0-123 MIL- L-22851 Ashless dispersant piston engine Typein oil. (Used principally by the Army for small aircraft engines.) 0-128 MIL-L-22851 Ashless dispersant piston en- Type II gine oil. MIL-L-7808 Three centistoke turbine engine 0-148 synthetic lubricating oil. 0-156 MIL- L-23699 Five centistoke turbine engine and gearbox oil.

152

12cs Chapter 8RECEPROCATING ENGINELUBRICATING SYSTEMS 292/ the churning effect inducedby the accessory DRY SUMP SYSTEM of the drive gears and scavenge elements The dry sump system is themost widely lubricating pump. used system in aircraft engines. Inthis system separate Heat Expansion the main oil supply is carried in a tank.Oildraining from the various engine the oil parts is collected in one or more sumpsand is In dry sump lubrication systems, to the tank is provided with expansion space,which returned by means of a scavenge pump the oil tank. Some of the larger enginesused in the allows for foaming and heat expansion of attached to oil. In addition, oil tanks are sometimes pres- Navy have two or more sumps surized slightly or vented to atmosphereto various sections of the engine,with separate partly retard foaming and at the sametime to scavenge pumps located in each sump. apply a head pressure on the oil at thelubri- All radial aircraft engines havethe dry sump lubricating system.It is obvious that no cating pump inlet to assure a morepositive be carried in the flow. Also, de-aerator trays are sometimesused great amount of oil could wherein the air crankcase of an engine of thistype without to separate air from the oil, Also, the great escapes to the outside via the ventline. flooding the lower cylinders. and amount of heat that is absorbedby the oil in In the wet sump oil system, foaming makes the heat expansion space is provided inthe crank- its movement ghroughout the system use of an external coolingsystem necessary. case since the oil levelonly partly fills the for the casing. De-aerator trays are also usedin most The complete system required from the lubrication of a dry sump engine issubdivided crankcases to make easy air removal interconnected, sys- oil, whereby air escapes through the oilbreather. into two separate, though tems; the engine internal lubricationsystem and the external lubrication system. Temperature Extremes The engine internal lubricationsystem consists of all the pressure and scavengepumps, devices,oil pas- The effectof temperature extremes on strainers, pressure control engine lubricating oil also affectsthe flow of sages, and allother components the engine pressure oil. A reciprocatingefigMe may be manufacturer incorporates into hisproduct. 100° F or The external lubrication systemincludes started where the air temperature is which the de- more, and within a shortperiod of time the all the oil system components altitude where signer of the airframe incorporatesinto the aircraft may be at 25,000 feet temperature the air temperature is approxrhatNy-30° F. aircraft. These include all storage, extrenie will greatly control, and external oil systemcomponents, Naturally, this temperature and con- affect the viscosity of the oil andOlow down its together with the necessary oil lines However, since the lubribating oilis nections to the engine lubricationsystem, as flow. well as oil temperature and oil pressureindi- antifreezing,it will not congeal, althoughthe higher than they cating systems. An oildilution system is oil pressure readings will be discussed would ordinarily be at sea level. incorporated in some aircraft. It is in later paragraphs. Efficiency of the EXTERNAL OIL SYSTEM Oil Venting System of Although the arrangement of the oil systems Another factor which affects the flow varies widely, as do the oil through the lubrication system isthe effi-, in different aircraft construction details of the variouscomponents, ciency of the oil venting system. If the pressure all parts of in the bearing compartments is notcontrolled, the functions and operations of from the main these systems are similar. Thestudy of one the oil does not flow properly Mate R will bearing oil jets. Some engines usevents alone; system by the Aviation Machinist's system to make clear the general operationand mainte- others,a breather pressurizing systems. assure proper oil flow tothe bearings. nance requirements of all

153

1 2 AVIATION MACHINIST'S MATE R 3 & 2

In any installation, the equipment is com- 4. Manual shutoff valves. pactly arranged between the engine and the 5. Atemperature-controlled diverter fire-wall and placed as closely to the engine as valve. practicable. Most of the components are fitted 6. A capacitance oil quantity system. into or attached to the engine or the engine 7. An oil dilution system. mount structure. 8.All the necessary plumbing. In multiengine aircraft, each engine has its Intheoperationofthisparticular oil own independent od. system, with some installa- system, the temperature is maintained auto- tions providing a reserve tank from which oil matically or by manual operation. Not all oil can be transferred to the individual engine. The systems in use in present-day naval aircraft components of the SP-2H external lubrication are automatic in operation and thus a closer system, their relationship with each other, and watch of the oil temperature must be maintained the path of flow of the oil in the system are at all times. illustrated in figure 8-1. Engine oil is supplied through a standpipe Each engine is provided with a complete in the tank sump; propeller feathering oil is external oil system, which includes the following supplied from a point below the engine oil units: standpipe level (multiengine aircraft only). Oil 1. A self-sealing tank and hopper assembly. flowing through the system makes a complete 2. Anoil foam tank,oilcoolers, and cycle from the tank to the ,engine and back to temperature regulator valves. the tank. 3.Oil cooler doors and.thermostatic con- Oil flows by gravity feed from the tank to trol system. the engine rear oil pump. A direct line from

OIL FOAM EXPANSION LEFT ENGINE TANK OIL TANK

DIVERTER VALVE

DRAIN VALVE

PROPELLER EMERGENCY FEATHERING aSHUTOFF PUMP 1.1111.14 VALVE DRAIN VALVE

SHUTOFF LEFT OIL DILUTION VALVE ENGINE Y-ORAIN SOLENOID VALVE FUEL VALVE TRAINER AIR EXIT DOOR TEMP REGULATING TH ERMOSTATIC VALVES CONTROL UNIT

MANUAL CHECK VALVE

OIL SUPPLY 4,1001* PROPELLER FEATHERING HOT RETURN TO COOLER \reftOIL DILUTION AIR EXIT DOOR COLD RETURN TO TANK NM DRAIN FUEL ACTUATING UNIT COLD RETURN TO HOPPER 0 VENT

AD.86 Figure 8-1.External oil system schematic.

154

d u /a3 Chapter 8RECIPROCATING ENGINELUBRICATING SYSTEMS

proper operating temperature.As the tempera- thetank carries the oil to the engine.Oil tank is returning from the engine is routedthrough an ture rises, the remaining oil in the oil temperature regulator valve. Theregulator warmed until it reaches the properoperating cooler(s), temperature. How this is accomplishedwill be valve(s) are attached to theoil to the which dissipate excess heat from the oil. explained later in the section pertaining Oil flows from the regulator valvethrough oil diverter valve. The oil tank can be cleaned with anapproved a thermostatic control unit, wherethe tempera- tetra- ture of the oil affects the positioning ofthe drycleaning solvent. Do not use carbon chloride or any causticcleaner.If a new oil cooler doors controlling the amount of air failure, flow passing through the oil cooler. engine is installed because of an engine Before the oil completes its cycle, it flows clean and inspect the inside of the tankand its component parts. Make certainthere are no through the temperature sensitive elements of present in thedivertervalve.This valve determines metallic particles or foreign matter whether the oil from the engine is returned to the tank which could be recirculated,possibly the main part of the tank or to the hopper causing another engine failure. The tankshould within the tank. During oil dilution, gasoline is be drained at the "Y" drain valve and atthe tank plate should introducedintotheoilsystem through the sump drain valve. The tank cover temperature sensitive elements of thediverter then be removed and the inside ofthe tank thoroughly cleaned. See figure 8-2 for descrip- valve;thevalve allows the mixture to be returned only to the hopper, where it isstored tion of the oil tank. until the engine is started again. An emergency shutoff valve is installed Expansion Tank inthe oil supply line at the firewall. This shutoff valve is operated by the emergency The oil foam expansion tank is notfound in most external oil systems, as thefoaming space shutoff lever mounted in the overhead at the tank itself. flight station overhead control panel. for the oil is incorporated in the oil The SP-2H oil foam expansion tank is analuminum type tank attached tothe top surface of the Tank upper stress panel and shaped tofit beneath the lines The oil tank in this particular system may enginenacelle fairings. Two plumbing type oil tank. It connectthe foam tanks with the oil tanks, or may not be a self-sealing to expand into the foam may also be a bladder typetank, depending on allowing foaming oil This is also tank. A third line vents the tank to theengine. the bureau number of the aircraft. gallons and true of other type of aircraft;therefore, always The foam tank has a capacity of 20 check the Maintenance Instructions Manualfor is protected by an insulated covering. the specific information needed. The tank is serviced through acappedfiller Oil Cooler and Temperature Control of the well which is accessible from the top heat wing. The filler well has a scupper drainline The oil cooler is designed to dissipate attached to it to drain excess oil over theside. picked up by the oilinits flow through the Each tank has a capacitancetype quantity engine, and to dissipate that heat to theatmos- transmitter. Each tank in this systemhas a phere. The amount of heat dissipated, orthe regulation of the oil-out temperature, is con- total capacity of 87 U.S. gallons. The tank can They be filled with 80 gallons of usable oilplus 2.5 trolled by various valves of various types. gallons which are retained in a wellin the exercise temperature control tyj routingthe oil propeller. through one of two paths through the oilcooler bottom of each tank for feathering the altogether when the This system also incorporates a20-gallon foam or bypasses the oil cooler expansion tank separate from the main oil tank. oil temperature is low enough.Additional tem- During cold starting operations, oil is re- perature regulation is provided bythe oil cooler quickly exit doors, which regulate the air flowthrough turned only to the hopper where it is shutters may returned to the engine. In this manner, asmall the cooler core. These doors or volume of oil may be quickly warmed tothe be thermostatically controlled as shownin the

155

131 AVIATION MACHINIST'S MATE R 3 & 2

sktIt.ftio

7 DETAIL A OIL TANK SUMP FITTINGS, DRAIN VALVE AND RETURN 10 LINE FITTINGS 11 12

A 13 14

_ . - Iti .

44'NN4 NOTE: ;191ff-' LEFT OIL TANK SHOWN- 7 RIGHT OIL TANK SIMILAR (aC,N.

OP% 004 16

AD.57 1.Diffuser cap. 11.Oil return to hopper. 2.Strainer. 12.Flapper valve. 3.Fillercap. 13.Diverter valve. 4.Quantity transmitter. 14.Sump assembly. 5.Oil cell. 15.Oil return to tank. 6.Dilution line. 16.Hopper assembly. 7.Scupper drain line. 17.Propeller feathering line. 8.Oil to diverter valve. 18.Sump drain valve. 9.Oil return line. 19.Sump fitting. 10.Baffle. 20.Oil to engine. Figure 8-2.Oil tank assembly.

156 7,C-- Chapter 8RECIPROCATING ENGINELUBRICATING SYSTEMS schematic diagram of the external oil system the oil cannot return through port B, butmust manually positioned by flow through the cooler, returning through portC in figure 8-1, or may be past the an electrically operatedscrewjack. across the thermostatic valve element, The SP-2H has two oil coolers mounted side check valve, and to the "oil out" port.(See by side for each engine installation. They are fig. 8-3.) mounted directly under the accessory section of Apart from its thermostatic function, the the engine. Each includes a17-inch aluminum surge valve overrides the naturalresistance of cooler upon which is mounted an oiltemperature the surge spring when the pressuredifferential regulator valve. The two oil coolers are con- between the OIL IN and the OIL OUT port nected in parallel in the oil return line.(See exceeds 55 psi. As the pressure dropsbelow 55 fig. 8-3.) psi, this spring forces the thermostatic surge Each oil cooler consists of a central core, valve back into position. This purelymechanical its which iscompletely enclosed by a warmingaction of the surge valve in no way affects jacket or muff. The core is built up of thin wall thermostatic action. aluminum tubes laid side by side horizontally. The thermostatic valve directs theflow of The tubes are divided into layers byhorizontal oil according to the oil temperature,varying baffles. The baffles are open at alternate ends, flow through the cooler core to maintain proper causing the oil flow to reverse at eachbaffle. temperature. This valve also operates as a A drainplug is provided at the bottom ofthe spring-loaded relief valve when pressure devel- warming jacket. (See fig. 8-4.) ops after it is closed. It willrelieve when the TEMPERATURE REGULATOR VALVE.A pressure differential acting on the valveexceeds temperature regulator valve is mounted on each 40 psi. The poppet check valve preventsoil the oil cooler. The valve automatically directs oilflow from backing into the cooler core when through the cooler passages and also relieves is under pressure. surges and excess pressures whichmight cause AIR SYSTEM.The cooling capacity of each damage to the cooler by bypassing the oilwhen- of the oil cooler assemblies depends uponthe ever a pressure buildup occursduring a cold amount of air that is allowed to passthrough the start or other adverse pressure conditions. cooler. Airflow through the cooler isgoverned In operation, the temperatureregulator by a controllable oil cooler door,which is located so that it restricts the opening of theoil valve worksin the following manner under by an normal conditions: cooler exit duct. The door is actuated The thermostatic surge valve bypassesthe electrically operated screwjack. A four-position return oil through the temperatureregulator switch on the copilot's console controlsthe valve until the oil temperature rises to ap-electrical circuits to the actuator. The four proximately 39.5° C so that excessive pressure switch positions are OFF, OPEN, CLCSE,and is not imposed upon the cooler. Asthe oil AUTOMATIC. temperature rises above 39.5° C, thether- (NOTE: Some aircraftoilcooler door mostatic surge element gradually opensthe oil installations are not automatic and the position cooler inlet valve while closing the disc valve. of the doors is maintained by the pilot,copilot, With the oil cooler inlet valve open and thedisc planecaptain,or flight engineer.) With the valve closed, the oil flows through thecooler switch in AUTOMATIC, the position of the oil inlet valve port (port A) into the cooler, through cooler door (and therefore the oiltemperature) the cooler bypass and back into the temperature is automatically regulated by athermostatic regulator valve through port B, throughthe unit through which the oil passes. thermostatic valve port into the chamber con- DOOR CONTROL CIRCUIT.Thiscircuit below taining that valve. includes a motor-driven actuator mounted The oil then flows through the check valve the accessory compartment floor in eachnacelle, port into the outlet chamber and throughthe automaticallycontrolled by a thermostatic "oil out" port. During this time the hot oilflows switch in the engine oil outlet linethrough a over the cooler, warmingthe oil within thefour-position switch on the copilot's switch cooler tubes. When the oil temperaturereaches console.The motor is a split field wound, 54.4° C, the thermostatic valve closes so that reversible, 24-volt d.c., and includes a magnetic

157

13J AVIATION MACHINIST'S MATE R 3 & 2 /a.

OIL OUT PORT OIL IN PORT OIL INLET CHAMBER OIL OUTLET CHAM8ER COOLER INLET VALVE THERMOSTATIC SURGE ELEM ENT CHECK VALVE

OIL TEMPERATURE REOULATINO VALVE3

PORT C (FROM CORE) PORTA PORT B (TO JACKET) (FROM JACKET) THERMOSTATIC VALVE OISC VALVE

OIL TEMPERATURE REGULATING VALVE (COLO OIL POSITION)

CODE

HOT RETURN TO COOLER OIL COOLERS MINNCOLO RETURN TO TANK

VAILVC lirCINAII MY

PORTS CONDITION OPERATION

A 8 C

ENGINE START OIL FLOW THROUGH VALVE CLOSED BYPASSED BYPASSED COLD OIL BYPASSING COOLER * BYPASSED OIL TEMPERATURE FROM 39.5 OIL FLOW THROUGH OPEN OPEN C. TO 43.5°C (I03°F TO 110° F ) WARMING JACKET ** NOTE: THERMOSTATIC VALVE OIL TEMPERATURE FROM OPEN THERMOSTATIC VALVE CLOSES-OPEN ABOVE 54.4°C OPEN CLOSED OPENS WHEN PRESSURE 43.3° TO 54.4°C (HOF TO 130° F ) (130°F ) ALL OIL FLOWS AT PORT "8" EXCEEDS THROUGH COOLING CORE ** PRESSURE AT PORT"C" 8Y MORE THAN 40 PS I SURGE-COOLER INLET PRES- DISC VALVE MOVES ENTIRELY BYPASSEDBYPASSEDBYPASSED SURE EXCEEDS OUTLET PRES- THROUGH ITS SEATOIL- FLOWS SURE BY MORE THAN 53 PS I THROUGH VALVE, BYPASSI NG (COOLER INLET VALVE OPEN ) COOLER *

° CHECK VALVE CLOSED **CHECK VALVE OPEN

AD.58 Figure 8-3.--Oil coolers and temperatureregulating valve. automat- brake to stop the motor quickly when thelimits circuit. Each actuator is controlled limit ically by a floating control thermostatinstalled of travel,as determined by integral right side switches, are reached. in the engine oil return line on the of each main wheel well, just aftof the firewall. Power is supplied from the 24-volt d.c. copilot's forward power bus through the same10-ampere Two switches are located on the circuit breakers which serve the cowlflap console for control of the oil coolerdoor cir-

158

13,1 /ic: Chapter 8RECIPROCATING ENGINELUBRICATING SYSTEMS

DOOR THERMOSTATIC CONTROLUNIT. The door thermostatic control unitis mounted FROM ENGINE in the oil return line on the rightside of the nacelle just aft of the firewall. The unitcontains two floating contact arms and a centralcontact arm thatisactuated by a bimetallic coil immersed in the oil in the returnline. One of the floating contacts is in theDOOR OPEN circuit;the other isin the DOOR CLOSED circuit. The two arms rest on a cam,which is constantly rotated by a small motor.Thus the floating contacts are constantlyvibratingtoward the central contact. If the oil temperature risesabove normal, the thermostatic element causesthe central contact to move toward the DOOROPEN contact so that as the contactvibrates, it intermittently closes the DOOR OPEN circuit. Asthe actuator is intermittently energized, thedoor is slowly openeduntil the oil temperature returnsto COOL OIL normal, at which time the centralcontact moves back to a neutral position. In anextreme case, WARM OIL where the oil temperature riseshigh above the normal value, the central contactwill lift the floating contact clear of the cam,completing a continuous circuit. The door willthen move toward the full open position, where alimit switch in the actuator will break thecircuit. normal, the AD.59 If the oil temperature falls below opposite direction Figure 8-4.Oil cooler assembly construction. central contact is moved in the (toward the DOOR CLOSED contact),causingthe door to close.In extreme cases, the central cults. The switches are of the four-position type, contact may lift the DOOR CLOSEDcontact from the cam, completing a continuouscircuit to the with OPEN, CLOSE, OFF, and AUTOMATIC to its fully positions.In the OPEN and CLOSE positions, motor and causing the door to move the thermostat is excluded from the circuit and closed position, where a limitswitch on the the actuator is energized directly: in AUTO actuator breaks the circuit. To preventexces- MATIC, the actuator is controlled by the thermo- sive hunting, a toleranceof plus or minus 2.7° C stat only. is maintained by adjusting the camfollower of AM DUCTS.Air entering the scoop in the the floating contact. lower cowl panel is fed through the lower cowl MAINTENANCE.The oil cooler assembly duct directly into the oil coolers. After passing requires only cleaning when necessary.Failures through the coolers, the air passes through the of the regulator are usually causedby dirt or exit duct (an integral part of the engine mount other obstructions under the valveseats. 1.1 the structure) and overboard through the thermo- valve fails to function thermally,the remedy is statically controlled oil cooler door. to replace the defective elementwith a new one. DOOR AND DOOR ACTUATING UNIT.The The thermal elements in the oiltemperature oil cooler door, fabricated from sheet metal, is by immersion piano hinged to the lower edge of the exit duct, regulator valve must be cleaned just aft of the oil coolers. A bracket attached to in solvent only and by blowingout immediately with an airstream. The valvebody should be the door provides an attachment point for the solution and door actuator. immersed in a suitable cleaning

159

135 AVIATION MACHINIST'S MATE R 3 & 2 /e28/ cleaned thoroughly, using a brush. Blow out With clean approved solvent, flush 30 min- with compressed air. utes, reversing flow once. Clean the oil cooler and temperature regula- Drain the cooler thoroughly and flush with tor valve as soon as possible after removal from clean light lubricating oil at a temperature of the aircraft. Otherwise, the petroleum varnish, 54.4° C. tar, and carbon compounds in the oil form a NOTE: After each flushing operation the hard coating, difficult to remove. filter screen should be examined. If metallic Remove the drain plug, drain plug gasket, particles are found, it is an indication that the temperature regulator valve, and valve gasket oil cooler was installed on an engine that failed. from the oil cooler. Drain all residual oil from Since there is no known method of determining the cooler. whether all metallic particles have been removed Immerse the cooler in a bath of oil cooler from thecore,everyoilcooler assembly cleaning compound, MIL-C-6864A. Allow the removed because of engine failure shall be cooler to stand in the bath for 5 minutes with tagged, giving the cause, and turned into supply. tubes vertical. Move the cooler up and down The maintenance of the oil cooler door occasionally to force liquid through the tubes actuating unit consists of wiping the unit with a and loosen grit; drain 10 to 15 minutes. clean rag dipped in approved solvent. If the motor Use only recommended solvents. Many brushes are worn excessively, they should be solvents satisfactory for cleaning copper oil replaced. The actuator support bearings should coolers are highly corrosive to aluminum and be lubricated at the intermediate inspection with will result in the destruction of the aluminum MIL-L-78'70. The drivescrew should be packed cooler if used. with grease as specified in the Periodic Sched- Remove the cooler from the bath and drain uled Maintenance Requirements Manual. See with tubes in a vertical position. Using an a 7 table 8-2 for oil cooler door actuating unit gun, blow out the tubes through the face of the troubleshooting. core to remove foreign particles. Iftheoiltemperature gageconstantly Attach the cooler to power flushing equip- registers below 77° C or above 82° C, check r =int,using only recommended solvents. The the gage for accurv.y; if inaccurate, replace cooler should be connected to a power flushing the gage. If correct, adjust the floating control system in such a manner that the solvent will ttermor,tzt of the door thermostatic control unit. enter the cooler through the outlet port. The oil cooler door thermostatic control If the flushing equipment has previously unit troubleshooting information is in table 8-3. been used with any cleaning materials or solvent other than that recommneded, the equipment Oil Temperature and should be washed out thoroughly and flushed Pressure Gages with MIL-C-6864A. The power system should be The actuating unit of the oil temperature equipped with a suitable filter to prevent re- gage is located in the engine oil inlet, and is circulation of foreign matter. A relief valye set connected to a temperature gage in the cockpit to relieve at 75 psi must be provided to prevent instrument panel. damage to the cooler from excessive pressure. The oil temperature gage consists of either With the bypass port closed and the inlet a thermocouple unit and a suitable meter, or a port open, pump solvent into the outlet port of resistance unit coupled through a Wheatstone the cooler. Flush for 60 minutes, reversing the bridge to a suitable meter. In either case, the flow each 10 minutes. This cleans the inside of gage heat unitis always a sensitive electric the core and warmup passage. meter calibrated in degrees centigrade. Opera- Open the bypass port, close the inlet port, tion of the electric oil temperature gage which and continue flushing for 5 minutes. This re- uses the resistance bull: :alit is based upon the moves dirt which may be trapped 1.1 the bypass principle that the conductivity of an element of passage. known resistance varies with the temperature. Rinse theunitthoroughly withsolvent The oil pressure gage is used to provide the PS-661b. pilot with a reading, in pounds per square inch,

160

136 I Chapter 8RECIPROCATING ENGINE LUBRICATING SYSTEMS

Table 8-2. Oil cooler door actuating unit troubleshooting.

Trouble Probable cause Remedy Failure to operate. Burned-out motor. Replace actuator. Faulty wiring. Check circuit and tighten all connections. Inoperative limit Replace actuator. switch. Jammed gear train Replace actuator. or screwjack. Door opens but will not Burned-out field in Replace actuator. close, or vice versa. motor. Burned-out limit Replace actuator. switch. Door does not completely Improper setting of Reset limit switches. open or close, or both. limit switches.

of the oil pressure being supplied to the engine. from draining into the engine compartment in A gage in the cockpit instrument panel is con- case the oil return lines are broken by fire or nected to the engine at a point downstream of the in other emergencies. Ifit is desired to drain engine oil pump. The pressure orifice (opening) the return lines, the check valve may be manually isrestricted in size to a No. 60 drill so that opened by moving the spring-loaded lever in a pressure surges and fluctuations of oilpressure counterclockwise direction. Normally, the lever will not be harmful to the gage. must be safetied in the down position. Inspect the manual check valve for leakage. Emergency Oil Shutoff Valve This is accomplished by disconnecting the oil return manifold at the firewall fittingandprying A shutoff valve controlled by the E-level is the manifold fittings ahead to check for leakage. provided in the oil supply line to each engine. If leakage exceeds 20 drops per minute, replace By closing this valve, all oil flow to the enginethe valve. Replace the valve at every aircraft may be cut off in the event of fire or other overhaul. emergency. The valve is in the wheel well, just aftofthe firewall, and is accessible from within the wheel well. The valve controls are Oil Drain Valve located aft of the pilot's seat. A Y-drain valve is located on the left side Manual Check Valve of each wheel well, aft of the firewall. The valve is a two-position, poppet type valve for draining A flappertypemanual check valve is theengineoil tank and system, except for installedintheoilreturn line,aftof the approximately 2 1/2 gallons which remain inthe firewall on the right side of each wheel well. tank for feathering the propeller. The valve This check valve prevents oil in the return lines should be safetied in the OFF position.

161

1.3( ,9z) AVIATION MACHINIST'S MATE R 3 & 2

Table 8-3 . Oil cooler door thermostatic control unit troubleshooting. _

Trouble Probable cause Remedy Failure to operate in Low battery in aircraft Replace the battery. manual or automatic. power system. Defective thermostat as- Replace the unit. sembly motor. Unit operates in manual but Thermostat motor burned Replace the unit. not in automatic. out. Center contact arm loose. Tighten the center contact arm. Loose connection at the Tighten all connections. contact points.

Door closes but does not Failure of thermostat Replace the unit, open, or vice versa, motor to turn cam. Excessive movement Incorrect setting on the Reset the points to the of the door. contact points, proper gap with the floating contact arm in the depression on the cam.

Oil present in the cover Leakage past the seal Replace the unit. box. on bimetal element shaft. Failure of the thermostat Worn-out brushes. Replace brushes. motor to turn the cam. Jammed gear unit. Replace the unit. Excessive chattering of Burned-out resistors. Replace the resistors and the contact points, the contact points. Failure to maintain the Loose or oscillating Reset and tighten in proper oil temperatures. contact points. place. Floating contact arms Oil the pivots lightly. binding on pivots. (Use SAE 10 lubricating oil. )

Oil Dilution System During dilution, a small amount of gasoline is mixed with the oil in both the engine and oil An oil dilution system is provided for each tank hopper assembly. Fuel for dilution is tapped engine oil system to provide good engine lubrica- from the main fuel strainer in the wheel well, tion during cold weather starting. and metered through a No. 47 hole restrictor. /3/ Chapter 8RECIPROCATING ENGINELUBRICATING SYSTEMS at the When the system is energized, fuel is fed through justment to the system is accomplished a solenoid-controlled valve and amanual shutoff power units. valve to the Vernatherm unit in the diverter. The three basic components(tank unit, valve. Within the diverter valve the cold fuel power unit, and indicator) compose acontinu- causes the temperature sensitiveunit to move ously balancing capacitance bridge circuit.The the valve to the hopper position, so thatdiluted tank unit, mounted in the oil tank, is acylindri- oil is only returned to the hopper. Control ofthe cal electrostatic capacitor in whichthe capacitance varies with changes inoil level and system is through momentary contact switches unit on the copilot's switch console. Theelectrical dielectric constant. Any change in tank circuits are so interconnected that when the oil capacitance will unbalance the bridge andsupply dilution solenoid is energized, the boost pump a signal to the amplifiersection of the power tank selected is automatically unit. The power unit will thenenergize the forthefuel The operated in HIGH BOOST operation. phase-sensitive motor in the indicator. A solenoid-operated oil dilution valve is indicator motor drives the balancingpotenti- located on the left side of each wheel well and ometer wiper in the direction required torestore is accessible from within the wheelwell. The the bridge to balance at the newpointof balance. valves are controlled by a momentary contact The indicator pointer, which isdriven by the switch located on the left side of thecopilot's same shaft as thepotentiometer wiper, is switch console. Gasoline is furnished to each positioned at the correct reading of oilquantity. valve by a small line attached to the fuel stramer, which is just aft of the valve. The gasolineis DITERNAL OIL SYSTEM delivered to the oil system byanother small line leading from the valve to the diverter valveat The pressure and scavenge oilsystems and the aft wheel well bulkhead. A small manual their components are covered in thissection. shutoff valve is installed in the line at the The model R3350-32W engine isconsidered a diverter valve. The shutoff valve must be lock- typical engine, as this engine utilizes a pres- wired closed at all times except duringdilution. sure, dry sump type oil system. The operational check of the oil dilution The purpose of the internal oilsystem is to moving valve is performed as follows: provide pressure oil for lubrication of 1. Close the manual shutoff valvein the parts, to aid in cooling of theinternal parts through oil circulation, and to flushand clean dilution line beneath the tank. moving 2.At the dilution solenoid valve, disconnect internal parts of foreign matter. All the line leading to the diverter valve. parts are lubricated by oilunder pressure 3. Set the mixture control at CUTOFF. except the piston rings, pistonpins, cylinder 4. Set the ignition switch at OFF. walls, intake and exhaust valves,crankshaft oil main bearings, and propeller shaftthrust and 5. Place an empty container under the lubricated by dilution valve. radial bearings, all of which are splash or jet. Another function of theinternal 6. Select a tank containing fuel. oil for the 7. Set crossfeed for normal flow. oil system is to provide operational 8. Turn the oil dilution valve switch to ON. following units: 9. Check to see that fuel has been delivered 1. Torquemeter system. by the valve. 2. Propeller and governor. 3. Oil-operated plate clutch. 10. Check to see that booster pump in fuel couplings. tank selected has been actuated in HIGH BOOST. 4. Power recovery turbine fluid The oil system also aids in preventingcorrosion Oil Quantity Indicating of internal parts of the engine. System Rear Sump A Minneapolis-Honeywell oil quantity indi- bottom of cating system is installed. This systemincludes The rear sump is located on the the rear supercharger section. It collects,cir- tank capacitor units, powercalibration units, acts as a indicator units, and necessary cabling.All ad- culates, and returns the oil. It also

163

1 3 ,j AVIATION MACHINIST'S MATE R 3 & 2 housing for the components. Usually the port Half of the disks are corrugated on the inner side is referred to as the pressure side; the edge and the other half on the outer edge. They starboard, as the scavenge side. are placed alternately in series to provide The rear sump housing is made of cast straining action. The oil enters the center of magnesium and contains the various units needed the strainer and then flows from the center to in the operation of the pressure and scavenge the outside. This prevents collapsing of the oil system. strainer. CHECK VALVE.-The check valve is made Pressure System of stainless steel and is located on the pressure Pressure oil leaving the rear sump supplies strainer. All oil going to the engine must pass the front supercharger section, front sump, through this check valve. There is a spring that rear supercharger cover, tachometer generator, keeps the valve closed when the engine is not engine-driven fuel pump bearing, and the oil- running, to prevent flooding of the engine with operated plate clutch. oil from the tank. REAR OIL PRESSURE PUMP.-The rear oil BYPASS VALVE.-The bypass valve is op- pressure pump is the cartridge type with two erated on a differential of oil pressure and is spur steel gears in a machined aluminum housing located in the :trainer cavity. It insures that (See fig. 8-5.) There are two openings on the top lubricating oil will get into the engine in the of the pimp for the inlet oil and one opening on event that the strainer is clogged Or the oil is the bottom for the pressure oil leavingthe pump. too heavy to flow through the strainer. PRESSURE STRAINER.-The pressure PRESSURE RELIEF VALVE.-The pressure strainer consists of a series of corrugated steel relief valve regulates oil pressure to the engine. disks separated by fine wire mesh screens and It is a double-ended bronie valve ina cadmium- secured together to form a cylindrical strainer. plated steel housing. This valve incorporates a

TO REAR COVER TO FRONT Oil TO TACHOMETER FUEL S. CRANKSHAFT PUMP HOUSING PUMP DRIVE SUPPORT

TO COCKPIT Oil PRESSURE GAGE

CLUTCH CONTROL VALVE 3/1111 PRESSURE OIL 11.111 SCAVENGE OIL

DRAIN OIL FROM SUPERCHARGER PRESSURE HIGH SLOWER LOW BLOWER I FRONT HOUSING POSITION POSITION RELIEF VALVE L- _ - BYPASS VALVE TO CLUTCH - FROM CLUTCH PREOil INLET DRAIN OIL FROM REAR SECTION OIL IN Oil OUT (FROM TANK) (TO TANK)

FROM FRONT SCAVENGE PUMP

114. ow *AA REAR INLET SCAVENGE CHECK VALVE PUMP

STRAINER MAGNETIC PLUG PRESSURE PUMP

AD.60 Figure 8-5.-Diagram of the rear oil pressure pump.

164 -14U /33 Chapter 8RECIPROCATINGENGINE LUBRICATING SYSTEMS

REAR SCAVENGESTRAINER.The rear spring and an adjusting screwwhich provide a the mesh screen type.It means ofregulating theoilpressure.Oil scavenge strainer is procedure is described strains all the scavenge oilfrom the rear power pressure adjustment section and aftof the rear powersection. later in this chapter. A magnetic plug is locatedjust below the SUPERCHARGER CLUTCH OILCONTROL metal, thereby pro- VALVE.The supercharger clutchoil control strainer to attract ferrous valve is located on the rear centerof the sump. tecting the scavenge pump. plate FRONT SUMP.The front sumpis located Itcontrols the oil to the oil-operated the front crankcase section. clutch. It is operated by a control inthe cockpit. on the bottom of It collects, circulates, andreturns the oil and acts as a housing forcomponents. The front Scavenge System sump housingis made of cast magnesium. The pressure section ofthe front sump valve.It The purpose of the rear sump scavenge contains anoil pressure control reduces the oil pressure fromthe rear pressure system is to strain and returnthe oil to the required for the front external oil system. (See fig.8-5.) This is pump to the pressure front and sump (35, plus orminus 5, psi). accomplished with units located in the the front sump rear sumps; however,all scavenge oil leaves The oil pressure passages in line on the right side supply oil to the front tappetannulus, torque- the sump by an external meter system, and thefruur cam assembly. of the sump. (See fig. 8-6.) REAR OIL SCAVENGE PUMP.The rearoil oil in scavenge pump is the cartridgetype. It has two FRONT SCAVENGE PUMP.Scavenge the forward portion of the powersection and the sets of spur steel gears in amachined aluminum flows by gravity to the housing. This pump has two inlets atthe bottom crankcase front section large scavenge pump in thefront pump and sump and one outlet at the top.

TO FRONT CAM ASSEMBLY TO FRONT TAPPET DRAIN OIL FROM TO REAR ANNULUS,ETC FRONT SECTION SCAVENGE PUMP EXHAUST SUMP DRAIN OIL FROM FRONT MAIN 4-(1 SECTION ClECK VALVE TO PROP SHAFT

MAGNETIC PLUG

#1,

PRESSURE CONTROL VA ..VE FROM LOWER ROCKER BOXES (CYLS. 8,9,10,11,la) 6,7 ii ROCKER BOX SCAVENGE PUMP FROM PRESSURE PUMP

111110 PRESSUREOIL f77-7"). SCAVENGE OIL

AD.61 Figure 8-6.Diagram of thefront oil pump.

165

14 AVIATION MACHINIST'S MATE R 3E:. 2 tV housing. Before the oil enters the return pump cover through a connecting tube into the rocker it passes over a magnetic plug, through an oil box drain manifold. strainer and then into the pump which is a spur Incorporated in the rocker box drain manifold gear type oil pump. The oil is then pumped back system are two sumps configured into the rocker through an external line to the front supercharger boxes of No. 10 cylinder. These sumps collect any housing and then internally to the rear sump oil that may drain down into the engine whenever outlet port. it is setting idle, but whenever the engine is op- ROCKER BOX SCAVENGE PUMP.- erating the oil is drawn from the sumps by the Drainage of the rocker boxes below the horizon- rocket box scavenge pump (first passing through tal center-line of the engine is accomplished by a strainer) and is returned to the rear sump a separate system. Scavenge oil flows by gravity outlet port via the same external line as the oil from the rocker boxes through the rocker box from the front scavenge pump. (See fig. 8-7.)

AD.62 1.Rocker box cover. 9.Front oil pump. 2.Drain manifold. 10.Left distributor pad in front 3.Cover to drain manifold tube. section. 4.Rocker box drain manifold 11.Cover and sump vent upper packing nut. tube. 5.Drain manifold strainer. 12.Cover and sump vent lower 6.Drain manifold to cover and left and right tubes. sump tube. 13.Cylinder No. 10 rocker box 7.Drain manifold to scavenge cover and sump. pump tube. 14.Rocker box scavenge manifold 8.Rocker box scavenge pump. support bracket. Figure 8-7.Rocker box drain system.

166

1 44 Chapter 8RECIP1WCATING ENGINE LUBRICATINGSYSTEMS / 35-

MAGNETIC SUMP PLUGS.The R-3350 whenever the troubleshooter has a knowledgeof engine incorporates in both the rear pump and oil the path of flow of the oil. sump and the front pump and sumpMAGNETIC In operation, each engine oil systemauto-. sump plugs. These plugs are removedwhenever matically maintains normal engine oil tempera- the engine is checked and the oil is drained at tures and a positive supply of oil to theengine these points. The purpose of the magnetic sump without the attention of the pilot, copilot, or plugs is to remove from the oil all types of plane captain. The engine oil is supplied tothe metal in the engine oil that are magnetically engine through a standpipe in the tank sump; attracted. Any indication of iron or steel on these propeller feathering oil is supplied fromapoint magnets should be investigated. Some engines below the engine oil standpipe level.Oil flowing from are now equipped with magnetic typesumpplugs through the system makes a complete cycle tank. Oil thatare connected to warning lightsin the the tank to the engine and back to the cockpit that will indicate to the pilot a pending flows by gravity feed through a flexiblehose the engine failure. assembly from the main oil tank through NOTE: The wet sump system is another Y-drain valve to the engine rear oil pump. type of lubricating system. The reservoir forms Oil returning from the engine isrouted the lower part of the engine crankcase, as in through an oil temperature regulator valve. The attachedto theautomobile. Theoilis picked up by a oil temperature regulator valves are pump and delivered to the pointsrequiring the oil coolers and determine the pathof flow lubrication. The oil then drains down into the through the oil coolers, around the air cooler crankcase andis pumped back through the jacket, or bypasses the oil coolers entirely.Any system. The Navy does not use the wet sump oneof these actionsis determined by the system extensively for the following reasons: temperature of the oil. It has a limited amount of oil supply, provisions Oil flows from the regulator valve through for cooling are difficult, oil temperatures are a thermostatic control unit,where the tempera- usually high, and it is not adaptable to unusual ture of the oil affects the positioningof the oil volume of flight attitudes. cooler doors. This unit controls the air flowing through the oil coolersby positioning MAINTENANCE the exit doors automatically. Maintenance of the oil system is a major Oil then flows through a manual checkvalve item of importance to the AviationMachinist's which prevents the return of oil from theexternal Leakage Mate R. It is necessary for him to bethoroughly system when the engine is secured. familiar with the oil system of the enginewith from this valve, back into the engine,should not which he is working, both the c?xternal and exceed 20 drops per minute. internal systems, so that he can effectively The diverter valve is the final temperature repair any lea.k or defect that may occur. control unit through which the oil passesbefore itreturns to the tank. This valve determines whether the oil returning from the engine goesto LOCATION OF LEAKS returned AND DEFECTS the main portion of the oil tank or is to the hopper within the tank. Usuallythe only The immediate location of any leak or defect time this takes place is when the enginehas been within the external or internal oil system in any just started and the oil is still cold. Theoil, in aircraft engine is of prime importance.The life this case continues to return to the hopperuntil of the engine is in its oil supply andwhenever a the surrounding oil in the tank warms up.When- leak developsor the oil flow is restricted ever oil dilution is used, gasolineis introduced because of a malfunction, a part failure or loss to the oil system at the temperaturesensitive of the engine may result. elements of the diverter valve and is returned tothehopperportionoftheoiltank. the External Oil System Thegasolineisthuscirculated from hopper to the engine and back to thehopper, Locating common defects in the external oil preventing the mixing of the dilutedoil with system componentsiseasilyaccomplished the main oil supply.

