DOCUMENT RESUME

ED 070 572 SE 014 119 TITLE Introduction to Sonar, Navy Training Course. INSTITUTION Bureau of Naval Personnel, Washington, R. C.-; Naval Personnel Program Support Activity, Washington, D. C. REPORT NO NAVPERS -10130 -B PUB DATE 68 NOTE 186p.; Revised 1968

EDRS PRICE MF-$0.65 HC-$6.58 DESCRIPTORS *Acoustics; Instructional Materials; *Job Training; *Military Personnel; Military Science; Military Training; Physics; *Post Secondary Education; *Supplementary Textbooks

ABSTRACT Fundamentals of sonar systems are presented in this book, prepared for both regular navy and naval reserve personnel who are seeking advancement in rating. An introductory description is first made of submarines and antisubmarine units. Determination of underwater targets is analyzed from the background of true and relative bearings, true and relative motion, and computation of target angles. Then, applications of both active and passive sonars are explained in connection with bathythesmographs, fathometers, tape recorders, fire control techniques, tfiternal and external communications systems, maintenance actions, test methods and equipment, and safety precautions. Basic principles of sound and temperature effects on wave propagation are also discussed. Illustrations for explanation use, information on training films and the sonar technician rating structure are also provided.. (CC) -^'

U.S DEPARTMENT OFHEALTH. EDUCATION 14 WELFARE OFFICE OF EOUCATION THIS DOCUMENT HASBEEN REPRO OUCED EXACTLY ASRECEIVED FROM THE PERSON ORORGANIZATION ORIG INATING IT POINTS OFVIEW OR OPIN IONS STATED 00NOT NECESSARILY REPRESENT OFFICIAL OFFICEDF EDU CATION POSITION ORPOLICY 1-1:1444646-

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This book is written for themen of the U. S. Navy and Naval Reserve who are seeking advancement in theSonar Technician rating. At this writing the general rating ofSonar Technician includes the service ratings of Surface SonarTechnician (STG) and Submarine Sonar Technician (STS)at the Third and Second Class levels. The general rating of Sonar Technician isat the First Class level and above. Although the Surface aad SubmarineSonar Technicians may operate different equipment, certain practicalfactors and knowledge factors apply toall Sonar Technicians. This bookcovers many of the factors common to both ratings. The scope of this training course doesnot permit inclusion of the fundamentals of mathematics,electricity, and electronics. If you need such information, you should study the appropriatetraining courses that appear in the reading list.. Because of securityclassifi- cation, some common sonar subjects cannot beincluded in this training course, but may be found in classifiedcourses and other publications. As one of the Navy Training Courses,this book was prepared by the Training Publications Division, NavalPersonnel Program Support Activity, Washington, D. C., for the Bureau ofNaval Personnel.

First edition 1960 Second edition 1963 Revised 1968

Stock Ordering No. 0500 - 036-0100 THE UNITED STATES NAVY

GUARDIAN OF OUR COUNTRY The United States Navy is responsible for maintaining control of the sea and is a ready force on watch at home and overseas, capable of strong action to preserve the peace or of instant offensive action to win in war. It is upon the maintenance of this control that our country's glorious future depends; the United States Navy exists to make it so.

WE SERVE WITH HONOR Tradition, valor, and victory are the Navy's heritage from the past. To these maybe added dedication, discipline, and vigilance as the watchwords of the present and the future. f- At home or on distant stations we serve with pride, confident in the respect of our country, our shipmates, and our families. Our responsibilities sober us; our adversities strengthen us. Service to God and Country is our special privilege. We serve with honor.

THE FUTURE OF THE NAVY The Navy will always employ 'new weapons, new techniques, and greater power to protect and defend the United States on the sea, under the sea, and in the air. Now and in the future, control of the sea gives the United States her greatest advantage for the maintenance of peace and for victory in war. Mobility, surprise, dispersal, and offensive power are the keynotes of the new Naciy.The roots of the Navy lie in a strong belief in the future, in continued dedication to our tasks, and in reflection on our heritage from the past. Never have our opportunities and our responsibilities been greater.

Poe ante by the Superintendent of Documents, U.S. Covernaint Printing Office, 'Washington, D.C., 20402 - Price $1.50

%. CONTENTS

CHAPTER Page

1. The sonar technician 1

2. Submarines and antisubmarine units 9

3. Bearings and motion 20

4. Physics of sound 34

5. Bathythermograph 57 6. Principles Of sonar...... 91 7. Basic fire control 110

8. Commtmications 132

9. Maintenance 146.

10. Safety; test equipment; test methods 154

APPENDIX

I. Training film list 176

INDEX 178

iii READING LIST

NAVY TRAINING COURSES Basic Electricity, NavPers 10086 Introduction to Electronics (chapters 1-6, 9), NavPers 10084 BasicElectronics, NavPers 10087 (chapters 1-11, 17, appendix II) Sonar Technician G 3 & 2, NavPers 10131 Sonar Technician S3 & 2, NavPers 10132 Basic Handtools, NavPers 10085

OTHER NAVY PUBLICATIONS Handbook of Test Methods and Practices(sections 1, 2, and 4.5), NavShips 0967-000-0130 NavShips Technical Manual (chapter 9670), NavShips 0901-000 0013 Maintenance and Material Management (3-M) Manual (chapters 1, 2, 3), OpNav 43P2 Application of Oceanography to ASW (chapters 2 and 3), H. 0. 781 Antisubmarine Classification Manual, NWIP 24-1(A) (chapters 1, 2, 3 STG); (chapters 1, 2, 5 STS)

USAFI TEXTS United States Armed Forces Institute (USAFI) courses for additional reading and study are available through your information and education officer* A partial list of those courses applicable to your rate follows.

CORRESPONDENCE COURSES Number Title C 885 Fundamentals of Radio B 887 Intermediate Radio A 788 Introduction to Electronics, Part I A 789 Introduction to Electronics, Part II D 290 Physics, Part I D 291 Physics, Part II

*"Members of the United States Armed Forces Reserve components, when on active duty, are eligible to enroll for USAFI courses, services, and materials, if the orders galling them to active duty specify a period of 120 days or more, or if they have been on active duty for a period of 120 days or more, regardless of the time specified in the active duty orders." CHAPTER 1 THE SONAR TECHNICIAN