167

4 AVIATION MACHINIST'S MATE R 3 & 2 /3,6 An emergency shutoff valve is installed in or bronze. A visual inspection to determine the the oil supply line at the firewall. This shutoff color and hardness occasionally is sufficient to valve is operated by the E-lever (emergency) at determine the kind of metal present. the flight station overhead control. One of the most common external oil system Knowing the operation and the path of flow of defects is high or low oil temperature. There- theoilis of prime consideration whenever fore, a chart as shown in table 8-4 will suffice trouble-shooting is to be attempted. The path of to help identify this trouble. flow and operation in the preceding paragraphs are those of the SP-2H aircraft engine, and we Internal Oil System have used ithere as a typical external and internal oil system. All recipocating aircraft Troubleshooting of the internal oil system is engine oil systems have essentially the same usually a matter of maintaining the proper oil characteristics as the one we have described temperature and pressures. Repair of leaks here anditis therefore possible to use a within the internal oil system is almost always standard set of troubleshooting procedures for restricted to the components of the engine that the oil system. can be reached and repaired from the outside One of the major causes of trouble in the without dismantling the basic engine structure, engine oil system is contamination by metal (pushrods, rocker boxes, accessory mounting particles. If metal particles are found in the oil pads, etc.). system, usually an engine change is required. For the Aviation Machinist's Mate R to There is also the possibility that the oil system effectively locate internal oil system defects it (tank, cooler, lines, and related engine acces- is also necessary for him to be thoroughly sories) is contaminated. Every precaution should familiar with the paths of flow of the oil as it be taken to keep contaminants from entering a progresses through the engine and returns tothe newly installed engine. Throughprompt identifi- external system. A brief description of the cation of contaminants, the loss of time and internal oil system flow path through the R-3350 materials required to flush the system may be engine is described in the followingparagraphs. avoided. NOTE: The information contained in these Metal particles found on the engine oil paragraphs is of a general nature and should not strainer and/or in the oil sumps usually are the be used as specific information. Always refer first evidence of failure of a part within the to the applicable Maintenance Instructions engine. The presence of any metal particles on Manual. the oil strainer or in the oil sumps, however, is Oil from the external tank enters the not necessarily an indication that the engine is pressure pump in the left side of the rear oil no longer suitable for service. Metal particles pump and sump housing. The pump discharges from a previously installed engine which failed the oil through the cored passages in the pump may have collected in sludge in the aircraft oil and sump body into the inside of the pressure system. This possibility should be taken into strainer, and then through the strainer into the account if metal particles are found in the sumps strainer cavity. A strainer bypass valve allows or on the strainers of the newly installed engine. the oil to bypass the strainer and provides the Carbon deposits in the engine frequently engine with oil for lubrication whenever the oil break loose in large pieces, which have the out- is too cold, or if the strainer should become ward appearance of metal when found on the oil clogged due tocarbon or possibly a part strainers and in the sumps. Carbon can be breakdown. A spring-loaded check valve at the distinguished from metal by placing the foreign inlet side of the strainer prevents the flow of oil material on a flat metal object and strikliAg it under gravity pressure from the tank whenever with a hammer. If the material is carbon, it the engine is not operating. chsintegrates when struck, whereas metal of any The pressure relief valve in the rear pump type either remains intact or changes shape, and sump housing regulates the oil pressure to depending upon its malleability. The particles of 70 psi, plus or minus 5 psi, during all engine metal found in an engine may be any of five operations. The quantity of oil flowing through kinds: steel, tin, aluminum, silver, and copper the valve varies with theengine rpm, oil

168

144 Chapter 8RECIPROCATING ENGINELUBRICATING SYSTEMS /37

Table 8-4.-011 temperature troubleshootingchart.

Trouble Cause Remedy High oil temperature. Insufficient opening of oil Open doors and cooler doors. watch temperature indicator for drop in temperature. Aircraft headed downwind. Head aircraft into wind and note temperature. Improper setting of Replace temperature temperature control control valve. valve. Oil cooler passages Replace with new or clogged. serviceable cooler. Oil cooler air passages or Locate and remove ducts plugged with obstructions. foreign matter. Internal oil passages Replace cooler as- partially blocked by sembly. sludge and foreign matter. Improper regulator valve Replace valve. operation. Low grade oil. Check specification of oil used. If improper oil, drain system and refill with correct grade of oil.

Low oil temperature. Oil cooler doors opened Close doors and check too far. for temperature rise. Improper setting of oil Replace temperature temperature control control valve. valve. Defective oil temperature Replace with new or indicator. serviceable indicator. Defective temperature Replace with new or indicator bulb. serviceable bulb.

169 AVIATION MACHINIST'S MATE R 3 & 2 temperature, and the engine's demand for oil. 2,600 rpm and an oil temperature of 85° C and An oil pressure control valve in the front pump observe the oil pressure. Adjust as follows if and sump housing reduces the pressure of the the pressure is not within the prescribedlimits. oil passing through it to 35 psi, plus or minus 1. Secure theengine,and remove the 5 psi. Another oil pressure control valve in the pressure valve cap. supercharger front housing reduces the pressure 2. Push out the locking pin which passes of the oil passing through it to 50 psi, plus or through the holes in the body of the valve and minus 5 psi. the slots in the valve seat. Tapped holes in the engine are provided for 3. Turn the valve in a clockwise direction attaching pressure gages to check these various to increase the pressure and in a counterclock- oil pressures. These holes are blanked off at wise direction to decrease the pressure. Use a all times except when it is necessary to check screwdriver with the proper blade width to avoid the pressureof theoilata given point. scarring the adjusting valve. 4.Set the front oil pressure to 35 psi, plus REPLACEMENT OF GASKETS, or minus 5 psi, install the locking pin. Install a SEALS, AND PACKINGS new gasket and the control valve cap, tighten, and lockwire. 5.Shut down the engine and remove the oil A large portion of the maintenance involved pressure gage. Secure the plug in the oil pump in the troubleshooting, replacement, and repair and sump housing after the engine has been run of various oil leaks and components of the oil up to the proper rpm and oil temperature and system will involve the use of new gaskets, the pressure has been checked to ascertain that seals,and packings. The greatest difficulty it is correct. encountered whenever a new gasket, seal, or packing is replaced is the proper installation. At all times, it must be ascertained that the Supercharger Front Housing mating surfaces are clean, old material re- Oil Pressure (R-3350 Engine) moved, and the new gasket, seal, or packing is replaced in the correct manner. Always refer When it is necessary to adjust the oil pres- totheapplicable MaintenanceInstructions sure to the power recovery turbines, the plug Manual for the correct procedure to follow. located directly aftof the pressure control valve in the supercharger front housing must be removed. This is the point at which the oil ADJUSTMENT OF OIL PRESSURES pressure gage is installed so that the pressure may be read. The engine should be operatedat a To identify defects in the oil system that are speed of 1,500 to 1,800 rpm with an oil inlet attributable to either high or low oil pressure, temperature of 85°C. If the oil pressure does refer to table 8-5. not fall within the prescribed limits of 50 psi, Always refer to the applicable Maintenance plus or minus 5 psi, then the pressure must be Instructions Manual for pressure limitations adjusted in the following manner: and the desired operating pressures for the 1. Remove the pressure control valve cap. engine with which you are working. 2. Push out the locking pin which passes through the valve body holes and the slots in the valve seat. Front Sump Pressure (R-3350 Engine) 3. Turn the valve in a clockwise direction to increase the pressure and counterclockwise Whenitis necessary to adjust the oil to decrease the pressure. pressure control valve in the front sump, re- When the correct pressure is obtained, move the pressure gage substituting plug from insert the valve body and seat lockingpin. Install the front sump. Connect an oil pressure gage at the control valve cap with a new gasket and lock- this location. Operate the engine at a speed of wire. Shut down the engine and remove the oil

170

14b a ENGINE LUBRICATING SYSTEMS /37 Chapter 8-RECIPROCATING

Table8-5 . Oil pressure troubleshooting chart.

Trouble Cause Remedy High oil pressure. Low oil temperature. Check temperature indicator. Check grade of oil.

Improper setting of re- Reset pressure lief valve. relief valve. Defective pressure Replace with new or indicator. serviceable indicator.

Low oil pressure. High oil temperature. Check temperature indicator.

Clogged oil strainer. Remove and clean oil strainer.

Improper setting of Reset pressure relief valve. relief valve. Defective pressure pump. Repair or replace pump.

Defective pressure Replace with new or indicator. seiviceable indicator.

Low oil level. Fill oil tank to the proper level.

Viscosity of oil is too Drain system; refill light. with correct grade of oil.

Air leak in the supply Locate and eliminate line. air leak. Leaky oil dilution valve. Remove fuel outlet line from valves. With fuel pressure applied and the valves off, no fluid should appear.If fluid appears, replace with new or serviceable valves.

171

14/ AVIATION MACHINIST'S MATE R 3 & 2 M pressure gage. Reinstall the plug in the super- 85° C and observe the main oil pressure gage charger front housing. in the cockpit. 2. Remove the oil pressure relief valve cap and packing ring. Rear Oil Pump Adjustment 3. Loosentheadjusting screw locknut (R-3350 Engine) sufficiently so that the pressure adjusting screw may be turned clockwise or counterclockwise The rear oil pump pressure of the engine is to increase or decrease the oil pressure. A the pressure with which the mechanic is most one-quarter turn of the adjusting screw in either often concerned. Whenever it is necessary to directionwillraiseor lower the pressure make an adjustmentof the rear oil pump approximately 11/2 pounds per square inch. pressure the following procedures should be 4. When the correct pressure is obtained, followed. tighten the locknut to the proper torque, install 1.Operate the engine at a speed of 1,500 a new packing ring over the relief valve body to 1,800 rpm with an oil inlet temperature of and install, tighten and safety the cap.

172

1 4cs ..

CHAPTER 9

RECIPROCATING ENGINEIGNITION SYSTEMS

.. ignition system differsfrom that normally In the chapterconcerningthe cycle of opera- that found in the automobile.The integral, indepen- tions in the enginecylinder, it was stated aircraft ignition system to ignite the air-fuel dent character of the the electrical spark used gives an added reliabilitydesirable in flight mixture charge wastimed to occur at some Failure of the battery-generator point before top dead centerof the compression operations. impair the func- system for producing, system in flight will in no way stroke. The electrical tioning of the ignition system. timing, and distributingthis spark to the cylin- systems are in general IGNITION SYSTEM. As itis Two types of itnit ion ders is called the use on Navyaircraft. They are theLOW- system, the ADRshould have a SYS- an electrical T ENSIGN SYSTEM andthe IIIGH-TENSION thorough understandingof the properties of job, but have of electromagnetism TEM. They perform the same magnets, and the principles different characteristics. induction. This information systems are shown and electromagnetic Basic Both types of ignition is contained in theRate Training Manual, (A) and (B). 10086-B, supplementary schematically in figure 9-1 Electricity, NavPers The various componentsof the engine igni- reading for this manual. engines used in tion system are describedin this chapter along All aircraft reciprocating with the general inspection,testing, handling, the Navy are equippedwith dual-ignition sys- removal and installation The use of a dual-ignition and storage, and the tems using magnetos. procedures for each. system serves two purposes:(1) It increases the increases engine output. safety factor, and (2) it SPARK PLUGS If a defect in the ignitionsystem occurs so that one one of the twosparkplugs inthe cylinder, or reliability of an stops firing, the other The maximum operating complete set of plugs, aircraft engine dependsto a large degree upon plug or set of plugswill continue toprovide of the spark plugs. dual-ignition system also the efficient performance ignition. The use of a Therefore, the importanceof proper servicing increases engine performanceover that possible to system by ignitingthe and installationteChniques are essential with a single-ignition efficient spark plugperformance. air-fuel mixture at twopoints in the combustion the best operating per- for a more rapid and In order to obtain chamber, thus providing formance, it is essentialthat all maintenance more completecombustion. This isparticularly familiar with the im- high-speed, high-volume personnel be thoroughly important in modern portant aspects of aircraftspark plugs. aircraft engines. There are many seeminglyunimportant The ADR should notethat in the normal the operation of the ignition system factors which can influence operation of the engine, spark plugs and which canmistakenly be taken functions independentlyof the other electrical spark plug is at fault,while that is, with the engine to indicate that the systems of the aircraft; actually, the trouble iscaused by some other running, the ignitionsystem performs itsfunc- ignition system, or ofthe connection to the battery- component part of the tion without electrical engine, Or by impropermaintenance or opera- generator system. Inthis respect theaircraft

173 AVIATION MACHINIST'S MATE 11 3 & 2

SECONDARY COIL -Ir- ITRANSFORMING CURRENT TO HIGH TENSION r -1

1 !

L L 1 1 MAGNETO DISTRIBUTOR SPARK DELIVERING ONLY OPERATING IN THE PLUG LOW-TENSION IMPULSES LOW-TENSION CIRCUIT

0 0 0 0 0 0 0 0 00 A I -: MAGNETO DISTRIBUTOR SPARK INCLUDING SECONDARY COILS OPERATING IN THE. PLUG WHICH DELIVER HIGH-TENSION CIRCUIT HIGH-TENSION IMPULSES

SOLID LINES DENOTE HIGH-TENSION CURRENT BROKEN LINES DENOTE LOW-TENSION CURRENT (NOTE THE LONG HIGH-TENSION LEAD) AD.63 Figure 9-1.Ignition systems. (A) Low-tension; (B) high-tension.

174 Chapter 9RECIPROCATING ENGINEIGNITION SYSTEMS ci 3 sealed within the core of someplug types to ting practices. In fact, thespark plug can often erosion of the electrode general indication, by its prevent or reduce the be used to give a during operation. appearance of faultyoperation of other ele- of the spark plug of improper The shell is the portion ments of the ignition system or that has the hexagonal sectionwhere a wrench maintenance of the engine. below this section are the charging un- may be applied, and The tendency of frequently threads with which the sparkplug is secured to satisfactory engine operation tothe spark plugs electrodes are secured of the temporary the cylinder. The ground prevails primarily because to the lower end of theshell. (See fig. 9-2.) The correction or remedy whichis often realized and a seal is which have become shell supports the core insulator, by replacing spark plugs, also provided to prevent theleakage of pressure fouled or have been in operationfor 30 hours the results of compres- overhauled spark plugs. into the spark plug from or more, with new or sion and combustion. As the spark gaps widenfrom use, more provides protection components of the The shielding barrel stress is thrown on the other to the communicationsystem of the aircraft ignition system; therefore, usingspark plugs metallic shield to the ignition sys- by presenting a grounded with large gaps, other parts of prevent the high-tensionlead or the center tem can be causing the sametrouble, but when electronic disturb- plugs are changed, the new oroverhauled spark electrode from emitting apparently correct the ances. The barrelof the spark plug contains plugs, having small gaps, an insulating sleevewhich insulatesit from trouble, but only temporarily. the center electrode sideof the spark plug Failures or poor performancecharacteris- of the barrel is threaded spark plugs, which gap. The upper end tics commonly attributed to for uniting the high-tensionlead with the spark new or overhauledspark plugs will sometimes correct, are as follows: plug. or pinholes 1. Weak insulation, moisture, INSPECTION AND TESTING in the ignition leads. sleeves. 2.Defective terminal contact Inspection of the spark plugbefore instal- 3.Defective or poorly installedgrommet prime importance. the elbow. lation in the engine is of where the shielding connects to The plug should be inspectedfor cleanliness, 4. Short insulation. Does notextend down the ceramic insulation, ferrule. proper type, integrity of flush with the contact spring the seat for the high-tensionlead spring wire 5.Defective spark plug elbows. contact, and to insure thatthe threads are in 6. Spark plugs and insulatorsimproperly good condition. cleaned. be accom- the engine. The testing of spark plugs can 7. Improper operation of plished by subjecting theplug to high voltage There are two types of sparkplugs in use in the ignition platinum electrode equivalent to the voltage present atthe present time; the system of the engine. Theplug is installed in (fine wire) type and the nickelalloy (massive) spark plug ele- an approved "bomb"tester in the pressure electrode type. The major chamber where it is subjected to apressure of ments are as follows: approximately 200 psi, usingcarbon dioxide. 1. The core insulator. While under pressure, a motor-drivenmagneto 2. The shell. to check the (is sometimes inte- supplies the necessary voltage 3. The shielding barrel firing capabilities of the plug.Each plug should gral with the shell). be given this test before it isinstalled in the The core insulator consistsof a body of fires inter- ceramic, and engine. If the plug fails to fire or nonconducting material such as mittently while in the tester, theplug should contains the center electrodewith a sealing device for preventing gasleakage around the be rejected. center electrode. The upperend of the center REMOVAL AND INSTALLATION electrode is in contact withthe spring contact of from the engine and the lower end forms Removal of the spark plugs the high-tension lead is a procedure with which theADR will become one side of thespark gap. A resistor isalso

175

1 5 AVIATION MACHINIST'S MATE R 3 & 2 W

INSULATOR BARREL

TERMINAL

INSULATOR SEAL SHELL GASKET SHELL SEALS

PLATINUM 18 MM THREAD CENTER MULTIPLE ELECTRODE ONE OF TWO TIP SIDE LARGE GROUND ELECTRODE ELECTRODES

AD.64 Figure 9-2.Spark plug construction. well acquainted. Always use the proper tools for letin (GPPB) No.3, latest revision, is MIL- removal. Removal of the high tension ldad 'from C-6529C, Type III. the spark plug is sometimes difficult. Care Install a spark plug gasket, and run the plug should be taken to remove the lead so that the into the cylinder spark plug bushing by hand. elbow is not bent or twisted and that the high- It should be possible to run the spark plug all tension lead ceramic sleeve is not cracked the way into the bushing until it bottoms; if or broken. not, it may be necessary to clean the threads Installation of the spark plug is the reverse within the bushing. Once the spark plug has of the removal procedure. Additional care should bottomed, complete the installation by tightening be taken during this procedure because if the with a torque wrench to the required amount of plugs are installed improperly, malfunctions torque applicable to the engine in which the will occur and result in unnecessary labor and spark plug is being installed. Install the high- replacement of spark plugs. If a plug is dropped tension lead and tighten the terminal sleeve it should be tested or replaced with a good plug. nut, again being careful not to bend or twist The insulating ceramic within the plug may the elbow. crack under any undue stresses or strains put upon it through aropping or unusual treatment. HANDLING AND STORAGE NOTE: To insure correct torque value, the shell threads must be lubricated on plugs Aircraft spark plugs are of sufficiently being reinstalled. It is not required when in- sturdy construction to withstand the demands stalling new plugs,for they are lubricated for which they are designed, but they are sus- atthetimeof manufacture. The lubricant ceptible to damage from careless handling. The recommended in General Power Plant Bul- plugs should be handled individually and should

176

154 /VS" Chapter 9RECIPROCATING ENGINE IGNITIONSYSTEMS

never be throwntogether as so much scrap MAGNETO material. They should becontained within their removed from the The DF18LN-2 magnetois a high-tension cartons or, after having been magneto which employs theprinciple of sta- cartons, should be placedin trays suitable for magnet to induce handling. If spark plugs havebeen dropped or tionary coils and a rotating inadvertently banged around,they should be a high voltage. The DF18LN-2magnetoidentification replaced with serviceable plugs. letters and numbers are asfollows: Moistureisthe worst enemy of spark plugs from plugs. After removing the spark Dual (two magnetos in asingle the sealed container inwhich they are issued, D ... they should be stored in aclosed cabinet in housing). of-heating element to F ... Flange type mounting. which there is some type Number of cylinders themagneto keep the air warm withinthe cabinet. This is 18 .. its function is to is designed to fire. called a a'hot locker,' and Left-hand rotation as viewedfrom lower the moisture content ofthe air in the L . 1 removed from the the drive end. cabinet. If plugs have been Manufacturer's letter designation hot locker to be installed in anengine and can- N .. reasonable amount of (Bendix Scintilla). not be installed within a Modification number. time, the plugs should bereturned to the hot -2 ... installed in the engine. locker until they can be This magneto is designedfor the R-3350 engine, and its mountingflange is secured with HIGH-TENSION IGNITION four bolts to the superchargerrear cover. The SYSTEM housing is made of cast-machinedaluminum, the laminated, soft The high-tension ignitionsystem is still in and cast integral with it are iron pole shoes and poleshoe extensions.There use in some Navyaircraft engines. The ADR outlets and four ground must be familiar with thissystem. It performs are four high-tension system; that is, outlets in the housing. Toprovide for cooling, the same job as the low-tension side of the hous- the proper cylinder external fins are case on each it furnishes dual ignition to ing. The nameplate is onthe upper side of the at the proper time. flange. It includes The high-tension systemconsists of either magneto near the 'mounting thetypeidentification letters andnumbers, two separate magnetos or oneduel magneto and part number. two distributors. In thosesystems that use two serial number, and manufacturer's separate magnetos, thedistributors are located in the magnetos. When adual magneto is used, Components used. two separate distributors are MAGNET.The magnet serves asthe source In the high-tension system,high-voltage that will induce an current is developed inthe magneto, as can of magnetomotive force figure 9-1 (B). The electromotive force (emf) in thecircuits neces- be seen by referring to sary to produce a sparkacross the sparkplug system also includes a harness,two spark plugs to as an ignition switch, and a electrodes.It is commonly referred for each cylinder, an 8-pole rotating magnet.It is made of Alnico starting vibrator. arranged clear understand- alloy. The poles of the magnet are so The ADR should have a that there are four northpoles and four south ing of the types and usesof aircraft magnetos, 45 degrees from the procedure for timingand installing of air- poles. The poles are staggered craft magnetos anddistributors, and the use of each other. CR OSS-SHAFT.Thecross-shaft provides a electricaltestequipment. This information and driving the cam. It is the proper mainte- means for mounting will enable the ADR to use supported in a vertical position,opposite the nance procedures whichin turn will improve magnet, by two semi- availability, lower operatingcosts, and make drive end of the rotating sealed ball bearings. Thecross-shaft is turned the job easier.

177

15 Li AVIATION MACHINIST'S MATE R 3 & 2 by a bevel gear which is secured to the cross- CONDENSER.The condenser reduces ex- shaft by means of a Woodruff key and nut. A cessive arcing of the points and aids in obtaining small pinion gear drives the bevel gear, and a rapid collapse of the primary field. these gears are located in the gear compartment. INDUCTION COIL.The induction coil is a The gear compartmentdoes not normally nonmechanical device which employs the prin- require lubrication between overhauls. ciples of induction to create a spark to fire the CAM.The purpose of the cam is to insure air-fuel mixture in the cylinder. that the spark occurs at the proper position HIGH-TENSION TERMINAL BLOCK.The relative to piston travel. It is secured to the end high-tension terminal block serves as a con- of the cross-shaft which protrudes from the nector between the secondary windings of the side of the magneto. The cam is made of chrome- induction coil and the high-tension leads. nickel steel and is referred to as a compensated cam. This is because the 18 lobes are unevenly DISTRIBUTORS spaced and of different shapes around the cam. The cam is secured to the end of the cross-shaft The distributors are located on the nose by means of a vernier ratchet, which allows fine section and are integralwith the harness adjustment of the cam for timing. manifold. They distribute the secondary cur- The vernier ratchet is made up of three rent,in firing order, by means of a rotating parts, which allow for adjustment of the cam for finger. The finger rotates at one-half crank- timing purposes. Thereare five important shaft speed, which will give the required spark markings on the cam. ineach cylinder for every two crankshaft 1. ArrowDirection of rotation. revolutions. The current is delivered from the 2. SlotIdentifies No. 1 lobe (fires No. 1 magneto to the finger via a center contact in the cylinder). distributor head, after which the finger directs 3. Master rodMasterrodlocation for the current to an electrode which is connected which cam is compensated. to an individual spark plug lead. of 4. Engine typeType engine on which HARNESS cam is used (R-3350). 5. E-gapNumber of degrees of E-gap for Theharness isprovided to conduct the No. 1 cylinder. current from the distributors to the spark plugs NOTE: There is a step cut inthe cam which through the ignition leads. In the high-tension is used to align the cam with the timing post system, to combat the problem of voltage leak- mark when checking timing. age and prevent interference with the aircraft BREAKER PLATE.The breaker platepro- communication system, it is necessary to provides a means of mounting the breaker points vide heavy insulation for the leads and to shield and to preload the cross-shaft bearings. The and ground the harness to reduce the inter- preload is set at overhaul by shims in the ference. breaker plate. A timing post is cast integral The DF18LN-2 harness provides a path for with the breaker plate, and a mark is scribed on the secondarycurrent toflow from the this post at a point where the breaker points electrodes of the distributor to the spark plug open at No. 1 E-gap position. An adjustable rack of the cylinder, in firing order. The harness mounted on the breaker plate is used to syn- manifold is made in three sections and con- chronize the front points to the rear points. nected together by the distributor covers. (See BREAKER POINTS.The purpose of fig. 9-3). There are 36 lead outlets for attach- breaker points is to make andbreak the primary ment of the spark plug lead to the cylinder. The circuit. They are mounted on the breaker plate. harness is a rewirable type; however, if exten- The breaker points are the pivotless type. The sive wiring is required, the harness should be contacts are made of platinum iridium, and an sent to overhaul. arrow on the assembly indicates the direction of run-in. Two friction screws are used to hold the LEADS points on the breaker plate, and an eccentric is Deliveryof thehigh-tension voltage to used to adjust the points. the spark plug is accomplished through the use

178

151 Chapter 9RECIPROCATING ENGINEIGNITION SYSTEMS

AD.65 Figure 9-3.High-tension ignition harnessassembly. of leads manifold outlet to the spark plug.They are of individual ignition leads. The type cable used depends on the engine sizeand whether the made of seven-strand stairless-steel ignition system is low or hightenswn. The with insulation. high-tension lead in older engines may runfrom The insulation consists of1/16-inch-thick the magneto on the rear accessorypad to the rubber directly over the cable. The rubberis spark plug or, as on the newermodel engines, covered by a 1/32-inch layer of neoprene.The harness or ignition coil neoprenein turn is coated with a layerof run from the ignition cable pre- on the individual cylinderto the sparkplug. lacquer. The rubber layer over the The leads of the DF18LN-2 arein two vents leakage of current from thecable. The sectionsone from thedistributor electrode layer of neoprene protects the rubberfrom oil to the manifold outlet, and theother from the orgasoline, which whould causeinsulation

179

150 W AVIATION MACHINIST'S MATE R 3 & 2 breakdown. The lacquer protects the neoprene Care should be taken whenever the lead is and greatly increases the resistance to in- removed from the spark plug to pull the cigarette sulation breakdown. (ceramic terminal, if used) fr om the plug so that The spark plug lead, from the manifold neither the ceramic insulation within the spark outlet, is encased in a flexible radio shielding, plug is cracked or broken, nor the cigarette which aids in reducing interference in the com- is broken. munication system of the aircraft. Upon installation of the lead, if it has been The cable has the date of manufacture removed completely, care should be observed stamped on it. The "shelf life" is 36 months to prevent the lead from twisting when itis from the date of manufacture. If rewiring is clamped to the cylinder baffles. Also, install required and the age of the cables to be used is the terminal in the plug with the same care as over 36 months, it must not be used forair- it was withdrawn and when tightening the cou- craft ignition. pling nut, do not bend, twist, or distort the elbow. This may cause shorting or grounding Inspection of the voltage and render the spark plug inoperative. Inspection of the ignition leads consists mainlyof checking the individual leads for OPERATION integrity of the ferrules, coupling nuts, and shielding; condition of the ceramic terminal The secondary current is conducted from sleeves, insulation condition, and the terminal the magneto to the distributors by means of high- contactspring. They should be checked for tension leads. These leads are attached to the chafing, routing, and evidence of cracking due distributor covers. The current is transferred to heat or age. through a high-tension block and electrode inthe Allignitionleads should be thoroughly coverto the distributorfinger, from the checked for the above listed items. If found traveling electrode on the distributor finger to defective, they should be replaced. thedistributor bowl electrodes, whichare attached to individual spark plug leads. The Testing distributor finger is driven at one-half crankshaft speed and is so timed as to fire the Testing of the high-tension leads can be cylinder according to manufacturer's speci- accomplished through the use of a high-voltage fications. insulation tester or with an ohmmeter. The As these magnetos have a compensated cam primary consideration is that the lead deliver with the lobes ground at unequal intervals, the all the voltage to the spark plug. The use ofposition of the high-tension electrodes in the the testing units named previously should re- distributor are also unevenly spaced. Therefore, main in the hands of competent personnel who it is important that the high-tension electrode are checked out in the procedures of useand of the distributor finger be set in the proper are qualified to accept or reject thematerial relation to the No. 1 distributor electrode. This in question. The ADR will learn thesemethods relation is governed by the timing mark engraved and procedures as he becomes more proficient on the distributor mounting pad on the engine. in his rating. The important phase, then, of the distributor finger timing is to make sure that a portion of the Removal finger electrode will always be over the distributor head electrode when firing takes place The ignition lead is connected to the spark from any one of the 18 cam lobes. plug at the cylinder end and to the ignition coil or the ignition harness at the other.Removal GROUND TURNUP AND CHECKS of the lead in most cases involves only the spark plug end of the lead. This will occur when the plugs are changed or when troubleshooting the The ground turnup and check procedure for ignition system. the high-tension system follow:

180

1 5 Chapter 9RECIPROCATING ENGINE IGNITION SYSTEMS il9

Ignition Switch Check DDual ignition. LLeft-hand rotation of the magneto. Move the mixture control toward IDLE NManufacturer (Scintilla). CUTOFF until the engine rpm drops down to 9Modification number. 300 rpm; move the mixture control back to The magneto is essentiallyan a-c AUTO RICH. The engine should return smoothly generator.It contains no secondary windings; to 600 rpm. Make this check with the magneto therefore, it produces only low-voltage, or low- switch on RIGHT (R) and then on LEFT (L). The tension,current.Itcontains four complete engine should be capable of performing this test primary circuits, each of which fires nine spark satisfactorily on either magneto switch position plugs. if the magnets and breaker points are in good The magneto is mounted on the rear case or condition. This test should not be made until the accessory section of the engine in a horizontal engine is warmed up sufficiently and tempera- position with the nameplate up, the drain holes tures are stabilized. facing down, and the electrical connection to the harness facing to the right. Ignition System Check It has the standard flange type mount, and four elongated holes for ease of timing to the The remainder of the ignition system check engine. The flange is cast with the outer housing is essentially the same as that for the low-tension and made of aluminum alloy to aid inpreventing system. or reducing radio noise. There are two drain holes. One is located in LOW-TENSION IGNITION the flange to prevent oil or condensation from SYSTEM draining into the magneto generator from the engine. The other drain hole is located in the The ignition system used on most recipro- outer housing to vent the magneto generator to cating aircraft engines in the Navy is the low- atmosphere. tension system. The low-tension ignition system An inner housing made of cast magnesium is favored over the high-tension system for the alloy fits inside the outer housing. Four sets of following reasons: Because of the much shorter pole shoes and extensions are designed as part high-voltage path in the low-tension system, it of the housing. These four sets of pole shoes, is less apt to be affected by moisture and high combined with the two 4-pole magnets, provide altitude operation. The low-tension system re- four individual magnetic circuits. A primary quires less maintenance, and malfunctions are coil is mounted across each set of pole exten- more easily located than in the high-tension sions, and the coils are interchangeable among system.Longer spark plug lifeis obtained themselves, but when they are secured on the with the low-tension system. extensions, they assume definite designations The low-tension ignition system, such as which are marked on the inner housing. that used on the R-3350-32W Wright engine, is Two primary coils are mounted horizontally comprised ofa dual magneto generator, a opposite each magnet. The coils mounted oppo- primary lead conduit containing four primary site the No. 1 magnet are labeled the RI and the leads (from the coils in the magneto) and one Ll coils; the coils mounted opposite the No. 2 spark advance relay lead, a starting vibrator magnet are labeled the R2 and the L2 coils. It is lead, a harness, two distributors, nine Y-leads, from this source that each circuit of the igntion an ignition switch, four switch leads, a start- system receives its designation. The No.1 mag- ing vibrator, and spark plugs. net produces current in the RI and Ll coils, and the No. 2 magnet produces current inthe R2 and MAGNETO GENERATOR L2 coils. (See fig. 9-4.) One end of the coil wire is grounded to the The DLN+9 magneto generator is mounted housing. The other end is connected to afive-pin on the supercharger rear cover at the rear of the cannon plug on the cover. engine. The letter and number designation is as The magneto generator cover is of cast follows: aluminumalloyandfitstightlyonthe

181

15( AVIATION MACHINIST'S MATE R 3 & 2 ice shaft. Nine dual impulses are needed. There- fore, the magnet shaft is driven at 1 1/8 engine speed on an 18-cylinder engine. The maximum , coming-in speed of the magneto generator is 250 rpm, but will more often be near 90 or 100 rpm. Coming-in speed is the speed at which the voltage induced is high enough to fire a 5-milli- meter gap evenly and consistently.

DISTRIBUTORS The purpose of the distributors is to direct the low voltage to the proper high-tension coil units at the proper timed interval to fire a spark plug. The distributors are mounted on the upper side of the nose section. The left distributor is .0 used to fire all the rear plugs in all cylinders. The right distributor is used to fire all the front plugs in all cylinders. They are of the conventional flange-mounted design, with three elongated holes in the flange for fine timing to the engine. (See fig. 9-6). The AD.66 housing is made of aluminum alloy and has a Figure 9-4.Magneto generator vent in the cover to allow the escape of ozone coil installation. gases and thereby prevent nitric acid formation. The heatof the arc combines the outerhousingtosealtheinteriorofthe nitrogen and ozone, and this forms a deposit on magneto. the dielectric parts, such as the rotor and seg- Two 5-pin cannon plug connectors are on ments, and forms a good conducting surface the cover, one for connectingthe magneto switch to the nearby grounded parts. By having adequate to the coils, the other for connecting to the ventilation, the fumes can be carried away be- harness. forethey have a chanceto do any harm. A timing plunger is also located on the The distributor cover is secured to the dis- magneto cover and is used to locate the E-gap tributor with a clamping ring. The segment plate position. When it Is depressed, it will slip into with the 18 segments arranged in 2 rows of 9 one of four slots milled into the endof the each is bolted in the top of the cover. The seg- magnet shaft. Each time the timing plunger ments are insulated from each other, and they falls into one of the slots, the magnet will be in have their own primary lead running to a coil an E-gap position for the No. 1 or rear magnet. unit and then to the spark plug. Also in the cap (See fig. 9-5). are three contact springs which, when placed A lip type clamp and four screws hold the over the distributor, come against a matching cover on the outer housing. The clamp is drawn bushing in the collector plate. This is how the tight by two screws, which should be tightened current enters the distributor. to the proper torque value. The two distributors are identical and are The two magnets are mounted on the same interchangeable from right to left. shaft and the poles are staggered 45 degrees In the body of the distributor are four sets from each other. Because the coils are mounted of breaker assemblies which are actuated by horizontally, eaCh E-gap will affect two coils at two 9-lobe compensated cams. The two cams one time. There are, therefore eight compensate for the top center variation which is consecutive dual impulses of low-voltage cur- characteristicofradialengines. Each cam rent produced for each revolution of the magneto actuates two breaker assemblies; that is, one

182 150 1.c/ Chapter 9REC1PROCATING ENGINE IGNITION SYSTEMS

DISENGAGED ENGAGED

IMMII=10 40Z07./.%Z.

LOCKRING

MAGNET SHAFT

STOP NOTCHES

AD.67 Figure 9-5.Magneto generator E-gap plunger. cam operates No. 1 retard points and No.2 picked up by the brush and transferred to the retard points; the other cam operates No. I innerrow of segments, and thence to aneven- advance points and No. 2 advance points. numbered cylinder. Because these points are of the pivotless On top of the distributor housing is a compo- type, there is no set clearance; instead a point sition collector plate with two collector rings duration of 22 degrees is used. For proper inner and outer. These two rings are insulated operation of the points, the spring that holds the from each other and are part of the primary cam follower agahist the carn must be strong circuit. The No.1 retard points and No. 1 enough to eliminate any tendency of the cam advance points are electrically connected to the follower to skip from lobe to lobe and miss inner collector ring. No. 2 retard and No.2 the hollows in between. This is called floating advance points are connected to the outer point and will cause a very erratic spark at the collector ring. plug. The main spring tension should be from 15 The rotor is secured to the end of the dis- to 32 ounces for proper operation. If the spring tributor above the collector plate. It carries tension is to o. great, this will cause the points four carbon brushes under spring tension, two of to bounce. which extend up from the rotor and two others If current is present in the inner ring of the which extend down from the rotor and make con- collector plate, it will be picked up by the brush tact with the collector rings on the collector making contact with the inner ring. As this plate. These brushes have a minumum length brush is connected to a brush facing up, that and are interconnected in pairs. brush will also become energized. It will be A distributor cap fits over the top of the making contact with a segment in the outer row distributor and provides the means for getting of segments, and transfer the current to the the current to the spark plugs. Each c.lp is particular transformer coil unit at the cylinder. designed with 18 segments arranged in two the outer Ifit should be the outer ring on the collector rows, nine in the inner row andnine in plate that is energized, the current will be row. The segments in the inner row arearranged

183

15 zi /5-;1- AVIATION MACHINIST'S MATE R 3 & 2 the coil units as a terrific surge. This surge through the primary coils of the unit induces the high voltage in the secondary to arc across the gap of the spark plug. The duration of the sec-. COVER ondary current is very short-lived and falls away quite rapidly. The two distributors are times exactly together, and when one (right) is firing the front plug in a cylinder, the other (left) is firing a rear plug in that same cylinder. In the base of the distributor there is a relay

-.4 which operates twocontacts,one for each ignition circuit. Each ignition circuit has an advance breaker and a normal firing (retard) breaker. The advance points are connected DISTRIBUTOR directly to ground, and the retard points are HARNESS CONDUIT grounded through the relay as shown in figure 9-7. With the relay control switch in the cockpit in the retard position (OFF), no current flows in CLAMPING the relay coil, and spring pressure holds the RING points in contact with each other. With the relay contacts closed, the primary current in the ignition circuit has a direct path to ground which prevents any interruption of the primary current when the rotating cam opens the advance points. As the breaker cam continues to turn, the retard points are opened and there is an immediate interruption of primary current followed by the normal cycle of ignition events. AD.68 With the relay control switch in the advance Figure 9-6.Distributor and cover. position, the relay coilis energized and the contacts are separated. The retard points no to send their impulses to the even-numbered longer are connected to ground; and when the cylinders and the segments in the outer row send advance points open, the primary current is their impulses to the odd-numbered cylinders. interrupted and ignition occurs. As long as the breaker points are closed, The relay points are held in the closed (re- there are two complete circuits in the system. tard or normal firing) position by spring pres- One is out through the breaker points to ground sure. If a relay should fail, the contacts would and back to the grounded primary coil; the other remain closed and normal firing would take is out through the distributor into the primary place. windings of the coil unit. The circuit through the Each of the breaker assemblies must be so points has a lower resistance than that of the adjusted or timed to insure that the current from circuit through the coil units; therefore, the the magneto generator is allowed to go to the current will take the path of least resistance high-tension coil unit at the proper time. The through the points as long as they remain closed. efficiency of the engine power depends very When E-gap is reached in the magneto generator much on the spark being delivered when it will and the current flow is at its peak value, the get the maximum horsepower available from points are opened by the cam and the current each cylinder. suddenly has no place to go but out to the coil The timing marks on the rotor and collector units. Because it was interrupted by the points plate are put there for a purpose. It can be when it was at peak value, it will travel through readily seen thatif the timing marks on the

184

1 tiu /513 Chapter 9RECIPROCATING ENGINEIGNITION SYSTEMS

DISTRIBUTOR 7 I r DISTRIBUTOR FINGER SECONDARY MAGNETO COIL r 1 NO.1 CIRCUIT

1(NORMAL ± FIRING RELAY BREAKER NORMALLY CLOSED

al.milloftge -1-. MOM .. ADVANCE NO.2 CAPACITOR SPARK BREAKER CIRCUIT --.. 011111. =MO. L______JL

1 1

1 COCKPIT 1= 24 VOLT CONTROL 1 - BATTERY SWITCH L RADIO FILTER AD.69 Figure 9-7.Schematicdiagram of ignition circuit. ignition system in time rotor do not align exactly withthe correct marks This will make the whole on the collectorplate at the moment ofpoint with the engine. opening or closing, thedistributor is not timed correctly. HARNESS The timing of the distributorrotor to the by use of the collector plate is accomplished The low-tension harness isdifferent from vernier:ratchet. harness in that it carries The No. 1 mark on therotor should align that of the high-tension only low-voltage current.The purpose of the with the time open mark onthe collector plate current from when the No. 1 points just startto open on No. 1 harness is to conduct low-voltage the time close mark the magneto generator to theignition coil units, lobe and should align with the distributors and just as the points close.The No. 2 points, if located on the cylinders, via timed properly, will also openwhen the No. 2 primary (Y) leads. with the time open The complete harnessassembly consists of mark on the rotor aligns the magneto to harnesslead, tubular harness, mark on the collectorplate and will close (Y) lead assem- when the mark on the rotoraligns with the time distributor covers, primary blies,ignition coil units, and thespark plug close mark. 9-8. It is very important thatthe points open at leads. These are shown in figure to the time of the The MAGNETO TOHARNESS LEAD (fig. the correct time in relation plug lead. Pins magnetic position in themagneto generator, 9-8, item 1) is a 5-pin cannon A, B, C, and D conductprimary current from which has been installed atthe engine firing coils to the when we ratchet the the magneto generator's primary position. Keep in mind that path for 28 volts the carbon brushes distributors. Pin E provides a rotor, we are also positioning direct current to thedistributors for spark so that they willalign with the proper segments when we install the cover onthe distributor. advance operation.