A substantial force of conventional and nu-qualifications required for advancement to Third clear-powered submarines, many of them capableClass Sonar Technician. Although this course is of launching nuclear missiles, represents a po-limited to unclassified material, much of your tential threat to our country's security and awork will deal with classified equipment and continuing challenge to our Navy's antisubmarine information. You should never discusswith forces. strangers details of your work, nor reveal in- To meet- this challenge, U. S.Navy ships and formation concerning equipment characteristics submarines continually conduct exercises in anti- and capabilities. These restrictions apply also submarine warfare (ASW) operations, revisingto shipmates who have no need to know the tactics and evaluating new methods and equipment information. Violation of security regulations can used for detecting and destroying enemy under-result in punishment by court-martial. water craft. Destroyers are our main antisub- The remainder of this chapter gives informa- marine (A/S)surface vessels. They providetion on the enlisted rating structure, the Sonar protection against submarines for major surfaceTechnician rating, requirements and procedures ships by forming a sonar screen around the ship.for advancement in rating, and references to Upon detection of a submarine trying to pene-help you work for advancement and to perform trate the screen,' the destroyer initiates an attack,your duties as a Sonar Technician. Also included and the main body turns awiffroth-the-contactare suggestions _ on how to make the best use area. Destroyers alio Operate in special A/Sof Navy Training Courses. Before you begin forces called hunter-ldller groups, whose function studying the rest of this course; therefore, you is to actively seek out and destroy enemy sub-should study the remainder of this chapter very marines. Our own submarines particularly nu-carefully. clear-powered types with their generally superior detection equipment play an equally important role in ASW. They are capable of selecting the ENLISTED RATING STRUCTURE depth that provides the best underwater de- tection conditions. Additionally, they have the endurance to conduct surveillance operations The two main types of ratings in the present over wide ocean areas. enlisted rating structure, are general ratings and service ratings. The Sonar Technician, whether aboard ship or submarine is a vital member of the Navy's GENERAL RATINGS identify broad ors, pa- ASW team. All Sonar Technicians must learn totionalfields of related duties and functions. operate the sonar equipment installed in theirSome general ratings include service ratings; ship. This requirement includes not only manip-others do not. Both Regular Navy and Naval ulating controls, but also interpreting data derivedReserve personnel may hold general ratings. from sonar, fire control, and associated equip- ment. Sonar Technicians also must be able SERVICE RATINGS identify subdivisions or to maintain the sonar in good working condi-specialties withina general rating. Although tion. service ratings can exist at any petty officer level, they are most common at the P03 and This textis a self-study training course P02 levels. Both Regular Navy and Naval Reserve designed to help you meet the professional personnel may hold service ratings. r ..I=1Ir

INTRODUCTION TO SONAR

SONAR TECHNICIAN RATING California; U.S. Navy Submarine School, New London, Connecticut; and Fleet TrainingCenters. The Sonar Technician rating is a general.Shore duty billets of a general nature, common rating in the deck group (group I). The funda- to all ratings, are also open to Sonar Technicians. mentaltask ofall Sonar Technicians is to Wherever you are stationed, one quality that provide underwater data for operational use.all petty officers must exhibit is leadership. As .Sonar Technicians operate and maintain sonaryou advance in rate, you will have more and equipment, perform duties required as membersmore responsibility, authority, and control over of antisubmarine (A/S) attack teams, and in-other men. You must strive always to set a good terpret target and oceanographic data. At theexample for the men under you by maintaining third and second class petty officer levels there high standards of personal conduct, as well as are two service ratings one for men assignedprofessional and military competency. In other to surface ships and one for men assigned towords, be 'a good Navyman. General Order Id submarine duty. outlines the leadership qualities expected of all persons in the Navy in a position of authority. SONAR TECHNICIAN G (SURFACE) (STG) ADVANCEMENT IN RATING Surface Sonar Technicians operate shipboard antisubmarine equipment. TMs equipment in- Some of the rewards of advancement in cludes sonars and underwater fire control sy stems rating are easy to see. You get more pay. used in solving ASW problems. Equipment opera- Your job assignments become mere interesting tion at the third and second class levels usuallyand more challenging. You are regarded with is limited to manipulating dials and interpretinggreater respect by officers and enlisted per- receiveddata. As an STG you must also besonnel. You enjoy the satisfaction of getting able to perform operational, preventive, and ahead in your chosen Navy career. technical maintenance on sonar, underwater fire But theadvantages of advancing in rating control, and associated equipment. are not yours alone. The Navy also profits. Highly trained personnel are essential to the SONAR TECHNICIAN S functioning of the Navy. By each advancement (SUBMARINE) (STS) in rating, -you increase your value to the Navy in two ways. First, you become more valuable Submarine Sonar Technicians operate sub-as a specialist in your own rating. And second, marine sonar and oceanographic equipment, andyou become more valuable as a person who can interpret data received from passive and active train others and thus make far-reaching con- sonars, submarine fire control equipment, andtributions to the entire Navy. associated auxiliary sonar equipment. As an STS you also must be able to construct and HOW TO QUALIFY FOR interpret submarine sonar plots, and perform ADVANCEMENT operational, preventive, and technical mainte- nance on submarine sonar and associated equip- What must you do to qualify for advancement ment, excluding fire control equipment. in rating? The requirements may change from time to time, but usually you must: DUTY ASSIGNMENTS 1. Have a certain amount of time in your The majority of sea duty assignments for present grade. Submarine Sonar Technicians are in submarines 2. Complete the required military and oc- and aboard submarine tenders. Most Surfacecupational training coulees. Sonar Technicians are assigned to destroyer - 3. Demonstrate your ability to perform all type ships. Other sea duty billets include de-the PRACTICAL requirements for advancement stroyer tenders, antisubmarine aircraft carriers,by completing the Record of Practical Factors, minesweepers, and certain cruisers. Some ofNavPers 1414/1. In some cases the Record of the locations of shore duty assignments, which Practical Factors may contain the old form usually consist of instructor billets, are: U.S. number, NavPers 760. Fleet Sonar School, Key West, Florida; U.S. 4. Be recommended by your commanding of- Fleet Antisubmarine Warfare School, San Diego, ficer, after the petty officers and officers super-

7 2 ;4

Chapter 1 T.HE SONAR TECHNICIAN

vi sing your wnrk have indicated that they consider All of the above information (except the you capab..e of performing the duties of the next examination score) is submitted to the Naval higher rate. Examining Center with your examination answer 5. Demonstrate your KNOWLEDGE by passing sheet. After grading, the examination scores, written examinations on the occupational and for those passing, are added to the other factors military qualification standards for advancement to arrive at the final multiple." A precedence in rating. list, which is based on final multiples, is then prepared for each pay grade within each rating. Some of these general requirements may be Advancement authorizationsare then issued, modified in certain ways. Figure 1-1 gives a more beginning at the top of the list, for the number detailed view of the requirements for advancement of men needed to fill the existing vacancies. of active duty personnel; figure 1-2 gives this information for inactive duty personnel. HOW TO PREPARE FOR ADVANCEMENT Remember that the qualifications for advance- ment can change. Check with your division officer What must you do to prepare for advance- or training officer to be sure that you know the ment in rating? You must study the qualifica- most recent qualifications. tions for advancement, work on the practical Advancement in rate is not automatic. Even factors,studytherequiredNavy Training though you have met all the requirements, in- Courses, and study other material that is re- cluding passing the written examinations, you may quired for advancement in your rating. To pre- not be able to "sew on the crow" or "add apare for advancement, you will need to be stripe." The number of men in each rate and rating familiar with(1)the Quals Manual, (2) the is controlled on a Navy-wide basis. Therefore, Record of Practical Factors, (3) a NavPers the number of men that may be advanced is publication called. Training Publications for Ad- limited by the number of vacancies that exist. vancement in Rating, NavPers 10052, and (4) When the number of men passing the examination applicable Navy Training Courses. The follow- exceeds the number of vacancies; some system ing sections describe them and give you some must be used to determine which men may bepractical- suggestions on how to use them in advanced and which may not. The system used preparing for advancement. is the "final multiple" and is la combination of three types of advancement systems. The Quals Manual Merit rating system The Manual of Qualifications for Advance- Personnel testing system ment in Rating, NavPers 18068-B (with changes), Longevity, or seniority, system gives the minimum occupational and military qualification standards for advancement to each The Navy's system provides credit for perfor- rate within each rating. This manual is usually mance, knowledge, and seniority, and, while it called the "Quals Manual," and the qualifica- cannot .guarantee that any one person will betions themselves are often called "quals." The advanced, it does guarantee that all men within qualification standards are of two general types: a particular rating will have equal advancement (1) military qualification standards and (2) occu- opportunity. pational qualification standards. The following factors are considered in com- MILITARY STANDARDS are requirements that puting the final multiple: apply toall ratings rather than to any one particular rating. Military requirements for ad- Maximum vancement to third class and second class petty Factor Credit officer rates deal with military conduct, naval organization, military justice, security, watch Examination score 80 standing, and other subjects which are required Performance factor of petty officers in all ratings. (Performance evaluation) 50 OCCUPATIONAL STANDARDS are require- Length of service (years x 1) 20 ments that are directly related to the work of Service in pay grade (yearsx 2) 20 each rating. Medals and awards 15 Both the military requirements and the occu- pational qualification standards are divided into 185 subject matter groups; then, within each subject