185

161 AVIATION MACHINIST'S MATE R 3 & 2

AD.70 1.Magneto generator to 4.Spark plug lead. harness lead. 5.Ignition coil unit. 2.Distributor segment 6.Primary (Y) lead. plate. 7.Harness. 3.Distributor cover. Figure 9-8.Low-tension ignition harness assembly. The HARNESS is tabular constructed and Y lead connection. Around the harness are 12 has 23 primary wires routed through it. Included connecting points-two for distributor cover con- are four primary leads from the magneto gen- nection, one for magneto to harness lead connec- erator, one lead for the 28-volt direct current tion, and nine for primary (Y) lead connection. to operate the spark advance relay, and 18 (See fig. 9-8, item 7.) primary leads directing primary current from The DISTRIBUTOR COVERS, as mentioned the distributor segment plate to the outlets for earlier, are an integral part of the harness and

186

164 Chapter 9RECIPROCATING ENGINE IGNITION SYSTEMS

START WITH CYLINDERS have a segment plate bolted to the top of them. 1 AND The segment plate has 18 segments arranged in 10 AOD 4 EACH TIME two rows of nine each. Attached to each segment is a primary lead, which is routed through the SO )445 ro harness to a Y lead connecting point. As pre- CIL. viously stated, they are insulated from each c.4b'tJ other. They are also numbered 1 through 18, inner row even numbered and outer row odd numbered. Do not mistake the numbering for At enginefiring orderrefer totable 9-1 and xp.0.; X 7- figure 9-9. eu0 There are also three contact pads on the segment plate, labeled Pl, P2, and BO. Pads P1 , and P2 receive prirhary current from the mag- qt,* neto generator and transfer it to the distributor 0 1.% IF TOTAL IS OVER 11, by means of a contact spring on the bottom of SOUR ACT ADO 4 AND 11 the segment plate (fig. 9-8, item 2). The BO SUITRICTI pad receives 28 volts direct current and trans- OD 4 AND SU1TRACT 11 fers it to the spark advance relay in the same ANEASY WAY TO DETERMINE THE DISTRIBUTOR SEMI ENT CON- NECTIONS WHEN YOU DO NOT HAVE A CHART FORREFERENCE.START manner as P1 and P2 does. WITHseGmEn s 1 AND 10. WHICH FIRE CYUNDERS I AND 10 RESPECTIVE- LYAVORK CLOCKWISE ADDING FOUR EACH TIME TC OBTAIN THE NEXT The PRIMARY (Y) LEAD (fig. 9-8, item 6) CY LEMER TO FIRE. isa shielded construction with four primary wires routed through it. It is constructed in the AD.71 shape of a Y, with two primary leads routed Figure 9-9.View of DLN-9 distri- through each fork of the Y. The 4-pin end con- butor segments, illustrating segment nects to the harness and the 2-pin ends each numbering and cylinder firing relation. connect to an ignition coil unit. The Y lead is not a rewirable lead; therefore, it must be re- ing, a secondary winging, and a coil core. It is placed when a malfunction occurs. here that the low-tension current is converted to the high-tension current requiredfor ignition. IGNITION COILS A coil unit is mounted on each cylinder of the Each coil unit contains two transformers, engine, furnishing high-tension current to the each transformer consisting of a primary wind- two spark plugs of that cylinder. A high-tension (coil-to-spark plug) lead carries the current from the coil units to each spark plug. A coil Table 9-1.Segment numbering unit is shown in figure 9-10. related to firing order. SPAR PLUG LEADS EVEN ODD The spark plug lead (fig. 9-8, item4) con- ducts the secondary current from the ignition Segment Firing Segment Firing No. order No. order

1 1 2 12 3 5 4 16 5 9 6 2 7 13 8 6 9 17 10 10 11 3 12 14 13 7 14 18 15 11 16 4 AD.72 17 15 18 8 Figure 9-10.Ignition coil unit.

187

1 6 AVIATION MACHINIST'S MATE R 3 & 2 coil unit to the spark plug to be fired. The low- tension spark plug lead is much shorter than that of the high-tension system; therefore, it does not allow dissipation of the current from the coil unit to the spark plug. The end results are a hotter spark at the plug andless fouling of the spark plugs.

SWITCH

The magneto primary circuits are wired through an ignition switch which gives the pilot OFF BOTH CIRCUITS NOT OPERATING control of the ignition system and enables him RIGHT CIRCUIT OPERATING to check for proper operation of each magneto R system. There are four positions on an aircraft LEFT CIRCUIT NOT OPERATING magneto switch-OFF, L (left), R (right), and L ILEFT CIRCUIT OPERATING BOTH. One side of the switch is connected to IRIGHT CIRCUIT NOT OPERATING ground. When the switch ig-fh the OFF position, it is closed, connecting the four primary coils. BOTH iBOTH CIRCUITS OPERATING of the magneto to ground. When the switch is at AD.73 BOTH, this circuit is open andthe primary coils Figure 9-11.-Single engine ignition switch. are no longer grounded through the switch. In the R position, the primary coils which supply it indicates that the primary coil of the magneto current to the left distributor are grounded; in is not being grounded. This is a dangerous con- the L position, the primary coils which supply dition because the pilot would no longer have current to the right distributor are grounded. positive control of the magnetos. This would be Therefore, when the pilot switches to R, the of particular importance in an emergency where engine is running on the right distributor, and the pilot would have to cut the igintion, as in a the pilot can check for normal operation of that crash landing. It is also dangerous even with circuit. With the switch in the L position, opera- the engine not running, as anyone moving the pro- tion of the other half of the ignition system can peller would be exposed to the danger of the be checked. An ignition switch for a single engine engine kicking over, since one magneto circuit aircraft is shown in figure 9-11. isstill ON. Although all Navy piston-engined An ignition switch designed for twin-engine aircraft have some form of idle cutoff system aircraftis shown in figure 9-12. This switch in the carburetor, it is very important that the combines two switches of the type shown in switch be capable of grounding the magneto. figure 9-11, with the addition of a push-pull knob The normal rpm drop that occurs when which operates the master emergency ignition switching from BOTH to either R or L is due switch. When the knob is pulled out to the OFF to the changed conditions in the combustion position, all ignition is cut off regardless of the chambers. With the switch on either R or L, position of the switch levers. In an emergency, one-half of the magneto is grounded and only the all ignition for both engines can be cut off by row of plugs served by the other half of the one movement of the push-pull knob to the magneto is firing. The charge is being burned OFF position. by a single point of ignition and therefore re- When switching from BOTH to either R or quires a longer time to burn. The resulting L, normal operation is indicated by a loss of slight loss of power is indicated by the loss in engine rpm. The amount of drop to be expected rpm. If the loss is greater than the allowable varies with the engine and the allowable maxi- maximum, usually 100 rpm, it indicates a mal- mum drop can be found in the flight manual of function of the magneto, distributor, harness and the engine concerned. If no drop in rpm occurs, wiring, or spark plugs.

188 6,1 Chapter 9RECIPROCATING ENGINE IGNITIONSYSTEMS result, the core of WHEN CENTER KNOB IS PULLED OUT, NO current is interrupted. As a the vibrator coil loses itsmagnetism, and the GNETOS ARE OPERATING. vibrator points are again closedby the action of a spring. Again currentflows through the vibra- torcoiland the magneto primary, andthe process is repeated. Whenthe vibrator points open, current stops flowing;when they close, current flows. Since these points arealternately opened and closed there is aninterrupted flow of current in the magneto primary.This interrupted current producesvoltage impulses in the magneto primary much likethe magneto does when it is operating. Theresultant voltage produced in the magneto secondary isdistributed in the same manner as the magnetospark. See figure 9-13 for schematic of startingvibrator circuit.

MAINTENANCE OFF --IBOTH CIRCUITS NOT OPERATING Maintenance of the ignition system, re- the make R IRIGHT CIRCUIT OPERATING gardless of the size of the engine or ILEFT CIRCUIT NOT OPERATING of the components in the system,is of importance to the mechanic. There are anumber of L jLEFT CIRCUIT OPERATING checks that can be made priorto and after 'RIGHT CIRCUIT NOT OPERATING periodic inspections, during groundoperations, and in the air (if an analyzer isinstalled). These BOTH IBOTH CIRCUITS OPERATING checks make it possible for themechanic to locate the source of specificdiscrepancies. NOTE: THE SAME CONDITIONS PREVAIL ON Failure to pass these checks willusually pinpoint RIGHT ENGINE. AD.'74 the defective component. in firing Figure 9-12.Dual engine ignitionswitch. The ignition system must deliver, order, and at a predeterminednumber of degrees ahead of the powerstroke in the individual STARTING VIBRATOR cylinder, high-voltage current to thespark plugs When turning with the starter tostart the of each cylinder in the engine.The voltage out- the magneto or put of the ignition system mustbe such that the engine, the rotational speed of electrodes under magneto generator is too slow toproduce suffi- spark will jump the gap at the to fire the any and all operatingconditions. cient voltage at the spark plug gap discussed plug. Therefore, provision mustbe made to The two types of ignition systems voltage to in this chapter consistprimarily of a magneto, supply the engine with the required plugs, and start the engine. The startingvibrator receives distributors, ignition harness, spark battery to aid in ignition switches. Proper maintenanceis an low voltage current from the component starting the engine. absolute necessity, as some of the When the starter switch is closed,battery parts of the ignition systemoperate at high rates Then battery cf speed requiring a finedegree of accuracy in current closes the relay contacts. air/fuel mixture in the current flows through thevibrator coil. The maintenance so that the closed contacts of cylinder may be ignited at thecorrect instant closed vibrator contacts the at all op- the relay and the magneto primarycoil. As cur- to develop the right amount of power rent flows through the vibratorcoil, the iron erating speeds of the engine. and causes the vibra- E,.ch of the units named may developcondi- core becomes magnetized lower resistance than tor points to open.In doing so, the battery tions where a higher or

189

1. 6 AVIATION MACHINIST'S MATE R 3 & 2

TO DISTRIBUTOR IGNITION SWITCH Cr6115111\--t _ran...._,

BREAKERY POINTSok RIGHT MAGNETO

oSTARTER MESH SWITCH i- ...II.-

---: I- MESHING SOLENOID

AD.75 Figure 9-13.Starting vibrator circuit.

normal could occur and thus affect engine opera- REMOVAL AND INSTAL- tion. Some of these conditions that may happen LATION OF COMPONENTS are as follows: The breaker points do not open far enough; the gaps between the distributor The timing of the magneto and distributors rotor and the harness electrodes are too large; is generally considered to be apart of the instal- oily terminals or carbon tracking. High or low lation procedure; however, to simplify the dis- resistances may be due to poor or damaged cussion, the timing procedure is discussed in the cigarettes (ceramic terminal) on the high tension section following the removal and installation leads; and spark plug gaps have too little or too procedure. much clearance. To obtain correct engine performance and Removal of Magneto Generator power, the internal timing of the magneto must be correct. The internal timing of the magneto Disconnect the ignition switch lead and the consists of the breaker point opening interval main primary lead at the magneto. Place pro- in relation to the position of the rotating magnet. tectivecovers overthe connections on the The position of the rotating magnet when the magneto. Remove the magneto attaching nuts and breaker points open on the No. 1 lobe of the washers and remove the magneto. Remove the cam is determined when the magnet E-gap marks gasket, if used. on the timing post and the cam step are aligned. Magneto-to-distributor-to-enginetimingwill Installation of Magneto Generator also affect the power and the performance of the engine. The breaker point opening must be timed Insure that the magneto has been inspected to the specified position of the engine crankshaft for correct assembly and operation and that the so that the spark will occur at the spark plug gap drive shaft nut is tight and cotter keyed. The at the correct instant. piston in No.1 cylinder should be set at the

190 1 60 Chapter 9RECIPROCATING ENGINEIGNITION SYSTEMS

before top center the direction opposite normal rotationand then prescribed number of degrees of rota- on the compressionstroke. If a gasket is used, bring it forward slowly in the direction mounting pad. tion until the piston is at the prescribednumber install a new one on the magneto compression Remove the spring clip from thetiming plunger of degrees before top center on the Depress the plunger and stroke.If the propeller has been removed, a on the magneto cover. another turn the magneto shaft untilthe plunger drops special turning tool is used. Meanwhile, man should push in on thetiming plunger. If the into one of the four notches inthe magneto shaft. will drop This insures the correct E-gapposition for the installation is correct, the plunger be held in into the slot just as the pistonreaches the magneto shaft. The plunger must center. while the magnetoisbeing installed. (See prescribed number of degrees before top fig. 9-14.) Torque the magneto attaching nuts. remove the Reinstall the spring clip on thetiming If the drive splines do not mesh, from magneto and rotate the magnetoshaft 90 degrees plunger. Remove the protective covers the next slot on the the magneto connections. Connectthe switch so the plunger bottoms in conduit. Lock- magneto shaft. Again install the magneto.Con- conduit first, then the harness tinue this process of rotating themagneto shaft wire the connections. until the splines will engage andthe studs are in the approximate center of themagneto mounting Removal of Distributor in this exact flange slots. Hold the magneto distributor position and secure with theattaching nuts and Loosen the distributor cover to clamping ring. Remove the distributorcover, 'washers. segments in the Check to make sure the magnetois mounted being careful not to damage the properly. One man should turnthe propeller in cover or the carbonbrushes on the distributor.

NAMEPLATE UP

PLUNGER DEPRESSE

AD.76 Figure 9-14.Installing magneto on engine.

191

16i AVIATION MACHINIST'S MATE R 3 lc 2 /6,)

ROTOR IN NO.1 Install protective covers at once on both the FIRING POSITION distributor and the distributor cover. Attach the distributor cover to a cqnvenient engine part temporarily with lockwire to avoid interference when removing and installing the distributor. Remove the distributor attaching nuts and remove the distributor from the engine. Installation of Distributor Before installing a distributor, always check the master rod designation plate on the distribu-

tor against the engine data plate to see that the STUDS APPROXIMATELY distributor has the correct cams corresponding CENTERED IN SLOTS to the master rod location in the engine. Do not AD.'77 remove the protective covers until the dis- Figure 9-15.-Correct positioning of the tributor is actually ready for installation. distributor on the mounting pad. First, rotate the engine in its normal direction until the No. 1 cylinder is at the normal ing ring in place. Tighten the clamping screw to firingposition, as prescribed in the engine- the proper torque. Lockwire the screw to the manufacturer's instructions. This is the same holes provided in the clevis of the clamp bracket. engine position you used for installation of the Some types of distributors contain two small magneto. plugs, one of which is solid and one of which has Remove the clamping ring and take off the a drain hole. If necessary, interchange the posi- protective cover from the distributor. Rotate the tions of these plugs so that the one with the hole distributor shaft until the line marked "1R" on is on the underside of the distributor, in order the rotor is lined up with the line marked TIME to provide drainage for any oil or water which OPEN on the collector plate. Keeping the shaft might enter the unit. in this position, install the distributor on its pad so that the studs are approximately in the middle TIMING of the elongated holes in the distributor mounting flange.(See fig. 9-15.)If the studs are not When a mixture of air and fuel is admitted approximately in the center of the elongated into the cylinder and compressed, the next step holes, remove the distributor from the pad. in the cycle of operation is the ignition of the Using the proper tools, remove the securingnut compressed charge at the correct time. The from the drive end of the distributor shaft. Shift ignition system furnishes high voltage peri- the drive gear one tooth on its spline; then put odically to the spark plug gap at a predetermined the nut on and put the distributor inplace on the position of piston travel inthe cylinder. Magneto pad again. Be sure the rotor is still lined up operation is timed to the engine so that a spark with the "1R" position. Recheck the position of occurs only when the piston is on the proper the studs in the elongated flange holes. If neces- stroke and at a specified number of degrees sary, shift the drive gear again on its splines before top dead center. The distributor routes until the distributor can be mounted in the proper the generated voltage to the various cylinders position. When the right setting for the drive in the firing sequence of the engine. gear is found, take the distributor off the pad, tighten the end nut, and install a nay, cotter pin Magneto (High-Tension) in the castellated nut. Put the distributor back Before installing a magneto, always make on the pad and install the holddown nuts. Do not sure that it has been properly checked and in- tighten the holddown nuts until the distributor spected.Itis assumed that the magneto has has been timed to'the engine and to the other been correctly internally timed and synchro- distributor. nized prior to installation. All adjustments for After the timing procedure is completed, timing must be made at the drive end of the replace the distributor cover, and put the clamp- magneto.

192

1 60 /el Chapter 9RECIPROCATINGENGINE IGNITION SYSTEMS

magneto to the engine, magneto has been set atthe correct position, In order to time the tighten the mounting nuts,making surethe the following ^4epsshould be followed: shift when the nuts are 1. Turn the enginecrankshaft until the magneto does not piston of the No.1 cylinder is in thefiring tightened. compression stroke in ac- 7. As a final check turnthe crankshaft position on the backward about 30 degreesand then forward cordance with the enginemanual. This position just starting to open with a piston position until the contact points are may be determined on the No. 1 lobesof the cam (use timinglight). indicator. The engine should nowbe at its exact No.1 2. Remove the magnetobreaker cover and straightedge placed on the (P) leads for safety pur- firing position, and a disconnect the primary breaker cam should line upwith the mark on the poses and propertiming light operation;then shaft to the position where breaker plate timing post. turn the magneto drive 8. Reconnect the primary(P) leads and then a straight edgeheld against the step ofthe cam lines up with the timingmark on the breaker install the magneto breaker cover. the breaker contact plate post. At this position (Low-Tension) points will be juststarting to open on the No.1 Magneto Generator lobe of the breaker cam. does not align The magneto is internallytimed at the fac- NOTE: If the straightedge is never adjusted inthe with the mark within onesixty-fourths inch tory or at overhaul and when the contact pointsopen, do not attemptto field. Return For efficient operationof the ignition sys- correct it by adjustingthe contact points. be installed at theE-gap bench and recheck thein- tem, the magneto should the magneto to the position tocoincide with theengine firing ternal timing. position. 3.Install the magneto onthe engine in this drive coupling in such a The first step is to rotatethe engine shaft in position, engaging the until the piston of No.1 contact points can beopened by its normal direction way that the cylinder is in the normalfiring position on the turning the completemagneto in the direction by the rotation compression stroke. Thepiston position indi- OPPOSITE to that indicated cator should be used forthis operation. arrow on the magnetohousing. The elongated until the timing flange provide forthis Rotate the magneto shaft slots in the mounting plunger bottoms in oneof the slots on the adjustment. Set the magnetoat the position where of the four E-gap the instant of opening magneto shaft, locating one the breakers are just on positions of the No. 1 magnet.Install the magneto on the No, 1lobes, at which position astraight- magneto must line up with its on the mountingpad of the engine, lithe edge held against the cams shaft splines will notmesh with the splinesin corresponding timing mark. magneto shaft to the next determine theposi- the engine, rotate the 4. Use a timing light to E-gap position, and againattempt to install the tion where the contactsstart to open. The useof bottomed until the between the contact pointsshould magneto. Keep the plunger a feeler gage magneto has been secured.(See fig. 9-14.) be avoided. synchronization of one- Put the magneto in placeand check again. 5. A variation in Continue this process ofrotation of the magneto half degree was permittedin setting the breakers This shaft until the splines engage.Then hold the at the time themagneto was assembled. position and tighten the barely perceptibledifference magneto in this exact may result in a stud nuts which secure themagneto to the engine, between the opening ofthe two breakers when for these nuts. The checked with the timinglight in the above proce- using the proper torque will not affect the elongated slots will take up anysmall amount of dure. This small variation the splines of themagneto operation of either theengine or the magneto. error in meshing 6. Always make surethat the straightedge generator. mark for the cam at the To check and be surethat the magneto is lines up with the timing mounted in the rightposition, slowly rotate the No. 1 firing positionbecause this mark will be procedures as a ref- engine shaft until it reachesthe normal firing used later in maintenance position for No. 1 cylinder.Push in on the timing erence for adjustingthe contact points. Whenthe

193

l 6 j AVIATION MACHINIST'S MATE R 3Z. 2

plunger;if your installationis correct,the Remove the clamping ring and take off the plunger will bottom. protective cap from the distributor. Rotate the Remove the protector covers from the can- distributor shaft until the No. 1R mark on the non plugs and connect the leads from the harness rotor is aligned with the time open mark on the and switch. Turn the spanner nuts until tight collector plate. Keeping the rotor in this posi- and then lockwire. Install the safety clip on the tion, install the distributor on its mounting pad timing plunger. so that the securing studs are approximately in the middle of the elongated holes in the mount- Distributors (High-Tension) ing flange. (See fig. 9-15.) If the studs are not in the center of the slots, There are several different types of high- remove the distributor from the pad. With a tension ignition system distributors. The type of 5/8-inch socket and a 17-tooth spline wrench, distributor and its method of timing discussed in remove the securing nut from the drive end of the following paragraphs is the tubular type the distributor shaft. Shift the drive gear one harness and distributor. tooth on its spline; then put the distributor in To time the distributor to the engine, it will place on the pad again. Be sure the rotor is still be necessary to loosen the housing andremove aligned with No. 1 and open. Check for mounting some of the spark plug leads attached to it. The studs centered in elongated holes. Ifnecessary, housing is loosened by removing the base clamp shift the drive gear again on its splines until the ring and loosening the manifold clamp rings. distributor can be mounted in the proper posi- Then the distributor housing is pushed back to tion. When the right setting has been found, expose the distributor finger. tighten the end nut and install a new cotter pin. The next step in distributor timing pro-. Put the distributor back on the pad and screw on ceclureis to remove the distributor finger to the holddown nuts. Do not tighten them now. expose the nut which locks the drive coupling. Connect timing light with red lead to the Then loosen the coupling nut and install the dis- connecter strip for No. 1R service points. The tributor timing tool. Rotate the coupling unit other lead is attached to the housing. Now car- against normal rotation until the edge of the tim- fully rotate the distributor clockwise on its ing tool is in line with the scribed line on the mounting pad until the timing light indicates parting surface. Tighten the coupling nut in this that the points are just opening. Holding the disposition after all backlash has been removed tributor in this position, tighten the flange nuts. from the distributor drive gears. The timing NEON type lightLight has just come on, tool can now be removed and distributor finger indicating points have just opened. FILAMENT installed. type lightLight has just gone out, indicating The distributor housing assembly can now points have just opened. be placed in position on the distributor base. In mounting the econd distributor on the Secure all ,lamp rings on the distributor and engine, follow the same procedure as for the install the spark plug leads that were removed. first. Then connect the timing light with a red Thedistributorcan now be lockwired as lead to No, 1R service points of each distributor necessary. and the black lead to ground. (See fig. 9-16.) Then back up the engine through No. lfiring Distributors (Low-Tension) position to see if both No. 1R points are opening at the same instant; if not, turn the second dis- Before installing a distributor, it is always tributor slightly on its mounting pad until both advisable to compare the master rod designation sets of points are opening at exactly the same plate on the distributor with the engine data instant, which must also be the instant the No. 1 plate to see that the distributor has the correct cylinder is ready to be fired. If installing only cams corresponding to the master rod location one distributor, be sure it is timed exactly to of the engine. the one already on the engine. It must also have Locate the No. 1 piston at thefiringposition the same type of spark advance mechanism. as prescribed by the engine manufacturer's Replace the distributor head and put the specification. clamping ring in place. Tighten the clamping /63 SYSTEMS Chapter 9RECIPHOCATINGENGINE IGNITION

LIGHT HAS JUST GONE OUT INDICATING POINTS HAVE JUST OPENED

the engine. AD.78 Figure 9-16.Timingthe distributor to the spacers whichconnect the inch-pounds torque, andlockwire by disconnecting screw to 30 breaker supports. holes provided. points should openwhen the screw to the of the The No. 1 advance If necessary,interchange the position the rotor isaligned with the portion of the the lA mark on plate. (See fig. small plugs locatedin the lower OPEN mark onthe collector distributor so that the onewith the hole is on in the normaldirection of to provide 9-18.) Turn the rotor should close the lower side ofthe distributor rotation. The No.1 advance points drainage for any oil orwater that wouldenter on the rotoris aligned with when the lA mark plate. (See the unit. the CLOSE mark onthe collector INTERNAL THVIDJGOE THE MANUAL AD- timing marks on fig. 9-19.) when the VANCE DISTRIBUTORS.The The No. 1 retardpoints should open collector plate of themanual rotor is alignedwith the OPEN the rotor and in figure IR mark on the advance typedistributor are shown collector plate. (Seefig. 9-20.) The should be checked forthe mark on the 1R 9-17. This distributor No. 1 retardpoints shouldclose when the timing of the followingevents: is aligned withthe CLOSE OPEN. mark on the rotor (See fig. 9-21.) 1.No. 1 advance points mark on thecollector plate. 2. No. 1 advancepoints CLOSE. points should openwhen The No. 2 advance aligned with the 3. No. 1 retardpoints OPEN. the 2A mark onthe rotor is 4. No. 1 retard pointsCLOSE. the collectorplate. (See fig. points OPEN. OPEN mark on 5. No. 2 advance 9-22.) 6. No. 2 advancepoints CLOSE. in the normaldirection of Turn the rotor should close 7.No. 2 retard pointsOPEN. rotation. The No.2 advance points No. 2 retard pointsCLOSE. isalignedwiththe 8. action withthe2A mark To get an indicationof breaker point CLOSE mark onthe collectorplate.(See lights,osilate the advance with the timing breakers fig. 9-23.) breaker assembliesfrom the retard

195 AVIATION MACHINIST'S MATE Ft 3 & 2

TIMING MARKS ON ROTOR

eIlIVZ apt

AD.81 Figure 9-19.Positionof No. 1 advance points CLOSE.

AD.79 Figure 9-17.Timing markson the rotor and collector plate of the manual advance type distributor.

AD.82 Figure 9-20.Position of No. 1 retard points OPEN.

The No. 2 retard points shouldopen when the 2R mark on the rotor isaligned with the OPEN mark on thecollector plate.(See fig. 9-24.) Turn the rotor in the normal direction of rotation. The No. 2 retard points should closewhen the 2R mark on the rotor isaligned with the CLOSE mark on the collectorplate. (See fig. 9-25.) NOTE: Reconnect thespacers between the AD.80 breaker supports. Figure 9-18.Position of No.1 NOTE:Ifthe breaker advance points OPEN. pointsetting is changed on either type of low-tensiondistribu-

196 I 7.4 Chapter 9RECIPROCATING ENGINEIGNITION SYSTEMS /i 5-

A.D.83 AD.85 Figure 9-21.Position of No. 1 Figure 9-23.Position of No. 2 retard points CLOSE. advance points CLOSE.

r"...... f.s.r...,1911.y.3 ti

AD.86 AD.84 Figure 9-24.Position of No. 2 Figure 9-22.Position of No. 2 retard points OPEN. advance points OPEN ers which connect the supports.Connect the tor, the point duration will be affected,and the timing lights across the No. 1 retard points. distributor must be retimed in accordancewith Secure the distributor in the position wherethe ove rhaul instruct ions. No. 1 retard points just open. Recheck for proper TIMING THE MANUAL ADVANCEDIS- timing and for synchronization with the other TRIBUTOR TO THE ENGINE.Using thepiston distributor. Reconnect the spacers. position indicator, locate the properfiringposi- tion of the No. 1 cylinder on thecompression Ground Turnup and Checks stroke. Turn the distributor shaft untilthe IR mark on the rotor is alinged with theOPEN After starting, warm up the engine at ap- mark on the collector plate, andinstall the dis- proximately 1,200 to 1,400 rpm, until the cyl- tributor on the mounting pad of theengine. inder head temperature is 125°C or more.With Isolate the retard breaker points fromthe ad- the throttle closed, the engine should idle at ap- vance breaker points bydisconnecting the spac- proximately 600 rpm.

197

17J /06 AVIATION MACHINIST'S MATE R 3 & 2 8. During the magneto check, it is recommended that readings of fuel flow, rpm, and BMEP be taken so that a cross-check of performance can be made with the other engines in a multiengine aircraft. A drop of 8 to 9 BMEP is considered equivalent to a 75-rpm drop. 9. When the rpm drop exceeds 150 and/or excessive roughness is encountered, retard the throttle to idle before returning the magneto switch to BOTH. In cases of known richer than normal carburetion, the following procedures are recommended if the limits in the general ignition check are exceeded: 1.Set manifold pressure (MAP) equal to AD.87 static gage pressure with the throttle. Figure 9-25.Position of No. 2 2. Lean mixture manually to best power retard points CLOSE. setting (maximum BMEP). 3.Enrich mixture to obtain approximately IGNITION SWITCH CHECK.The ignition 2-BMEP drop. switch check is accomplished with the ignition 4. Conduct the magneto check as indicated switch in all four positions while the engine is earlier in this section. If the limits continue to operating in the idle range. be exceeded, the conditions should be investi- GENERAL IGNITION CHECK.The next gated and corrective action should be taken. step is to make a general ignition check, and for MANUAL SPARK ADVANCE CHECK.The this discussion a typical magneto check based on :Lanual spark advance system (if installed) may the SP-2H follows: be checked with an ignition analyzer by noting 1. With the propeller set at LNCREASE the pattern shift when switching from ADVANCE RPM (low pitch), open the throttle to obtain to RETARD. Required spark advance is 7 de-. static gage pressure indicated on the manifold grees, plus or minus 1 degree, as measured on pressure gage. Do not check the magneto at No. 1 and No. 2 cylinders in accordance with the manifold pressures above static gage pressure. analyzer manufacturer's instructions. 2.Note the rpm with the ignition switch in If the advance limits are exceeded, or if the the BOTH position. out-of-synchronization limits, as shown on No. 1 3. Place the ignition switch in the LEFT and No. 2 cyhnders, exceed 2 degrees, corrective position. Observe the rpm and BMEP change. action should be taken as soon as possible. 4. Return the switch to the BOTH position. Ifitis established that a distributor is 5. Allow the engine speed to stabilize be- locked in RETARD (not ADVANCE), the engine fore repeating steps 3 and 4 for the RIGHT may be operated until the discrepancy is cor- posit ion. rected. 6. Atmospheric conditions and spark timing NOTE: The analyzer is not to be used for will influence the readings obtained. checking basic ignition timing in either AD- 7. On engines that are equipped with manual VANCE or RETARD. spark advance, a loss of up to100 rpm and 10 The following procedure is for ground op- brake mean effective pressure (BMEP is con- eration only and may be used to check the sidered satisfactoryif no engine roughness is advance -mechanism" without the use of an encountered. ignition analyzer: NOTE: The above limits are acceptable if no 1.Set 2,000 rpm with the throttle, and lock. engine instabilityis encountered. Where both 2. Lean the mixture to obtain 1,950 rpm. rpm and BMEP limits are given, the rpm limit 3.Placetheignition switch on LEFT, iscontrolling and the BMEP additional sub- select ADVANCE spark, and notethe stantiation. change inrpm/BMEP.Returnthe spark

198 1 7,1 Chapter 9RECIPROCATING ENGINEIGNITION SYSTEMS /6 7 to RETARD and the ignitionswitch to BOTH. 4. Repeat the procedure in step3 with the ignition switch on RIGHT. 5. Check for a definite rise of2 to4 BMEP or approximately 25 rpm.If no rise occurs, the mechanism may be locked in eitherADVANCE or RETARD. Until the,discrepancy is corrected do not use any power above thatspecified for MAXLVIUM CRUISE in the recommended operating schedule.

TEST EQUIPMENT

Inmaintaining ignition systems on aircraft reciprocating engines, youwill find that certain equipmentwill prove invaluable. In order to use the test equipmentcorrectly and to thoroughly understand theignition system, it is necessary to have a workingknowledge of basic electricity. The necessarytest equipment for maintaining ignition systemsis briefly discussed here. More detailedinformation may be obtained from the publications issuedwith the equipment. AD.88 Ohmmeter Figure 9-26.Ohmmeter. The ohmmeter will be used on thelow- tension ignition system to checkfor continuity, High-Voltage Insulation Tester amount of resistance, or forinfinity, in a circuit, or part of a circuit.The ohmmeter has its own Several typesof high-voltage insulation (batteries); therefore, before testers are now in use. One typeis shown in source of power figure 9-27. All of the testers canbe very using, always insurethat the circuit being ground lead checked is not live. This will preventdamage dangerous if improperly used. The ohmmeter is must always be connectedto a good earth to the ohmmeter. One type of ground before turning on the tester.When test- shown in figure 9-26. connected to that To use the ohmmeter, first turnthe ohm- ing a lead, the tester must be meter switch ON, Touch the probestogether and adjust the pointer to read 0 byturning the adjusting knob. Set the selector switchto either HIGH or 'LOW, depending on thecircuit you are going to test. The LOW settingwill give you a reading in ohms. The HIGH settingwill give you a reading in ohms times1,000. For testing, put that part of the circuit to be testedbetween the two probes. An infinity readingindicates an open circuit. Readings between zero andinfinity indicate the number of ohms resistancein that circuit. When you have finished using theohmmeter, the AE.22I turn the ohmmeter switch OFF to conserve tester. batteries. Figure 9-27.High-voltage insulation

199

1 70 AVIATION MACHINIST'S MATE R 3 & 2

lead before turning on the test voltage switch. A safe procedure is to operate the equipment and secure the leads with one hand only. The positive test voltage lead is connected to the conductor of the part to be tested. The negative test voltage lead is connected to the insulation of the part to be tested. Consult the latestpublication on the particular tester before using it.

Piston Position Indicator

The piston position indicator, or Time-Rite, is used to locate the desired position of the piston. One is shown in figure 9-28. Because of the variations in spark plug locations and piston dome shapes, various pivot arms and calibrated scales are available for use on different engines. Be sure to use the proper arm and scale for the engine on which you are working. Make sure the piston is on the compression stroke and not too near the top of the stroke; then screw the indicator into the front spark plug bushing of the No. 1 cylinder. Turn the cap so that the slot is vertical and the scale is on the right-hand side. (See fig. 9-29.) Turn the engine in the normal direction of AD.90 rotation so that the piston travels through the Figure 9-29.-Indicator installed in top dead center position. This will leave the slide master rod cylinder. pointer at the highest point of piston travel. (See fig. 9-30.) slide pointer opposite the desired timing position Set the sliding scale so that the 0 mark on on the scale. (See fig. 9-32.) the scale is aligned with the reference mark on Now turn the engine in the normal direction the slide pointer. (See fig. 9-31.) of rotation until the pivot arm just touches the Turn the engine back through the top center slide pointer, causing the bulb to light. This position so that the piston is near the bottom of indicates that the piston is at the exact timing its stroke. Without moving the scale, set the position. (See fig. 9-33.) Timing Lights SCALE FRICTION

SPARK PLUG Timing lights are used for ignition timing THREAD operations to determine the instant the breaker points open or close. There are several different 11,)441 targ-A- types of timing lights in use. On some, the light K 1, goes OUT when the points start to OPEN. On others, the light comes ON when the points start BULB . ' BODY to OPEN. Timing lights are usually equipped with 2 bulbs and 3 leads (2 red leads and 1 black SLIDE CAP POINTER ASSEMBLY SCALE PIVOT ARM ground lead). A switch conserves the batteries when the lights are not being used. AD.89 When using the lights to check the timing of Figure 9-28.-Piston position indicator. the points, the primary leads to the points must

200

17 Chapter 9RECIPROCATING ENGINEIGNITION SYSTEMS /69

e))

AD.91 Figure 9-30.Bringing master rod piston to top dead center. be disconnected. The ground lead isconnectedto a good ground. The redlead (orleads if two sets of points are being checked) isconnected to the insulated side of the points. As the cam op- perating the points is rotated, thelights will indicate point OPENING and CLOSING.

USE OF DIAGRAMS, DRAWINGS, AD.92 AND CHARTS Figure 9-31.Setting scale. Schematic drawings of the ignition system of the engine you are maintaining arevaluable aids in tracing out the wiring to eachunit within wiring connecting them is possible throughstudy the system. The mechanic should beable to of the schematics of the system and theactual draw on paper the basic schematic forthe sys- wiring diagrams that can be found in theService tem that he maintains and be able totrace the Instructions Manual for a particularengine. in the cockpit Additional information on the use ofdiagrams system from the ignition switch 10 of this to the magneto, distributors, andspark plugs. and drawings is included in chapter Familiarity with the units in the system andthe training manual.

201

17( AVIATION MACHINIST'S MATE R 3 & 2

BULB LIGHTS AT EXACT TIMING POSITION

AD.93 AD.94 Figure 9-32.Setting slide pointer Figure 9-33.Obtaining exact timing at desired timing position. position.

202 1 70 /7/

CHAPTER 10.

RECIPROCATING ENGINEACCESSORIES

rushes by unused. Theprinciple of the baffle Mounted onthe reciprocating enginein cylinders is illustrated present day aircraft are anumber of accessories system for cooling the that are not presented as apart of a system or in figure 10-1. systems in the otherchapters of this manual. There are numerous problemswhich arise in COWLING engine that can be maintaining an aircraft and The cowling of theair-cooled radial engine solved, provided the ADRhas a thoroughunder- and streamlines of accessories and improves the cooling efficiency standing of the various types the powerplant. The cowling,in some instal- their purpose. lations, consists of a ring-shapednose section, rocker box ears. COOLING SYSTEM supported on the cylinder

It is essential that theoperating temperature be maintained within REAR of the reciprocating engine GYUNDER BAFFLES safe operating limits.Excessive heat will cause FRONT detonation and preignitionwithin the cylinder CYLINDER head and lead to ultimatefailure of some part or unit within theengine. The reciprocating engineaircraft in flight has a continuous flow ofcooling air passing over AIR IlLOW all of the power section.This cooling airflow keeps the engine temperatureswithin the range that assures the most efficientoperation of the engine. When tbe aircraft is onthe ground and the engine is operating,the propeller will supply air in sufficient quantity tothe engine to keep it cool, provided the periodsof operation of the engine are not too extended.The simplicity of the reciprocating engine coolingsystem makes it practically free from failures andthus simplifies maintenance problems in this area.

CYLINDER BAFFLES The cylinder baffles aredesigned to force the incoming air over thecylinder cooling fins. AD.95 The baffles direct the airin close around the for forming hot pools Figure 10-1.--Baffle arrangement cylinders and prevent it from twin-row engine. of stagnant air whilethe main stream of air

203

1.73 7.3 AVIATION MACHLNIST'S MATE R 3 & 2

Stringersextend from the cowling nosering plug or by a bayonet type fitting that is inserted section to the rear cowling support ring, which into a hole at the rear of the cylinder just below is supported by the rocker box ears of the rear the spark plug. cylinderson a twin-row engine. Removable One type of device used to measure the panels are attached to the structural members cylinder temperature is the spa k plug gasket ofthecowling and are easily removed for type thermocouple shown in figure 10-2. This maintenance and inspection of the engine. The type of thermocouple is a junction of two dif- rear cowling support ring also provides attach- ferent metals. When the junction is heated, an ment points for the cowl flaps. electromotive force is developed in proportion to the temperature of the cylinder at the base of COWL FLAPS the spark plug. The strength of this electromotive forceisindicated on a sensitive voltmeter The volume of the airflow around the calibrated in degrees C (centigrade). The instru- cylinders of the engine is regulated at the rear ment itself is located on the instrument panel of the engine where the air exits to the outside in the engine group of instruments. by opening or closing the cowl flaps. The cowl The spark plug gasket type thermocouple is flaps are operated from the cockpit by a switch installed in the place of the regular copper which controls a motor-operated jackscrew(s). spark plug gasket. The thermocouple is installed The cowl flaps of any engine should be in in the cylinder of the engine that has proven the full open position for all ground operations; through testing to be the hottest cylinder opera-. and in those aircraft equipped with reversing ting under most conditions. Of the two thermo- type propellers, reversing operations should be couple wires, one is of constantan and the other kept to the minimum necessary for checking out of copper. Each wire is designed so that it may the reversing system. When the propeller is be properlyinstalledonthe cylinder head reversed, there is very little, if any, cooling temperature gage in the cockpit. airflow through the engine, and engine temperatures build up quickly. ELECTRICAL SYSTEM

BLAST TUBES Itis necessary for the ADR to have a knowledgeofbasicelectricityinorder to There are a number of sizes of blast tubes better understand the electrical functions of that carry cooling air to sections of the engine. some of the engine accessories. Individual tubes lead to each of the rear spark Primarilythereare twosources of plugs of the engine. The tube is an integral part electrical energy in an aircraft other than the ofthe top baffle of each cy.inder; ram-air magneto-the generator, in which mechanical en- pressure for cooling is directed to the top of ergy delivered by the engine through the gear each cylinder where it is delivered to each rear plug through its blast tube.

Several of the accessories have blast tubes CONSTANTIN WIRE connected to them for the purpose of maintaining theoperating temperature of the accessory within prescribed limitations. The cooling air for these units is either pickedup at the forward side of the firewall or is ducted off from the oil COPPER WIRE cooler airscoop. The accessories cooled in this manner are the generator(s) and/or the alternator(s).

TEMPERATURE MEASUREMENT AD.96 The temperature of the engine is sensed by Figure 10-2.-Spark plug gasket type one or more thermocouples mounted at the spark thermocouple.

204 /73 Chapter 10RECIPROCATDIG ENGINE ACCESSORIES train is converted into electrical energy;and constructed to supply either alternating current the battery, in which chemical energy is con- or direct current, or both. verted into electrical energy. The engine-driven generator is usually a An understanding of the fundamentals of direct-current device, since one of the prime electricity is essential in becoming a proficient requirements of a generator is the furnishing of charging the reciprocatingengine mechanic. An excellent a source of direct current for presentation on these fundamentals is presented aircraft battery.This type of generator is in Basic Electricity, NavPers 10086-B. Men shown in figure 10-3. seeking advancement to ADR3 should obtain a It is impossible to charge a storage battery copy of this basic training manual andstudy it, with alternating current without first converting particularly the first eight chapters. An under- (rectifying) the alternating current into direct standing of the fundamentals of electricity is current. This necessitates the use ofadditional assumedinthesection following, which is heavy equipment. Some generators are equipped devoted to coverage on aircraft generators, with two sets of windings, designed tosupply batteries, alternators, and starters. If you do both alternating and direct current. not already have an understanding of the funda- Since it is imperative that the weight of a mentals of electricity, study NavPers 10086-B generator be kept to a minimum, it becomes first. necessary to increase the output of thegenerator without a corresponding increase in weight.This has been accomplished by stepping up armature GENERATORS speeds until they approach the maximum safe limits. A generator is a device which converts One factor which has limited the power mechanical energy into electrical energy (EMF). output of a generator has been the productionof Electrical power required for the operation of destructive heat as a byproduct. Cotton, silk, or enamel insulation used on generator wiringwill the various electrically operated aircraft units making it is supplied by a generator mounted on the rear break down under extreme heat, (accessory) section of the engine. When the necessary to keep generator temperaturesbelow demand for electrical power exceeds the output the critical heat limit. This is accomplished by of the engine-driven generator, anauxiliary the use of built-in fans and the addition ofblast electrical powerplant may be installed tosupply tubes which carry cooling air to the generator the additional requirements of the multitudeof from the slipstream. Some generators use spun units found on large aircraft. glass insulation which does not break down under Since the maintenance of an aircraft genera- extreme temperature. Such improvementshave tor is generally considered to be one ofthe made it possible for the modern generatorto older aircraft dutiesofAviation Electrician's Mates,no more than double the output of the attempt will be made here to describe the minute generators without any corresponding increase detailsofoperation.However,itis highly in weight. desirable thatyou, as an ADR, have some Under normal flight conditions, current con- generalinformation regarding this piece of sumption is not great. On the other hand, large equipment because it is so vital to theoperation quantities of current are needed for starting, of the aircraft and is closely associatedwith forlanding lights, and for the operation of the engine for which you are responsible. landing gear and flaps through short periods of The type of generator used on any particular timeon aircraft using electricallyoperated aircraft depends upon the amount of power re- units.Consequently,thegenerator must be quired and the nature of current neededto capable of very quickly recharging a practically operate the individual units. Radio communica- exhausted battery. tion equipment generally requires alternating The generator on an aircraft engine is current for its operation. Other unitsrequire operated by a shaft driven by the main acces- direct current. Therefore, generators may be sory drive shaft of the enginethrough a gear

205 AVIATION MACHWIST'S MATE R 3 & 2 / ?V

AD.97 Figure 10-3.D-c generator. arrangement. A separate regulating n:ecnanism The constant speed drive unit is a hydraulic (voltage regulator) takes care of the intermittent transmission which may be either electrically or load requirements whileatthe same time mechanically controlled. It is designed to deliver preventing overcharge of the battery. a constant rpm output, provided the input from the engine remains within a minimum and a ALTERNATORS maximum rpm. In operation, the constant speed drive unit is similar to the overdrive of an The maintenance of the alternator or a-c automobile engine. The constant speed drive (alternating current) generator is one of the unit enables the alternator to produce the same duties of Ehe Aviation Electrician's Mate, as is frequency at speeds slightly above idle rpm as the d-c generator, and no attempt is made here itwould at maximum power or at cruising to describe the many details of its operation. It speeds. is desirable that you as an ADR have some The a-c generator itself is rated according general knowledge concerningthis piece of to kilovolt-amperes (kva), power factor, phases, equipment, as it is vital to the operation of the voltage,and frequency. One generator, for electrical power systems of our modern' day example, may be rated at 40 kva, 208 volts, 400 aircraft. cycles, three phase, at a 75 percent power factor. Since the various devices that operate on The kilovolt-ampereindicatetheapparent a-c require a certain voltage and frequency, the power. This is the kilovolt-ampere output, or speed of the generator should be donstant. The the relationship between the current and voltage engine speed varies considerably from the idle at which the generator is intended to operate. range an the way through to full power output; The power factor is the expression of the thus, the a-c generator is driven by the engine ratio between the apparent power (volt-amperes) through a constant speed drive unit installed and the true or effective power (watts). The between the engine and the generator. number of phases is the number of independent

206

1 64 1,75" Chapter 10RECIPROCATMG ENGINE ACCESSORIES voltagesgenerated.Three-phase generators cranking electricstarterforreciprocating generate three voltages 120 electrical degrees engines. apart. Both single- and three-phase generators This starter contains a series-wound elec- are commonly used. tric motor, speed reduction gears, an overload clutch, and an automatic engagement jaw. The BATTERIES torque developed in the motor is transmitted to the jaw through a gear reduction system. Be- The batteryisthe other source of an cause of the high-speed characteristics ofthe electromotive force in the aircraft. The function motor and the lightweight structural design, the of the aircraft storage battery is to provide a overall weight is reduced to a minimum and, at reserve source of electrical power for operating the same time, maximum cranking torque is theelectrical systems of the aircraft. The maintained. The high speed of the motor is battery also functions in such a manner that it reduced by gear reduction between the motor eliminates the commutator ripple which is pro- armature and the low-speed starter jaw. duced by the d-c generator. During normal A torque limiting clutch incorporated in the aircraft operations, the generator supplies the housing prevents damage either to the starter or primary source of electrical energy and main- theengine when the Moving starter jaw is tainsthebatteryina charged state, The engaged with the stationary engine jaw. The battery supplies power to the aircraft only clutch plates will slip when the torque exceeds when the speed of the engine or generator drive the clutch setting of the starter. As the torque system becomes so slow that the generator's decreases to a value less than the clutch setting, output voltage falls below the battery voltage. the clutch plates will again be held stationary The battery is the emergency power source and allow the jaw to rotate at the speed of the for the aircraft. For this reason, extreme care motor through the reduction gearing. must be taken to see that every precaution is The starter jaw is automatically engaged made to maintain the battery in perfect con- with the engine jaw by means of a spiral spline dition. Therefore, the battery should never be actuating device. When the engine starts, the used for starting engines or servicing equip- sloping ramps of thejaw teeth cause the ment if another source of power is available. disengagement of the starter and engine jaws. Such unnecessary usage tends to shorten the Oil seals are provided to prevent leakage of life of the battery and keeps the battery in poor engine oil into the starter. condition to meet emergency operating require- Starting motors are of the intermittent-duty ments. During the periods when the engine is type. They MUST be allowed to cool between idlingor beingstarted, the electrical load starting intervals in order to prevent overheating should be kept to a minimum. The service life of the battery depends a great deal upon the frequency and quality of care it is given. Bat- TERMINALS teries that are abused or that receive careless treatment and servicing generally have their service life ended prematurely.

STARTER An aircraft engine starter is a mechanism for developing a considerable amount of mechanical energy that can be applied to the engine to causeitto rotate. The starter must develop sufficient power and be dependable, lightin weight, and simple to operate and maintain. The typeofstarter used for cranking AE.139 reciprocating engines is the direct cranking Figure 10-4.Typical direct cranking starter. Figure 10-4 shows a typical direct electric starter.

207 180 AVIATION MACHINIST'S MATE R 3 & 2 and possible damage. Consult the applicable manual for specific information on the particular starter for the aircraft with which you are working.

EXHAUST SYSTEM The purpose of the exhaust system is to conduct the exhaust gases from the engine to the outside atmosphere with a minimum resistance of exhaust back pressure. Some naval aircraft are equipped with short exhaust stacks, used singly for each cylinder, or they are designed to accommodate two or three cylinders. These stacks conduct the exhaust gases through spaced openings in the cowling around the rear of the engine power section. On other aircraft, the short individual stacks join to a collector ring which, in turn, expels the hot gases through one large tailpipe.

EXHAUST STACKS

The R-3350 engine installed in multiengine AD.98 aircraft has a power recovery system composed Figure 10-5.Exhaust stack configuration. of three blowdown turbines (power recovery turbines) mounted 120 degrees apart on the turbine for a total of 450 horsepower to the supercharger front housing. The exhaust gases horsepower output of the engine at maximum from sixcylinders are expelled through a allowable power. Each PRT utilizes the exhaust power recovery turbine. These gases are di- gases from six cylindersthree front and three rected to the power recovery turbine via various rear. (See fig. 10-7.) types of exhaust stacks. Figure 10-5 shows the The gases enter the turbine at the nozzle configuration of the long L, short L, T, Y, and assembly and cause the turbine wheel to spin at F type stacks. high speed. A hollow shaft, splinedtothe turbine wheel, passes through a support clamped to the POWER RECOVERY TURBINES adapter on the supercharger front housing. A vibrationdamperassembly, consisting of The R-3350-32W and -34 engine models spring-loaded plates and discs, assists in damp- incorporate three interchangeable exhaust power ening the lateral vibration and the whip of the recovery turbines (PRT's). Figure 10-6 is a turbine shaft. A coupling, splined at each end, cutaway view of the power recovery turbine used connects the turbine shaft to a bevel drive gear in compounding these engines. Each of these in the supercharger front housing. The drive gear turbines is clamped to adapters that are mounted meshes with a larger bevel gear, connected by a on the supercharger front housing and spaced drive shaft to the fluid coupling impeller. The 120 degrees apart. fluid coupling rear half (runner) is connected by a splined shaft to a pinion, which meshes with Operation the PRT crankshaft drive gear coupled to the engine crankshaft. Figure 10-8 illustrates the The PRT's utilize the energy of the exhaust transmission of the exhaust gas energy to the gases coming from the cylinders and transmit turbine wheel and back to the crankshaft. this energy back to the engine crankshaft. They To prevent damaging effects from the high will add approximately 150 horsepower per temperatures of exhaust gases, cooling air is

208 /77 Chapter 10RECIPROCATING ENGINE ACCESSORIES

drawn from a duct between the cylinders and final exit of the exhaust gases to the atmusphere. conducted to the turbine assembly. A tube and The complete system is to be checked for any duct assembly delivers the air between the evidence of gas leakage at the Joints, cracks in nozzle support and the cooling air shield. An the piping, looseness of clamps, and the security impellerisprovidedto force the cool air of all units in the system. NOTE: Clamps should through the assembly and to discharge it, tobe tightened to specific torque listed in the gether with the exhaust gases, from the outer aircraft maintenance instructions manual. Do shield outlet. Cooling air is sealed under the not overtighten, as heat expansion may lead to turbine wheel by the labyrinth seal facing the failure. When replacing any units in the exhaust underside of the impeller. The seal prevents system, care should be maintained to use the the mixing of the exhaust gases and cooling air proper type nuts, bolts, and cotter pins or safety until both are discharged from the outer shield. wire. Do not use aluminum nuts, bolts, washers, Oil from the turbine drive shaft is kept from or material that is made of any soft metal in any entering the stream of cooling air by the bellows- part of the exhaust system. loaded seal, which fits tightly in the turbine CAUTION: Lead depabits in exhaust system shaft oil seal support. are poisonous; wash hands thoroughly before Oil under reduced pressure, is brought from eating, drinking or smoking. Use caution in the pressure control valve located in the super- removing exhaust components to avoid inhalation charger front housing by way of internal passages of deposits. to the PRT fluid coupling support. From the fluid coupling support, oil flows through passages HYDRAULIC SYSTEM in the supercharger front housing to an annulus in the turbine coupling gear shaft bushing and A complete aircraft hydraulic system is through passages in the support to the fluiddrive made up of two or more power systems and a shaft. From the coupling gear shaft bushing, a number of actuating systems, the number of passageinthefrontsupercharger housing actuating systems depending upon the design of carriesoiltothe fluid drive shaft. The oil the aircraft. Current specifications require at entering from either end of the shaft lubricates least two power systems. the bushing on the shaft and passes through a A power system is generally considered to setof holes into the fluid coupling, supplying include a fluid reservoir, pump, and all the other the necessary pressure for operation. components leading up to, but not including, the When the engine is being started, before oil selector valves. The selector valves direct the pressure is built up in the fluid coupling, the flow of fluid to the various actuating units, and impeller will not drive the runner. When suf- each selector valve :s considered to be part of ficient oil pr e s sur e is built up in the coupling its related actuating system. after starting, the runner will then follow the The portion of the hydraulic system with impeller with a certain amount of slippage which which the ADR is primarily concerned is that will act to absorb any undesirable amount of section of the system forward of the firewall, vthrational cornict between the crankshaft and consisting of the supply and the return lines and the PRT unit. As engine rpm increases, the the hydraulic pump; however, if the ADR is a amount of slippage between the runner and the plane captain, he should be familiar with the impeller decreases. The fluid coupling is a complete system. vortex type, giving a swirling action to the oil A brief discussion of hydraulic principles, to prevent sludge formation which might freeze followed by a brief description of pumps, is the halves of the coupling together and nullify presented in the followingparagraphs. For more their effect. detailed information on hydraulic principles, reference should be made to Fluid Power, Maintenance NavPers 16193-A. For the plane captain who is interested in more detailed information on the The maintenance of the exhaust system con- complete aircrafthydraulic system. a good sists of a visual inspection of all sections of the source is Aviation Structural Mechanic H 3 & 2, system from the cylinder exhaust ports to the NavPers 10310-A.

209

1 h

)7? Chapter 10-RECIPROCATING ENGINE ACCESSORIES

Nomenclature for figure 10-6.

1.Cooling shield assembly. 19.Shaft. 2.Nozzle solid vane. 20.Vibration damper. 3.Cooling shield flange ring. 21.Upper thrust washer. 4.Nozzle flange. 22.Shaft oil seal ring. 5.Labyrinth seal. 23.Cooling air impeller spacer. 6.Inlet pipe retaining bolts, nuts, 24.Nozzle assembly to nozzle and washers. support cap screws. 7.Inlet pipe. 25.Cooling air impeller. 8.Cooling air duct. 26.Nozzle split vane. 9.Shaft support. 27.Turbine wheel. 10.Shaft support and adapter packing rings. 28.Turbine wheel buckets. 11.Lower thrust washer. 29.Flight hood locating lug. 12.Gear coupling. 30.Wheel retaining nut. 13.Supercharger front housing. 31.Cooling shield support. 14.Shaft gear. 32.Outer shield. 15.Mounting pad. 33.Intermediate shield. 16.Clamp. 34.Pylon support. 17.Nozzle support and adapter locating pins. 35.Cooling shield inner flange. 18.Shield and seal assembly. 36.Inner shield.

FUNDAMENTALS OF HYDRAULICS law states: Pressure applied to an enclosed or confinedfluidistransmitted equally in all The word hydraulics is based on the Greek directionswithoutloss and acts with equal word for water, and originally meant the study force on equal surfaces. of the physical behavior of water at rest and Although Pascal's principle applies to both in motion. Today, the meaning has been expanded liquids and gases, a liquid is used in hydraulic to include the physical behavior of all liquids, systems because liquids are practically in- including hydraulic fluid. compressible.Under terrific pressure,the volume of a liquid can be decreased somewhat, Pascal's Law but the decrease is so slight that it is of no consequence in hydraulic applications. Because Hydraulicsis based on the idea that a of this fact, hydraulically operated mechanisms confined liquid will pass on any pressure applied are almost instantaneous in action. toituntil the pressure at any given point is equalized. This principle was first stated in the Force and Pressure year 1693 by the French scientist, Pascal, and is commonly known as Pascal's law. Pascal's In order to understand how Pascal's principle is applied to hydraulics, you must distinguish

TOP OFF.NGINE GOTT? OF ENGINE carefully between the terms FORCE and PRES- SURE. Force may be defined as a push or pull. It is the push or pull exerted against the TOTAL AREA of a particular surface and is expressed in pounds. Pressure is the amount of push or pull on a UNIT AREA of the surface acted upon. In hydraulics, the unit of area is the SQUARE INCH;therefore,pressureisexpressed in pounds per square inch, abbreviated psi. It is important to bear in mind that when AD.100 referring to pressure, we deal with the amount Figure 10-7.-Exhaust system arrangement. of force acting upon one square inch of area.

211

181 AVIATION MACHINIST'S MATE R3 L 2

P -

41F WD

EXHAUST AIR

COOLING AIR AD.101 Figure 10-8.Transmission of exhaust energy back to the crankshaft.

Computing Force, the sake of brevity and simplicity, let us condense Pressure, and Area this statement into symbols:

A simplified form of writing a long statement F or sentence with the use of symbols is known as a formula. For example, rather than say "length times width equals area," we simply write: TO FIND AREA.Since area equals force divided by pressure, we merely state: LxW=A F When dealing with pressure, force, or area, a similar method of shorthand is used. TO FliND FORCE.It is known that force Figure10-9illustrates adevicefor equals pressure times area. Substituting F for recalling the above mentioned formulas. Any force, P for pressure, and A for area, we have. letter in the triangle may be expressed as the product or quotient of the other two, depending F=PxA upon its position in the triangle. For example, to determine the formula for TO FIND PRESSURE.It has been found finding area, consider the letter A as being set that pressure equals force divided by area. For off to itself, followed by an equals sign. Now

212 Chapter 10-RECIPROCATING ENGINE ACCESSORIES

PISTON B 20 SO. IN AREA PISTON A 2 MIK AREA

10 LI. FORCE

MO LB. FORCE

CYLINDER A CYLINDER B AD.103 Figure 10-10.-Transmission of pressure AD.102 by liquids. Figure 10-9.-Device for determinine force, area, and pressure formulas. If 10 pounds of force is exerted on pistonA, and its area is 2 square inches, thenthere are look at the other two letters. The letter F is 5 pounds of pressure being exerted oneach above the letter P; therefore, square inch of undersurface.

A = (P =-1, or P=-10-= 5 psi)

In order todetermine the formula for finding According to Pascal's law, this 5 psi pres- pressure, consider the letter P asbeing set off sure is transmitted inall directions without by itself and look at the other two letters. The loss, and acts with equal force on equalsurfaces. letter F is above the letter A; therefore, Therefore, the pressure being exerted against the undersurface of piston B is 5psi. Ifthe area of piston B is 20 square inches, thetotal force being exerted against piston B is equalto 20 times 5, or 100 pounds. Thus, Likewise,to determine the formula for finding force, consider the letter F as being set (F = P x A) off to itself. The letters P and A are sideby In the above example, the total forceagainst sides therefore, the large piston is 10 times as great asthat F=PxA against the small piston. If pistonA were made smaller, the pressure created in the liquidwould be greater, and the total forceacting upon Transmitting of piston B would be increased. Pressure by Liquids For example, if the area of pistonA was 1 square inch, the vessure createdwould be 10 Figure 10-10 illustrates how a small force psi, and the total force exerted againstpiston B may be multiplied into.a largeforce through the would be 20 times 10, or 200 pounds. transmission of pressure by liquids. A small From these basic facts it can be seenthat cylinder and a large cylinder are connected there is practically no limit to thetotal force filled that can be obtained through the useof liquids with tubing, and the entire assembly is used in the with a liquid. under pressure. This is the principle Each cylinder contai^q a tight fittingpiston. common hydraulic jack andthe hydraulic lift, Piston A, in the smaller cylinder, is 2 square and is the principle according towhich all the inches in area; piston B, in the larger cylinder, mechanisms in an aircraft hydraulicsystem are is 20 square inches in area. actuated.

213 AVIATION MACHLNIST'S MATE R 3 & 2

BASIC SYSTEM OPERATION Basically, any hydraulic system must contain the following units: 1. A reservoir to hold a supply of hydraulic fluid. 2. A pump to provide a flow of fluid. 3. Tubing to transmit the fluid. 4. A selectorvalve to direct the flow of fluid. 5. An actuating unit to convert the fluid pressure into useful work. A simple basic system using these essentials is shown in figure 10-11. The flow of hydraulic fluid can be traced readily from the reservoir through the pump to the selector valve. With the selector valve in the position shown, the flow of fluid created by the pump flows through the valve to the right-hand end of the actuating cylinder. Fluid pressure then forces the piston to the left and at the same time the fluid which is on the left-hand side of the piston is forced out, up through the selector valve, and back to the reservoir through the return line. When the selector valve is moved to the position indicated by the dotted lines, the fluid from the pump then flows to the left-hand end of theactuatingcylinder, thusreversingthe process. Movement of the piston can be stopped at any time simply by moving the selector valve to neutral. In this position, all four ports are closed and pressure is trapped in both working lines. This basic system is one from which any hydraulic system can be derived. Additions may be made toit for the purpose of providing additional sources of power, operating additional AD.104 cylinders, making operation more automatic, or 1. Reservoir. 7. Hand pump. increasing the reliability; but these additions are 2. Power pump. 8. Pressure gage. all made on the framework of the basic hydraulic 3.Filter. 9.Relief valve. system diagrammed in figure 10-11. 4. Pressure 10. Selector regulator. valve. HYDRAULIC PUMPS 5. Accumulator. 11. Actuating 6.Check valves. unit. All aircraft hydraulic power systems have one or more power-driven pumps and may have Figure 10-11.Basic hydraulic system. a hand pump as an additional source of power. Power-driven pumps are the primary source of installed for testing purposes and for use in power and may be either engine driven or elec- emergencies. The pump with which we are con- tric motor driven. As a general rule, motor- cernedin this chapter is the engine-driven driven hydraulic pumps are installed for emer- pump. gency use, or for use when the engine-driven The engine-driven pump is mounted on the pump is inoperative. Hand pumps are generally accessory section of the engine or the rear cover

214 1ou / 5/3 Chapter 10RECIPROCATING ENGINE ACCESSORIES

plate. Pumps are classified according to the VACUUM PUMP type of pumping action utilized, and may be either the gear type or the piston type. Pumps may be Another major accessory mounted on a further classified according to whether they are drive pad on the accessory section of the engine designed for constant displacement or variable is the vacuum pump. This pump unit is of the displacement. rotary, four vane, positive displacement type, A constant displacement pump is one that suitable for operatwn in either direction of displaces or delivers a constant fluid output for rotation.The unitconsists primarilyof a anyrotational speed. For example, a pump housing containing a sleeve in which an offset might be designed to deliver 3 gallons of fluid rotor with four moving blades is driven by a per minute at a speed of 2,800 revolutions per splined shaft which is coupled to the accessory minute. As long as it runs at that speed, it will gear train of the engine. continue to deliver at that rate, regardless of The pump is designed to provide suction the pressure in the system. For this reason, fortheoperationof flight instruments and when the constant displacement pump is used in pressure for operating de-icing equipment of a system, a pressure regulator or unloading the inflated-tube variety. valve must also be incorporated in the system. A variable displacement pump has a fluid USE OF SCHEMATIC DIAGRAMS, output that varies to meet the demands of the DRAWliNGS, AND CHARTS system. For example, a pump might be designed to maintain a system pressure at 3,000 psi by Troubleshooting of the various engine ac- varying its fluid output from 0 to 7 gallons per cessories isthe process of locating a mal- minute. When this type of pump is used, no functioning component or mechanism. In order pressure regulator unloading valve is needed, to troubleshoot intelligently, the ADR must be since no pumping action takes place except when familiar with the system at hand. He must know pressure is required in the system. the function of each component and have a mental picture of the location of each component in LOCATION OF LEAKS relation to other components within the system. External leaks in a hydraulic system where This can best be achieved by studying diagrams fluid is escaping from a cylinder, valve, or fitting or drawings of the system. may generally be found by a visual check. A leak Each manufacturer of engines and aircraft in the system usually causes an accumulation of is required to furnish diagrams and drawings of hydraulic fluid. It may happen that the actual leak the various systems, subsystems, and major is not located directly above the accumulation of components. These diagrams and drawings may fluid, since the hydraulic fluid tends to follow the be found in the various maintenance manuals structure or tubing to a lower point before supplied by the manufacturer. dropping off. When leaks are located or noticed, notify the hydraulic shop immediately. DIAGRAMS Internal leaks are caused by fluid under pressure slipping past an unseated valve or worn The most commonly used diagram is the packing ring into the return line to the reservoir. shcematic.Schematic diagrams are used tu The indications of internal leakage are sluggish illustrate the various electrical circuits, fuel operation of an actuating system or a dropoff in systems, lubrication systems, etc. The com- system pressure. A drop in gage pressure or an ponents of electrical circuits are usually repre- indicatwn of insufficient pressure on the gage sented by electrical symbols, the must common may be caused by an internalleak. When internal of which are shown in figure 10-12. leakage is suspected or known to be in the A schematic diagram of a starter vibrator hydraulic system, the symptoms should be noted, circuit is shown in chapter 9, figure 9-13. In an effort made to locate the leak, and the hy- chapter 8, figure 8-1 is an example of an oil draulic shop notified so that remedial action may system schematic. be taken to repair or replace the unit or units In figure 8-1, the various lines supply, hot suspected of causing the difficulty. return, cold return, dilution, vent,etc.) are

215 nil )r AVIATION MACHINIST'S. MATE R 3 ts:. 2

FUSE SPL I CE GROUND POLAR I TY DC

_41E.... ELECTRICAL 1-- PO3ITIVE NEGATIVE toA DI3COMMECT

C IRCUITBREAKERS digt, Cr.)4,6 d\P er",b crib ezt, -1111110 SWITCN MOMENTARY CURRENT t". AUTONATIC PUSH PU3N REM IIATTERY PULL OFF TYPE SWITEN TYPE LIMITER ;Us pESET RESET

SWITCHES 0 0 0... 04 coo 0.... co4 Cmw= a a 0 a 0 IMETALLIG SPST SPOT SPOT 3P3T SPOT SPOT SPOT THERMAL moMERTARY ON CENTER OFF NORMAL OR CENTER OFF MONENTARY ON OMNI. oN MOMENTARY PRE33URE CUTOUT NOMENTARY CONTACTS 0 CONTACTS PUSH-BUTTON Clwn TYPE o 6 c40.; 0 NORMAL PO3I1ION 0 Or 0 D.p 0 0 MOMENTARY NORMAL 818 NONEMTARY POSITION 1 04 ON ON ROTARY NORMAL OR MPST 0 MOMENTARY IOW CONTACTS CENTER OFF MECNANICAL LINKAGE (------CONNECTORS------% P $ S r RELAYS REMOVAIILE FIXED A og 4 Ci 4 044 NOT ALL ALL t--tn 0 ci o y- PINS PINS SOLEROID SHOWN KIST SPOT MPOT NOM NORMAL OR NORMAL OR P DESIGNATES PINS ON MOMENTARY MOMENTARY 3 DESIGNATES SOCKETS CONTACTS CONTACTS AD.105 Figure 10-12.Electrical symbols. In chapter 7 are some good examplesof shown in different colors for easyidentification is a of each line. Each component is illustratedand several types of drawings. Figure 7-1 the cutaway drawing of a fuel strainer, with arrows identified by name, and arrows indicate filter direction of flow through each line. showing the flow of fuel through the Block diagrams are also used toillustrate element. In the Exploded views are often used to show how the systems of aircraft and engines. This type block diagram, each component isrepresented complex components are put together. of drawing is useful in disassemblingand re- by a block. Near each block is usuallywritten is an the name of the component representedby that assembling components. Figure 12-11 exploded view,showing the block. example of an Block diagrams, like schematic diagrams, principal parts of a propeller domeassembly. are useful in showing therelationship of the Orthographic drawings are used toshow the system. actual dimensions and constructiondetails of components with each other within the and are They may also show the sequence inwhich they parts, components, and other objects, primarily for use by the man who is to manu- operate. facture the object. Usually two or Moreviews of the object are shown in orthographicdrawings, DRAWINGS and all dimensions necessary formanufacturing the object are given on the drawing. TheADR is Drawings are commonly used to show con- seldom confronted with this type ofdrawing; struction details and operatingprinciples of however, detailed instructions on readingortho- various components and mechanisms.Some of graphics, as well as all other types ofdrawings, the most commonly used types of drawings are are contained in the RateTraining Manual, Sketching,NavPers thepictorial, exploded, cutaway, and ortho- BlueprintReadingand graphic. 10077-B.

216

- 194; /KS-

CHAPTER II

RECIPROCATINGENGINE REPAIR

onation of the best powermixture. Enriching ENGINE PERFORMANCE the best power mixtureprovides extra fuel that .. cylinder heat and carries of RPM, MAP, andBMEP absorbs much of the The effects it out through the exhauststacks. interrelationships on enginesand engine per- that an engne will put important to the °Aviation The amount of power formance are very out is usually determinedby the amount of air- Machinist's Mate R. consumed by the engine discussion of engine fuel mixture that can be The first concern in the per unit of time.It is evident that upto certain performance is to designatethe power ranges of cylinders (or an en- delivered by an aircraft limits an engine with more the engine. The power gine with largercylinders) will give greater engine usually falls intothree categories. Power cham- percent of rated poweris power. Size and shapeof the combustion output up to about 25 ber is also anotherbuilt-in factor thathelps considered to constitutethe IDLE range. Power of power developed. to about 60 percentof determine the amount output from 25 percent Aside from the built-in(or construction) the CRUISE range.The which rated power constitutes and factors, there areseveral main factors power output of60 percent of rated power, subject to contiol thatdirectly HIGH POWER range. are variable and above, make up the affect engine power output.These include revo- In the cruise range, anair-fuel mixture ratio and per gallon. lutions per minute ofthe engine (RPM) can be usedthat gives most miles (MAP), which is anotherterm is called the BESTECON- manifold pressure This air-fuel mixture 15 to 1; for the amount ofair-fuel mixture consumed OMY MIXTURE andis approximately however, as the mixtureenters the cylinder, it per minute. might easily be 18 or20 to 1. In the first third of thehigh power range a MAP richer air-fuel mixtureis used (60% to75%), engine with a given air- BEST POWER MIXTURE. When considering an and this is called the fuel mixture, the poweroutput will be a function Above 75 percent of rated power,a still richer RPM. These two variables the FULL RICHMIX- of MAP and engine mixture is used, called are hookedtogether in such a mannerthat de- TURE. crease in RPM willnecessitate an increasein The additional fuelused to enrich the best specific power output;and obtain full rich is notadded MAP to maintain any power mixture to conversely, an increasein engine RPM willcall primarily to provide anadditional source of if there is to be nochange coolant. The best powerair- for a decrease in MAP power. It acts as a in engine power output. fuel ratio is capable ofdeveloping the required requires operation into the upper part of the Efficient power control power when carried up of the engines at maximumallowable combustion high power range.Enriching the mixturebeyond MAP is directly re- has a tendency to cut pressure in the cylinders. the value for best power lated to this pressure.Therefore, for all power down power output, butthe heat generated in be specified so that such outputs an engine RPM must the upper part of thehigh power range is not cause allowablecyl- by the normal cooling the related MAP will that it cannot be dissipated inder pressures to beexceeded. Each engineis method. This excess heatwill tend to cause det- 217

19,1 AVIATION MACHINIST'S MATE R 3ta 2 / 7:6

actually rated according to allowable RPM for losses in the engine. To distinguish between the various power outputs so that maximum effi- total mean pressure available and themean ciency of operation will be present at all times pressure converted into brake horsepower, two withoutexceedingthelimitsofcylinder terms are in common use-indicatedmean ef- pressures. fective pressure (IMEP) and brake mean effective pressure. RPM Indicated mean effective pressure can be calculated from an indicator card which is a chart of the pressures inside the combustion If it is assumed that power depends on the chamber of the complete operating cycle of the amount of air-fuel charge taken into the cylin- engine. ders per minute, an increase in RPMwill result in the cylinders being charged oftener, witha consequent increase in the amount of air-fuel BMEP OR TOP mixture taken in per minute. Therefore, power increases as engine RPM increasesup to a point, The brake mean effective pressure (BMEP) but thereafter power falls off even though the or torque oil pressure (TOP) can be calculated RPM continues to increase. This is due pri- once the brake horsepower of the engine is de- marily to the three following factors: termined by a dynamometer test or othermeans. 1. The size of the inlet port and time that In order to determine the BMEP ofan engine, the inlet valve is open. This will admit onlya the following equation can be used: certain amount of air-fuel mixture in a given period of time. BMEP -BHP x Constant of the engine 2. The size of the exhaust port and the time RPM that the exhaust valve is open. This permits only a certain amount of exhaust gas tobe pushed out By substituting the TOP constant in place of in a certain period of time. As engine RPM in- the BMEP constant, the same formulacan be creases, the time that these ports remain open used for determining the TOP, therefore, becomes less and less. 3.Friction loss. Friction losses increase TOPBHP x Constant of the engine with an increase in RPM. It requires a greater RPM fraction of the indicated mean effective pressure to move the engine parts at higher speed, Most of the large Navy engines have a torque which means that brake mean effectivepressure indicating system installed. The torquemeter (BMEP) and consequently brake horsepower system is contained in the front crankcasesec- (BHP) will be lessened. tion of the R-3350 engine. It is connected by The mean or average pressure exerted on passages to a torque transmitter, located in the the surface of the piston head during the power accessory section of the engine, then electrically strokeisan important factor affecting theto a gage in the cockpit, which registers, in horsepower output of an engine. In combination BMEP or TOP, the power being delivered to with the amount of total piston area and other the propeller shaft of the engine. factors, the pressure on the pistons during the The ADR assigned as a plane captainor power stroke directly affects the torque or flight engineer will be concerned with calculating twisting moment exerted by the propeller shaft. brake horsepower (BHP). The followingequa- Since the brake horsepower developed by the tionscan be used to calculate BHP using engine is a function of torque and RPM, themean BMEP or TOP constants. effective pressure on the piston isa direct factor in the production of power. Only apart of BMEP x RPM BHP the total -pressure exerted on the piston is de- Constant livered to the propeller shaft in the form of brake horsepower.Part of the pressure is BHP -TOP x RPM required to overcome friction and other power Constant

218

1 94 /77 Chapter 11-RECIP1WCATING ENGINEREPAIR

The constants used for the R-3350engine are 1. Perform the compression test as soon 236 for BMEP and 142 for TOP. By referringto as possible after engineshutdown, but not more uniform the appropriate Service InstructionsManual the than 12 hours later in order to provide constants can be found for the engineconcerned. lubrication of cylinder walls and rings. 2. Remove the front spark plugfrom the MAINTENANCE cylinder or cylinders and install the compres- Reciprocating engine repair is very impor- sion testing fixture in the sparkplug insert. accidental tant to a squadron in accomplishingits mission CAUTION: Take precautions against The firing of the engine. and maintaining high aircraft availability. valve) and ADR is required to replace variouscomponets, 3. Open the bleed valve (shutoff make adjustments, and even makeminor re- attach the quick disconnect fittingof the air pairs. In performing these tasks theADR will hose to the fixture in the sparkpluginsert. This contribute a great deal to the availabilityof will establish a pressure of 15to 20 psi in the approved cylinder when both valves are closed.CAUTION: assigned aircraft, provided he uses the rotation of the methods in accomplishing each assignedtask. Take precautions to prevent There is an old adage, "Why is there never propeller during the compression test. enough time to do a job right, but alwaystime 4. Turn the propeller in thedirection of to do it over." Lost time in thismodern Navy rotation by hand until the piston ofthe cylinder being tested is coming up on compressionstroke is lost availability. against the 15 to 20 psi air pressureand con- COMPR ESSION TESTS tinue turning slowly until the pistonreaches top Cylinder compression, which determines center. Reaching top center is indicatedbyaflat the engine's power, depends uponthe proper spot or sudden decrease in forcerequired to ro- functioning of the valves. Although it ispossible tate the propeller. If the propeller isrotated too for the engine to lose compressionfor other far, back up at least one-half revolutionand start the most part over again to eliminatebacklash in the valve reasons, low compression for piston rings can usually be traced toleaky valves. Conditions operating mechanism to keep the which will affect engine compression are: seated on the lower ring lands. Close the bleed valve. Check the regu- 1.Incorrect valve clearances. 5. 2. Worn,scuffed,or damaged pistons. lated pressure and adjust to 80 psi, if necessary. and cyl- CAUTION: Care must be exercisedwhenclosing 3. Excessive wear of piston rings is suf- inder walls. the bleed valve because the air pressure 4. Burned or warped valves. ficient to rotate the propeller at leastone-half 5. Carbon particles between theface and turn if the piston is not at top center. 6.If the minimum acceptable pressureis the seat of the valve or valves. GREB 207, it is evi- 6.Early or late valve timing. not achieved, as listed in Cylinder compression in aircraftengines is dent there is leakage. The S1 type 7. The following is a listing of twocondi- checked with a compression tester. the means is the only authorized testerfor reciprocating tions that may affect the pressure and engines. The tester is a two-gagetype which to correct the conditions. checks cylinder sealing by applyinglow pres- Condition Correction sure air to the cylinderwith the piston at top center and checking for the minimumacceptable (1) Slight carbon build-Remove the rocker pressure. up between the box covers and after The procedure for use of the SI type com- valve face and checking for proper pression tester involves the applicationof air seat and also car- valve clearance, tap pressure to the cylinderbeing tested with the bon buildup be- the rocker arm di- piston at top center, using two gagesintercon- tween the valve rectly over the valve nected with a 0.040-inchrestrictibn in the line guide and stem, stem with a fiber between gages. The detailed procedureandpre- preventing the drift and a 1- or 2- cautions to be observed are asfollows: valve from closing. pound hammer.