3 INTRODUCTION TO SONAR

#t E3 #E4 t E5 REQUIREMENTS El to E2E2 to E3 to E4 to ES to E6 t E6 to E7t E7 to E8t E8 to E9

4 mos. 36 mos. 36 mos.24 mos. service as E-6. as E-7. as E-8. or 8 8 of 11 10 of 13 6 mos.6 mos. 24 mos. SERVICE comple- 12 mos. years years Hon ofas E-2.as E-3.as E-4.as (-5. total total total enlisted recruit service service service. training. must bemust be -enlisted.enEsted.

f., Clogs A Class B . Rocruit4% for FR3, SCHOOL for AGC Training:, , DT3, PT3. , MUC, AME 3, ,' MNC. .., NM 3 , , , Locally PRACTICAL Iprepared Records of Practical Factors, NavPers 1414/1, must be FACTORS check- completed for E-3 and all PO advancements. Pfl.s. , Specified ratings must complete PERFORMANCE 'r 0 .,,: applicable performance tests ts be- TEST 11 t-1. 44 fore taking examinations. ,

ENLISTED As used by CO Counts toward performance factor credit in ad- PERFORMANCE when approving vancement multiple. EVALUATION advancement.

Locally See Navy-wide examinations required Navy-wide, EXAMINATIONS** PrliPa..,.. *as. below,for all PO advancements. selection board.

PS.

7.. Correspondence alL 4- Required for E-3 and all PO advancements NAVY TRAINING,; unesls waveecaueid b ochoo comps-l ' courses and COURSE (INCLUD- :', sf s recommended tion, but need not be repeated if identical ING MILITARY s'1 reading.See course has already been completed.See REQUIREMENTS) ':''''' NavPers 10052 ...;',1,,',4--' NavPers 10052 (current edition). (current edition). ..-,?,-... ;11-

Commanding U.S. Naval Examining AUTHORIZATION Bureau of Naval Personnel Officer Center

.

* All advancements require commanding officer's recommendation. t 1 year obligated service required for E-5 and E-6; 2 years for E-6, E-7, E-8 and E-9. * Military leadership exam required for E-4 and E-5. ** For E-2 to E4, NAVEXAMCEN exams or locally prepared tests may be used. Figure 1-1.Active duty advancement requirenients. Chapter 1 THE SONAR TECHNICIAN

REQUIREMENTS* El to E2E2 to E3E3 to E4E4 to ESES to E6E6 to E7 El E9

TOTAL TIME 4 mos.6 mos.15 mos.18 mos.24 mos.36 mos.36 mos.24 nos. IN GRADE

TOTAL TRAINING 14 days14 days14 days14 days28 days42 days42 days28 days DUTY IN GRADE t

Specified ratings must templet* applicable PERFORMANCE performance tests before taking exami- TESTS nation.

DRILL Satisfactory participation as a member of a drill unit. PARTKIPATION

PRAalCAL FAaORS Record of Practkal Factors, NavPors 1414/1, must be completed (INCLUDING MILITARY for all advancements. REQUIREMENTS)

NAVY TRAINING COURSE (INCLUDING Completion of applicable tours* or courses must be entered MILITARY REQUIRE- in service record. MENU)

Standard Exam, Standard Exam Standard Exam Selection Board. Standard EXAMINATION or required for all PO Also Pass Mil. Exam Leadership Rating . Advancements. Training. Exam for E4 and E-5.

. Commanding U.S. Naval Examining Bureau of Naval AUTHORIZATION Officer Center Personnel .

Recommendation by commanding officer required for all advancements. t Active duty periods may be substitutod for training duty.

Figure 1-2.Inactive duty advancement requirements. INTRODUCTION TO SONAR Alrr. safamis

matter group, they are divided into PRACTICALtioned earlier, is used to keep a record ofyour FACTORS and KNOWLEDGE FACTORS. Practical practical factorqualifications. This form is factors are things you must be able to DO. Knowl- available for each rating. The form lists all edge factors are things you must KNOW in orderpractical factors, both military and occupational. to perform the duties of your ating. As you demonstrate your ability to perform each In most subject matter areas, you will findpractical factor, appropriate entries are made both practical factor and knowledge factor quali- in the DATE and INITIALS columns. fications. In some subject matter areas,you may Changes are made periodically to the Manual find only one or the other. It is important toof Qualifications for Advancement in Rating, remember .that there are some knowledgeas-and revised forms of NavPers 1414/1 are pro- pects to all practical factors, and some practicalvided when necessary. Extra space is allowedon aspects to most knowledge factors. Therefore,the Record of Practical Factors for entering even if the Quals Manual indicates that there areadditional practical factors as they are published no knowledge factors for a -given subject matterin changes to the Quals Manual. The Record of area, you may still expect to find examinationPractical Factors also provides space forre- questions dealing with the knowledge aspects ofcording demonstrated proficiency in skills which the practicalfactorslisted in that subjectare within the general scope of the rating but matter area. which are not identified as minimum qualifica- You are required to pass a Navywide military/ tions for advancement. leadership examination for E-4 or E-5,as ap- Until completed, the NavPers 1414/1 is usually propriate, before youtakethe occupational held by your division officer; after 0.-.3pletion, examinations. The military/leadership examina-it is forwarded to the personnel office for in- tions are administered on a schedule determinedseetion in your service record. If you are trans- by your commanding officer. Candidates areferred before qualifying in all practical factors, required to pass the applicable military/leader-the incomplete form should be forwarded with ship examination only once. Each of these exami- your service record to your next duty station. nations consists of 100 questions based on infor- You can save yourself a lot of trouble by making mation contained In Military Requirements for sure that this form is actually inserted in your Petty Officers 3 and 2, NavPers 10056 and inservice record before you are transferred. If other publications listed in Training Publications the form is not in your service recor'1,you for Advancement in Rating, NavPers 10052.be required to start all over :Igatirt refr The Navywide occupational examinations forqualify in the practical factors which nave Stread;; pay grades E-4 and E-5 willcontain150 questionsbeen checked off. related to occupational areaof your rating. If you are working for advancement to second NavPers 10052 class, remember that you may be examinedon third class qualifications as well as on second Training Publications for Advancement in class qualifications. Rating, NavPers 10052 (revised), is avery The Quals Manual is kept current by means of imnprtant publication for anyone preparing for changes. The occupational qualifioations foryour advancement in rating. This bibliography lists rating, covered in this training course,were requiredandrecommendedNavyTraining current at the time the course was printed. ByCourses and- other reference material to be the time you are studying this course, however, used by personnel working for advancement in the quals for your rating may have been changed. rating. The NavPers 10052 is revised and issued Never trust any set of quals until you have checked once each year by the Bureau of Naval Personnel. it against an UP-TO-DATE copy in the QualsEach revised edition is identified by a letter Manual. following the NavPers number. When using this publication, be SURE that you have the most itecord of Practical Factors recent edition. If extensive changes in qualificationsoccur Before you can take the servicewide examina- in any rating between the annual revisions of tion for advancement in rating, there must bean NavPers 10052, a supplementary list of study entry in your service record to show thatyou have material may be issued in the form ofa BuPers qualified in the practical factors of both the mili- Notice. When you are preparing for advancement, tary qualifications and the oc-upational qualifi- check to see whether changes have been made cations. The record of prang.. al factors,men- in the qualifrons for your rating. If changes 116 .wor

Chapter 1 THE SONAR TECHNICIAN

have been made, see if a BuPers Notice hasedition by checking the NavPers number and been issued to supplement NavPers 10052 for yourtheletter following this number in the moat rating. recent edition of List of Training Manuals and The required and recommended referencesCorrespondence Courses, NavPers 10061. (Nay- are listed by rate level in NavPers 10052. IfPers 10061 is actually a catalog that lists all you are working for advancement to third class,current training courses and correspondence study the material that is listed for third class.courses; you will find this catalog useful in If you are working for advancement. to secondplanning your study program.) class,study the materialthat is listed for Navy Training Courses are designed to help second class; but remember that you are alsoyou prepare for advancement in rating. The responsibio for the references listed at thefollowing suggestions may help you to make the third class level. best use of this course and other Navy training In using NavPers 10052, you will notice thatpublications when you are preparing for advance- some Navy Training Courses are marked with anment in rating. asterisk (*). Any course marked in this way is MANDATORY that is, it must be completed at tha 1. Study the military qualifications and the indicated rate level before you can be eligible tooccupational qualifications for your rating before take the servicewide examination for advancementyou study the training course. Remember, you in rating. Each mandatory course may be com-are studying the training course primarily in pleted by (1) passing the appropriate enlistedorder to meet these quals. correspondence course that is based on the manda- 2. Set up a regular study plan. It will prob- tory training course; (2) passing locally preparedably be easier for you to stick to a schedule if tests based on the information given in the train-you can plan to study at the same time each ing course; or (3) in some cases, successfullyday. If possible, schedule your studying for a completing an appropriate Class A course.' time of day when you will not have too many Do not overlook the section of NavPers 10052interruptions or distractions. which lists the required and recommended ref- 3. Before you begin to study any part of erences relating to the military qualificationthe training .course intensively, become familiar standards for advancement. Personnel of ALLwith the entire book. Read the preface and the ratings must complete the mandatory militarytable of contents. Check through the index. Look requirements training course for the appropriateat the appendixes. Thumb through the book without rate level before they can be eligible to advanceany particular plan, looking at the illustrations in rating. and reading bits here and there as you see things The references in NavPers 10052 which arethat interest you. recommended but not mandatory should also 4. Look at the training course in more detail, be studied carefully. ALL references listed into see how it is organized. Look at the table of NavPers 10052 may be used as source materialcontents again. Then, chapter by chapter, read for the written examinations, at the appropriatethe introduction, the headings, and the subhead- rate levels. ings. This method will give you a pretty clear picture of the scope and content of the book. As Navy Training Courses you look through the book in this way, ask your- self some questions: There are two general types of Navy Train- What do I need to learn about this? ing Courses. RATING COUR:ES (such as this What do I already know about this? one) are prepared for most enlisted ratings. How is this information' related to information A rating training course gives information thatgiven in other chapters? is directly related to the occupational qualifi- How is this information related to the quali- cationsof ONE rating. SUBJECT MATTERfications for advancement in rating? COURSES or BASIC COURSES give information 5. When you have a general idea of what is in that applies to more than one rating. the training course and how it is organized, fill Navy Training Courses are revised from timein the details by intensive study. In each study to time to keep them up to date tecimically.period, try to cover a complete unitit may be The revision of a Navy Training Course isa chapter, a section of a chapter, or a subsection. identified by a letter following the NavPersThe amount of material that you can cover at one number. You can tell whether any particulartime will vary. If you know the subject well, or copy of a Navy Training Course is the latestif the material is easy, you can cover quite a INTRODUCTION TO SONAR

lot at one time. Difficult or =familiar material Some of the publications described here are will require more study time. subject to change or revision from time to time 6. .In studying any one unitchapter, section, some at regular intervals, others as the need or subsectionwrite down the questions thatarises. When using any publication that is sub- occur to you. Many people find it helpful toject to change or revision, be sure that you have make a written outline of the unit as they study,the effective (latest) edition. When using any or at least to write down the important ideas.publication that is kept current by means of 7. As you study, relate the information. inchanges, be sure you have a copy in which the b aining course to the knowledge you already all official changes have been made. Studying have. When you read about a process, a skill,canceled or obsolete information will not help or a situation, try to see how this informationyou to do your work or to advance in rating; ties in with your own past experience. it is likely to be a waste of time, and may even 8. When you have finished studying a unit,be seriously misleading. take time out to see what you have learned. Look back over your notes and questions. Maybe PUBLICATIONS some of your questions have been answered, In addition to the material presented in the but perhaps you still have some that are notreading listat the front of this book, many :Answered. Without looking at the training course, other publications are available for you to study write down the main ideas that you have gottento further your knowledge and aid you in advance- from studying this unit. Don't just quote the book. ment. Taking a correspondence course, for ex- If you can't give these ideas in your own words, ample,is a very good method of learning a the chances are that you have not really mastered subject. the information. Other sources of information are the tech- 9. UseEnlisted Correspondence Coursesnical manuals for each piece of equipment. whenever you can. The correspondence coursesThese manuals usually are published by the are based on Navy Training Courses or on otherequipment manufacturer, and consist of several appropriate texts. As mentioned before, com-sections giving a general- description of the pletion of a mandatory Navy Training Courseequipment, installition and operation instruc- can be accomplished by passing an Enlistedtions, and preventive and corrective maintenance Correspondence Course based on the Navy Train-procedures. ing Course. You will probably find it helpful Tactical doctrines, which also must be studied, to take other correspondence courses, as wellconsist of Naval Warfare Publications (NWPs) as those based on mandatory training courses.and Allied Tactical Publications(ATPs). Of Taking a correspondence course helps you togreat interest to Sonar Technicians is NWP 24, master the information given in the trainingAntisubmarine Operations, which sets forth anti- course, and also helps you see how much yousubmarine doctrine and tactical instructions for have learned. surface ships, aircraft, and submarines. Many 10. Think of your future as you study NavyNWPs have supplements, known as Naval War- Training Courses. You are working for advance-fare InformationPublications (NWEPs), which ment to third class or second class right now,give detailed technical instructions on how to but sonieday you will be Norldng toward higher carry out the doctrine found in the NWP. Some rates. Anything extra Mkt you can learn nowexamples are: NWIP 24-1, Antisubmarine Classi- will help you both now and later. fication Manual; and NWIP 23-8, Submarine Ap- proach and Attack Manual. Also of interest is ATP 1, Vol. I, Allied Naval Maneuvering In- SOURCES OF INFORMATION structions. One of the most useful things you can learn TRAINING AIDS about a subject is how to find out more about it. Most ships and stations carry a supply of No single publication can give you all the in-training films that are a valuable source of formation you need to perform the duties of your supplementary information on many technical and rating. You should learn where to look for ac-operational subjects. A selected list of train- curate, authoritative up-to-date information on ing films is given in Appendix I to this training all subjects related to the military requirementscourse. Magnetic tapes also are available for for advancentent and the professional qualifi-training in sound recognition, target classifica- cations of your rating. tion, and otheraspects of sonar operations.