219 190 irir AVIATION MACHINIST'S MATE R 3 & 2

(2) The amount of oil Turn the engine of compression lost depends on the degree of film present on through several rev- burning and will ordinarily be at least 50 pounds. the cylinder wall olutions before re- affecting the pis- checking compres- CYLINDERS ton ring seal. sion. The reciprocating engine cylinders are de- NOTE: The above conditions may exist in signed to operate over a specified time before varying degrees; however, if the conditions can normal wear will be cause for their overhaul. be corrected the cylinder shouldnot be rejected. If the engine is operated as recommended and 8. ,Excessive leakage at the exhaust valve proficient maintenance is performed, the cylin- can be detected by listening for air leakage at ders normally will last until the engine is the exhaust port; at the intake valve by escaping removed for high-time reasons.Itis known air at the carburetor or master control; and past from experience that materials fail and engines the piston rings by escaping air at the engine are abused through incorrect operation; this has breather outlets. a serious effect on the cylinder life. Another 9.If excessive leakage is detected and can- reason for premature cylinder change is poor not be corrected by the means listed in the chart maintenance. Therefore, the Aviation Machin- above, the cylinder must be replaced. ist's Mate R should exert special care to insure Three alternate methods of locating leaky that all the correct maintenance procedures are intake and exhaust valves are as follows: adhered to when working on the engine. 1. The wheeze test for locating leaking intake and exhaust valves is also a recommended Removal procedure. In this test, as the piston is moved to top dead center on the compression stroke, the The reasons for cylinder change are given faulty val-Ve may be located by listening for a in table 11-1. . wheezing noise in the exhaust collector or intake Several other conditions found on inspection duct, thus indicating air leaking past the re- of cylinders are causes for removal. They are: spective valve. 1.Cylinder head cracks. Cylinders may be 2. Another method is to admit compressed considered serviceable if they meet the following air into the cylinder through the sparkplug hole. conditions: The piston should be restrained at top dead cen- a. There must be no cracks in rear ter (compression stroke) during this operation. spark plug area. A leaking valve can be located, as with the b. There must be no exhaust or oil wheeze test, by listening for ndises in the exhaust leakage from a crack. 1 collector and intake duct. c. Logbook entries must be made to 3. The third method is described as fol- identify the cylinder, the cracked area, and the lows. Just before stopping the engine, turn it up to extent of the crack. approximately 1,000 rpm and move the mixture cl.Followup inspections must be made control to IDLE CUTOFF. The engine will turn at major check periods. over 6 or more revolutions after combustion e. No cracked cylinders are to be in- ceases. A burned exhaust valve will be evi- stalled during line maintenance. Cylinders that denced by a pronounced shush from the stack show evidence of leakage or exhibit cracks that into which the affected cylinder is exhausting, are too long or too deep should be removed this sound occurring each second revolution of from service. the engine. When tins sound has been heard, pull 2.Cylinders involved with burned pistons. the engine through by hand and find the approxi- An engine in which a piston has experienced a mate source. (The best positwn for detection hole burned through the dome or down the side is as near the exhaust outlet as possible.) Then must be rejected. test the compression in the suspected cylinders. 3. Breakage or loosening of cylinder hold- The cylinder with the faulty value will have less down screws. If at any time after engine opera- compression than the others. The exact amount tion, one or more of the cylinder holddown

220 1 s, /Yr Chapter 11RECIPROCATINGENGINE REPALR

Table 11-1. Reasons for cylinder....,===..,change. Remedy Trouble Probable cause Replace cylinder. Improper idling of engine. Sticking valves; low compression in one or more cylinders; broken valve spring. Dead cylinder. Cylinder check Engine runs rough. (magic wand or engine analyzer).

Sucking valves or valve Replace cylinder tappets. or valve tappets. Low compression. Check cylinder and replace, if necessary.

Broken valve spring. Replace cylinder. Inoperative cylinder. Check cylinder; Torching (afterfire). replace, if necessary. Replace cylinder. Loss of compression. Warped or sticking valves; warped valve seats; or collapsed valve. Worn or stuck piston rings. Locate trouble by compression check; , replace cylinder and piston assembly.

Cracked pistons or Cylinder check; com- cylinders. pression check; replace cylinder, if necessary.

Piston-cylinder blowby. Replace cylinder and Oil loss through piston assembly. engine breather. Hole burned in piston. Change engine.

Excessive oil con- Worn or broken piston Replace cylinder. sumption. rings; incorrect installation of piston rings; or worn valve guides. Replace cylinder. Improper valve , Stretched valve stem; or clearance, valve collapsed. Broken exhaust rocker arm Replace cylinder and Damaged intake push damaged push rod. rod, in same cylinder causing excessive pressures. Replace cylinder. Both spark plugs in Cylinder pumping oil. one cylinder cutting out.

221

1 9 r AVIATION MACHINIST'S MATE R 3 2

screws are found to be loose or broken at any location, the cylinder involved must be replaced and all holddown screws used on that cylinder scrapped. A tag bearing the reason for removal should be attached to the removed cylinder and the cylinder returned to the Aviation Supply Office for appropriate disposition. Details for replacing cylinders and piston assemblies are too numerous to be covered in this course; the variety of reciprocating engines also prohibits this coverage. The information and illustrations given are general and apply to the R-3350 engine. Detailed information on specific engines is to be found in the appropriate Service Instructions Manual for each engine. Replacing the cylinder requires removal of the following parts: intake pipes, exhaust pipes, front and rear cylinder intake and exhaust air deflectors, rocker box drain mamfold (for lower cylinder), external oil tube (certain cylinders), crankcase main front section oil drain tube ds- sf,". (certain cylinders), spark plugs, push rod hous- - ings, push rods, and valve tappet sockets and ;44, springs, and fuel injection tube, if installed. NOTE: Insure that the pistion is at top dead center of the compression stroke before removal AD.106 of push rod housings and push rods to relieve Figure 11-1.Loosening cylinder holddown tension on the push rods. screws. Break the lockwire on the cylinder holddown screws, using a puller. On engines incorporating Installa protector, as shown in figure cylinder holddown screw lock plates, remove 11-5 (A), on the articulating rod. A master rod the plates. All cylinder holddown screws should guide plate should be installed on the master rod be loosened next, using the cylinder holddown cylinder mounting pad. (See fig. 11-5 (B).) screw wrench. (See fig. 11-1.) With the exception It is important that the master rod be held of two holddown screws spaced 1800 apart, re- nearthe center of the hole to prevent the move all holddown screws with a speed wrench bottom rings on adjacent pistons from drop- (fig. 11-2). When pneumatic equipment is avail- ping below their cylinder skirts. able, it may be used. Make sure that the piston is at the top of the Installation cylinder and remove the two remaining holddown screws. Withdraw the cylinder far enough In order to reassemble and install a cylinder to expose the articulating rod. Hold the rod while on an engine, a detailed procedure should be the cylinder is removed to preventit from followed. This procedure is set forth in the Serv- hitting the crankcase main section. (See fig. ice Instructions Manual for the particular engine 11-3.) on which thc Aviation Machinist's Mate Iis Insert a piston pin removing tool, as shown working. in figure 11-4, in the inside diameter of the piston The first step is to clean the barrel, flange, pin. Support the piston in a manner to prevent the and skirt of the cylinder with a clean lintless piston boss from striking the rod and tap the cloth and Stoddard solvent. Insure that there are plug from the pin. Install the puller in the piston no burrs on the cylinder skirt. Apply clean pin and pull the pin. engine oil to the first 4 inches of the cylinder

222 -1 90 Chapter 11RECIPROCATLIG ENGINEREPAIR /97

AD.107 Figure 11-2.Removing cylinder holddown screws. barrel. Insure that the old oil sealring is removed from the cylinder skirt.Coat a new oil seal ring lightly with sealingcompound (Tite- seal). Install the ring on the skirtadjacent to the mounting flange. Some cylinder crankcasemountingpadsac- AD.108 commodate only 7/16-inch capscrews.Other crankcases accommodate four7/16-inch cap- Figure 11-3.Removing cylinder. parting line (two on screws at the crankcase Care each side) and 1/2-inch capscrews atthe other the plug cap and the arbor press ram. locations on the pad. The7/16-inch capscrews should be exercised to exert only sufficient pres- hardnesses. The high- sure to bottom the shoulderof the plug against are available in two installing the hardness capscrews are identified bytwo shal- the end of the piston pin. When the head. DO piston on the rod, be sure that thepiston pin is low slots milled across the top of the pro- NOT MIX 7/16-inch capscrews ofdifferent hard- installed with the piston pin plug facing peller end. ness on a cylinder mountingpad. articulated Place a spherical washer over eachcylinder Remove the protector from the to the rod or the master rod guide platefrom the cyl- holddown screw. Apply rubber cement Position the first few threads of the holddown screws.Insure inder mounting pad, as applicable. neck and the correct piston for the cylinder onthe rod and that the spherical washer, the pin through underside of the holddown screw head,and the slide the unplugged end of the piston spherical seat in the cylinder attachingflange the piston and rod. Bottom the pinagainst the boss within the piston. (See fig. 11-6.) are entirely free of cement. No.4 Lubricate the pilot diameter of thepiston pin Insure that piston rings No. 1 through side marked TOP facing plug with clean engine lubricationoil. Use an are installed with the plug into toward the top of the piston and ring No.5 (bot- installing tool to press the piston pin marked TOP the piston pin, using the installingtool between tom ring) is installed with the side

223

1 9 d AVIATION MACHINIST'S MATE R 3 & 2

(A)

AD.109 Figure 11-4.Pulling piston pin. facing down, away from the top of the piston. AD.110 (See figure 11-7 for proper ring configuration. Figure 11.5.(A) Protector installed for Refer to the latest revision of the applicable the articulating rod; (B) guide plate General Reciprocating Engine Bulletin (GREB for master rod. 114) for engines with chrome-plated cylinders installed. down over the bottom ring and remove the clamp. NOTE: The No. 5 ring (bottom ring) is (See fig. 11-8.) installed with the side marked TOP facing down Position the cylinder against the mounting toward the bottom of the piston to enable the ring pad and install two cylinder-to-crankcase lo- to scrape oil toward the cylinder dome. cating screws, 180° opposite. Then start 19 Coat the piston and rings with castor oil, cylinder holddown screws. unless the cylinder barrel is chrome plated; Tighten the two cylinder-to-crankcase lo- use clean engine oil for chrome-plated cyl- cating screws with a torque wrench. Run the 19 inders. Stagger the gaps 180°. Compress the top cylinder holddown screws in with a speed wr ench four piston rings, using a clamping tool, and or a pneumatic wrench. Using a torque wrench, carefully slide the cylinder over it. Loosen the tighten the 19 screws in a pattern to insure uni- clamp and reposition on bottom ring. There is no form loading around the flange. (See fig. 11-9.) positive retention of the piston pin until the Remove the two locating screws and install cylinder is installed. The piston pin plug will the regular thread holddown screws. Tighten the then bear against the cylinder wall, holding the screws to the correct torque value. pin in place. Recheck to insure that the piston Lockwire the screws in groups of five or six pin has been properly installed. Slide the cylinder unless lock plates are used to secure the screws.

224 20 Chapter 11-RECIPROCATINGENGINE REPAIR /93

AD.111 Figure 11-6.Installingpiston and piston pin. AD.113 Several GREB's giveinformation on cyl- cylinder over bottom their importance Figure 11-8.-Sliding inder.One example to show ring of piston. follows.It concerns chrome-platedcylinders. Among other items ofimportance, it gives identification of chrome-platedcylinder bores and piston rings installationfor chrome-plated cylinders. These two items arementioned because and of their importancewhen changing cylinders pistons of an engine.

AD.114 AD.112 Figure 11-9.-Tighteningcylinder holddown Figure 11-7.-Piston pinand piston rings screw with a torquewrench. installed (cutawayview).

225

20.1. / 99 AVIATION MACHINIST'S MATE Ft 3&I 2

VALVES ROCKER ARM VALVE SPRINGS a WASHERS The intake and exhaust valves used in air-. --1-9 INTAKE VALVE craft reciprocating engines open and closethe passageways which admit the air-fuel mixture, or air alone, and release the exhaust gases. Two valves are used in each cylinder: intake and exhaust. Valves are usually made of chrome- VALVE TAPPET nickel steel or tungsten steel alloy. Bothmetals retain their strength at relatively hightern- peratures. VALVE TAPPET ROLLER Components UPPER CAM The valve operating mechanism consists of REDUCTION GEAR those components necessary' toopen and close the valves at the correct points in the operating cycle. CRANKSHAFT In a radial engine, a cam ring,on which FRONT GEAR there are cam lobes, rotates to actuate camfol- lowers or tappets. Each carn follower actuatesa push rod, causing it to move againsta rocker arm. The rocket arrn action opens the valve. The valve is closed by spring tension providedby double concentric springs. These components may be seen in figure 11-10. LOWER CAM The cam ring is mounted concentrically REDUCTION GEAR with the crankshaft and is driven by the crank- CAM RING shaft at a reduced speed throughone or more carn reduction gears. The cam ring has two CAM LOBE parallel sets of lobes spaced around theouter AD.115 diameter; one set, or cam track, for the intake Figure 11-10.Valve operating mechanism. valves, and the other set for the exhaust valves. The carn follower assembly consists ofa The valve spring assembly consists of twoor tappet; a tappet guide; a tappet roller;a tappet more valve springs the necessary valve spring ball, or push rod socket; anda tappet spring. retaining washers, and the locking devices for The tappet assembly converts thecam lobe con- securing the spring assembly to the valve. These tour into reciprocating motion and transmits locking devices are known as keepers or split this motion to the push rod. keys, and are generally made in the form ofa The push rod is constructed of hollow steel split cone. The function of the valve spring as- tubing with hardened ball-shaped ends. The push sembly is to close the valve and hold it securely rod transmits motion from the tappet assembly on the valve seat. to the rocker arm. The pushrodis enclosed in a tubular housing that extends from the crank- Clearance Adjustment Procedures case to the cylinder head. The rocker arm is mounted on a shaft in the A slight clearance must be provided between rocker box, which is in the cylinder head. The the rocker arm and the valve tip. If there were no rocker arm transmits the motion of the push rod clearance, the valve could be held slightly off to the valve tip. The rocker arm hasan adjusting its seat when it should be closed. This condition screw which provides for adjustment of the would cause improper operation of the engine. clearnace at the valve tip. The clearance ispro- Adjustment of valve clearances should be vided to allow for heat expansion, enabling the made only when the engine is cold.Since the ad- valve to close fully. j,istment procedures and valve clearances vary

226 Chapter 11RECIPROCATING ENGINEREPAIR /9c for different engines, the appropriateService Instructions Manual should be referredto for this information. It is very important that the valveclearance adjustments be properly made; otherwise reduced power output and possiblebackfiring into the induction system might occur. The valve clearance adjustmentprocedures for the R-3350 engine are discussed. The Aviation Machinist's Mate Rshould first remove the rocker box covers fromthe cylinders on which the valves are to beadjusted. One spark plug may be removedfrom each cylinder to relieve compression. Afterremoving the spark plugs,install screened protective plugs in the spark plug busings. The tools required for adjusting the valves on any engine are listed in the ServiceInstructions Manual for each engine. To adjust the valve clearances on anindi- vidual cylinder, proceed as follows: AD.116 1. Turn the propeller shaft in thedirection of rotation until the piston inthe cylinder in Figure 11-11.Loosening adjusting screw which the valves are to be 'adjustedis at top lock screw. center on the compression stroke.Raise the adjusting screw end of the rocker armslightly to insure that the valve tappetball socket slides freely in its guide. 2.With both valves in the cylinderclosed, loosen the adjusting screw lock screwwith a suitable box wrench. (See fig. 11-11.) 3. Turn the adjusting screw out one ortwo turns with a broad-blade screwdriver orAllen head wrench, as applicable. 4.Insert a 0.010-inch feeler gage between the valve tip and the adjusting screwand turn the adjusting screw in with a broad-blade screwdriver. (See fig. 11-12.) When any furtherturn- ing of the screw would open the valveslightly, there will be an appreciable increasein torque and the feeler gage will be tightlyclamped. Loosen the screw only enough toallow the feeler gage to be withdrawn. 5. Tighten the adjusting screw lock screw to 425 to 450 inch-pounds. 6. With a screwdriver and a torque wrench on the adjusting screw, checkthe clamping action of the lock screw, as shown infigure 11-13. when 450 AD.117 The adjusting screw must not move valve inch-pounds of torque are applied. Do not exceed Figure 11-12.Feeler gage between 450 inch-pounds to obtain the breakawaytorque. tip and adjusting screw.

227

2 o d AVIATION MACHINIST'S MATE R 3 & 2 9e0

AD.118 Figure 11-13.Checking breakaway torque on adjusting screw. 7. Recheck for lock screw clampingaction. AD.119 When it is necessary to adjust valve clear- Figure 11-14.Piston position indicator ances on all the cylinders, remove and replace installed in No. 1 cylinder. the following parts: rocker box drain manifold, all rocker box covers, and the front spark plug from each cylinder. Establish true top dead center on the compression stroke with a piston position indicator. This is illustrated in figure 11-14 and also in chapter 9. A timing disc or protractor should be installed on the right-hand fuel pump drive pad with its pointer setting at the zero indication (fig. 11-15). After true top dead center has been established,itshould be rechecked prior to making any adjustment on the valves, since slippage of the adjustable arm on the piston position indicator or binding of the pointer on the timing disc could cause an error in the reading obtained. After this has been accomplished, proceed to adjust all the valves as follows: 1.Rotate the crankshaft until the pointer on the protractor (timing disc) indicates zero with allbacklash removed from the gear train. 2.Cylinder No. 1 is then in position for valve adjustment. 3.Loosen the adjusting screw lock screw, AD.120 using a suitable box wrench. Turn the adjusting Figure 11-15.Timing disc installed on the screw out one or two turns. Using a 0.010-inch fuel pump mounting pad.

228 Chapter 11RECIPROCATINGENGINE REPAIR clearance check between the valve tip and 6. Conduct a second valve feeler gage, insert it and loosen to 0.010 inch any screwbelow 0.007- the adjusting screw tappet,and turn down on the inch clearance. adjusting screw until the feeler gageis tightly tighten the ad- clamped. Loosen the adjusting screwonly far 7. Using a torque wrench, justing screw lock screw.Torque to 425-450 enough to allow the feeler gageto be withdrawn. torque of 450 lock screw enough inch-pounds. Check the breakaway Tighten the adjusting screw inch-pounds on the adjusting screwwith the to hold the adjusting screwin this position. head wrench. (See fig. 4. Rotate the crankshaft in theif...ection of proper driver on Allen indicates 31 11-13) The adjusting screw mustnot move when rotation until the timing disc pointer 450 inch-pounds of torque areapplied. Do not degrees on the disc. This will positionthe piston exceed 450 inch-pounds toobtain breakaway in cylinder No. 12, at the topcenter on the com- when the valves in this cylin- torque.If the adjusting screw turns pression stroke. Adjust the breakaway torque is applied, arelated discrep- der as described in step 3. ancy may exist inthe affected parts. 5. Adjust the valves intheremaining cylin- clearance check 11-2. 8. Conduct a third valve ders in the order shown in table and again loosen anyadjusting screw below 0.007-inch clearance and anyexcessive loose clearance above 0.017 inch.The clearance will be brought down by theamount that will not result in less than0.007-inch clearance on a order and previous tighter cam location. Table 11-2.Valve adjusting 9. Remove the timing discpointer and the timing disc readings. timing disc. Use a newgasket and replace the Pointer reading on fuel pump or substituting cover,washers, and Cylinder number timing disc self-locking nuts. (degrees) Troubleshooting 1 0 12 31 This section outlinesthe most common 5 80 symptoms of valve andvalve operating mech- 16 111 their possiblecauses, and 160 anism troubles, 9 remedies. Locating andcorrecting these trou- 2 191 by first studying 13 240 bles should be accomplished 271 the symptoms carefullyand then checking each 6 with the most proba- 17 320 possible cause, beginning 10 351 ble, until the exact causeof the trouble is 3 *400 (360 4-40) determined. Because thesymptoms of some of 14 431 (360 +71) troubles are revealedin only one range 7 480 (360 +120) engine speed, theengine's operation shouldbe 18 511 (360 +151) critically observed atlow, medium, andhigh 11 560 (360 +200) 591 (360 +231) speeds wheneverpossible. 4 Before attempting towork on an engine 15 640 (360 +280) faulty in flight, 8 671 (360 +311) which has been reported as consult the pilot's flightreport for any pertinent information which mightgive a clue as to the *Since the timing disc has only360°graduations cause of thetrouble. (ONE complete revolution),and since the com- Whenever irregular ground orflight operat- pletion of all four strokes inall cylinders re- can definitelybe attributed quires 720° of crankshaftrotation (TWO coming characteristics positions set at to engine malfunctioningor wheneverreplace- plete revolutions), all piston requiring considerable more than 360° requirethat the timing disc ment of an engine part 360° mark to the number labor is anticipated, itis advisable to remove pointer rotate past the drain the sump, and in- of degrees indicated inparentheses in the table. the main oil strainer,

229

2u;-) AVIATION MACHINIST'S MATE R 3t: 2 M spect the oil and strainer for metal particles Table 11-3 shows that the most common before attempting to locate the trouble or re- troubles with valves and valve operating mech- place any parts. This procedure may eliminate anisms are improper valve clearances, broken unnecessary labor. valve springs, and sticking valves.

230 Chapter 11RECIPROCATINGENGINE REPAIR rql

Table 11-3. Valve andvalve operating mechanismtroubleshooting. Cause 4 Remedy Trouble Adjust valve clearance. Improper idling. Improper valve clearance. Sticldng valve. Change cylinder assembly.

Broken valve springs. Change cylinder assembly. Adjust valve clearance. Excessive cylinder Incorrect valve clearance. head temperature. Improper valve operation. Check valve operation; check for improper valve clearances; replace cylinder if necessary; adjust valves.

Broken valve springs. Replace cylinder as- Loss of compression. sembly.

Sticking valves. Replace cylinder assembly.

Warped or pitted valve Change cylinder. seat; excessive carbon Remove carbon by plac- or foreign matter ing a fiber drift on between valve and seat. rocker arm directly over valve stem and strike it with a 1- to 2-pound hammer.

NOTE: The extremely high temperatures at which the valve operates sometimes causes the head or the stem to become warped.Either condition will prevent the valve from closing tightly. Often when a valve has been burned, it will be found to be warped.

231.

2o, AVIATION MACHINIST'S MATE R 3 & 2

Table 11-3. Valve and valve operating mechanismtroubleshootingContinued.

Trouble Cause Remedy Loss of compression Valve stem covered with Clean with emery cloth. Continued. scale. Replace if necessary. NOTE: Scaling is the result of burning, although it is mild in form. When this occurs, small flakes form on the valve seat. These are blown away by the exhaust gases, which results in the valves being rough and uneven, destroying perfect compression. Loss of power. Sticking valves. Lubricate sticking valve. Replace cylinder, if necessary. Broken valve springs. Replace cylinder. Broken or bent parts in Replace cylinder and the valve system. discrepant valve train parts.

2u0

232 c3e/

CHAPTER 12

PROPELLER OPERATIONAND MAINTENANCE

6. HUB. The centralportion of the pro- The propeller converts the poweroutput of is fitted to the pro- needed to move peller. (See fig. 12-1.) It the engine into forward thrust peller shaft and securesthe blades by their the aircraft. through the air. roots. Therare two general types ofpropellers The forward or "cut- and the cont rollable- 7. LEADING EDGE. in use todaythe fixed-pitch ting edge of the blade(fig. 12-1) that leads in pitch. The fixed-pitch typeis used on small turning. The 2-blade propeller thedirection the propeller is liaison aircraft. It is usually a other edge (rear edge) iscalled the TRAILING and is often made ofwood, although some are The EDGE. made of steeloraluminumalloy. Referencelines, permits adjustment 8. BLADE STATIONS. controllable-pitch propeller usually designated frommeasurements made of the blade angle duringoperation of the engine the vub. These station ground. Blades are usually from thecenterof in the air or on the numbers are used to discussand locate positions made of steel oraluminum alloy. The pitch designated operated hydrau- on the propellerblade, and are usually changing mechanism may be at 6-inch intervals.(First station is normally lically or electrically. 12 inches from the centerof the hub.) Figure12-3 Due to the limited useof the fixed-pitch prop'eller, ordy the controllable-pitchtype propeller is discussed inthis training manual. Before discussing thepropeller,it would be well to note itsprincipal parts as well as LEADING EDGE the terms used in thediscussion. The parts TIP and terms describedin the following para- HUB graphs are illustrated infigures 12-1 through 12-4. TRAILING 1. BLADE. One armof a propeller from 4.! the butt to the tip.Propellers may have two or EDGE vf, more blades. (See fig.12-1.) BACK ofthe ,SHANK 2. BLADE BACK. Thesurface JA blade that can be seenby standing in front of the aircraft. (See fig.12-1 and 12-2.) 3. BLADE FACE. Thesurface of the blade (fig.12-1) which can be seenby standing directly behind the airplane. ,,,.: , 4. SHANK. The thickenedportion of the blade (figs. 12-1 and 12-3) nearthe hub of the propeller. The shank is sometimesreferred to as the ROOT. AD.121 the blade (figs.12-1 5. TIP, The portion of Figure 12-1.Propellernomenclature. and 12-3) farthest promthe hub.

233

20u AVIATION MACHINIST'S MATE R 3 & 2

PLANE OF ROTATION TIP SECTION NOSE OF BLADE AIRCRAFT ANGLE 1111BLADE FACE

141LONGITUDINAL AXIS 441 BLADE BACK

4 BLADE PROPELLER

AD.122 Figure 12-2.A 4-blade propeller. shows the blade stations of a typical propeller blade. CENTER OF HUB 9. PROPELLER RETAINING NUT. The nut that locks the hub to the propeller shaft. AD.123 Itis part of the propeller rather than of the Figure 12-3.Blade stations. engine. 10. BLADE ANGLE (PITCH). The angle opposite direction to that normally produced by formed by the chord of a section of the blade the propeller in flight. and a plane perpendicular to the axis of rotation. Reverse thrust is used during landing of (Seefig.12-4.) The blade angles shown in large aircraftin reducing the length of the figure 12-4 are selected to illustrate those of landing roll. This is a safety feature when it atypical propeller. These angles will vary is necessary to sue short or icy runways. with different propeller installations. 11. FEATHERING. Special feature incor- OPERATING PRINCIPLES porated in most propellers used on multiengine aircraft. The purpose of the feathering feature An aircraft propeller is an engine-driven is to reduce the drag of a windmilling prcpeller device designed to impart motion to an aircraft. on a dead engine,and to stop rotation to The primary function of the propeller is to push prevent further damage. Figure 12-4 illustrates or pull the aircraft through the air. It converts a feathered propeller. the rotary force developed in the engine into a 12. REVERSING. A reversing propeller is pulling force acting on the aircraft, which it one in which provisions are made for obtaining moves through the air in the same manner in a negative blade angle. With a negative angle, a which propeller blades of another type drive propeller produces a thrust which acts in the boats through the water.

234 Chapter 12PROPELLEROPERATION AND MAINTENANCE

HIGH PITCH 57' FULL FEATHERED LOW PITCH 22° ) 90' 2.

AD.124 Figure 12-4.Propellerangles. A propeller is essentially a"rotating wing," or airfoil. in principle, apropeller is equivalent to a screw. During eachrevolution through which a screw is rotated,it moves forward a certain distance. (See fig.12-5.) When the aircraft engine turnsthe propeller, AD.125 relative motion is developedbetween the wing- like propeller blades andthe air. As it pulls Figure 12-5.Propeller.action. itself through the air, thepropeller carries along takeoff conditions it, within the limita- improve cruising conditions, anything that is attached to suffered. Taking an aircraftoff the ground with tions, of course, of the powerdeveloped. The blade-angle position is (within certain limits), the propeller at a high faster the propeller spins much the same as setting acar into motionin the greater is the resultingpull (or thrust). is not able to produce FIXED-PITCH. high gear. The engine The first propellers were full horsepower becausethe high blade angle These were designed mainlyto get the aircraft much to enable it to turn off the ground. The pitch(blade angle) was loads the propeller too quickly turn over over at the full rpmof the engine. small so that the engine could in design that met the utilize its full horsepower The first improvement to its full rpm and apparent defects ofthe fixed-pitchpropeller was for takeoff. Once anaircraft with a fixed-pitch propeller. It enabled a pilot propeller having a low bladeangle is in the air, the two-POSITION for limited because the pro- to use a low bladeangle (high rpm setting) its forward speed is takeoff, climb, and necessaryoperational ac- peller will turn too fast tobite efficiently through change the propeller result, the engine must celeration; and then to the onrushing air. As a blade angle in flight to ahigher blade angle be throttled to preventexcessive overspeeding. With this propeller, the fixed-pitch (low rpm setting) for cruise. The first improvement over full engine rpm couldbe developed for takeoff, propeller was theGROUND ADJUSTABLE- speed could be accom- blade angle (pitch) while increased aircraft PITCH type. On this type the plished at cruise with a decreasein engine power could be changed oradjusted on the ground by propeller takes larger manually twisting theblades in the hub to the because the high-pitch desired angle. When theangle was increased to bites out of the air.

235

211 AVIATION MACHINIST'S MATE R 3 & 2 .70 The two-position propeller did not, however, dynamically, then, thrust is the result of the produce the mt,s, efficient and economical use of propeller shape and the angle of attack of the engine horsepower for all the numerous inter- blade. mediateflight conditionsencounteredby The BLADE ANGLE is also an excellent aircraft. method of adjusting the angle of attack. As Constant-speed propellers were eventually shown in figure 12-6, the blade angle includes designed to automatically maintain a preselected the angle of attack of the propeller. On constant rpm. With the constant-speed propeller, the speed propellers then, the blade angle must be selected rpm is maintained by automatically adjusted to provide the most efficient angle of turning the propeller blades to a lower angle, attack at all engine and aircraft speeds. The taking a smaller bite of air whenever the load most efficient angle of attack is very small; it on the engine is increased; for example, when varies from 1 to 4 degrees positive angle. The heading the aircraft into a gradual climb at the actual blade angle necessary to maintain this selected rpm or decreasing the throttle opening. small angle of attack varies with the forward Likewise, the propellerbladesmove auto- speed of the aircraft because the blade motion matically to a higher blade angle and takea is the resultant of the forward speed of the larger biteof air whenever the load on the aircraftaswellasthe propeller rotation. engine is decreased; for example, when heading Therefore, with constantly increasing aircraft the aircraft into a nose-down attitude (dive) or speeds and highaltitudeoperations due to increasing throttle opening. engine supercharging, it is necessary to have a wide range of blade angle settings. This range BLADE ANGLE AND ANGLE OF ATTACK (BLADE PATH) RELATIVE WIND OF THE BLADE To understand the operation of the propeller, consider first its motion, which is both rotational and forward. Thus, as shown by figure 12-5, a section of the propeller blade, during the lower half of its cycle of rotation, moves downward and forward. As far as the forces are concerned, however, the result is the same as if the blade element were stationary and the air coming at it from a direction opposite its path. The angle at which this air (relative wind) strikes the propeller blade is calledthe ANGLE OF ATTACK and, as with a wing, the deflection of the air produced becuase of this angle causes the dynamic pressure at the aircraft side of the propeller blade to be greater than atmospheric; thus, it creates thrust. .. The shape of the blade element also creates CHORD / thrust, as it is like the shape of a wing. Con- OF SECTION MI. IIIIIMMINS OM MOWN. sequently, as the air flows past the propeller, FORWARD VELOCITY the pressure on one side is less than that on LINEAR VELOCITY the other. As in a wing, this produces a reaction a :ANGLE OF ATTACK (ANGLE FORMED BY RELATIVE WIND force in the direction of the lesser pressure, AND CHORD) and the force is upward (lift). In the case of the 8:PITCH OR BLADE ANGLE propeller, which is mounted in a vertical instead of horizontal position, the area of decreased AD.126 pressure is in front of the propeller, and the Figure 12-6.Aerodynamic factors of a force is in a forward direction (thrust). Aero- propeller.

236

214 Chapter 12PROPELLEROPERATION ANDMAINTENANCE and the increase iv air- propeller to conditions in slipstream velocity of settings must adapt the speed. The angle ofattack is still small,for encountered in takeoff, climb,and cruising. has been increased with forward motion of here too, the blade angle During takeoff, when the an increase inairspeed. the aircraft is at lowspeeds and when maximum speed from a required, the constant- When it is desired to increase power and thrust are particular cruise speed,the blade angle is speed propeller sets up alow propeller blade rpm). Then, as manifold blade angle keeps the decreased (to increase angle or pitch. The low pressure (andpower) is increased withthe angle of attack (with respectto the relative wind) propeller keeps the At throttles, the constant-speed small and efficient at thelow aircraft speed. setting by increasingthe blade the propeller to "slice rpm at the new the same time, it allows angle to increase the massof air handled per it thin" and handle asmaller mass of air per absorbed by the allows the engine to revolution and the power revolution. This light load propeller. The greaterresulting thrust gives turn at maximum rpmand to convert themaxi- the fuel into greateraircraftspeed. And, of course, mum amount ofheat energy in the still keeps the angle ofattack mechanical energy. The high rpmalso creates greater blade angle small and efficient. maximum thrust; for,although the mass of air handled per revolution issmall, the number of revolutions per minute are many,the slipstream FORCES ACTING ON THEPROPELLER velocity is great, andwith the low aircraft maximum. speed, the thrust is Oneofthemain requirementsof any After takeoff, the speedof the aircraft in- withstand severe propeller propelleris the ability to creases,andtheconstant-speed stresses. These stresses,which are always changes to a higher angle(or pitch). Again, the greatest near the hub, aredescribed in the higher blade angle, withhigher speeds, keeps Constant-speedpro- (with respect to the relative followingparagraphs. the angle of attack pellers utilize some ofthese natural forcesto wind) small and efficient. Byincreasing the mass propeller blade angles. revolution, it decreasesthe aid in controlling the of air handled per See figure 12-7,forces acting onpropeller rpm of the engineand reduces fuelconsumption and engine wear, butkeeps the thrust at a blades. maximum. Centrifugal Force For climb after takeoff,the power output of decreas- the engine is reducedto climb power by The greatest force acting uponthe propeller ing the manifold pressureand lowering the rpm FORCE. This force angle. The greater mass blade is CENTRIFUGAL by increasing the blade tends to pull the bladeof a spinning propeller of air handled persecond in this case is more prevent the blades frombreak- slipstream velocity and out of its hub. To than offset by the lower ing into fragments orflying off into space, the the increase in airspeed(above that prevalent section near the Hence the torque (horse- blade is made thicker in cross right after takeoff). hub, and the hub itself ismade from a strong power absorbedby the propeller) isreduced to match the reduced powerof the engine. The steel forging. small by the angleofattack is again kept Thrust Bending Force increase in bladeangle with an increasein. airspeed. There is also a THRUSTBENDING FORCE At cruising altitude,when the aircraft is blades. A spinningpropeller and less power isrequired to that acts upon the im level flight tries to forge aheadbut is held back by thehub produce a higher airspeedthan is used in climb, aircraft it is pulling.The reduced by lowering the and the load of the engine power is again blade tips, which arethinner and lighterthan manifold pressure andincreasing the blade forward. The sum of rpm). Again, this reduces the blade shank, bend angle (to decrease these bending forces onthe blades is carriedat torque to match thereduced engine power,for, Hence, the section ofthe handled per revolution and near the hub. although the mass of air blade at the hub must beproportionately thicker is greater, it is morethan offset by the decrease

237

2 1 AVIATION MACHINIST'S MATE R 3 & 2 ..20&

Pend backward throughout its length against the direction of rotation. ( Aerodynamic Twisting Force Another force tries to rotate the blades in the hub so that the blade angle willbe increased. \--"' ---4. This is called the AERODYNAMIC TWISTING CENTRIFUGAL TORQUE FORCE FORCE. The point at which this force is exerted BENDING FORCE most strongly on the chord of the airfoil is THRUST LOAD known as the center of pressure. Since under normal conditions, this center of pressure is nearer the leading edge of the propeller, the THRUST force tends to rotate the blades to a higher BENDING pitch. When the aircraft goes into a dive, the FORCE center of pressure moves backwards and may even fall behind the center of rotation. Centrifugal Twisting Force CENTER OF ROTATION The CENTRIFUGAL TWISTING FORCE on the blades tends to twist them to a lower pitch CENTER OF angle. This is because all parts of the propeller PRESSURE try to remain in a plane parallel to the plane AERODYNAMIC CENTRIFUGAL of rotation of the propeller. TWISTING FORCE TWISTING FORCE Propeller Vibration AD.127 Figure 12-7.Forces acting upon Sometimes, in the face of these forces, a propeller blades. propeller loses some of its rigidity. The result is a FLUTTER, a type of vibration in which the for this reason also. Centrifugal force and thrust tips of the blades attempt to twist rapidly back bending force oppose each other to some extent. and forth while the propeller is turning. Flutter-, ing causes a distinctive noise, which is nearly Torque Bending Force drowned out by the exhaust noises of the engine. Fluttering will weaken the propeller and may Another bending force to be considered is the result in structural failure unless detected early TORQUE BENDING FORCE. The rotation of the so that corrective measures may be taken. propeller is caused by the turning force supplied by the engine crankshaft. Operated in a vacuum, PROPELLER AND ACCESSORIES the engine would have an easy task, as air (43E60 AND 24260) density could be disregarded; however, the blades of the revolving propeller actually meet Before discussing the hydromatic propeller, with varying values of resistance due to the itshould be understood how itreceives its density of the air. This resistance results in a designation. A breakdown of the designation for torque on the crankshaftacting in a direction the'43E60 propeller is as follows: opposite to the torque power force provided by 4Indicates the number of major changes the engine. , incorporated in the propeller. Since every portion of each propeller blade 3Number of blades. takes some part in producing this torque, the . EBlade shank size. (The use of a LETTER full length of the blade is also subjected to a here also indicates that the blades are made of share of the load. Consequently a blade tends to aluminum. A NUMBER here would indicate the

238

21 4 r 0 7 Chapter 12PROPELLEROPERATION AND MAINTENANCE

shank size and also thatthe blades were made of steel, as in model24260.) 60Indicates the spline size ofthe propeller shaft. A number followingthe "60" indicates the DOME CAP functional and installationcharacteristics of the propeller. As the word 4hydromatic" maysuggest, these propellers arehydraulically operated. A 43E60 propeller isshown in figure 12-8. LOW PITCH STOP The Hamilton StandardReversing Hydro- LEVER ASS'Y znatic propeller permitsconstant-speed opera- tionwithin the limits of thepitch changing propeller in flight, mechanism, feathering of the DOME and reverse pitch operationwhich greatly improves the ground or waterhandling characteristics of multiengineaircraft. The two types of propellers discussed inthis chapter are the 43E60 and 24260 models,and the model 5U18 double-acting constant-speedcontrol, which is the same for bothpropellers except for minor modifications. Instead of the two-slope camsused in the nonreversing type, three-slopecams are used in the reversing model,the third slope being utilized for reverse-pitchoperation. A reverse- pitch stop ring limits theblade angle in reverse pitch on the 43E60 and24260. The low blade stop lever OIL TRANSFER angleislimited by a low-pitch HOUSING assembly. An oil transferhousing is used to direct oil to and from thepropeller. Oil from HUB the constant-speed controlis directed to either the inboard or outboardside of the piston through the oil transfer housing. A cam assembly on theNo. I blade shank actuates a blade controlswitch on the barrel during unreversing andunfeather operation. A similar cam on the No. 2blade on three-bladed propellers and on the No. 3blade onfour-bladed propellers actuates anotherblade control switch on the barrelduring feathering andreversing operations. A slipring assembly,which provides a means of currenttransmission from abrush block assembly mounted onthe nose section of AD.128 the engine to the bladecontrol switch on the 43E60 propeller. 43E60 propeller, is mounted onthe inboard end Figure 12-8.Model of the propeller barrel.The slinger ring is used control of the propeller. fluid to the blades and is sliprings for deicing and to distribute anti-icing Deicing on this modelpropeller is done elec- attached to the slipringassembly. Nozzles direct the leading edge of propeller blades. The24260 trically, using heaters in the fluid to the each blade. propellerutilizesboth face and drum type

239

21 AVIATION MACHLNIST'S MATE R 3 & 2

BARREL ASSEMBLY ically directed to the proper side of the propeller piston to produce the desired blade angle change. The barrel assembly of the 24260 propeller is machined from a one-piece steel forging in-. AUXILIARY PUMP corporating a cylindrical central bore and four cylindrical blade arms. The blades are retained An electrically driven auxiliary pump is by four races of ball bearings. The inner race used with those propellers which have feathering for these bearings is on the blades, the outer and reversing features. It furnishes the high-. race isin the barrel. Each blade is free to pressure oil which is necessary during feather- turn about its axis under coutrol of the dome ing and unfeathering, and reversing and un- assembly. reversing operation. It is usually mountedin the The barrel assembly of the43E60 propeller engine accessory section. An auxiliary pump is is made in two pieces, and they are machined shown in figure 12-9. and balanced as a pair and kept together for the life of the propeller. The barrel halves are held SYNCHRONIZER together by the barrel bolts and nuts. The bolts are hollow and may be filled with lead A SYNCHRONIZER is used in many multi- wool as required to achieve final propeller engineaircraftto provide for simultaneous balance. selection of the desired engine rpm for all engines by the manipulation of one control. The CONSTANT-SPEED rpm of one engine is controlled by the pilot or CONTROL (GOVERNOR) flight engineer with the master lever. All other engines are slaved to the master engine by the synchronizer. The double-acting constant-speed control The synchronizer control utilizes the air- directs oil to either the inboard or the outboard craft's tachometer generators for sensing the side of the piston in the dome, changing the difference of engine rpm between the master blade angle in order to maintain the selected engine and one or more slave engines. The engine rpm. It is mounted on the nose section master engine is used for rpm reference, and of the engine. The control is made up of three the slave engines will follow the master engine assemblies: head, body, and base. The 5U18 whenever they are under control of the synchro- control utilizes a stepmotor electric head tonizer. Amechanical limiting device in the adjust the position of the speeder rack, which system limits thp synchronizing to approxi- in turn changes the compression on the speeder mately 3 percent of the master engine rpm. Thus, spring. This sets the control to maintain any selected rpm within the operating range of the constant-speed control. The stepmotor electric head may be controlled through a synchronizer system or by a manually operated toggle switch in the cockpit. The electric head eliminates mechanical linkage between the cockpit and the constant-speed control. The constant-speed control also includes flyweights, a gear type pump which produces oil pressure for the operation of thepropeller,and various valves which control and direct the flow of oil to the propeller. An electrically driven auxiliary pump is used as a source of high-pressure oil during the four auxiliary operations. These are the feathering, unfeathering, unreversing, and reversing cycles. The output of the auxiliary pump is led AD.129 to the constant-speed control and is automat- Figure 12-9.Auxiliary pump.