8 CHAPTER 2

SUBMARINES AND ANTISUBMARINEUNITS

During World War II, submarines sent millions HISTORY AND DEVELOPMENT of tons of shipping to the bottom. Early in the war, England's lifelines were nearly strangled The first successful submarine was built in by German submarines. American submarines 1620 by Cornelius Van Drebel, a Dutohphysician. played a large role in the defeat of Japan byDuring repeated trials in the Thames River, he sinldng nearly all her merchant marine. Ob-maneuvered his craft successfully at depths of viously, the submarine is a potent weapon, 12 to 15 feet beneath the surface. requiring equally effective countermeasures. The Various other European designers of that United States and Great Britain were successfultime constructed submersible craft also, but in developing equipment, weapons, and tacticsthey failed to arouse the interest of any navy in that enabled the destruction of the German sub- an age when the potentialities of submarine war- marine force. Japan, however, never was able fare were inconceivable. to develop an effective defense against our Most of the early craft were of wooden frames submarines. covered with greased leather or similar material, Since World War II the submerged endurance and propelled by oars. Different methods of of the submarine has become sufficient to cause submerging were thought of and some were even difficulty in locating it. The problem increases tried. One inventor's design consisted of a number as the submarine goes constantly faster, deeper, of goatskin bags built into the hull, each connected and stays down longer. To cope with the modern to an aperture in the bottom. He planned to sub- submarine, we now have better detection devices,merge the craft by filling the skins with water, more modern weapons, and newer ships, butand to surface it by forcing the water out of the the battle for supremacy is a never-ending one. skins with a "twisting rod." Although his vessel was never built, it seems that this design was the first approach to the modern ballast tank. THE SUBMARINE Another inventor actually submerged his craft by reducing its volume as a result of contracting All Sonar Technicians are concerned with the the sides through the use of hand vises. hunt for and destruction of enemy submarines. Ideas were plentiful, some of them fanciful It is of especial importance, therefore, that youand grotesque, but some contained elements know the capabilities of enemy submarines, and capable of practical application. Lack of full know them well. Innumerable questions will comeunderstanding of the physical and mechanical to you over a period of time or after a courseprinciples involved, coupled with the well-nigh of events in antisubmarine warfare (A8W) opera- universal conviction that underwater navigation tions: 'How fast can a submarine dive or turn?was impossible and of no practical value, kept How does the submarine use depth? What is thepostponing the attempt to utilize a submarine in submarine's top speed when submerged? Because naval warfare during the early period. this text is unolassified, Many of the manors A submarine was first used as an offensive are of a general nature. In your studies, though, weapon during the American Revolutionary War. you will learn many details about submarine The Turtle, a one-man submersible designed chiricterittiOs and teak:m.1Mb lanwledge makes by an American inventor named David Bushnell it' Meier kir you to detect submarine* and bold and handoperated by asarewpreqieller attempted content after detection. Most of this tattoo:awnsto Birk a British f-war inNew York Harbor. our own submarines, but foreign navies usually The plan was to attach a charge of gunpowder to have submarines of comparable ability. the ship's bottom with screws and explode it with

9 INTRODUCTION TO SONAR

a time fuze. After repeated failures to force theaccurate device for locating a submerged sub- screws through the copper sheathing of the hullmarine. This device was a trainable .hydrophone, of HMS Eagle, the submarinegave up and with- which was attached to the bottom of the ASW drew, exploding its powder a short distancefrothship, and used to detect screw noises andother the Eagle. Although the attackwas unsuccessful, sounds that came from a submarine. Although it caused the British tomove their blockading the committee disbanded after World War I, ships from the harbor to the outer bay. the British made improvementson the locating On 17, February 1864, a Confederate craft,a device, during the interval between thenand hand-propelled submersible, carryinga crew ofWorld War II, and named it asdic afterthe eight men, sank a Federal corvette thatwas committee. blockading Charleston Harbor. The hitwas ac- American scientists further improvedon the complished by a torpedo suspended ahead ofthedevice, calling it sonar, a name derived fromthe Confederate Hun ley as she rammed theUnion underlined initials of the words sound navigation frigate Housatonic, and is the first recorded and _ranging. instance of a submarinesinking a warship. At the end of World War II, the United States The submarine first becamea major com- improved the snorkel (a device for bringing air ponent in naval warfare during World WarI, to the crew and engines when operating sub- when Germany demonstrated its full potentiali-merged on diesels) and developed the Guppy ties. Wholesale sinking of Allied shippingby (short for greater underwater propulsion power) the German U-boats almostswung the war inis a conversion of the fleet-type submarine of favor of the Central Powers. Then,as now, the World War II fame. A Guppy submarine isshown submarine's greatest advantagewas that it could in figure 2-1. The superstructurewas changed operate beneath the ocean surface wherede-by reducing the surface area, streamliningevery tection was difficult. Sinking a submarinewas protruding object, and enclosing the periscope comparatively easy, onceit was foundbut shears in a streamlined metal fairing. Perform- finding it before it could attackwas anotherance increased greatly with improved electronic matter. equipment, additional battery capacity, and the During the closing months of World WarI, addition of the snorkel. the Allied Submarine Devices InvestigationCom- The world's pioneer nuclear-powered sub- mittee was formed to obtain fromscience andmarine is the USS Nautilus (SS(N) 571). (See technology more effective underwaterdetectionfig.2-2.) The Nautilus,commissioned in Sep- equipment. The committee developeda reasonablytember 1954, is 320 feet in length, witha

71.10461 Figure 2-1.- -Guppysubmarine*

10 Chapter 2 SUBMARINES AND ANTISUBMARINE UNITS

^.",^ . . we:

11.111016...-

71.1 Figure 2-2. USS Nautilus (SSN571).

4t.' 4..2

71.1 Figure 2-3.-1168 Mariano Vallejo (SSB(N) 658).

11

114 INTRODUCTION TO SONAR standard surface displacement(ssd) of 3180tanks. To surface the submarine, compressed tons, and is designed for traveling faster underair expels the water from the tanks. the water than on the surface. An intensive building program for nuclear Probably thesmallest submarines in the submarines has been in effect for several years,world belong to the ex-German Seahound class and many new ships have joined the fleet. The(now in Russiaii possession). They are 49 feet UM George Washington (SSB(N) 598) was thelong and displace only 15 tons. Somewhat heavier, first submarine designed to launch, while sub-but still in the midget submarine class, are the merged, the Polaris missile. The USS Mariano,U. S. Navy's X-1 and the British Shrimp class. Vallejo (SSB(N) 858), shown in figure 2-3, isThe X-1 is less than 50 feet long and displaces the 40th, out of a programed 41, fleet ballistic25 tons. Boats of the Shrimp class are slightly missile subMarine to be commissioned. Herlonger and displace 30 to 5 tons. speed is in excess of 20 knots, and shecan At the othor extreme are the bulk of the dive below 400 feet. U. S. Navy's submarines. Included are the latest One of our fastest submarines is the USSnuclear-powered submarines. Some of these ships Skipjack (98(N) 585) (fig. 2-4), whose hull isaare over 400 feet long and displace more than radical departure from the conventional idea7000 tons (ssd). Others, designed for speed and of submarine hulls. Her diving planes areon maneuverability,are not quite as long, and dis- the sail, resulting in increased maneuverability.place less tonnage. Some submarines can cruise in excess of 20 knots submerged. A type of diesel submarine SUBMARINES IN GENERAL used by the Germans in World War II, and now a part of the Russian fleet, can dive at a rate A submarine ranges in length from aboutof 1 1/2 feet per second, and can turn 900 in 50 feet to more than 400 feet. Diving isac-a little over 1 minute, using full rudder and 5 complished by controlled flooding of ballastknots of speed.

;'!'

.:4=r0:4

4W-4 ;: lY t. .e C

Chapter 2SUBMARINES AND ANTISUBMARINE UNITS

PROPULSION Torpedoes Conventional submarines use diesel engines The torpedo is a self-propelled underwater for propulsion when surfaced, and batteries whenweapon having either a high-explosive or a submerged.Nuclear-powered submarines getnuclear warhead. Conventional warheads are their propulsion from atomic reactors. loaded with up to 1000 pounds of HBX explosive. Underwaterexplosion,of the torpedo warhead Conventional Submarines increases its destructive effect. When a pro- jectile explodes, a part of its force is absorbed When on the surface, a submarine's twinby the surrounding air. Upon explosion of the screws are turned by electric propulsion motorstorpedo warhead, the water transfers almost the powered by generators driven by diesel engines.full forceof the explosion to the hull of the Upon submerging on snorkel, virtually the sametarget ship. performance can be had, but depth of submergence Fleet-type and Guppy submarines are fitted is limited to the length of the snorkel mast.with 10 tubes, 6 in the bow and 4 in the stern. Submerged to greater depths, the submarine reliesSpare torpedoes are carried in ready racks near on large banks of storage batteries to drive itsthe tubes. On war patrol, a submarine of this electric propulsion motors because combustiontype usually puts to sea with a load of 28 torpe- engines require far more air than is available.does aboard. Here, endurance is limited strictly to the con- Torpedoes are propelled by gas turbines or dition of the batteries. Theoretically, if batterieselectric motors. Turbine types have maximum are well charged, a speed of 1 knot can be main-speeds of 30 to 45 knots, with a maximum ef- tained for about 50 or 60 hours. At full speed,fective range of as much as 7 1/2 miles. Elec- however, the batteries are exhausted after ap-tric torpedoes usually have less speed and range proximately 1 hour. than turbine types, but from the submariner's One way of forcing a battery-powered sub-point of view, they have the advantage of leaving marine to the surface is to outwait its stayingno visible wake. power. The submarine eventually must use its Torpedoes are of the straight-running, acous- snorkel, or surface, to recharge batteries andtic homing, or wire-guided types. The straight- replace air. running torpedo has automatic control devices that hold it on a preset course at a preset depth, whereas the acoustic homing type can steer it- Nuclear Submarines self toward its target. It may be either active or passive. The active acoustic torpedo sends Atomic power has brought close to reality theout pulses of sound and homes on the echoes that dream of having a true submarine, that is, one ofreturn from the target. Passive types home on unlimited submerged endurance and range. Thethe noises emanated by the target. The wire- Nautilus refueled for the first time over 1 yearguided type of torpedo is directed to the target after she commenced operating. The Tritonby signals sent through the wire from the launch- circumnavigated the world completely submerged.ing submarine. The Nautilus and Skate pioneered exploration of Two new submarine weapons are Astor and the north polar seas beneath the icecap, allmadeSUBROC. Astor is an electric-propelled Mk 45 possible only by nuclear energy. The human factor,torpedo with a nuclear warhead. It is wire- and the quantity of supplies that can be carried,guided to the target, and has a range of over are the main limitations to the endurance of10 miles. The' SUBROC is an antisubmarine modern submarines. rocket with either a conventional or a nuclear warhead, and has a range of over 20 miles. After it is launched from thesubmerged SUBMARINE ARMAMENT submarine, SUBROC's solid-fuel motorigsi, and the rocket enters the air. At some point Armament of a submarinedepends on its in its trajectory the rocket motor separates design and mission. The attack-type submarinesfrom the missile. The missile, which is di- normally carryonly torpedoes, but they mayberected to its target by an inertial guidance employed as minelayers. Fleet ballistic missilesystem, makes a supersonic reentry into the submarines carry 16 Polaris missiles, and theywater, sinks to a predetermined depth, and have 4 torpedotubesforward. explodes. or, INTRODUCTIONTO SONAR