240

2.1.0 Chapter 12PROPELLER OPERATIONAND MAINTENANCE

move toward a higher pitch.The constant-speed an abnormal increase ordecrease in the rpm of from the inboard the master engine or even failureof the master control permits oil drainage engine(s) rpm to sideofthe piston when the bladeangle is engine cannot cause the slave increased. When the blade angle isdecreased, change beyond this limit. Whenthe master oil to the control is advanced to the fullincrease rpm the constant-speed control directs feature inboard side of the piston andallows drainage position (calibrate), the synchronizing propeller piston is cut out so that failure of themaster engine from the outboard side of the effect upon the slave back totheinletsideofthe pump in the on takeoff will have no constant-speed control. Both the pressureoil and engines. the drain oil flow through separatepassages in the oil transfer housing, whichis screwed into ANTI-ICING AND the propeller shaft. Thepropeller piston may DEICLNG SYSTEMS move outboard until a steelsleeve in the piston rests against the levers of thelow-pitch stop Protection against icing conditions is pro- held outward vided by either an electrical deicingsystem or lever assembly. These levers are Electrical deicing is by a wedge so that they will engagethe sleeve a fluid anti-icing system. blades reach the accomplished by supplying currentperiodically in the piston as the propeller low-pitch setting. to a heating element mountedeither on or in the desired, oil leading edge of each blade. Atimer unitmounted When reversing operation is controls the deicing pressure from the governoraided by oil pres- in the aircraft fuselage actuates the servo current impulses to all propellers.The electri- sure from the auxiliary pump to form on the unit of the low pitch stoplever allowing the cal deicing system allows ice levers down and blades; heat supplied periodicallymelts the ice piston sleeve to cam the stop is thrown off by the move forward to the reverseposition. This sufficientlyso thatit allows the levers to move inward sothat the centrifugal force acting on thepropeller blade. by the levers, The fluid anti-icing system preventsthe forma- sleeve in the piston may pass Fluid is distributed allowing the blades to go pastthe low-pitch tion of ice on the blades. reverse pitch. Thelimit of to the leading edge of eachblade from a hub limit and into collectors on each revers is reached whenlugs of the reverse pitch slinger ring, through tubes, to up against blade. Shoes mounted on theleading edges of stop ring on the rotating cam come steel blades lugs on the stationary cam.The No. 2 blade blade and cuff (cuffs are added to switch, which is actuated by a camattached to to improve aerodynamic coolingof the engine) distribution of anti-icing the blade shank of either No.2 or No. 3 blade, are grooved to insure shuts off the auxiliary pump afew degrees fluid over the blade surface. Constant-speed control WARNING: The alcohol used fordeicing beforefullreverse. and is a deadly oil pressure then moves theblades into the propellers is isopropyl alcohol full reverse position. In the reverseposition, poison when takeninternally. slotted ports in the piston sleeve areopened to act as a dump valve,permitting the high oil PROPELLER OPERATION pressure on the inboardside of the piston to dump through the ports to theoutboard side of The most significant naturalforce affecting blades is the centrif- the piston. the angle of the propeller the auxiliary pump ugal twisting moment, whichtends to move the During unreversing, blades to a flat or a zero bladeangle. This furnishes high-pressure oil to theconstant- speedcontrol,which directs the oil to the force is always present when apropeller is allows oil to rotating. Oil pressure from theconstant-speed outboard side of the piston and drain from the inboard side of thepiston. When control must overcome thecentrifugal twisting where the moment in order to move theblades to a higher thepiston las moved to a point higher oil forward end of the piston sleeveis well past blade angle when desired. Therefore, lever assembly, pressure is required to increaseblade angle. the levers of the low-pitch stop outboard side the levers are forced outwardby spring tension Oil pressure directed to the auxiliary pump is cut off of the propeller piston causesthe blades to on the wedge and the

241

21( AVIATION MACHINIST'S MATE R 3 & 2 by the No. 1 blade switch. The pistonthen moves back until the sleeve rests against the levers of the low-pitch stop lever assembly. During feathering, the auxiliary pump furnishes high-pressure oil to the constant-speed control, where it is combined with governor oil pressure and is directed to the outboard side of the piston and allows drainage from the inboard side of the piston. This moves the piston inboard and the blades to the feather position. Lugs on the high-pitch stop ring (located on the rotating cam) contact lugs on the stationary cam to stop the blades in the feather position. For unfeathering, high-pressure oil from the auxiliary pump is supplied to the constant- speed control which directs it to the inboard 10 side of the piston, moving the piston outboard and the blades to a lower angle. As the propeller begins to windmill, the governor boost pump starts to operate and will aid the auxiliary II pump to move the blades out of feather. The auxiliary pump is shut off by releasing the feather button when a low rpm is reached. 12 This terminates the unfeathering cycle and 13 allows the constant-speed control to maintain full decrease rpm, which is selected prior to AD.130 unfeathering. 1.Electric head. 2. Pump. CONSTANT-SPEED CONTROL 3. High-pressure relief valve. OPERATION 4. Shuttle valve. 5. Low-pressure relief valve. A cutaway view of the constant-speed con- 6. Pressure cutout switch. trol is shown in figure 12-10. 7.Drive gear shaft. The stepmotor electric head provides a 8. Speeder spring. means of controlling the compression of the 9.Flyweight. speeder spring (8). This compression deter- 10. Solenoid valve. mines the rpm necessary to hold the flyweights 11. Selector valve. (9) in a balanced or onspeed condition. If com- 12. Auxiliary pressure check valve. pression on the speeder spring is increased, 13. Pilot valve. more rpm is required to cause the flyweights 14. Low rpm adjustment. to move outward to attain the onspeed condition. 15. High rpm adjustment. If compression is decreased, less rpm is needed. Whenever the flyweights move in, the pilot Figure 12-10.Cutaway view of the 5U18 valve (13) moves down. When the flyweights constant-speed control. move out, the pilot valve moves up. The position of the pilot valve determines whether oil is lower positioning chamber. If the greater force directed to the inboard side of the piston or to is on the top of the positioning land, the pilot the outboard side of the piston. During constant- valve will move down. If the greater force is speed operation, the pilot valve (13) is positioned on the bottom of the positioning land, the pilot by the forces of the flyweights and the speeder valve will move up. spring. During the four auxiliary conditions, it The pump (2) boosts engine oil pressure to is positioned by oil pressure in the upper or the pressure required to operate the propeller

242

2.10 Chapter 12PROPELLEROPERATION AND MAINTENANCE

The solenoid valve(10), is energized during during constant-speed operation.This does not directs oil pres- conditions mentioned unfeathering and reversing. It include the four auxiliary sure to the upperpositioning chamber causing previously. downward, thus creating valve (3) limits the the pilot valve to move The high-pressure relief an artificial underspeedcondition. maximum oil pressure foroperation of the (14) provides a for a normal The low rpm adjustment propeller except when correcting means of setting theminimum governing rpm underspeed condition. of the speeder The selector valve directshigh-pressure oil by limiting the upward travel spring rack. to back up the spring sideof the low-pressure (15) provides a unfeathering, The high rpm adjustment relief valve during the feathering, means of setting themaximum governing rpm reversing, unreversing, andnormal overspeed travel of the speeder operations. The low-pressurerelief valve pre- by limiting the downward vents pressure from building upsufficiently to spring rack. actuate the servo unit of thelowpitch stop lever during ground operation. MAINTENANCE During all conditions exceptnormal under- oil is directed to the speed, high-pressure The maintenance that the ADRperforms on spring side of the low-pressurerelief valve by the amount of the propeller and accessoriesis limited to the selector valve, increasing servicing, replacement,adjustments, and minor pressure necessary to openthe low-pressure in the following relief valve and allowing pressureto build up repairs. These are discussed until it is relieved by thehigh-pressure relief paragraphs. valve. By controlling the pressureduring a normal underspeed condition,the low-pressure Propeller inadvertent reversal relief valve prevents an Propeller maintenance consistsmainly of during ground operation. minorblade to direct high- removal and installationand The shuttle valve (4) is used repairs. The installationand removal pro- pressure oil to theplunger side of the pressure return oil to the spring cedures are discussed inthe following para- cutout switch (16) and graphs and blade repair isdiscussed later in side of the pressure cutoutswitch. The pres- to the chapter. sure cutout switchis used on some models installation, after the blades reach INSTALLATION.Prior to release the feather button clean the propeller shaft andengine thrust nut the full feather position. of clean engine oil valve (12) per- thoroughly. Put a light coat The auxiliary pressure check shaft.Install the split rear mits the entry of high-pressureauxiliary pump on the propeller control during the cone on the propellershaft, making sure that oil into the constant-speed the surfaces of the cone aredry and clean. four auxiliary conditionsand allows for positive the shaft It also directs oil Installthe spider-shaft spacer on positioning of the pilot valve. next to the rear cone.Install the 0-ring seal to the following placeswhenever it is in opera- pencil of the pilot valve, on the shaft nextto the spacer. Make tion: The pressure chamber marks on the forward endof the propeller the solenoid valve, andthe lower positioning locations of the locking chamber of the pilot valve tocreate an artificial shaft to indicate the It prevents holesof theshaft.This will facilitate the overspeed for feather and unreverse. alignment of one of the slotsin the retaining oil from the pump of theconstant-speed control nut with a hole in thepropeller shaft. from pressurizing the auxiliary pumpline during propeller retaining constant-speed operation. Italso has a small Place the front cone, nut, and snapring inposition in the propeller bleed hole for winterization,which allows a the hub enough to oil to enter the auxil- hub, turning the blades in slight amount of .control allow these parts to beinserted past the blade iary line during constant-speedoperation. This the in this line during gear segments. Aswith the rear cone, will prevent oil congealing surfaces of the front coneshould be clean and cold weather.

243

21d AVIATION MACHINIST'S MATE R 3 & 2 dry. Apply a thin coat of thread lubricant to the After removal, if another propeller is not threads of the propeller shaft. tobe installed immediately, clean,oil, and Using a power wrench and sling assembly, cover the propeller shaft. If the propeller is lift the propeller onto the shaft. If the propeller to be stored for any length of time, preserve shaft has an index splme or an index screw, the propeller in accordance with current in- align the blank spline of the propeller hub with structions. it and slide the propeller back on the shaft. As the propeller is pushed fully into position, tighten Dome the retaining nut by hand to insure that there is not binding or cross threading. Tighten the The dome assembly of a reversing Hydro- retaining nut with a short bar until it is snug. matic propeller includes the propeller pitch- Using the power wrench, tighten the retaining changing mechanism by means of which oil nut to the proper torque, and align bne of the pressureistransmittedinto blade-turning locking slots in the retaining nut with one of forces. The assembly is illustrated in figure the locking holes in the propeller shaft. 12-11, and it consists principally of the cams, Place the oil transfer housing gasket against the piston, and the dome shell. the plate inside the propeller shaft. Clean the When the dome assembly is installed in the threadsof the oil transfer housing and the propeller hub, the STATIONARY CAM provides internal threads of the propeller shaft and apply support for the remaining parts in the dome unit. a light coat of thread lubricant or engine oil to The stationary cam is rigidly held in the barrel them. Carefully screw the oil transfer housing on thestationary cam-locating dowels. The into the shaft by hand. Tighten the oil transfer ROTATING CAM is supported within the station- housing to the proper torque, aligning the splines ary cam by means of ball bearings, which also on the housing with the splines on the inside of serve to take the gear reactions and piston oil the retaining nut to receive the lock segment. force. Piston motion is transmitted through the Install the lock segment and secure with the stationary cam to the rotating cam by means of lock segment lockwire. four or five sets of cam rollers. These are NOTE: Never back off the retaining nut to carried on shafts supported by the inner and align a slot with a hole. If necessary, back the outer walls of the piston. retaining nut all the way off and retighten to the Both the stationary and the rotating cams proper torque. Insert the propeller retaining contain inclined cam tracks on which cam rollers nut lock through the hole in the shaft and into operate totransform the back-and-forth motion the slot in the retaining nut. of the piston into the rotating motion of the NOTE: If for any reason the oil transfer rotating cam. The tracks of the stationary cara tube is removed from the dome or the setting are inclined in the opposite direction to those of the low-pitch stop lever ass embly is disturbed, on the rotating cam. This arrangement provides these must bereset according tocurrent twice the rotary motion (for a given straight propeller overhaul instructions. This also ap- line motion of the piston) than would be provided plies to the reverse- and high-pitch stop rings. with only one cam track. Care must be taken not to damage the oil The rotating cam is machined from steel. transfer tube during dome installation and The cam tracks and teeth are casehardened for removal. longer wear. The cam tracks are machined in REMOVAL.The removal procedures are the cylindrical body portion of the cam. These thereverseoftheinstallation procedures. tracks are machined with three slopes, one each While the dome or the propeller is being for feathering, constant speed, and reversing. removed, special care must be taken that no (See fig. 12-12.) electrical circuits are energized from the cock- The stationary cam is similar in construc- pit.If the auxiliary pump were turned on, a tion to the rotating cam. Its cam tracks are stream of oil (often . hot) under pressure would identical in design with those of the rotatingcam be sent out the propeller shaft, causingpossibly except that they are inclined in the opposite serious injury to anyone in front of the propeller. direction.

244

A24 U d26 Chapter 12-PROPELLER OPERATIONAND MAINTENANCE

Nomenclature for figure 12-11.

1.Dome cap 0-ring9.Stationary cam. seal. 10.Cam inboard bear- 2.Dome shell. ing. 3.Dome retaining 11.Cam roller as- nut. sembly. 4.Dome cap bush- 12.Rotating cam. ing. 13.High- and low-pitch 5.Lever sleeve stop rings. bushing. 14.Stop ring spacer. 6.Piston assembly.15.Dome to barrel 7.Cam bearing 0-ring seal. nut. 16.Gear preload 8.Cam outboard shim. .bearing. The piston is machined from analuminum forging. It provides the mechanismfor converting oil pressure into forceswhich act through the cam assemblies and turnthe propeller r1011111111* separately by 3411144Darlg. blades. The piston is balanced 0111111 drilling metal out of the inboardface of the inner wall. Supplementary unitsinclude a ledge (land or groove) on the outerpiston wall just outboard of the cam roller shaftbosses. A steel sleeve inside the piston wallcontacts the low pitch stop lever assembly sealrings and forms the inner oil seal between thehigh-pressure and

REVERSE FEATHER CONSTANT

-sest*

4. sT,4P% MX\ S\\t,C. sNT. Ja.4: `". \ '

ROTATING CAM GEARTEETH CAM TRACK

AD.132 AD.131 Figure 12-12.-A three-slope camtrack. Figure 12-11.-Dome assemblycomponents.

245

2 2 .1. c,2/r AVIATION MACHINIST'S MATE R 3 & 2 low-pressure sides of the piston. small bleed In order to establish the proper gear- holes are incorporated in the outer piston wall. meshing load pressure between the rotating cam These holes allow circulation of a small quantity gear and the blade gear segments, shims are of warm oil between the inboard and outboard included between the base of the stationary cam sides of the piston to prevent the oil from and the barrel shelf. These are called GEAR congealing during cold weather operation. PRELOADING shims and are made of solid Motion of the piston is transmitted to the brass. They incorporate holes which permit rotating cam by means of the cam roller installation of the shims over the stationary assembly. cam-locating dowels. Two STOP RINGS are provided in the dome INSTALLATION.-Prior to dome installa- assembly to limit travel of the rotating cam and tion each blade should be turned in the hub to thereby to regulate the feather and reverse either the specified feathered setting or to the blade-angle settings. The stop rings are indexed proper low pitch setting, and the rotating cam with the small teeth at the base of the rotating in the dome should be set to the corresponding cam. These rings have two lugs which contact angle. Although installation at either setting the stop lugs machined on the stationary cam. will give the same results, it is recommended One ring sets the reverse blade angle, and the thatthe method of setting the units at the other sets the feather blade angle. (See figure feather angle be used. However, both methods 12-13.) Propellerblade-anglesettingsare are explained. limited to the predetermined settings of the To install the dome with the blades set at stop rings. the FEATHER ANGLE, the blades must be set The DOME SHELL forms the cylinder in by aligning the feather angle marked on the blade which the piston operates. It is fastened to the buttwith the barrel index lines. Using the base of the stationary cam with capscrews. The correct tool on the rotating cam gear, turn the outboard end of the dome shell incorporates a cam until the feather stop ring lugs contactthe threaded bushing. This bushing is fitted with a lugs on the base of the stationary cam. This dome cap which is removed to drain oil from the stopring should, of course, be checked to dome and is replaced with a dome lifting handle assure that it is accurately indexed. during removal and installation. A dome retain- Place the required number of shims over ing nut and dome-barrel seal are supplementary the cam-locating dowels. Total shim thickness parts of the dome shell. is marked on the barrel shelf. Do not install the dome-barrel seal at this time. Screw in the dome lifting handle. Lift the dome and align it with the locating dowels in STOP LUG STOP RING the barrel. Because of the dowel arrangement, ---,' the dome will fit in only one angular position. Just before installing the dome, check that the rotating cam. is tight against the stop lug. Then ROTATING install the dome and tighten it down with the CAM dome retaining nut wrench until it is firmly seated on the barrel shelf.(See figs. 12-14 STATIONARY and 12-15.) CAM Align the hole in one of the retaining nut lugswith oneof the crescent slots in the STOP RING outboard edge of the barrel; carefully mark this location of the retaining nut. Remove the dome. Install the dome-barrel seal andagainplace the dome in position, using the same tare as STOP LUG before. Tighten it down until the previously marked aligned holes are lined up. AD.133 NOTE: With the dome assembly properly Figure 12-13.-Dome assembly. seated in the barrel, the front face of the dome

246 22 Chapter 12PROPELLER OPERATION AND MAINTENANCE &/ c

blade. By applying this correction angle to the angle measured at the reference station withthe protractor, the true effective aerodynamic angle may be found. The correspondingangles of each blade in a propeller should be within 0.5° of the specified setting, and alike within 0.2° total variation. Remove the dome lifting handle and, with a blade turning device, manually turn the blades to low pitch. Again check the settingwith a protractor in the manner described above. Insert the dome retaining nut lock screw and safetyit with a cotter pin. Install the dome cap sealand dome cap, using the proper torque, andlock in place with a cotter pin (or setscrew andcotter AD.134 pin). Figure 12-14.Installing the dome and To install the dome with the blades setat engaging the retaining nut thread. the LOW PITCH ANGLE, set all blades atthe proper low pitch (takeoff) angle by meansof the retaining nut will be approximately flush with blade butt graduations and the barrel index lines. the outboard edge of the barrel. Failureto Use the same precautions as previously men- properly tighten the dome retaining nut in the tioned. Check to make certain that the propeller hub may result in elongation or failure of the piston sleeve has not moved away from thelow dome shell retaining screws, and oilleakage pitch stop levers. Install the dome onto thehub around the dome retaining nut. in the manner as described before. Check the feather angle at the reference REMOVAL.In general, the procedure for station with a protractor and blade template. removing the dome isthereverseof the Blades used on certain installations are aero- installation procedure. dynamically balanced, where slight aerodynamic Remove the cotter pin (or setscrew and unbalanceiscritical. Each aerodynamically cotter pin) locking the dome cap, and unscrew balanced blade has a correction angle etched on the cap. Since the dome is filled withoil, some the butt surface. This correction angle should provision should be made to catch this oilat also be marked on the camber surface ofthe removal of the dome cap andalso whenthedome "assembly is disconnected from the hubassembly. Install the dome lifting handle and unscrew the dome retaining nut; then removethe dome (with the stop lever assembly and oil transfer tube in place) by pulling it straight awayfrom the hub,keepingit centered as closely as possible with the axis of the propeller shaft. Be careful not to damage the exposedend of the oil transfer tube during removalof the dome and while setting the dome down onits side after removal. Governor (Constant Speed Control)

Themodel 5U18propellergovernor (constant speed control)is covered in this AD.135 chapter as a typical example. Figure 12-15.Tightening the dome INSTALLATION.A general discussion of retaining nut. installation procedure is given here. The ap-

24'7

22,5 c>2/60 AVIATION MACHINIST'S MATE R 3 & 2 propriate technical publications should be con- isrecommended becauseifadjustmentis sulted for specific instructions. attempted with the control shaft stop lugs in If the propeller governor (constant-speed contact with either of the stop screws, the stop control) is to be installed on a new or overhauled bracket assembly may be damaged. engine, remove the mounting pad cover from the To adjust the rpm on the electric head engine nose. Make sure that the shipping gasket control,loosen theself-locking nut on the included between this cover and the engine pad required stop screw and then turn the stop is also removed. Failure to remove this gasket screw in the direction indicated on the stop would affect the flow of engine oil to the control plate.Each complete turn of the screw is and would cause malfunctioning of the control. equivalent to approximately 50 rpm. When installing the propeller governor constant- To adjust the high rpm on the mechanical speed control, care must be shown in regard to head control, turn the adjustment screw on the the oil control plugging. The.plugging indicates head clockwise to decrease rpm and counter- the method by which the governor can be adapted clockwise to increase rpm. One complete turn to either clockwise or counterclockwise rotation. of the screw is equivalent to approximately 25 For clockwise rotation governors, the pump rpm. In extreme cases the pulley stop pin may output check valve is placed in B port and the be relocated. A change from one hole to the input sleeve is placed in A port. For counter- next is equivalent to approximately 250 rpm. clockwise rotation governors, the pump output To adjust the low rpm, it is necessary to remove check valve is placed in A port and the input the head, take out the rack assembly, loosen the sleeve is placed in B port. Correct rotation taper lock screw, and reposition the low rpm can be determined by observing the governor adjusting screw in the rack. Each complete turn mounting pad on the engine while the engine is of the low rpm screw is equivalent to approxi- being pulled through in the direction of rotation. mately 225 rpm. Clean the surfaces of the mounting pad and BENCH TESTING.-The bench testing pro- base of the control. Install a new gasket-on the cedure for the constant speed control is listed mounting pad with the raised portion of the metal in the test bench operation manual. The correct screen of the gasket facingup. Install the control testing procedure and governor settings are on the studs of the mountingpad. The one proper found,intheoverhaulinstructionson the position of the control on the mounting pad is governor. indicated by the shape of the joining surfaces. The safety precautions pertaining to the Make sure that the splines of the control shaft test bench operation should be complied with. are properly aligned with the internal splines in Care should be exercised to prevent excessive the engine pad and that the circular boss in the pressures from being exerted on the governor base ofthecontrolfits properlyinto the during testing. The test bench shouldbe warmed circular recess in the engine pad. Install the up properly before attempting to test the gover- washers and new locknuts and tighten evenly to nor. Figure 12-16 shows a propeller governor the proper torque. Lockwire the nuts in pairs. test stand. Connect the auxiliary high-pressure oil line To check the propeller governor on the from the auxiliary connecter on the control. test bench, install the governor on the test Make the electrical connections to the solenoid bench mounting pad. The first check should be valve, and other units. the rpm stop settings, and they are as follows: REMOVAL.-The removal of the constant- 1. Maximum rpm must be set within 5 rpm speed control is the reverse of the installation of the desired setting. procedure.If another control is not installed 2. Minimum rpm must be set at 1,200 rpm immediately, install a gasket and cover on the and within 5 rpm of the desired setting. mounting pad. 3.Aftermaking rpm adjustments, the ADJUSTMENTS.-The rpm adjustments of maximum rpm adjustment should be lockwired. the stepmotor electric head should be made only 4. Recheck of the maximum and minimum when the head has been operated away from the rpm must be within plus or minus 25 rpm of the maximum and minimum stops. This procedure desired setting.

248 Chapter 12PROPELLER OPERATIONAND MAINTENANCE C/2

;VI

A ."

AD.136 Figure 12-16.Propeller governor teststand.

the The pump capacity test isaccomplished by 5. Each turn of the adjusting screws on 1,750 rpm and then stepmotor electric head is equivalentto approxi- setting the governor head at adjust the back pressure to150 psi and the mately 50 rpm. minus 15 psi. The next check is to inspectthe governor supply pressure to 40 plus or The pump capacity must bebetween 16 and 20 for external leakage whileunder pressure of the pump approximately 1,100 psi on output sidefor at quarts per minute. At 2,800 rpm capacity must not fall below19 quarts per least 1 minute. internalleakage while minute. Next, check the The relief valve pressure test isconducted operating at a back pressureof 150 to 200 psi valves at the plus or minus 15 psi. by setting the pressure relief and a supply pressure of 40 particular model If leakage exceeds 1to 20 quarts per hour, specified relief setting for the several drive gear shafts andpilot valves governor. This test mustbe continued for combination 1 full minute. On feathering typegovernors the should be tested until a satisfactory auxiliary pump inlet fitting mustbe left open is found. Do not reduceinternal leakage below adjusted by normal minimum, as a stickypilot valve may during this test. Relief valves are use of shims. result. accomplished by When checking the counterbalance rpm,it The feathering test is 2,200 rpm. This setting the governor speed atapproximately should be between 2,000 and the connector by using different balance 2,000 rpm. Supply oil pressure to rpm can be adjusted check valve and check opening pressureof the springs.

249

220 AVIATION MACHENIST'S MATE R 3 & 2 check valve. A reduction in rpm will indicate The only acceptable method of removing correct featheringoperation. The auxiliary damage is that by which the metal containing connector check valve should reseat when pres- the damage and the adjacent area is removed sure is relieved. from the blade with diemakers' rifflers (#8, 10, For the reversing test, set the governor and 17 "0" cut) and emery cloth. All traces of speed at approximately 2,000 rpm and energize the damage should be worked from the blade the solenoid valve at 18 volts d.c. An increase and the resulting depression should be smoothly in rpm will indicate correct reversing operation. faired into the surrounding blade surface. Do When the solenoid valve is deenergized, the not attempt to relocate any of the metal in the governor should return to its original rpm. damaged area by cold-working. The number of The opening pressure of the pressure cutout repairs in a given area on a blade is not limited switch should be checked. This switch should be provided their locations with respect to one checked while installed on the governor, and it another do not form a continuous line of repairs should open at 650 psi differential pressure. that would materially weaken the blade structure. The rpm adjustments will be made and the For an illustration of minor repairs to the opening pressures of all valves will be adjusted aluminumalloypropellerblade,refer to within tolerance while on the test bench. 'figure 12-17. In general, a steel blade having a crack, Blade Repair bend, or bullet hole is cause for the removal of the propeller. No attempt should be made to The repair of minor injuries to aluminum repair damage of this nature. alloy propeller blades usually consists of dress- The raised edges of cuts, scars, scratches, ing down and smoothing out cuts, nicks, and etc., are dressed off by handstoning. The amount scratches in the blade surface. of metal removed should be as small as possible, Cuts,scars, scratches, surface cracks, so that there will be no abrupt change of section nicks, etc., are completely removed, forming a "saucered out" depression smoothly faired into the blade surface. This area must be carefully examined with a three-power magnifying glass to make certain the bottom of the damage has SURFACE BURR been completely removed. Also, local etching is necessary to be sure that there are no cracks at the bottom of the rework. To avoid removing an excessive amount of metal, this local etching check should be made at intervals during the processof removing the damage.Ifitis necessary during the rework to remove more metal than is allowed in the repair limits given in the blade dimensional forms of the applicable publications, the propeller shculd be removed from service and sent to overhaul. Blades requiring removal of metal which would form a finished depression more than 0.125 inch in depth at its deepest point, 0.375 inch in width, and 1 inch in length, should be sent to overhaul. NOTE: The information noted here is general in content and does not apply to a specific SURFACE CRACK type aluminum propeller blade. Refer to appli- NICKED EDGE cable Operation and Service Instructions for the specific methods to use on a particular model AD.137 of propeller. Figure 12-17.Before and after rework.

250

92rj Chapter 12PROPELLER OPERATIONAND MAINTENANCE c3./1

tending with clean water. NOTE: Too muchwater may that would cause a stress concentration defect and thereby to induce a crack at any point.Under no circum- remove the solution from a stances should any other metal beremoved, nor spoil the check. used for 5.If thereis a crack or other defect should other abrasives or tools be extending into the metal, it will appear as a this purpose. Small, shallow dents located on theleading dark line, or other mark. By furtherexamination the tip, are of no through a magnifying glass, smallbubbles may or trailing edge, or near be seen forming in the dark line ormark. consequence,and therefore do notrequire other locations may be 6. Removal ofthesedefectsisac- repairs.Dentsat fine snad- removed, provided that; complished by means of crocus cloth, 1. The necessary tools areavailable. paper, and fine-cut riffle files.Several applica- of the tions of the caustic solution may benecessary 2. The strength and performance has been blade are in no way injured. to determine if the shallow defect 3. The surface is restored topractically removed. Immediately upon completionof the final check, all traces of caustic sodamust be its original shape. removed with nitric acid solution,which in turn is thoroughly rinsed off withfresh, clean Inspection water. The blade is then dried andcoated with clean engine oil. the Aluminum alloy blades are examined care- N0TE: Because they attack metal, fully for cracks or other failures,and for caustic solutions are kept in glass orearthen- bends, nicks, scratches, andcorrosion. The ware containers. If anyquantity of solution is application of engine oil to the bladesaids in spilled,it should be immediately flushedoff this inspection, and a magnifyingglass is also the surface on which it was spilled(particularly used. If there is any doubt as tothe extent of if the surface is metal) with freshwater. etching should Steel blades may be visuallyinspected by certain types of injuries, local noted, be performed. themagnetic method. As previously covering the blades with.oil orrust-preventive The purposes of local etching are: obscure 1. To determine whether visiblelines and compound aids in revealing otherwise of the blade defects. The full length of the leadingedge other marks within small areas of the actuallycracksrather than (especially near the tip), the full length surfacesare trailing edge, the grooves and shoulders onthe scratches. removal shank, and dents and scars should bechecked 2. To determine, after a minimum scratch must of metal, if shallow crackshave been removed. carefully for cracks. Each apparent otherwise not be examined carefully through a magnifyingglass 3. To expose small cracks to determine whether it is a scratch or acrack. appar ent . 4. To provide a simple meansfor ac- Special equipment is needed to check pro- removingor pellers by the magnetic method. Toperform the complishing this work without mounted in a disassembling the propeller. check, the steel blade or part is specially built machine. With a powersupply of The procedures for local etching are: blade is 1. The area of the aluminumalloy blade to 2,000 to 3,000 amperes, at 6 volts, the cleaned and magnetized by rapidly making andbreaking the be etched should be thoroughly black powder dried. Masking tape may be placedaround the circuit through it 2 or 3 times. A for ad- or red mixture of ironfilings (Magnaflux) and suspected area to provide protection the same joining areas. kerosene is poured over the blade at smooth off the time thatitis energized. North andsouth 2. With No. 00 sandpaper, magnetic poles will be set up oneither side area. the 'fon filings 3. With a small swab orstick, apply to the of any crack in the metal, and suspected area a small quantityof caustic will line up in the magnetic fieldthus created. A black or red line (depending uponthe color solution. there is a 4.After the area is well darkened,thor- mixture used) will appear wherever oughly wipe it off with a cleancloth DAMPENED crack in the blade.

251

22( AVIATION MACHINIST'S MATE R 3 & 2

Cleaning suitable solvents, such as approved paint and varnish remover. All foreign substances must be removed from the propeller surfaces to prevent corrosion Testing and to facilitate inspection. Steel propeller hubs are cleaned with soap Propeller and propeller accessories must and water, or with an approved cleaning solvent. be checked by the Aviation Machinist's Mate R Tools and abrasives that will scratch or other- during theground operational check of the wise damage the surface should not be used. propeller. The propeller controls in the cockpit Propeller blades should be cleaned withthe of a two-engine aircraft may be located as same materials used on the hubs. Except in the illustrated in figure 12-18. case of etching and repair, scrapers, power CONSTANT SPEED.Place the propeller buffers, steel wool, steel brushes, or any other controlin FULL INCREASE RPM position. tool or substance that will scratch or otherwise Then set the throttle to obtain maximum cruising damage the blade must not be used. In special rpm. Move the propeller control towards the cases, where polish is desired on aluminum DECREASE RPM POSITION until a drop of not alloy blades, an approved metal polish may be over 300 rpm is noted. Now slowly increase and used, provided that on completion of the polishing decrease the throttle setting and note that the alltracesof polish are removed. This is engine rpm remains constant. necessary to prevent corrosion by acid contained MINIMUM GOVERNOR RPM.Place the in the metal polish. propellercontrolintheINCREASE RPM All cleaning substances must be removed position. Then set the throttle to obtain ap- immediately upon completion of the cleaning of proximately 300 rpm above the required low any propeller part. Soap in any form is removed rpm setting. Move the propeller control to the by thoroughly rinsing with fresh water, after FULL DECREASE RPM position. The engine which all surfaces are dried. rpm will decrease to the minimum governing Immediately after the inspection and other rpm setting of the governor. Next, move the work following each cleaning or etching, and propellercontroltotheINCREASE RPM upon completion of each day's flying, all exposed position and note that the engine rpm returns surfaces of the blades and hubs are coated with to the original setting. clean engine oil or the specified rust-preventive MAXIMUM GOVERNOR RPM.Place the compound to prevent corrosion. propeller control in the FULL INCREASE RPM The oil or rust-preventive coating serves position. Then move the throttle forward until two important purposes: the proper manifold pressure is attained for 1.It protects the exposed surfaces of the maximum power. The engine rpm will increase propeller from rust and corrosion. to the maximum rpm setting of the governor and 2.ft seeps into cracks that might develop remain constant. NOTE: On some installations inthe blade or hub, making the otherwise it is impossible to obtain the full takeoff rpm in obscure cracks stand out. the chocks. Propellerson aircraftoperating on or FEATHER ING.With the governor set at near salt water must be treated carefully to maximum rpm, and the engine operating at prevent corrosion of blades and hub. As soon 1,500 rpm, depress the feather switch button. as possible after a flight near salt water, all When the engine speed has dropped to 1,200 rpm, traces of salt are removed by thoroughly flushing manually pull out the pushbutton switch to its the propeller with fresh water. All parts are neutral position. The engine should return to then dried and coated with clean engine oil or 1,500 rpm. This test indicates that the feathering rust-preventive compound. pump is operative and that the feathering line Except during etching, causticmaterial is open. must not be used on any propeller. The removal NOTE: A full feathering test on the ground of enamel and similar substances from all is generally not required, since the test outlined propellers will be accomplished by the use of above shows that the units in the system are

252

220 Chapter 12PROPELLEROPERATION AND MAINTENANCE blades pass through zero pitch, amomentary rpm surge will occur.Proper operation can further be determined by notingincreased amperage on ammeterswhen the auxiliary feathering pump is energized.An increase of approximately 60 amperes perpropeller is normal. The duration of thereversing cycle should be 1 to 2 seconds. Afterthe propeller is reversed, apply the specifiedmanifold pressure and note engine rpm. Checkthe other propellers in the same manner and notethe rpm difference between engines. This differenceshould not exceed 100 rpm with the samemanifold pressure setting. (Since these values varywith different engines, check the applicabletechnical publications for the correct values.) NOTE: Do not operate thepropeller in reverse pitch longerthan necessary, asreversed slipstream prevents adequateengine cooling. Move thereversing lever to the IDLE position. Unreversing should occurat 1,000 to 1,200 rpm. An increase in amperagewill again be noted as the auxiliaryfeathering pump is energized during the unreversingoperation. NOTE: Propellers may bechecked individually or simultaneously. Afterground operational check, thoroughly inspectthe propeller for oil leaks and security.Install spinner nose assembly, if required. DEICING.The following proceduresapply AD.138 to the propeller deicerinstallation on a two- engine aircraft. 1.Manual control switches. sufficient 2. Indicator lights(maximum 1.With the engines running at increase or decreaserpm). rpm to place thegenerators in service, move the copilot's switch 3. Resynchronize switchbutton. the deicer control switch on 4. Master selector switch. console to FAST CYCLE, thento SLOW CYCLE. The amber indicator lightbeneath the switch 5. Master control lever. either position. 6.Feather switch buttons. should glow with the switch in 2.Close the left propeller deicercircuit propeller controls. breaker and open the right circuitbreaker. Figure 12-18.Location of Check the operation of the timerby noting in the readings operative. Completely feathering apropeller on periodic increase and decrease engine is shut down) of the ammeters during thedeicing cycle. The the ground (unless the and off for presents a serious fire hazard.After performing heaters should be on for 20 seconds the engine to run at 60 seconds with the controlswitch set at FAST the feathering test, allow and off for 180 1,000 rpm for at least 2 minutes sothat the oil CYCLE, and on for 60 seconds seconds at SLOW CYCLE. Adeviation of plus or pumpwillbe ableto scavenge the sump for the time inpreventing the engine frombecoming overloaded minus 10 percent is allowable tervals. with oil. 3. Repeat the check with theright propel- REVERSING AND UNREVERSING.While closed and the left the engine is idling, slowly movethe reverse ler deicer circuit breaker throttle lever into the reverse range.As the circuit breaker open.

253

22J .Q.a.2_ AVIATION MACHINIST'S MATE R 3 & 2

4. Close both the left and right propeller deicing circuit with AUXILIARY power. Feel deicercircuit breakers and again note the the blades to determine which are not being ammeter readings while the deicers are in op- heated. eration. The circuit should be energized for CAUTION: To avoid overheating the blade 40 seconds and off for 40 seconds when the heatersduringgroundcheckswhenthe control switch is set at FAST CYCLE, and on engines are not running, do not operate the for 120 seconds and off for 120seconds at SLOW deicing system for more than 3 FAST con- CYCLE. secutive cycles (generally 20 seconds on and NOTE: During this combined operation, each 60 seconds off). Do not exceed 28 volts at circuit functions separately, as described in theheaters and allowat least 30 minutes steps 3 and 4 and illustrated in table 12-1. between periods of operation. Under no con- 5. Check that all four-blade heaters on dition should a slower cycle be used during a each propeller are operating by noting the total static ground check. ammeter reading. Approximately 240 amperes Propeller accessories should be should be indicated. If the heater on one blade cleaned with approved solvent prior isinoperative,thetotal amperage will be to visual inspection. Units suchas approximately 180 amperes. If only one blade thepropellergovernorandthefeather- heater is operating, approximately 60 amperes ing pump and motor should be in-. will be indicated. spected dailyfor evidence ofleakage 6.If the, check in the preciding step indi- andforsecurityofmounting.Propeller cates that one or more of the blade heaters are accessoriesrequirenolubricationduring inoperative, stop the engines and operate the routine maintenance.

Table 12-1. Deicer timer operation.

Interval Interval Interval Interval No. 1 No. 2 No. 3 No. 4

Both propellers ON ON OFF OFF

Propeller No. 1 ON OFF OFF OFF

Propeller No. 2 OFF ON OFF OFF

NOTE: FAST CYCLE intervals-20 seconds; SLOW CYCLE intervals-60 seconds.

254 CHAPTER 14

GROUND HANDLING EQUIPMENTAND PROCEDURES

and new air- than to service and maintainaircraft systems As naval aviation progressed is ground support equip- craft were developed, newequipment was also or equipment. This service,protect, handle, test, ment (GSE). developedto The USN-numbered mobileground support maintain,inspect,and assemble these air- to the Inter- Although Aviation SupportEquipment equipment is normally assigned craft. mediate maintenance activityand the trans- Technicians maintain aviationground support department of the Intermediate main- portation or public works equipment, they do so at the supporting activity, and furnishedto the squad- tenance level only. The useractivity is charged ron on a subcustodybasis. with the day-to-daymaintenance (daily and which is not etc.) of the equip- NOTE: Only that equipment preoperational inspections, required (trucks, mobile cranes,etc.) in the ment in their custody. Thisday-to-day main- is maintained by and servicing day-to-day support of aircraft tenance as well as the operation the transportation or publicworks department. of the equipment is assignedto personnel of of space, facilities, various aviation ratings.Therefore, the ADR However, due to limitation types, uses, and personnel, equipment, etc., it maybe necessary must be familiar with the to have certain Intermediatefunctions accom- care of various aircraftground handling equip- departments/centers ment that he will be using inthe operation and plished by public works ashore. maintenance of aircraft. GSE is also furnished tothe squadrons by The assignment of aircraftground handling subcustody basis. squadron depends on the supporting activity on a equipment to an operating The maintenance of theGSE is the responsibility the number and types ofaircraft assigned and except for daily and squadron. There- of the supporting activity the assigned mission of the preoperational inspections Indservicing, which fore, the equipment will vary(except the basic of the using activity. equipment) from activity to activityand it would are the responsibility be impossible to cover allof this equipment in one chapter. Inthis chapter, only the basic MAINTENANCE equipment that the ADR willbe using in the requirements and maintenanceofaircraftis The prescribed maintenance operation for most aircraft groundsupport equipment are discussed. presented to the maintenance manin sets of Daily, Preoperational, and PeriodicMaintenance TYPES AND USES Requirements Cards. NOTE:Daily and pre- essentially the same supportequipmentis operational inspections are Aircraftground inspection and cover the sameitems of equip- divided into two categories: will have sets of ground support ment. Most new equipment 1. USN-numbered mobile preoperational cards only.Therefore, the only equipment. inspections described in thischapter are the 2. Equipment directlyrelated to fulfilling By following the maintenance function. This equip-. preoperational and periodic. an aircraft sequence set forth inthe card sets, the mini- ment normally does notfulfill any purpose other

263

231 AVIATION MACHINIST'S MATE R 3 & 2

mum inspection requirements of the equipment ladder assembly mounted on a caster-equipped will be satisfied. base which enables maintenance personnel to work in safety at heights varying from a minimum Preoperational Inspections of 3 feet to a maximum of 7feet. (See fig. 14-1.) The B-4A maintenance platform is control- Preoperationalinspectionsare accom- lable throughout its platform height range of 3 to plished prior to the first use of the subject 7 feet by means of a hand operated hydraulic equipment forthatday. This inspection is pump, mounted on the rear of the work platform. basically a combination of requirements for To raise the platform, the pump handle is moved checking equipment that required a daily verifi- in several back and forward motions until the cation of satisfactory functioning, plus require- desired platform height is attained. To lower the ments that prescribe searching for and correc- platform, the release valve lever on the pump tion of relatively minor problems to prevent assembly is moved in a counterclockwise direc- their progress to a state that would require tion, which releases the hydraulic pressure. major work to remedy. NOTE: The platform assembly is equipped Other items which require inspection at with two safety lockpins, which must be engaged intervals more frequent than prescribed for in position whenever the platform is in use. periodic inspections are also included on the Remove the lockpins before raising or lowering preoperational inspection and are accomplished the platform. Do not operate the pump handle along with the preoperational inspection on the or release valve while standing on the ladder. day they become due. Preoperational inspections are the only inspections performed by the using activity. MAINTENANCE WORKSTAND Discrepancies noted on preoperational in- (B-1 AND B-2) spections must be corrected as soon as possible in accordance with local maintenance proce- The B-1 workstand (view (A), fig. 14-2) con- dures. If corrective action is beyond the capa- sists of a stair structure and work platform bilityoftheactivity using this equipment, mechanically linked together in such a way as to assistance must be obtained from or corrective enable both (stairs and platform) to remainlevel action taken by the Intermediate level activity. througnout the height range of the stand. Stair Periodic Inspections support members and handrails are rigged in such a manner to make them self-aligning at all These are limited overall examinations of platform levels. Because of the handrails on the specific item of equipment. They are ac- both the stairs and the work platform, this stand complished by the activity having prime custody enables personnel to work at various heights in of the equipment, usually the Intermediate level relative safety. activity. Special provisions are made for extending the B-1 platform height by an additional 4 feet. WORKSTANDS AND SERVICING This is accomplished by placing another stand EQUIPMENT (view (B),fig.14-2)into theplatform post sockets, which are designed to accommodate There are various types of workstands and this additional structure. The post sockets on servicing equipment used in the Navy today. An the B-1 platform provide for either the attach- understanding of the uses of each will enable the ment of platform handrails or installation of the ADR to perform his task in an easier and safer extra stand for greater height. manner. The following paragraphs describe a The B-2 maintenance stand (view (C), fig. few of these items. 14-2) is the B-1 stand permanently mounted on a base extension structure of fixed height. The MAINTENANCE PLATFORM (B-4A) extension base, fabricated of angle iron and steel tubing, is 10 feet in height. This arrangement The aircraft maintenance platform, Type results in a maintenance stand which has abase B-4A, is a hydraulically operated platform and structure of fixed height and an upper stair

264

2 34 Chapter 14GROUND HANDLINGEQUIPMENT AND PROCEDURES

RAISED AD.140 Figure 14-1.Aircraft maintenanceplatform, Type B-4A. which can be is used to adapt the engineto the stand. On the structure and work platform vertical portion of the stand aretwo adjustable hydraulically varied in height. crossmembers, which can be raised orlowered as required. Thelegs of the engine mount may ENGINE STANDS be bolted to these members. hooked onto There are a number of enginestands used in There are two work platforms fly-away, and the horizontal member ofthe stand. These the Navy, such as the turn-over, platforms enable work to be done Oneither the build-up (L) stands. safety. The turn-over type is usedmainly by over- side of the engine with ease and haul activities. Itcan be adaptedto various sections or the complete engineaseembly. It AIR CONDITIONERS 360 degrees vertically and hori- can be rotated One of the most widely used airconditioners zontally, which allows forpositioning the engine isthe model NR-3. (See fig.14-4.)Itis a at various attitudes for easeof installation or ventilating and cooling engine. mobile, self-contained repair of components on the unit. This air conditionersupplies air within The fly-away type isusually a very low limitations to the cabin stand. A cradle for thelower cylinders of the proper temperature conditioningandcooled equipmentsystems the engine to rest on and apost (with adapter) testing of the air- supporting the propeller shaft are pro- during ground checkout and for craft's various systems. Theair-conditioning vided on the stand. This standmakes it pos- engines are not sible to transport a completeQEC to outlying unit is utilized when the aircraft operat ing. areas by cargo typeaircraft. The NR-3 is a trailer mounted,Freon- The most commonly usedengine stand for driven, mobile isthe"Lin stand cycle, 120-horsepower, engine thereciprocating engine unitcapableofdelivering (fig. 14-3). The name is derivedfrom the shape air-conditioning and 180,000 BTU net, or 294,000BTU gross of of the stand.It is utilized in building up 100 pounds tearing down QEC's. The aircraftengine mount conditioned air. This designproduces

265

23d AVIATION MACHINIST'S MATE R 3 t.:2

to furnish highly concentrated illumination upon a centered object, or to illuminate abroad area. There is a great variation in the types of ar- rangements that can be made in setting up the floodlights. Four mounted stanchions are provided on the top of the trailer on which floodlights can be mounted and rotated 360 degrees in the vertical axis and 230 degrees in the later- ial axis, and locked in any position. Alsopro- vided with the set are five tripod extensions and five 100-foot, reel-mounted, floodlight power cables. This enables the .operator to have four top-mounted floodlights and one tripod mounted with a 100-foot extension power cable. (fig. 14-5) (A) or five floodlights mounted on tripods with 100- foot extension power cables. (See fig. 14-6.) Two or more cables can be interconnected if required. Flexibility and latitude in the utilization of thefloodlightsetforillumination are un- limited. The short time factor involved in setting up the floodlight set for operation and unrestricted mobility offers a high asset to any operational requirement. NOTE: Before towing the floodlight set, insure that all gear is properly stored. The operator of the towing vehicle should familiarize himself with restrictions on turning radius and road clearances of the trailer before towing.

(3) (C) TOWING, STARTING, AND HOISTING EQUIPMENT AD.141 Figure 14-2.B-1 and B-2 maintenance Towing, starting, and hoisting equipment workstand. are important to the ADR in that he must use all of these items in the performance of his per minute of cool, moisture free air throughout duties. Being able to select the right piece of a range in temperatures from 50° F to 110° F equipment for the job will make the job safer when measumd at sea level. The equipment is and easier. designed to operate at altitudes up to 5,000 feet The tow tractor is the only means of pro- above sea level. It is self-sustaining and carries pulsion for a majority of aircraft when on the enough fuel and water to provide 4 hours of ground and the engines not running. The tractor's continuous operation. Provisionsforduct maneuverability depends on its size and turn-. storage are provided in the front of the vehicle. ing radius. Another factor is the drawbar pull, A tow bar retainer allows the tow bar to be which is the force the tractor can exert. The stored in the vertical position when not in use. drawbar pull is rated maximum for dry con- The parking brake provides a means of securing crete surfaces. the fully loaded unit on grades up to 35 percent. Starting unitsin use today vary with the type aircraft. The NC-5, which supplies d-c FLOODLIGHT TRAILERS power for starting plus a-c and d-c power for servicing purposes, is discussed in this section. The model MC-2 floodlight set is trailer There are many types of hoisting equipment, mounted and diesel engine driven. It is designed each havingitsown specific design. When

266

23g Chapter 14GROUND HANDLING EQUIPMENTAND PROCEDURES D,9.7

AD.142 Figure 14-3.Reciprocating engine stand. 125° F. It is powered by a V-8 gasolineengine selecting hoisting equipment, keep inmir.d the transmission, 1 following factorsweight to be lifted,height it and equipped with a 6-speed reverse and 5 forward,and 4-wheel drive. It must be raised, distance to bemoved, and the drawbar pull angle or attitude of the final positioning. weighs 25,000 pounds and has a rating of 18,000 pounds, Due tothe size of the TA-18, thesteeringis power assisted and TA-18 TOW TRACTOR has a turning radius of 24 feet10 inches. The to tow service brakes are vacuumassisted. The TA-18 (fig. 14-7) is designed Tractor large aircraft, such as patrol type, onvarious CAUTION: The size of the TA-18 types of surfaces in the various kindsof in-. limits the view of the operator.When operating clement weather, from a minus25°F to plus near an aircraft,another man should be used 125

267

23o AVIATION MACHINIST'S MATE R 3 & 2 r-vavaliMMent71,14,40wir::,

'4=

FRONT/LEFT-HAND SIDE VIEW

itC ".f. 1.11`,/::: ."r . :, " b, '-"" -..,t1tArzige

,".,0'.

)4+,4 - J4ift :

REAR/RIGHT-HAND SIDE VIEW

AD.143 Figure 14-4.NR-3 mobile air conditioner. to direct the operator to prevent damage to with an automatic transmission and power aircraft or possible injury to personnel. assisted steering,with a turning radius of 10feet.The TA-75 weights 10,500 pounds TA-75 TOW TRACTOR and has a drawbar pull rating of 7,500 pounds. The service brakes are the standard hydraulic The TA-75 (fig. 14-8) is designed to tow internal expanding type. all aircraft, on shore, up to75,000pounds A gas turbine compressor may be mounted gross weight.Itis powered by a Chrysler at the rear of the tractor to provide pneu- industrial six-cylinder engine.It is equipped matic power in the form of compressed air for

268

230 oaq AVIATION MACHINIST'S MATER 3 & 2

AD.144 Figure 14-5.MC-2 floodlightset.

AB.254 AD.145 Figure 14-7.TA-18 towtractor. Figure 14-6.Floodlightsmounted on tripods.

269

23i c>23z) AVIATION MACHINIST'S MATE R 3 & 2

AB.253 AB.255 Figure 14-8.TA-75 tow tractor. Figure 14-9.MD-3 tow tractor. operation of large class pneumatic equipment, tances.Factors such as length of time the such as aircraft main engine starters, air- unitisin use and the effect on direction and conditioning systems, and other type consumers concentration of exhaust resulting from nearby of compressed air. jet/prop plast and local wind require care in aircraft spotting and handling.. MD-3 TOW TRACTOR The catastroche aboard the ENTERPRISE on 14 January 1969 may have been avoided if The MD-3(fig. 14-9)isprimarily de- the aforementioned had been adhered to. Pre- signed for use aboard carriers. The overall liminary indications are that the exhaust from heights is 36 inches, which enables it to be a gas turbine compressor ignited a Zuni rocket operated on crowded hangar and flight decks warhead mounted on an F-4J, initiating the by driving under the winds of parked aircraft. subsequent explosions and fires. The MD-3 can tow aircraft on various sur- Attention must also be paid to the positioning faces in the various kinds of inclement weather of these tractors equipped with gas turbine that may be experienced through a temperature compressors so that the turbine wheel plane of range of minus 25°F to plus 125° F. It weighs roation presents a minimum hazard to per- 12,000 pounds and has a drawbar pull rating sonnel and equipment in the evcnt of turbine of 8,500 pounds. disintegration. A gas turbine compressor, mounted at the rear of the tractor, provides pneumatic power STARTING UNITS (NC-5) in the form of compressed air for the operation Starting equipment will vary with the type of large class pneumatic equipment, such as aircraft to be started. The Waukesha, NC-5, aircraft main engine starters, air-conditioning NC-6, NC-12, and the gas turbine compressor systems, and other type consumers of com- are various types of starting equipment depressed air. signed foraspecific starting system. The The main powerplant of the tractor is an NC-5 is one of the most widely used units and inlinehorizontal four-stroke cycle, internal is discussed in the following paragraphs. diesel combustion type engine. The steering The NC-5 unit is self-propelled and may be system is hydraulically assisted, with a turning driven from place to place in the same manner radius of 11 feet, and the service brakes are as any other motor vehicle. (See fig. 14-10.) assisted by compressed air. It has provisions for delivering three different CAUTION: Tractors equipped with gas tur- kinds of power, each through a separate cable. bine compressors must have a minimum dis- Itwill deliver d-c power for servicing pur- tance of 8 feet maintained between the exhaust poses. It will also deliver sufficient d-c power outlet and aircraft when the gas turbine com- for starting jet engines, but only for 1 minute at pressor isin use. For those equipped with a time. Bother servicing and starting power are 85 series turbines, with upward exhaust ports, taken from the same generator; however, this a minimum of 6 feet must be maintained. It generator will deliver only one type of power at is emphasized that these are minimum dis- a time.

270 2 3 Chapter 14GROUND HANDLING EQUIPMENTAND PROCEDURES

AD.146 Figure 14-10.NC-5 starting unit. In addition to d-c servicing and starting power, the NC-5 will deliver a-c powerfor servicing a-c equipment' in the aircraft and rectified d-c power for servicing during the starting cycle. The NC-5 being a self-propelled unit, should be treated with as much care as an automobile, Servicing materials and procedures are similar to those for two tractors. The NC-5 should be operated only by a qualified and authorized operator. CRANES There are various types of cranes in use in the Navy. They are designed to lift smallloads to loads of several thousand pounds, and under AD.147 various conditions, such as the angle or attitude Figure 14-11.Mobile cranes. from which the item must be approached. Due to the large variety of cranes, only the NS-50, crane is equally suitable forsimilar duty on MB-1A, and the M-65 cranes arestiscussed in the shore stations for both aircraft landing areaand following paragraphs. paved or unpaved operational areas. When selecting a crane for use, keep in mind This crane, a self-propelled vehicle,is the factors mentioned earlierweight to be lifted, mounted on four electrically powered wheels. height it must be raised, distance to be moved, Heavy-duty d-c electric traction motorsand the angle or attitude of the final positioning. gear reduction units built within thewheel rims The maximum performance of a crane de- provide motive power for the crane. Each wheel depends on the ability of the operator toproperly motorisequipped with multipledisc type operate the crane. Therefore the operator must spring-loaded brakes for emergency stops and be thoroughly familiar with the contents of the parking. Whenevertheelectricalpower is applicable technical manual before attempting to secured, the brakes are set by spring force. operate a crane. All normal operations required for maneuverability of the crane are managed fromthe NS-50 Crane operator's station. A remote control panel on the rear of the crane permits controlof thp The NS-50 mobile crane (fig.14-11) is hook and boom at a point near the load. designed primarily to lift and carry aircraft The crane is 40 feet long without the boom. on the flight deck of an aircraftcarrier. The With the boom extended 23 feet, theoverall

271

2 3j AVIATION MACHINIST'S MATE R 3 & 2

length is 64 feet 9 inches. The overall height The crane is 8 feet 8 inches high with the is 33 feet. The gross weight of the crane is boom retracted, It is 17 feet 8 inches long with 7300:pounds. boom retracted and 24 feet 4 inches long when The crane is capable of lifting 50,000 pounds boom is extended to its maximum. The maxi- when its boom is positioned anywhere between its mum elevation of the boom is 75 degrees. The minimum and 23-foot outreach. The crane is gross weight is approximately 21,000pounds. capable of exerting a drawbar pull of 42,000 The crane is equipped with hydraulic as- pounds for towing operations. sisted front and rear wheel steering. The turning radius for front wheel only is 30 feet, with MB-1A Crane front and rear wheel steering, 17 feet. The MB-1A mobile crane (fig. 14-11) is designed primarily for lifting, maneuvering, AIRCRAFT HOISTING and removing crashed aircraft from air station ruriways and surrounding areas. The MB-1A Before hoisting an aircraft the sling should is made up of a 2-wheel vehicle (prime mover) be inspected for cable fraying, security of all attached to a 2-wheel crane. attach fittings, and proper attachment to the The prime mover is powered by a diesel aircraft or components. The sling assembly engine driven through atwin-disc clutch, a is used to hoist the entire aircraft in various 5-speedtransmission,ahigh/lowspeed stages of disassembly as well as the complete auxiliary transmission, and a torque- aircraft. proportioning differential. The auxiliary trans- On the SP-2H aircraftthere are four mission in combination with the 5-speed trans- fittings attached prior to attaching the sling. mission results in 10 speeds forward and 2 Two fittings are attached to the top of the speeds in reverse. The wheels of the crane are fuselage, just aftof the cockpit, and one to not powered. each wing, top aft of the engine nacelle. After An a-c generator, driven from the engine installation of the fittings a three-cable sling flywheel, supplies current for powering the hook, isattached, as shown in figure 14-13. The jib,boom, and the steering motors. These cables are attached by means of shackles and motors are controlled by fingertip switches bolts. All movable points of the sling, such as located at the operator's station. A remote shackles and bolts, should be lubricated prior control boxisprovided for controlling the to use to prevent a sudden jerk during hoisting, hook,jib,and boom motors from a position due to a stuck shackle or bolt. near the point of pickup. NOTE: Prior to hoisting a complete air- The crane is 41 feet 7 inches high with craft, insure that the aircraft gross weight does the boom retracted. Itis 59 feet 9 inches long not exceed the designed landing gross weight. with the boom retracted and 84 feet long when Prior to hoisting the complete aircraft or any the boom is extended toits maximum. The of the major assemblies, attach stead lines gross weight is approximately 100,000 pounds. atconvenient pointsto prevent oscillation. The craneiscapableof lifting 80,000 At no time should personnel be under the air- pounds when its boom is positioned anywhere craft or major assemblies during hoisting oper- between 7 feet and 17 feet behind the centerline ations. of the wheels. PNEUMATIC LIFTING BAG M-65 Crane The M-65 crane (fig. 14-12) is designed The pneumatic bag (fig. 14-14) is a device for off the road operation in rough terrain. It which lifts crippled aircraft from terrain where is powered by a three-cylinder,two-cycle it is impractical or impossible to use standard diesel engine, with 4-wheel drive transmission. aircraft jacks. The pneumatic bag has a lifting Itis equipped with a 3-ton capacity boom capacity of 12 tons and inflates to a height of 90 crane and 75,000 foot-pound line power winch inches.Internal bulkheads maintain the "box for lifting, towing, and related operations. shape" of the pneumatic bag. The outer material

272 Chapter 14GROUND HANDLING EQUIPMENT AND PROCEDURES

AD.148 Figure 14-12.M-65 crane. is one-ply nylon fabric specially treated for pneumatic bag. When such hazards are un- extreme atmospheric temperatures. Theinlet avoidable,they should be carefully padded. valve is located on the front upper left-hand Caution should also be taken to prevent the corner (refer to fig. 14-14), whenin deflated aircraft from nosing over or shifting and yet state. An air hose assembly is attached to this allowing upward movement. valve, and air is pumped in until the required The bag is inflated by attaching an air hose height of the pneumatic bag is obtained. On to the inlet valve and slowly pumping inair until the lower left-hand corner of the rear side the desired height or maximum bag pressureis and on the upper right-hand corner of the obtained. The maximum bag pressure is3.5 front side of the bag are two outlet assemblies. psi. After the repair is accomplished, openthe These assemblies allow the penumatic bag to outlet assemblies and allow the bag todeflate. be deflated. Nav Air 19-1-59, Operation and Service Instruct- The pneumatic bag is stored in a protective ions, should be referred to for moredetailed tarpaulin assembly. After removing the pneu- operation instructions. matic bag from the tarpaulin protective assembly, the tarpaulin is placed under the area SAFETY desired to be lifted. The penumatic bag is then placed on the tarpaulin under the area to be Operationalreadinessofa maximum lifted. number of aircraft is necessary if navalaviation CAUTION: Insure that the ground and under- is to successfully perform its mission.Keeping side of the aircraft have no sharp projections its aircraft in top operating conditionis the or roughness which could puncture ortear the principal function of naval aviation maintenance

273

241 AVIATION MACHINIST'S MATE R 3 Z.: 2 ,Q3y

*140 grO

..--."...''":-..,...... ,':''

DETAILB WINS HOISTING FITTING ASSESIBLY

DETAILA FORWARD PUSELAIC HOIST ASSEWSLY AD.149 Figure 14-13.Aircraft hoisting. personnel.Itisessentialthat maintenance The concept of aircraft maintenance safety work be performed with a minimum of injury should extend beyond concern for injury to per- to personnel and damage to equipment and air- sonnel and damage to equipment and aircraft. craft. Safe work habits go hand-in-hand with flying safety. Tools left in aircraft, improper torquing .of fasteners, poor housekeeping around aircraft, and improper and careless operation of ground support equipment can cause conditions which may claim the lives of flying personnel as well as cause strike damage to aircraft. Safety on the ground is equally as important as safety in the air. Technical knowledge plays a large part in a good maintenance program. The complexity of our modern equipment demands the attention of well-informed and expert maintenance personnel; otherwise, our weapons systems cannot be operated and maintained. Technical knowledge is a function of education and training which, incidentally, does not end with graduation from Class A school. Graduation is only the beginning. An ADR worthy of the rating is continually training and learning through self-study and application, and through a personal desire for AD.150 proficiency and self-betterment. But technical Figure 14-14.Pneumaticlifting bag. knowledge by itself is not sufficient unless it is

274 24,< Chapter 14GROUND HANDLING EQUIPMENT ANDPROCEDURES c;2-35" coupled with an old-fashioned and craftmanship It is a continuing duty of every person con- in doing any job well. The ADR who wishes to nected with aircraftmaintenance to try to contribute to safety and reliability improve- discover and eliminate unsafe work practices. ment must know his job and must develop Accidents which are caused by such practices professionalprideinthequalityofhis may not take place until a much later date and work. their severity cannot be predicted.

275

24 ,1 sr,Q3 60

CHAPTER 15

LINE OPERATIONS AND MAINTENANCE

Line operations and maintenance is one of personnel, and an essential objective should be the most important responsibilities of the ADR. to perform maintenance work without injury to The term line operations and maintenance is personnel and without damage to equipment or defined as the process involved to insure that aircraft. Therefore, the one thing that must be operational aircraft (including guided missiles), strongly stressed at all times is SAFETY FIRST. aircraft equipment, and aircraft support equip- When working on the line around propeller- ment are ready and safe for the type of flight driven aircraft, the first general precaution oroperation for which they are scheduled. that you must observeis to BEWARE OF This work is performed on or in aircraft or PROPELLERS. When you see a propeller, let equipment located on a flight line, flight deck, itbe a constant reminder to "Stay Clear!" or other places normally used by the activity In general, do not cross in front of moving to park aircraft. It is usually-performed prior propellers,as whirling propellers are not to or between scheduled flights, without re- easily seen. The area around an aircraft must moval of the aircraft from the flight schedule. be kept clear of loose gear and debris. Line operations and maintenance includes Another constant danger on the lineis servicing; daily, preflight, and postflight inspec- fire. Because of the large quantities of easily tions; ground tests; troubleshooting; correction ignited fuel, carelessness with gasoline, static of minor discrepancks; compliance with appli- electricity, or the improper handling of tools cable instructions for adjustments and replace- may cause a spark and start a serious fire. ment of parts (which do not require removal of The most common fire prevention rules units, assemblies, and subassemblies); and the are as follows: security and proper ground handling of aircraft 1.Covered metal containers must be pro- and associated support equipment. vided and used for storing supplies of clean As previously stated, line operations and rags, waste, and other combustible materials maintenanceisoneofthe most important for immediate use. responsibilities of the ADR. It is essential that 2.All used waste, rags, and other com- he know the engine as thoroughly as possible. bustible material must be deposited in plainly He must have a working knowledge of the marked covered metal containers. complete aircraft to which he is assigned and 3. Containers, plainly identified and kept he must be familiar with and observe all safety separate from those in item 2 above, must be precautions. used for oil and paint-soaked materials. 4. Dispositionof these containers must SAFETY be made with such frequency and in such a way that they will not become a fire hazard. Operational readiness of a maximum num- 5. No smoking and no open flames are ber of aircraft is necessary if naval aviation permitted within 50 feet of parked aircraft, is to successfully perform its mission. Keeping hangars, shops, or other buildings in which its aircraft in top operating condition is the highly flammable materials are stored or being principal function of naval aviation maintenance used.

276

2 4q Chapter 15LINE OPERATIONS AND MAINTENANCE

6. Grounds, particularly around buildings 2. Always consider an ejection seat as and aircraft, must be kept free of fire hazards, loaded and armed. such as trash and dried vegetation. 3.Before entering a cockpit, be checked 7.Suitable fire lanes for passage of fire- out on the location of the ejection seat safety fighting equipment should be designated, marked, pins and be certain they are installed. If you .1 kept clear. are not checked out, stay out of the cockpit. 4.Only authorized personnel may work on POWER-OPERATED EQUIPMENT ejection seats and components and only in an authorized area. As naval aviation progressed and aircraft The canopies of several modern day recip- became larger and seemingly more complex, rocating engine aircraft are power operated as provisions were made to assist in the operation are all jet engine aircraft. These canopies are of such equipment as control surfaces, speed so designed that they can be opened in an brakes, canopies, and landing gear doors. Also, emergency. seatejection mechanisms were installed in Aircraft manufacturers use various meth- most aircraft. Although these were designed ods of actuating the canopy. Normal opening with safety in mind, they broaden the danger and closing may be accomplished pneumatically area for ground personnel. Some of the safety (with compressed air), electrically,hydrau- precautions that must be observedwhen working lically,ormanually.In most aircraft, two on or around aircraft are discussed in the methods are provided; thus, if one system fails, following paragraphs. the other may be used. The closing operation of the canopy can be dangerous if care is not Ejection Seats and Canopies taken.Power operated canopies can cut off fingers and break bones. Normally, the Aviation Machinist's Mate R will not come in contact with ejection seats, Movable Surfaces as they are found in jet engine aircraft; however, a word of caution is mentioned here. If Movable surfaces such as flight control the reciprocating engine mechanic has an occa- surfaces, speed brakes, and landing gear doors sion to ride the brakes or aid in the performance constitute a major hazard to flight line per- of work on an aircraft with this type of equipment sonnel. These unitsare normally operated installed,heshould keephishands off of duringground operations and maintenance. red-flagged lanyards and other units painted red Therefore, care should be taken to insure that inthecockpit. All safety precautions must all personnel and equipment are clear of the be strictly observed when working around air- area before operating any movable surface. craftequipped with an ejection seat. These The General Information and Servicing safety precautions cannot be overemphasized, as section of each Maintenance Instructions Manual accidental actuation of the firing mechanism contains specific information concerning the can result in death or serious injury to anyone various movable surface hazards and specifies in the cockpit area. the safety locks which must be used. Personnel Each ejection seat has several ground lock involved with line operations and maintenance safety pins, the exact number depending upon should pay particular attention to this informa- the type of seat. These safety pins are provided tion since some of these units move extremely on red-flagged lanyards for use at every point fast and with terrific power. ofpotential danger. They must be installed whenever the aircraft is on the ground or deck, TAXIING, TOWING, AND JACKING and must never be removed until the aircraft is ready for flight. No one is permitted to taxi an aircraft The following general safety precautions except such persons as are authorized to fly should always be kept in mind: it and those who have been specifically desig- 1.Ejection seats must be treated with nated and authorized by the commanding of- the same respect as a loaded gun. ficer.

277

240 c>35/ AVIATION MACHDNIST'S MATE R 3 & 2

All taxiing must be done at safe, authorized should be installed at the jacking points. The speeds and in a manner appropriate to the type jacking points are usually located inrelation of aircraft being taxied, care being takenthat to the aircraft's center of gravity so thatthe the path ahead is clear of other aircraft, equip- aircraft will be balanced on the jacks. For ment, and obstructions. some aircraft, however, it maybe necessary Sufficient ground control personnel must to add weight to the tail or to the nose to achieve be available to provide for the safetaxiing a safe balance. Sandbags or shotbags areusually or aircraft in the vicinity ofobstructions of used for this purpose. other aircraft. Tha jacks used for jacking the aircraft, Only approved standard aircraft taxi sig- whether for jacking the complete aircraft or nals are to be used. The approved fixedwing just a wheel, must be in good working condition. and helicopter taxi signals are illustratedin A leaking or damaged jack should never be the Airman Manual, NavPers 10307-C, chap- used and its maximum capacity must never ter 12. be exceeded. The area around the aircraft Aircraft are usually moved about on the should be roped off while the aircraft is on line by towing. After the proper authorization jacks. Climbing on the aircraft should beheld to move an aircraft has been obtained, an to a minimum, and noviolent movements authorized and qualified operator must be in should be made by persons who are required to theaircraft,ready to operate the aircraft go aboard. Any cradles or necessarysupports brakes when necessary. designed for that purpose shouldbep1,4ced under Towing couplings should be thoroughly in- the fuselage or wings of the aircraft atthe spected prior to towing. Only approved attach- earliest possible time, particularly if the air-. ment devices are to be used. Attachments are craftis to remain jacked for any length of made secure to couplings on the aircraft pro-. time. vided for this purpose. When only a wheel is to be raised, for Only qualified personnel are permitted to instance, when changing a tire or greasing move or operate towing equipmentand attach- the wheel bearings, all remaining wheels must ments.Itmust be made certain that allis be chocked both fore and aft.If the aircraft clear and in readiness prior tooperation of is equipped with a tailwheel, it must be locked. raised equipment. The wheel to be worked on should be Towing speed should never exceed 5 miles only high enough to clear the deck and no perhour.Sudden startsor stops must be more. avoided. Extreme caution must be exercised when towing an aircraft over rough or muddy COMPRESSED AND LIQUID GASES ground, or into or through a congested area. When towing an aircraft near hangars Fluids under pressure are a potential or obstructions, a wing walkershould be sta- hazard on the flight line unless strict safety tioned at each wingtip to insure adequateclear- precautions are observed. Some of the pres- ances. At night the wing walkermust carry surized fluids with which the ADR should be a flashlight or luminescent wand. familiar are in the form of a gas; others are The ADR must be familiar with the jacking in liquid form. Some of these gases and liquids of aircraft and the safety precautions tobe are discussed in the followingparagraphs. observed. As jacking procedures vary fordif- ferent types of aircraft, only the general jacking Carbon Dioxide procedures and safety precautions aredis- cussed here. Consult the applicable maintenance Carbon dioxide (CO2) is a colorless, odor- instructions manual for the specific procedures less gas. It can be condensed into a colorless to be used for specific aircraft. liquid and stored as such, under pressure, in When an aircraft is to be jacked, it must cylinders. When the cylinder valve is opened, be located in a level position, well protected gaseous CO2 escapes and, due to therapid from the wind. The aircraft should be moved drop in pressure and temperature, forms carbon intothehangarif possible. The jack pads dioxide snow.This snow, when compressed

278 Chapter 15LINE OPERATIONS AND MAINTENANCE c:=,3 into blocks or cubes is what we know as .`dry contact with oxygen cylinders, valves, regula- ice." tors, gages, and fittings. Contamination with Because it will neither support combustion hydrogen,oils,or grease may result in a nor form explosive mixtures, CO2 is one of serious fire or explosion. the chief fire-extinguishing agents in use today. 2. Never lubricate oxygen valves, regula- Itis also used for inflatable gear, such as tors, gages, or fittings with oil or other flam- liferaftsand lifevests.However, there are mable substances. some safety precautions which you must observe. 3. Do not handle oxygen cylinders or ap- Do not enter an area or compartment containing paratus with oily hands or gloves. hazardous amounts of carbon dioxide without 4. Never use oxygen from a cylinder with- being equipped with a breathing mask and an out reducing the pressure through a suitable independent supply of oxygen. Although carbon regulator. dioxide is not toxic, the obvious fact is that, 5. Use only approved oxygen regulators, poisonous or not, the more gas that is present, hose, and other appliances. the less breathable oxygen there will bepresent. 6. Never attempt to use oxygen cylinders Men going into these places run the risk of for other than oxygen service. smothering to death. 7. Never use oxygen as a substitute for compressed air. Itis dangerous to use oxygen for pneumatic tools, for starting diesel engines, Gaseous Oxygen forguilding up pressure inoil reservoirs, for paint spraying, for blowing out pipelines, Gaseous oxygen is a colorless, odorless gas and similar purposes for which compressed air which does not burn, but it supports the combus- is normally used. tion of other things. Even steel will burn in 8. Never use compressed oxygen or any pure oxy gen. other compressed gas for cooling the body or Gaseous oxygen is normally contained in for blowing dust from the clothing. cylinders and identified as one of two types: (1) aviators' breathing oxygen or (2) industrial or technical oxygen. There is no difference Liquid Oxygen in the purity of the oxygen itself in these two types. The only difference is in the moisture Many naval aircraft are currently equipped content of the cylinders. Cylinders containing with liquid oxygen systems. aviators'breathing oxygen have been dried Aircraft liquid oxygen systems are similar inside, before being charged, to prevent failure togaseous systems except that the several of breathing apparatus due to the formation of cylinders of gaseous oxygen are replaced by ice under high altitude freezing conditions. a single liquid oxygen container known as a To simplify the supply system, aviators' converter. breathing oxygen is the only kind stocked by The liquid oxygen converter is located in ships and is used on shipboard for welding and the oxygen system compartment. In some in- cutting operationsas well as for breathing stances the oxygen compartment may be located purposes. on the left-hand side of the aircraft and in Industrial or technical oxygen, supplied for othersitis on the right-hand side. In either nonshipboard use in welding and cutting opera- case,locationis such that the filler valve tions, can be and is used for breathing pur- can be reached by a man standing on the ground poses, other than aviation, because its purity or wing. The latest systems are designed so isidentical with that of aviators' breathing that the converter may be removed from the oxygen, and freezing conditions at low altitudes aircraft for filling at a remotely located filling either do not exist or can be eliminated. The station. safety rules that must be observed for oxygen There are a number of additional safety are as follows: precautions to be observed when handling liquid 1. Never permitoil,grease,or other oxygen. Someofthese parallelthesafety readilycombustible substancesto come in precautions outlined for the handling of gaseous

279

2 4 AVIATION MACHLNIST'S MATE R 3 & 2 c1 clothing, the repeating that liquid oxygen is spilled on oxygen; however, they are worth immediately. to help prevent accidents. Anypossible danger clothing should be removed that may occur is based on thegeneral charac- Compressed Air teristics of liquid oxygen. First, therate of regard to com- combustion of most materials can begreatly The safety precautions with pressed air are much the same asfor the other increased by liquid oxygen; second,contact compressed air is with liquid oxygen (-297° F) can causesevere compressed gases. Of course, neither poisonous nor flammable,but at the frost-bite and damage to equipmentvulnerable in liquid oxygen, same time you shouldnot become careless to freezing conditions; and third, it. Compressed air tanks,lines, and if confined, will eventually evaporateand build handling fittings have exploded, injuring menand prop- up a tremendous pressurewhich could result careless men have in the rupture of the tank in whichit is stored. erty. Literally thousands of Because of these possibilities, there are a blown dust or harmful specksinto their eyes must be by the negligent handlingof compressed air number of safety precautions which outlets. Because compressed air seemsso safe observed. is in comparison with theother gases, do not let The ADR,if he is a plane captain, someone responsible for the observance of allsafety overconfidence lead to your own or even though heis not actually else's injury. precautions Although landing gear shockstrut servicing performing the work of servicing the aircraft. personnel of the AMH The following safety precautionsshould be is the responsibility of system rating, the ADR plane captainmust be familiar observed while recharging an oxygen during the deflation on the flight line, or theflight deck, if aboard with the hazards involved personnel and inflation procedure. ship.Only qualified personnel or with hydraulic being trained and under the directsupervision Shock struts are first filled allowed to fluid while in the compressedcondition, then of a qualified person, should be by inflating with operate liquid or gaseous oxygentrailers or extended the proper amount insure highpressure air or nitrogen.Some struts storage tanks. The plane captain should require nitrogen, others usedry air. An inthat the following conditions existwhile the the strut, lists the system is being serviced: struction plate, attached to type of gas to be'used. 1. The aircraft is in an open area. always make 2. The aircraft is not being fueled. Before deflating a shock strut, certain that all personnel,workstands, jacks, 3. The aircraft is electricallygrounded. of the aircraft. 4. The APU or startingunits are not and other obstacles are clear vicinity of On some aircraft, thewingtip drops several connected to, or operating in the struts is deflated. the aircraft. feet when one of the shock immediately Alwaysdeflatethestrut by gradually 5. A CO2 fire extinguisher is loosening the hex head swivel nutin the high- available. pressure air valve.When loosening the swivel 6.All personnel are kept clearof the nut,make sure the larger hexbody nut is overboard vent. held tight with a 7. The deck under and in theimmediate either lockwired in place or wrench. If the hex body nut isloosened before vicinity of the overboard vent isfree from serious injury grease, oil, or any combustiblematerial. the pressure has been released, In addition to the abovementioned items, may result. trailer near gas Make certain the shock strutcompresses as never park a liquid oxygen the pressure is released. In somecases it may trucks, oil bowsers, or foreignmaterial re- aircraft to insure always be necessary to rock the ceptacles. Wluie servicing the aircraft, strut. wear the proper protectiveclothing. Do not complete compressing of the part of To inflate a strut, always use aregulated permit liquid oxygen to flow onto any high-pressure source of dryair or nitrogen. the body or clothing, or intopockets, cuffs, bottled gas, other than gloves, shoes, and the like, where itmight be Never use any type of trapped and cause severe freezing. In theevent air or nitrogen.