Mines ANTISUBMARINE UNITS Navy mines are thin-cased underwater weap- Antisubmarine (A/S) iorces are composed of ons with a heavy load of high explosives. Theyspecial design ships, aircraft, and submarines. may be laid by both aircraft and surface craft,Their purpose is to seek out and destroy enemy but submarines are employed for mine layingsubmarines. Aircraft carriers of the CVS type when secrecy is required, or when the area to(with fixed wing aircraft and helicopters em- be mined is beyond the range of aircraft. Minesbarked), together with a number of destroyers, may be of the bottom, moored, or drifting type.form hunter-killer (11/K) groups, whose primary Bott Om mines rest on the ocean floor, and aremission is to deny an enemy the effective use highly effective in shallow water. Moored minesof his submarines. Guided missile destroyers, are positively buoyant. A cable, attached to anwhose chief functionis defense againstair anchor on the sea bottom, holds the mine at aattack, also have A/S capabilities. Nuclear at- predetermined depth beneath the surface. Drift-tack submarines are also assigned to 11/K groups. ing mines float freely at or near the surface.The SSNs are especially effective in A/S opera- Mines may be actuated by contact with a vessel,tions because of their ability to select the depth by a vessel's magnetic field, by noise, or byproviding the best sonar conditions, their long pressure differences created when a vesselendurance and maneuvering capabilities,and passes over the mine. Acoustic-, pressure-, andthe type of weapons they carry. Elements of a magnetic-influenced mines may be set to permittypical hunter-killer group are shown in figure the passage of several ships,then explode under2-5. the next one to pass over. SHIPS Missiles The destroyer-type ships (DDs) are the prime Specially designed fleet ballistic missile sub-submarine hunter-killers. They operate in 11/K marines, as mentioned earlier, carry the Polarisgroups, screen convoys, carriers, and other naval missile, adding tremendous strildng power to thevessels against submarine attacks, and provide submarine fleet. The latest Polaris model, theprotection against air attack. AS, has a 1-megaton nuclear warhead, with a Destroyers range in size from 2100 tons to range of 2500 miles. An improved Polaris, callednearly 8000 tons displacement. From about 5000 the Poseidon, will have the same range astons up they usually are designated frigates (DLs). Polaris, but double the payload, with multi-Destroyer escorts (DEs) are somewhat smaller ple warheads to confuse enemy defense sys-than regular destroyers, although the latest type tems. of escort is larger than many World War II destroyers. Ships with guided missile capability have the letter G added to their designation MANEUVERABILITY (DDG, DLG, DEG). Antisubmarine armament carried by frigates Modern nuclear submarines present a seriousof the type shown in figure 2-6 consists of problem to antisubmarine (A/S) forces. HolddownASROC (antisubmarine rocket), located behind tactics used to force conventional submarines tothe forward missile launcher, and A/S homing Melee or snorkel to recharge batteries, aretorpedoes amidships on each side. Some of the ineffective against nuclear submarines becauselatest DLGs fire ASROC and Terrier missiles they do not use batteries for submerged opera-from the same launcher. tions. They can remain submerged on nuclear Guided missile destroyers have essentially power for indefinite lengths of time. The attack-the same A/S armament as frigates. The arrange- type submarines are faster when submerged thanment varies between classes. Some DDGs have on the surface. Moreover, they exceed the speedsthe ASROC launcher forward, behind the 5"/54 Of many types of surface ships. Their sail-gun; others have it amidships, as seen in figure mamted diving planes permit radical maneuvers2-7. almost like those of an airplane. Actual operating Conventionaldestroyers (DDs)that have depths are classified, but the modern submarineundergone the fleet rehabilitation and moderniza- can go considerably deeper than the World Wartion (FRAM) program have either ASROC or II Wm DASH, in addition to their Ws torpedoes. (The Chapter 2 SUBMARINES AND ANTISUBMARINE UNITS 11M11111,

."'" . . , ...

_ ir

F

194.102(71) Figure 2-5.A typical ASW hunter-killer group.

134.84 Figure 2-6.USS Gridley (DLO 21).

15 INTRODUCTION TO SONAR

-a-

38.272 Figure klezziASROC launch from USS Henry B. Wilson (DOG 7).

.,..., .

., . ,- .7-.7-*- ... iii --4, ...... I. '.--1 '41,...--- ;',...... :::;7.-;?....'r. it 4". z -1,00se.. '541. ''''.* ,..p.101.44,,

..-- .-ft, L-..',:ftr'. .,

^4.20.1 44- ,:rrs 41.4111Milar9111 trX;1'

Ma.

3.130 .Figure 2-8.DASH taking off from a destroyer.

16 Chapter 2 SUBMARINES AND ANTISUBMARINE UNITS

t

ET

134.87(1047) Figure 2-9.USS vole WE 1047).

3.115 Figure 2-10.ASW bilicopter using clipping goner. INTRODUCTION TO SONAR word dash is formed from the underlined letters a new naval tactical data system (NTDS) for of the term drone antisubmarine helicopter.) antisubmarine warfare (ASW) application. (See fig. 2-8.) It is a pilotless, remotely con- All the destroyer-tyPe ships mentioned have trolled helicopter, capable of carrying 2 homing the latest sonar equipment compatible with the torpedoes or a nuclear depth charge to a target type of ship. The newer ships have bow-mounted several miles away. sonars. Some ships also have variable-depth sonar (VDS) installed on the stern. The ASROC is the shipboard counterpart of Practically all destroyer-type ships are con- the submarine's SUBROC.Itis a solid-fuel ventionally powered, the exception being the few rocket that carries either a homing torpedo or ships in the USS Bainbridge (DLGN 5), which a nuclear depth charge to a range of 5 miles. have nuclear-powered propulsion systems. The Like the SUBROC, it is unguided during flight. Navy of the future, however, will doubtless have When the torpedo is used, a parachute slowsa greater proportior of nuclear-powered sur- its descent to the surface. On contact with the face ships, just as our submarine force has sea, the parachute separates and the torpedo today. Conventional destroyers mist refuel every begins its active acoustical search. few days, restricting their freedom of movement. The destroyer escort USS Voge (DE 1047), In contrast, the Bainbridge, in company with shown in figure 2-9, Is one of -newest shipsUSS Entermise (CVAN 65) and MS Lona Beach in the modern design DE 1040 class. She carries (CGN 9), made a 30,000-mile voyage around the ASROC and A/S torpedoes, and win evaluateworld without refueling or replenishing supplies.

KV

.71

1%"1

r

.awzi., .= - -- - , ra- --,0,, .-...k trt,..-w...

4, Vile!-

134.95.5 Figure 2-11.-5-2 Tracker, A/S search and attack aircraft, with MAD probe extended.

18 Chapter 2 SUBMARINES AND ANTISUBMARINEUNITS

AIRCRAFT by variations in the earth's magnetic lines of force. Aircraft also use other devices for detecting the presence of submarines. One of these devices The use of aircraft in conjunction with ships is the sonobuoy, which is dropped into the water and submarines adds greater capability andby the aircraft and then monitored by radio. versatility to ASW. Areas of surveillance can Sonobuoys are described in chapter 8. be enlarged, ranges extended for detection and The aircraft also can be usedas a tactical attack, and a diversified use of weapons utilized. device to carry a weapon to the submarine. Among Two types of aircraft are used in ASW: the the weapons that can be launched froman aircraft helicopter for close ranges, and the fixed-wingare the homing torpedo and the nuclear depth aircraft for long ranges. The helicopter uses a charge. Figure 2-11 shows an aircraft of the dipping sonar; that is, one that may be lowered type carried aboard a CVS. Another type ofair- from the aircraft for searching, as shown in craft used in ASW is the P3 Orion, which is land- figure 2-10, and retracted for flight. Fixed-wingbased. The Orion is a long-range patrol plane, aircraft use magnetic anomaly detection (MAD) and carries highly sophisticated electronic de- equipment whereby they detect the submarine tection equipment.