280 Chapter 15LINE OPERATIONS AND MAINTENANCE

The proper amount of extension is always There are two methods of refueling aircraft-. given on the instruction plate attachedto the gravity and pressure fueling. These, along with strut. the related safety precautions, are discussed in the following paragraphs. AIRCRAFT SERVICING Refueling Safety Precautions Servicing of aircraft includes replenishing ofthefuel,oil,hydraulic fluid, and other Aviation gasoline is a'highly volatile liquid consumable materials. The general procedures which gives off a vapor. This aircraft fuel for these servicing operations, along with the vapor is heavier than air and will settleto the related safety precautions, are discussed in ground, accumulating in dangerous amounts in the following paragraphs. depressions, troughs, or pits; and when combined NOTE: All aircraft servicing should be with air in the proper proportions, forms an performed in accordance with the applicable explosive mixture. set of Maintenance Requirements Cards. The ignition of vapor from aircraft fuel may occur from static sparks, sparks fromtools, FUEL REPLENISHMENT hot exhaust pipes, lighted cigarettes, electrical devices, and similar sources. A violent explo- Aircraftreciprocating enginefuels are sion followed by fire will result if liquid gaso- presently classified into types and grades in line is present. the following manner: Allexistingfireprecautions must be adhered to during the fueling process. Smoking U.S. U.S. is not permitted in the aircraft during fueling. NATO Also, no smoking or naked lights (such as are Military Commercial Color Symbol Grades Grades produced by oil lanterns, candles, matches, exposed electric, switches, sliprings or commu- 80/87 80/87 Red F-12 tators, a dynamo or motor, any spark-producing 91/98 Blue F-15 electrical equipment, or any burning material) 91/96 aircraft 100/130 100/130 Green F-18 are permitted within 100 feet of an 115/145 115/145 Purple F-22 being refueled, or of fuel storage tanks. No lights other than approved explosion-prooflights Current plans provide for the use of a are permitted within 50 feet of theseoperations, single grade of Av Gas (aviation gasoline) on a and no light of any sort may be placed where it worldwide basis in the event of hostilities. At may come in contact with spilled fuel.Warning present, 115/145 Av Gas is the primary fuel for signs should be posted as a precautionary reciprocating engine aircraft both overseas and measure. within the continental United States. All accidental spillage of aircraft fuels or Many aircraft operate satisfactorily on all other combustible liquids must be immediately approved fuel grades. Whenever a lower grade removed by washing, covered with a foam blan- of Av Gas is used, the applicable flight manual ket to prevent ignition, or neutralized by other must be referred to so that power settings may means. The proper fire authorities mustbe be revised, commensurate with the grade of notified any time a large amount of aviation fuel in use. When going to a higher grade fuel, fuel is spilled. the published power settings or curves must Aircraft fuel tanks must be filled, purged, be adhered to for all flight conditions. NOTE: or have an inert gas (such as CO2) overthe gas When changing from one type of authorized fuel in the tanks before storing aircraft in hangars, to another,itis not necessary to drain the since this leaves no space for explosive vapors aircraft fuel system before adding the new to form. fuel. The engine operating limits for operating Nonspark tools must be used when working on mixed grades of Av Gas mustbe the limits on any part of a system or unitdesigned for forthe lowest gradeof fuel in the tanks. storing or handling combustible liquids.

281

2 4 AVIATION MACHINIST'S MATE R 3 & 2

The use of leaky tanks or fuel lines is not soon as the fueling operation has been com- permitted. Repairs must be made on discovery, pleted, the truck should be removed from the with due regard to the hazard involved. The aircraft's vicinity. The truck manhole covers fuel must be strained if there is the slightest should be kept closed, except when a tank is chance that water may be present. Most fueling actually being loaded, or when pumping fuel trucks and underground storage systems have at 25° F or below, because at such temperatures filter/separators which automatically filter vent valves may be inoperative. water out of the gasoline before delivering it NOTE: The operation of fuel trucks at many to the aircraft tank. These filter/separators air stationsis performed by civilian crews. should be checked daily for dirt and water. Even though the ADR may not be called on to This system serves the same purpose as the operateordrive fuel trucks, he must be sediment bulb or tank in an automobile gasoline thoroughly familiar with the entire procedure to system. insure safety of the fueling operation, in which Aircraft should be fueled in a safe place. he will be involved frequently. Do not fuel or defuel an aircraft in a hangar Refueling crews usually include a minimum orother enclosed space except in case of of three men. One person stands by with the emergency. Aircraft should be free from fire firefighting equipment; another stays with the hazards, have engine switches off, and chocks truck; and the third man handles the fuel hose placed under the wheels prior to fueling or at the aircraft and fills the tanks. A member defueling. of the crew makes sure that both the aircraft CAUTION: Guard against breathing hydro- and the truck are properly grounded to prevent carbon (fuel) vapors as they may cause sickness sparks from static electricity. A check should or may even befatal.Do notletfumes be made to see that all radio equipment and accumulateuse adequate ventilating measures. unnecessaryelectrical switches are turned Also, avoid getting fuel .on clothes, skin, or in off.Outside electrical power should not be theeyes, because of the high lead content. connected to the aircraft unless it is necessary Fuel-saturated clothing should be removed as to operate the equipment involved with refueling. soon as possible, and the parts of the body Care should be taken to identify the aviationfuel exposed to fuel washed thoroughly with soap before beginning the refueling operation. Re- and water.Wearing clothing saturated with fueling trucks have the type fuel contained in fuel creates a dangerous fire hazard, andpainful the tanks painted across the side of the tank blisters may be caused by direct contact with in black letters. An ADR who is involved with fuel in the same maimer as fire burns. When servicing aircraft should become familiar with fuel has entered the eyes, medical attention the various grades of fuel and the aircraft's should be obtained immediately. fuel requirements in order to insure that the When an aircraft is to be fueled by a appropriate fuel is always used. truck,it should not be located in the vicinity of possible sources of ignition such as grinding, Gravity Fueling drilling, or welding operations. When practicable, a minimum of 50 feet from other air- Gravity fueling is accomplished by ground- craftor structures and 75feet from any ing the nozzle (fig. 15-1), inserting the nozzle in operating radar set should be maintained. Con- the cell filler neck, and filling the tank to the sideration must be given to the direction of the bottom of the filler neck port. wind so that fuel vapors will not be carried The nozzle should always be grounded prior toward a source of ignition. to being placed in the filler neck in order to The tank truck should be driven to a point preventsparks caused by static electricity. as distant from the aircraft as the length of The nozzle should be supported while in the the hose permits, and preferably to the wind- filler neck to prevent damage to the filler neck ward (upward) side of the aircraft. It must be and in the case of aircraft which use bladder parked parallel to or heading away from the type fuel cells (cells made from a type of rub- wing,orin such a position thatit may be berized nylon cloth) to prevent the possibility driven away quickly in the event of fire. As of damaging the cell with the end of the nozzle.

282

20 Chapter 15LINE OPERATIONSAND MAINTENANCE The pressure nozzle shownin figure 15-2 GROUNDING JACK is permanently attachedto the refueler hose. GRAVITY The pressure nozzle isequipped with a ground FUELING wire which is used todrain off any static NOZZLE electricity which may havebuilt up in the nozzle. However, once the nozzleis attached its own ground. GROUNDING to the aircraft, it acts as RECEPTACLE As the connection ismade, the pressure nozzle opens a spring-loadedvalve within the inlet to the fuel tanks. Oncethe connection is made, there is nofurther need for grounding the other cells or tanks.Aircraft which employ the pressure fuelingsystem are equipped with automatic equipment forshutting off the fuel flow when the tanks are full. The following is a generalprocedure for pressure fueling an aircraft.Since the controls FILLER CAP differ from one aircraft toanother the applicable Maintenance InstructionsManual should AD.151 to pressure fueling Figure 15-1.Gravity fueling. always be checked prior an aircraft. fueling receptacle When a tank is nearly full, therate of 1. Remove the pressure safety cap by turningcounterclockwise. Pull gasoline flow should be reducedfor topping off nozzle dust cover up and the tank. The tank should beslowly filled to the pressure fueling to one side of the outershell. the top without spillage. 2. Ground the nozzleby inserting the grounding plug into itsreceptacle on the air- Pressure Fueling craft. handles into aircraft are 3.Lift the nozzle by its Most of the newer naval position and engage thelower slot over the refueled by the pressure fuelingsystem. This receptacle. Tip the faster "operational turn lower lug on the fueling is employed to enable nozzle so that the upper slots engagethe upper around" of the aircraft. firmly so that all Pressure fueling is usuallyaccomplished lugs. Press the nozzle in from this point is three nozzle lock keys aredepressed. Lock from a single point. Fuel the lifting handles clock- supplied to the various wing andfuselage tanks. the nozzle by rotating wise. In some cases, the droptanks and flight re- switches in the fueling package may also berefueled from 4. Set the refueling panel proper position andapply electrical power to this point. the aircraft the aircraft. The pressure fueling station on 5. Position the vent monitors asnecessary is equipped with apressurefuelingand defueling applicable Maintenance electricalcontrol panel. in accordance with the receptacle and an Instructions Manual. NOTE:The vent monitors (see fig. 15-2) The pressurefueling receptacle various fuel system ventsto is standard on all aircraftwhich use the pressure are assigned to the panel and con- insure that the aircraft's fuelcells are venting fueling method. The electrical properly. Should the cells notvent properly, trolsdiffer from one aircrafttoanother, rupturing the cell and of thefuel there is a possibility of depending upon the complexity structural damage. system. The more complex systems mayrequire even causing major General Infor- 5. With the nozzle lockedin place, the several switches and lights. The turn whenever fueling mation and Servicing section ofthe applicable opening handle is free to istobe started. To startfueling turn the Maintenance Instructions Manualcontains il- position. Rotating the concerning the pres- handle to the FULL OPEN lustrations and instructions opening handle more than180 degrees opens the sure fueling system.

283

251 AVIATION MACHINIST'S MATE R 3 & 2

PRESSURE FUELING AND DEFUELING ADAPTER VALVE

FUILINS Oil CRICK SWITC11 niorVoN - TANK off MUNE PIRIYARY SECONDARY OFF OFF

SWITCH PANEL PRESSURE FUELING AND DEFUELING NOZZLE GROUND WIRE MANUAL FLOW AND NO-FLOW VALVE

AD.152 Figure 15-2.Pressure fueling. poppet valve in the nozzle and locks it in the Defueling OPEN position. Position the appropriate switch on the fuel panel to the FUEL position. The fuel Defueling is necessary for various reasons should shut off automatically when the cells are such as fuel cell repairs, removal of external tuU fuel tanks, and changing the fuel load. CAUTION; During pressure fueling the fuel Aircraft which utilize pressure fueling are system should be inspected carefully for leakage. normally defueled from the pressure fueling If any leaks are apparent, fueling should be adapter. This allows the entire system to be stopped and corrective action should be taken. defueled from a single point. Older aircraft 7; When fueling is complete, the pressure have one or more defueling valves which are fueling nozzle is removed by rotating the lifting constructed so that the defueler hose may be handles counterclockwise until the nozzle is clamped on. When defueling external aiel tanks, unlocked from the fueling receptacle. The dust it may be necessary to insert the detheler hose cover should be pulled up cver the nozzle face in the filler port. immediately and the safety cap replaced on the When defueling aircraft, always follow the aircraft receptacle. instructions and safety precautions contained in Every safety precaution must be taken to the applicable Maintenance Instructions Manual. insure that no dirt or foreign matter enters the nozzle and that the nozzle nose is completely clean before it is connected to the aircraft. The OIL REPLENISHMENT dust cover must be kept on the nozzle at all times except when actually fueling an aircraft. After the aircraft's fuel tanks are filled, The pressure fueling nozzle can be damaged the oil tanks are checked. These tanks should by careless handling. Guard against dropping NOT be filled to capacity. Never fill an oil tank the nozzle or allowing it to swing heavily against above its FULL mark. When oil becomes hot, it structures or equipment during handling. Never expands; at high altitudes it bubbles and expands. drag the nozzle on the deck. The extra space in theoil tank allows for Never force the operating action of the expansion and prevents overflowing. Check the nozzle.If the unit does not couple freely or engine's oil requirements and no substitutions open or close readily, locate and correct the should be made for the type of oil used. When misalignment or mechanical jam. filling the tanks, be sure that rags or other

284 25 Chapter 15LINE OPERATIONSAND MAINTENANCE absorbing dust and grit tanks. Foreign material possibility of the fluid debris do not get into the from the air. Currentinstructions require that in the oil may causeengine failure. very all empty hydraulic fluidcontainers be destroyed Lubricating oil itself is nonexplosive, not used to store orhandle difficult to ignite in bulk, andnot normally immediately combustion. The vapor of any other fluid. capable of spontaneous Newer type aircrafthydraulic reservoirs the oil, however, isexplosive when mixed with that Vapors of many are filled from afill stand similar to airin certain proportions. shown in figure 15-3. Thefill stand is connected petroleum products are highlytoxic when inhaled hydraulic system at aquick or ingested. It istherefore necessary that all to the aircraft handling lubri- disconnect whichisprovided for reservoir precautions be observed when filling. Some aircraftsystenfs provide for cating oil. filling several reservoirsfrom a single point for filling each HYDRAULIC FLUID REPLENISHMENT while others have provisions reservoir individually. visible means Aircraft hydraulic fluids areidentified by Most of these aircraft have a (usually sight gages) for checkingfluid level; their military specificationnumber. Hydraulic with lights which fluid, MIL-0-5606, is nowbeing used in the however, some are equipped aircraft. This indicate fluid level. hydraulic systems of all naval Information concerning servicingof the fluid is also used in the shockstruts, shimmy particular type air- dampers, and brake systemsof all aircraft. hydraulic reservoirs of a MIL-0-5606 hydraulic fluid iscolored red, has a petroleum base,and comes in red,1-gallon AIR PRESSURE containers. REGULATOR HYDRAUUC PRESSURE GAGE AIR PRESSURE Servicing Hydraulic Systems GAGE

SELECTOR Older type aircraft hydraulicsystems are VALVES serviced by checking thefluid level (on a sight gage which is usuallylocated on the side of the HYDRAUUC PRESSURE HYDRAULIC PRESSURE AND RETURN UNES reservoir) and filling to theprescribed level. ADJUSTABLE RELIEF Before addingfluidto this type reservoir, VALVE always check the reservoirinstruction plate for the proper filling instructions.The instruction plate will be either attachedto the reservoir the filler opening AIR PRESSURE or the aircraft structure near SHUTOFF VALVE of the reservoir. Theinstruction plate contains the following information: Total capacity of the system. HAND PUMP Reservoir capacity. Refill level. Specification and color of fluid. AIR PRESSURE Correct position of allactuating cylinders during filling. Any other instructionsconsidered necessary during filling ofthe reservoir. Fluid is usually added to thistype reservoir by pouring directly from the caninto the filler neck of the reservoir. NOTE: After opening a canof hydraulic fluid the entire contentsshould be poured into reservoir or into a portablefill AM.204 an aircraft Figure 15-3.Hydraulic systemfill stand. stand immediately.Thiswilleliminate the

285

25i AVIATION MACHINIST'S MATE R 3tz 2 c,2

craft is contained in the applicable Maintenance ground operation of the aircraft. The postflight Instructions ManuaL inspection is mainly a check for obvious defects (hydraulic, fuel, and oil leakage or structural ALRCRAFT INSPECTIONS damage) and the installation of the necessary safety locks and pins. Operating aircraft are subject to a variety 5.Calendar Inspections. These are limited of stresses, strains, vibrations, and detrimental overall examinations of the aircraft. Calendar environments.If not inspected regularly, the inspections are conducted at the expiration of a aircraft would soon become inoperable. Main- specified number of calendar weeks. They tenance, such as correcting of discrepancies and consist of requirements that must be inspected timely lubricating, .is performed in conjunction at every calendar inspection plus requirements with inspections and enables the aircraft to be that are inspected at less frequent intervals. flown safely until the next inspection is due. Most of the items that are to be inspected at Types of inspections which are performed less frequent intervals are divided evenly so by activities responsible for the maintenance of that approximately half of the items are checked naval aircraft are as follows: on the first (or ODD) calendar inspection and 1. Acceptance Inspections. A minimum ac- the remainder are checked on the second (or ceptance inspection consists of an inventory of EVEN) calendar inspections. Subsequent cal- installed material and loose gear, configuration endar inspections repeat the same ODD-EVEN verification, functional test of appropriate emer- cycle. gency systems, and a thorough daily inspection. 6.ConditionalInspection. A conditional Accepting activities may elect to increase the inspection is an inspection that depends upon depth of inspection if the aircraft conditions occurrence of certain circumstances or con- warrant. ditions, or a maintenance action with a pre- 2. Daily Inspection. Daily inspections are scribedintervalotherthanthepreflight, accomplished between the last flight of the day postflight, daily, or calendar inspection cycle. and the next scheduled flight, if no more than Periodic maintenance requirements for 72 hours elapse between the inspection and the every model aircraft are promulgated by the next scheduled flight.If more than 72 hours Naval Air Systems Command. With every ac- elapse between the inspection and next flight, tivity using the inspection criteria prescribed the inspection must be repeated. This inspection for their assigned aircraft models, it follows is basically a combination of requirements for that any given aircraft model is subject to a checking equipment that requires a daily veri- standardized program of periodic maintenance fication of satisfactory functioning, plus require- wherever it is being operated. ments that prescribe searching for and correc- Standardizationof periodic maintenance tion of relatively minor problems to prevent procedures is accomplished by use of a Periodic their progress to a state that would require Maintenance Requirements Manual (PMRM), major work to remedy. Other items which various sets of Periodic Maintenance Require- require inspection at intervals more frequent ments Cards (MRC's), sequence charts, and than prescribed for calendar inspections are related forms and reports. These publications also included on the daily inspection and are and forms and their use are described in the accomplished vlong with the daily inspection following paragraphs. on the day they become due. 3. Preflight Inspection. The preflight in- PERIODIC MAINTENANCE spection consists of checking the aircraft for REQUIREMENTS MANUAL (PMRM) flight readiness by performing visual examinations and operational tests to discover defects The Periodic Maintenance Requirements and maladjustments that, if not corrected, would Manual contains all the planned periodic main- cause accidents or aborted missions. tenance requirements for the applicable aircraft 4. Postflight Inspection. The postflight in- model for its entire anticipated service life. spection consists of maintenance requirements The maintenance requirements contained in the which are accomplished after each flight or manual are set forth in a manner to specify the

286 254 Chapter 15LINE OPERATIONS ANDMAINTENANCE V7

the equipments to be inspected or examinedand the The work plan, or order of performing condition to be sought in each case. Sincedefects requirements,specified on the Maintenance result Requirements Cardsis prearranged in two that are discovered during inspections and daily in unplanned maintenance, and thismaintenance manners. The preflight, postflight, cannot be accurately predicted orplanned for, work is performed item by item insequential this type of maintenance requirement isnot orderarranged on consecutively numbered cards. The calendar inspection workis con- included in the manual. Maintenance personnel items must referto the pi-operpublications and trolled by the order of arrangement of the onthe MRC's and,in addition, employs a directives for assembly, disassembly, check, of the MRC's. test, and repair procedures. sequence chart for scheduling Where conflict may exist between thein- The calendar MRC's are not necessarilysched- formation contained in the PMRM andother uled in numerical card number sequence. maintenance directives, the manualwith one NOTE: No part of any scheduled maintenance exceptiontakes precedence. This exception is iscertified (signed off) on the Maintenance the information given on any MaintenanceRe- Requirements Cards.Therefore, the MRC's quirements Card with a later date than the may be used as manytimes as their condition latest change date given in the PMRM.Although permits. the information given in both of these directives SEQUENCE CONTR OL CHAR TS the cards can be, and should be identical, (SCC's) usually are, changed before the manual. Calendar Sequence Control Charts are used as a guide forthe preparation of the schedule and MAINTENANCE REQUIREMENTS actual calendar maintenance work a means of controllingthe assignment of work CARDS (MRC's) and personnel. These chartsindicate what MRC's are to be compiled with, thenumber and The Maintenance Requirements Cards are the times the working documents for squadron inspections specialty of the personnel required, and preventive maintenance actions. These are during which the separate jobs arescheduledfor 5 x 8 cards arranged by rating and work area accomplishment, and the electric andhydraulic to provide the most efficient sequenceof ac- power conditions("power on" or "power off") complishment. Assembled into sets and num- required during the work. The SCC's are planned so as toeffectively bered in sequence, the cards containpertinent work in a information required by each maintenance man integrate all periodic maintenance task in- manner whichwill reduce the total out-of- to complete each task. Data for each periodic thetime required to service time required for the complete cludes a description; maintenance job. The SCC's mayconsist of perform the task; the power tools,equipment, to the and material requirements; anddetailed infor- one,two,or three sheets according requirements of the aircraft model.Generally, mation on such items as adjustments, pres- removal sures, and torque values. Alsoincluded, when small aircraft not requiring engine in which during calendar inspection will haveonly one necessary, is a diagram of the area engine re- the work is to be accomplished. chart containing both airframe and quirements to be accomplished on eachcalendar Individual sets of MRC's are prepared for for preflight, postflight, daily, and calendar inspec- inspection.If engine removal is required tions. For aircraft models having odd and even accomplishment of the calendar inspection, an calendar intervals, the calendar MRC setis engine SCC is provided for useby the work further divided into three groupscalendar,odd center performing the engineinspection. calendar, and even calendar.The calendar Three charts are provided foraircraft contains requirements that must be models having inspection requirementsdivided group intervals and checked at every calendar inspection, whilethe between odd and even calendar other two groups are used alternately withthe requiring engine removal for inspection. Calendar Sequence Control Chartshave no calendar MRC's. Therefore, at each calendar daay, or inspection, two, and only two, of theforegoing application to the preflight, postflight, groups in the calendar set are used. progressive aircraft rework requirements.

287

250 AVIATION MACHINIST'S MATE R 3 & 2 Q.V5)

A plastic cover is placed over the chart the time the aircraft is returned to an opera- when in use to facilitate marking of progress by tional status. the supervisor. The chart and the plastic cover are therefore reusable for as long as their Preflight/Daily/In-Flight condition warrants. Maintenance Record A portable workstand is used by the Cal- endar Maintenance Supervisorto provide a This record form is used in conjunction local work control center for the accomplishment with the Daily Schedule Maintenance Planning of calendar maintenance. This stand consists of Record to enable scheduled work to be assigned four stowable legs, a deck tiedown assembly, in a preplanned manner between calendar in- plastic chart holder, and a partitioned carrying spections. This form controlsand assigns case for MRC control and storage. A center responsibility for preflight, postflight, and daily storage section is provided for reference main- scheduled maintenanceincluding the special tenance manuals. This stand, with the Sequence and conditional work that may be required. Control Charts, becomes the control center These forms can be prepared daily or made for the supervisor of the entire calendar in- up in numbers sufficient to cover adesired spection. period of time. Local conditions provide the best indication of the method to be employed.

MAINTENANCE RECORD FORMS INSPECTION PROCEDURES Maintenance record forms are used to Calendar enable aircraft maintenance activities to schedule daily maintenance requirements, assign work Under the direction of the activity mainte- in a preplanned manner, establish responsibility nanceofficer,Maintenance Control holds a for work performed, and record component planning conference several days in advance of replacement and discrepancies discovered, as the calendar inspection due date with repre- well as the corrective action taken. The following sentatives of Quality Assurance, the production paragraphs describe the forms provided. divisions, the designated Calendar Maintenance Supervisor (CMS), and key members of the Daily Schedule Maintenance forthcoming calendar inspection team. Planning Record The purpose of the conference is to prepare the sequence control chart by adding on any The Daily Schedule Maintenance Planning existing additional requirements. Representa- Record is used to plan and project the dailytive items added on at this time are recent scheduled maintenance requirements for each localor command maintenance items, dis- individual aircraft between calendar periodic crepancies,component replacements, change maintenance periods.It aids in assuring that incorporations, and other likeitems which required maintenance is scheduled on time and either cannot be anticipated or cannot be pro- enables supervisory personnel to plan workloads gramed into all inspections on a fixed basis. accordingly. The form provides a number of After the preinspection planning conference, spaces for each day in which to enter MRC the marked up SCC is forwarded to Quality numbers that require compliance on a basis Assurance whose personnel certify that local other than every day (7 days, 14 days, con- inspection procedures are incorporated and that ditional, etc.) and provides a means for writing necessary MRC's publications, and required in all other scheduled maintenance due during maintenance personnel are available and alerted. the calendar maintenance period designated for The marked copy of the chart is then forwarded the aircraft. This form is filled out to cover to the CMS who prepares the necessary forms the calendar period. This is accomplished while required for the inspection. the aircraft is undergoing calendar periodic To initiatethe calendar inspection, the maintenance so that all scheduled maintenance supervisorissues MRC's,inthesequence for the subsequent operating period is known at prescribed by the Sequence Chart, to personnel

288

250 Chapter I5LINE OPERATIONSAND MALNTENANCE

thecards when thepreflightinspection is of each rating who make upthe inspection crew. Action Form (MAF) completed. A single copy Maintenance The Preflight/Daily/In-FlightMaintenance is issued to check crewpersonnel each time a in completely prior to issued for accom- Record should be filled segment of the card set is returning itto the line shack.Inasmuch as plishment. When the inspection orservicing may be in process cards are ful- several preflight inspections requirements specified on the at the same time, itbecomes especially im- filled, the MAF is completedby the person and MODEX (orside leader and portant that the BUNO accomplishing the work or his crew number) spaces be accuratelyfilled in. In some returned with the MRC's to thesupervisor. be locally preprinted SCC to indicate cases these records may The supervisor marks the with the necessary basicinformation (applicable the cards issued. Returnof completed cards to rating), and the person per- reflected on the chart. card number and the supervisor is also forming the work needsonly to complete the Even though the workstandprovides a physical completed and necessary spaces inlonghand. accounting, by separation, of the Daily inspections areaccomplished in the uncompleted MRC's, the supervisordouble- the preflight inspections. checks the return of each MRCby noting it on same manner as are The accomplishment ofthe items on thedaily the chart. A markshould exist on the chart reported on the Pre- each card not in inspection cards is also for each completed card, flight/Daily/In-Flight MaintenanceRecord. The possession of the supervisor,and each card contain the minimum completed due to parts on daily inspection card sets that could not be daily, special, and conditionalmaintenance re- order or unscheduled maintenance. aircraft. Those of each quirements for the applicable Accomplishment and completion card requirements that areto be performed on issue MRC are theresponsibility of the ap- titled "Daily.* Those of the inspection crew. every daily inspection are propriatespecialist card requirements that aretitled "Special" and Each card must be completedby the specialist at the appropriate supervisor. Uncompleted "Conditional" are performed and returned to the period which is determinedby elapsed flight MRC's are returned to thesupervisor and the mission requirements, or Must contain entries hours, aircraft status, Maintenance Action Form other consideration.Whenever these special listing the number of cardsand items com- items are to be includedin the pleted, and a notation in detailof which items or conditional dailyinspection,theappropriate cards are were not completedand why. concerned as part ofthe Control of the status andscheduling of the issued to the persons calendar inspection is theresponsibility of the daily card set. Itis essential that alldiscrep- supervisor. GROUND SUPPORTEQUIPMENT ancies discovered clearthrough him. The super- CARDS visor issues the necessaryMaintenance Action MAINTENANCE REQUIREMENTS centers for the Forms to the appropriate work The Aviation Machinist'sMate may be re- correction of discrepancieswhich cannot be periodic inspections onthe corrected by the calendarmaintenance crew. quired to perform aircraft maintenance support equipment peculiar to his rating. Tofacilitate the inspection Preflight, Postflight, andDaily and repair ofaircraft maintenancesupport equipment, sets of Dailyand Periodic Mainte- nance RequirementsCards have beendeveloped A set of Preflight,Postflight, and Daily equipment. By following is maintained for each major type of Maintenance Requirements Cards the sequence set forthin the card sets, the in the line shack for eachaircraft assigned. requirementsof the Prior to each flight, theplane captain and minimum inspection issued the pre- equipment are satisfied. other applicable personnel are The Daily MaintenanceRequirements Cards flight cards appropriate totheir rating or job. for daily inspections, it is signed off on set forth the requirements As each item is completed, which are performedby the activity usingthe aPreflight/Daily/In-Flight Maintenance Record which is returned to theline shack along with equipment.

289 c) re AVIATION MACHMIST'S MATE R 3I.:2

The Pericdic Maintenance Requirements NOTE: If there is unusually high friction, Cards delineate the requirements for calendar have the spark plugs removed from the lower inspections, which are performed by personnel cylinders and drain all liquid, as the presence of the Aviation Support Euipment Technician of any quantity of liquid in a combustion cham- (AS) rating. ber is likely to cause serious damage. Never turn the propeller opposite to engine rotation, as this may force liquid into the intake pipes, RECIPROCATING ENGINE OPERATION from where itis apt to be drawn back into the cylinder when the engine is started. One of the duties of the ADR is the turning Turn the switch to left for left engine and to up and checking of reciprocating engines. The right for right engine. Hold the switch to turn basic turnup procedure varies with different each propeller through 4 revolutions (12 blades). types.of aircraft, but by checking the applicable 2.Left andrightauxiliary fuel pump technical manual for the specific aircraft, the switchesON. ADR should be able to turn up and check the air- 3. Master ignition switchON (PUSH IN). craft with limited supervision. 4. ThrottleCRACK OPEN FOR APPROXI- Actual engine performance is an extremely MATELY 1,200 PRM. important part of the inspection procedure. The 5. Starter switchON AND HOLD. factors involved in the inspection of engines 6.Ignition switchBOTH. during engine turnup and shutdown are similar After propeller has turned 2 revolutions, for various types of aircraft. In the following set ignition switch to BOTH. discussion the S-2D aircraft is used as atypical NOTE: Continuous cranking should not ex- aircraft. ceed 30 seconds. If the engine does not start, Before an aircraft engine is turned up, release the starter switch and allow the starter certain precautions must be taken. Make sure to cool. that chocks are in place at the wheels of the 7. Primer switchON. aircraft, and that the aircraft is tied down, if Move primer switch to ON intermittently required by local policy. Remove such things until engine fires; then hold ON while gradually as control surface battens, control locks, and opening throttle to clear up exhaust and obtain pitottube covers. Check to insure that the smooth operation. ignition switch is in the OFF position, and that NOTE: Excessive throttle opening and inter- themixture controlisthe IDLE CUTOFF mittent priming after the engine has fired are position. Check the ramp around the aircraft the principal causes of backfiring during start- to insure that the area is clear of debris. Check ing. Gradual opening of the throttle while prim- the fuel and oil tanks for proper grade and ing continuously will reduce the initial over- quantity. The man at the controls must be fully rich mixture to a smooth running, best power qualified in the type of aircraft which he is to mixture as theengine picks up speed. An turn up. Make sure that a fireguard is posted overrich mixture is sluggish but will not back- with the required firefighting equipment, and fire. that the fireguard and the man at the controls 8. Mixture controlRICH. clearly understand the signals to be used by Watching tachometer, move mixture con- them. trol to RICH after engine is operating smoothly on primer. Release primer switch as soon as Starting a drop in rpm indicates that engine is receiving additional fuel from carburetor. Before starting the engines, check to see If the oil pressure indicator does not show that all personnel are safely clear of the pro- pressure within 30 seconds, stop the engine pellers and that the wheels are chocked. Make and investigate. certain that standby firefighting equipment is 9. ThrottleADJUST. manned. Adjust throttle after transfer from primer To start the engines, proceed as follows: to carburetor has been accomplished-800 to I.Starter swit chON. 1,000 rpm.

290 Chapter 15LINE OPERATIONS ANDMAINTENANCE 5"/

NOTE: Start the other engine by repeat- When oil reaches satisfactoryoperating temperatures, open oil cooler doors asrequired. ing steps 5 through 9, above. doors 10. Generatorandtransformer-rectifier Return switch to OFF to stop operation of warning lightsNOT GLOWING. at desired setting. These warning lights should not beglowing. 5.Fire detector test switchTEST. momentarily. 11. External power suppliesDISCONNECT. Set the test switch to TEST Instruct ground personnel to disconnect ex- The fire warning lights should light. the ternal power. ELECTRICAL SYSTEM CHECKCheck If an engine fire develops during thestart- electrical system as follows: ing procedure, continue cranking tostart the 1.Gefierator andtransformer-rectifier engine does warning lightsCHECK. engine and blow out the fire. If the 650 rpm not start and the ground crew signalsto cut the Check lights with engines idling at to see that they'are NOTGLOWING. engine, proceed as follows: be 1. Mixture controlIDLE CUTOFF. NOTE: Both a-c and d-c power must 2, Emergency fuel and oil shutoff switch continuously supplied in the aircraftfrom the provide stable CLOSE. time of engine starting in order to 3. Emergency hydraulic oil shutoff switch power to the electronic equipmentinstalled. 2. ThrottlesADJUST. CLOSE. 800 to 4. Cowl flaps switchCLOSE. Adjust throttles for idling speed of Auxiliary fuel pump switchOFF. 1,000 rpm. 5. 3. Voltmeter-115 ± 2.5 VOLTS. 6.Fuel selector valve controlOFF. 7. Individual ignition switchOFF. 4. Frequency meter-400 ± 4 CYCLES. NOTE: Do not attempt a restartuntil the NOTE: Persistent wild fluctuationof the reason for the fire has beendetermined and frequency meter indicates failure of theconstant the cause corrected. speed drive. 5. Left and rightgeneratorcontrol switchesOFF-RESET. Turnup Checks All electrical power in aircraftshould be lost. After the engine has been started,itis 6.Left generator control switchON. necessary to ascertain ifthe various engine Left generator should be reenergizedand components and systems areoperating nor- power should be restored toaircraft instruments and warning lights. The NO R GENand LOSS mally.In order to do this, the ADRshould perform the following proceduresbefore per- OF TR warning lights should glow. 7. Right generator control switchON. forming the remaining turnup checks: aircraft 1. Thr ottl eADJUS T. All power should be restored tothe Run engines at 1,100 to 1,300 rpm. and ALL warning lights should go out. NOTE: Spark plugs will foul rapidly atlow NOTE: If generators fail to reenergize, not adjusted battery failure is indicated. idle rpm if the idle mixture is equip- properly. 8. Communication and electronic 2.Oil pressure indicatorsCHECK. mentCHECK OPERATION. After I minute, 40-psi oil pressure should 9.Pilot's and copilot's electricallydriven be indicated (15-psi minimum atidle). instrumentsCHECK. functioningof in- 3.Oil temperature indicatorsCHECK. Checkforproper Warm up at 1,100 to 1,300 prmuntil oil struments. temperature reaches 40° to 95° C. HYDRAULIC SYSTEM CHECK.Check NOTE: An excessive rise in oil pressure the hydraulic system as follows: system when throttlesare advanced indicatesthat 1.Left and righthydraulic pressure gagesI,400 to1,500 psi. further warmup is necessary. indicator 4. Left and right oil cooler doorswitches 2. Landing gearposition OPEN. CHECK.

291

25d AVIATION MACHINIST'S MATE R 3 & 2 c23.;-

Check landing gear position indicator to times; then return to INCREASE. Engine rpm determine that gear is down and locked. should change due to propeller pitch change. FUEL SYSTEM CHECK.Check the fuel This procedure will also expel any air in the system as follows: propeller control oil lines. 1. Fuel flowCHECK. AUTOMATIC PROPELLER FEATHERING Check fuel flow from left tank to right CHECK.Perform theautomaticpropeller engine and from right tank to left engine for 2 feathering check as follows: minutes with rpm over 1,200. Return system to 1.Propeller feathering button lights (both) normal, left tank to left engine and right tank to GLOWING. right engine. 2. Automatic feathering arming switch 2.Fuel quantity, and fual quantity gage test ARMED. Armed lightGLOWING. switchLEFT MOMENTARILY, THEN RIGHT. 3. ThrottleSET FOR 1,200 RPM (approxi- Applicable gage pointer should move toward mately). Torque pressureBELCW 125 PSI. lower end of dial. Pointer should then return to Left automatic propeller feathering test its original position when test switch is re- switchHOLD IN TEST POSITION. leased. After approximately 1 1/2 seconds, engine 3. Warning lights test switchHOLD TO rpm should decrease as feathering starts. TEST (momentarily). Fuel low level warning NOTE: Check that manual feathering button lightsGLOWING. moves to the depressed position. CARBURETOR ALTERNATE AIR CHECK. 4.Test switchRELEASE TO OFF (after a Check the carburetor alternate air as follows: dropof approximately 200 rpm). Unfeather 1. ThrottlesSET TO 1,200 to 1,400 RPM. manually. 2.Carburetor air switchALTERNATE. 5. Arming switchRECYCLE TO OFF AND Checkfor rise in carburetor air tem- ARMED. . perature within approximately 30 seconds. 6. Repeat steps 3through5 for right 3.Carburetor air switchDIRECT. propeller. INSTRUMENT CHECK.With the propellers 7. Advance both throttles approximately set for FULL INCREASE and the engines op- 200 rpm so that torque pressure is at least erating at 1,500 rpm, perform the instrument 150 psi, and check that holding left and right check as follows: test switches in TEST position for at least 1.Oil temperatureCHECK. 1 1/2 seconds has nO effect on feathering Grade 1100 oil-85° to 95°C. of propellers. 1 Grade 1065 oil-65° to 75°C. NOTE: In the event the start of propeller 2.Oil pressures-65 to 75 psi. feathering results in the loss of a generator, 3.Fuel pressures-23 ± 2 psi. replacement of the associated supervisory panel Check with the auxiliary fuel pumps OFF isindicated. Electrical power from the live and then ON. engine is restored by operating the associated 4.Cylinder headtemperatures-100° TO generator control switch to the OFF-RESET 245°C. position and then back to ON, or by operating the 5.Carburetorairtemperatures-5° to a-c bus tie switch momentarily to ON. 38°C. FIELD BAROMETRIC MAP POWER 6.Constant speed drive oil temperatures- CHECKPerform thefield barometric MAP 80° to 120°C. power check as follows: With propellers at FULL PROPELLER CHECK.Perform the pro- INCREASE, set throttles to that manifold pres- peller check as follows: sure which equals current field barometric 1. Parking brakeLOCKED. pressure. At standard sea level conditions rpm 2.Propeller rpm control leversFULL should read 2,250 1:50 rpm. On a cold day, INCREASE (LOW PITCH). check rpm will be less than 2,250; at higher 3. ThrottlesSET FOR 1,500 RPM. altitudes (reduced barometric pressure) check 4. Operate propeller rpm control levers rpm is higher. through complete range from FULL INCREASE IGNITION CHECK.Perform the ignition to FULL DECREASE (high pitch) three to four check as follows: With propellers at FULL

292

2 bU Chapter 15LLNIE OPERATIONS ANDMADITENANCE ca c3

left DICREASE, set throttles so thatmanifold pres- 2. Repeatthisprocedure for the sures equal field barometric pressure.Clear engine. 15 seconds; 3. The Flight Manual should bechecked engines in NORMAL mixture for conditions then return to RICH. Move rightengine ignition for maximum limits and operational switch from BOTH to R and backto BOTH, then to be observed. BOTH. Allow rpm NOTE: A check should be made to insure from BOTH to L ancLback to and that to stabilize on BOTH beforeswitching. Normal that the aircraft is properly chocked dropoff in either L or R position is 50to 75 rpm; the high power tiedown of the aircrafthas been Repeat fore- completed. A last minute check shouldbe made maximum allowable is 100 rpm. debris going procedure for left engine. to be sure that there is no loose gear or IDLE MIXTURE CHECK.Checkclosed- near or behind the aircraft thatwould be affected throttle idle mixture by manuallyleaning mix- by the propeller blast. ture until a noticeable decreasein rpm is obtained. There should be a slightrise of 10 to Stopping Engines 20 rpm just prior to the noticeabledecrease in rpm, and no change inmanifoldpressure, during this process if the mixture adjusting screwhas In stopping the engines, perform thefollow- been properly set for a BESTPOWER mixture. ing steps: With the throttle still set to theIDLE position, 1. Main wheelsCHOCKED. hold the primer switch to theapplicable posi- 2. Propeller automatic feathering arming tion (LEFT for left engine,RIGHT for right switchOFF. engine) until a noticeable decrease in rpmis 3.Propeller rpm controlsFULL IN- obtained. There should be no increasein rpm CREASE. pressure during this 4. Mixture controlsIDLE CUTOFF. or decrease in manifold (after process if the mixtureadjusting screw has been 5.Individual engine switchesOFF properly set for a BEST POWERmixture. engines stop). NOTE: Idling for a few minuteswith a 6. Master ignition switchOFF. manually leaned mixture is betterthan operating 7. ThrottlesCLOSED (fully). at high power to burn outcarbon deposits. 8.Fuel selector valve controlsOFF. FULL POWER CHECK.In the event afull 9.All electrical switchesOFF. isrequired, the procedure is 10. Alf hatches and doorsCLOSED. power check After the operational runup has been com- listed below: that the 1. Advance right throttle to obtain2,750 to pleted, the plane captain must insure 2,800 :pm, manifold pressure 53 to56.5 in. Hg. Preflight/Daily/Inflight Maintenance Record is Decrease rpm immediately to idle(650 rpm). initialed and signed.

293