ar,

19 CHAPTER 3 BEARINGS AND MOTION

In studying bearings and motion, you mustequipment we are able to compensate for many remember that they are of two types. The of the variables and obtain exact positioning two types of bearings are true bearing, whichinformation. Electromechanical computers are uses true north as a reference, and relativeutilized insolving many of the problems of bearing, which uses ship's head as a reference.target bearing and motion. It must be borne True motion is the movement of an object acrossin mind, however, that direction and distance the earth. Relative motion is the movementmust be obtained first, then reported by the of one object in relation to another object.operator before the computer can be set up This chapter discusses both types of bearingsto produce a correct solution. Thus, the ability and both types of motion. It shows how theyto determine and report the correct bearing are applied in determining the location andand range as speedily as possible is of the movement of an underwater target, such asutmost importance to the entire attack problem. a submarine. With modern sonar, it is possible to locate SONAR INFORMATION and track a submarine with dependable accuracy. In order to make full use of precision equipment, Sonar provides the tem items of informa- it is necessary to evaluate bearings and motiontiondirectionand distance from which we correctly and thus avoid setting erroneous valuesderive all subsequent data. Direction and distance into the equipment computers. are referred to as bearing and range. Correct interpretation and transmittal of bearing and REQUIREMENTS FOR LOCATING range informaron are deciding factors in success- SUBMARINES fully conducting any attack. Many landmarks and familiar objects onBearing land can be utilized for establishing a position and determining the location of a particular . The direction of the echo from the sound point. In civilian life we were accustomed totransmission source is called the bearing. Bear- such descriptive terms as "The third houseing is measured clockwise in degrees of azimuth on the right," or "Just a mile down the highwayin three figures from 000° through 380°. Azimuth at the big signboard." At sea, though, we mustis defined as a horizontal arc of measurement adjust ourselves to doing without the convenienceof the horizon in degrees. One quarter of a of familiar objects and use other means at our circle is 90° and a full circle is 380°. disposal for locating a target. Targets visible Until a few years ago, an allowance of 2-1/2° on the surface or in the air can be pointed out,for error in bearing was considered within limits but an unseen underwater object must be locatedof tolerance in antisubmarine attacks. Today, in a manner that is both clear and accurate.this standard of tolerance has been reduced to This method of location is accomplished byapproximately 1'. A bearing error of 2 -1 /2' at using sonar to determine the object's direction100 yards amounts to a position error of 4.36 and distance from the sound transmitting ship.yards; at 2000 yards this error is 87.3 yards. In chapter 4 you will read about the numerous With a bearing error of 1°, we are off target variables affecting the travel of sound beams inonly 1.75 yards at 100 yards, and 35 yards off watet. These variables greatly affect the pre- at 2000 yards. As you can see, modern equipment cision with which the exact location of an under-has provided greater bearing accuracy. No doubt water target can be determined. With present-day future sonars will give even better accuracy, rmivivoltImvirewo9trt,..VVE4-1,14M"MITr.7

Chapter 3BEARINGS AND MOTION but remember that the finest equipment will 3000 "Rangethree thousand, closing." always need a competent operator. 2500 "Rangetwo five hundred.". 1750 "Rangeone seven five zero." Range 1100"Rangeone one hundred." The distance from the sound source to the 1000"Rangeone thousand." target is called range. In sonar, range always 800 "Rangeeight hundred." is expressed in yards. With modern sonar equip- 660 "Rangesix six zero." ment, range detection varies from less than 150 "Rangeone five zero." 100 yards to thousands of yards. Ranges can be 400"Rangefour hundred, opening." measured to an accuracy of 1 percent of the range scale in use. To achieve this accuracy It should be noted that the word "yards" is you must have up-to-date knowledge of water never included in a report, because ranges conditions and be able to make adjustments to always are given in yards. the equipment to compensate for variations in One range report by itself is insufficient to the velocity of sound. conduct an attack, although such information as Range is reported in thousands and hundreds whether the range is opening, closing, or constant of yards. Some sample ranges, and the manner is of vital significance. A succession of both in which they are reported, are listed here for bearing and range reports is required to deter- your information. mine target location and motion.

SONAR CONTACT, BEARING 130

SONAR CONTACT, SEARING 045

SONAR CONTACT, BEARING 230

. 71.3 Figur3-1. True bearings are independent of ship's head.

21 r.

INTRODUCTION TO SONAR

BEARINGS operpting procedures are based on true bearings. You need to understand relative bearings,how- In establishing a bearing, we invariably mustever, inasmuch as casualties to thegyrocompass have a reference point to ensure that thedirection necessitate shifting torelativebearing pro- is always the same. True bearing is referencedcedures. to true north regardless of the directionor Relative bearings are read in degrees clock- motion of the ship. Relative bearing isalways wise from the ship's bow, which is always 000°. referenced to the ship's bow. In allinstances, If a contact is broad on your ship's portquarter, bearings are reported in degrees andare readthe relative bearing is 225°. Ifa contact is on clockwise. your starboard beam, the relative bearing is Sonar bearings are reported in three figures, 090°. Figure 3-3 diagrams these twoexamples, and you say "zero" instead of "oh." Asonar illustrating how relative bearings are determined. contact due east of your ship is reportedas When the ship changes course, the relative "Sonar contact, bearing zero niner zero."If bearing of a target changes. In figure 3-4the the contact were due west, it would be reported ship changes course 60° to the right. Thiscourse as "Sonar contact, bearing two sevenzero. change causes the relative bearing of thetarget Notice in the foregoing examplesthat the to change from 090° relative to 030° relative. word "true" is not used. Unless stated other- Relative bearings can be read on thesonar wise, always assume that bearingsare reported as true bearings. console from the same dial that givestrue If a gyro failure occurs,bearings, although not at the same time. Ifa relative bearings must be used, and the sonar\complete gyro failure shouldoccur, this dial operator will add the word "relative" to hisautomatically indicates relative bearing. Occa- bearing report. If he wishes, the operatorcan sionally,the gyro may act erratically fora avoid saying "relative" after each reportby few moments, causing the pictureon the scope stating "All bearings will be relativeuntil to jump, making it &Moult for the operatorto further notice." t track the target. To obtain a presentationwith morestability, the operator can control the TRUE BEARINGS equipment so th&t a relative picture ispre- sented on the scope, the dial indicating relative To i llustr ate that true bearings are independent bearing. of the ship's heading, figure 3-1 shows three Figure 3-5 typifies a bearing indicator from different bearings. The ship and the contacthave which true and relative bearingsmay be read been drawn in to show that, although the shipsimultaneously. This type of indicator, used in has a different course, the true bearing ofthe earlier sonars, is a good example forshowing contact remains the same. In the illustration,the comparison of true and relativebearings. compare the examples on theleft with the The outer dial, which is fixed,indicates examples on the right. relativebearing. The inner dialis free to All shipboard and submarinesonar sets utilize rotate. When connected electrically to theship's a gyrocompass repeater to provide true targetmaster gyrocompass, it acts asa gyro repeater bearing by reading the sonar bearing markerand shows ship's course and true bearing.The against the dial. Figure 3-2 shows this dialas diamond-shaped pointer between the two dials it is in a standard shipboardsonar set. Theindicates the direction in which the soundre- section enclosed within the dotted lines isthe ceiveristrained.Both relative bearing and area visible to the sonar operator through thetrue bearing are read by observing theposition glass window. The marker at the top,which of the pointer. can be seen through the transparent bearing True course is read on the inner dialopposite dial, indicates the bearing to which theoperator 000°R on the outer dial. As shown infigure 3-5, has trained the cursor on thescope. Because ship's course is 0456, anda contact broad on the. cursor normally is positioned in themiddle the starboard bow (045°R) hasa true bearing of the target presentation,the dial marker of 090°. indicates the center bearing of the contact. STERN LINE INDICATOR RELATIVE BEARINGS With modern scanning sonars,the sonar True bearings are the ones .of principaloperator has an ideal picture of antisubmarine concern to Sonar Technicians 'because standardaction. He not only receives the audioresponse, Chapter 3BEARINGS AND MOTION

45.29(71)A Figure 3-2. Bearing dial assembly.

BOW OF YOUR SHIP DEAD ALWAYS IS 000° AHEAD RELATIVE 000° A PORT I' BOW ALL BEARINGS \ MEASURED ;4 CLOCKWISE FROM THE BOW 030° RELATIVE BROAD UN 0 BROAD ON PORT 2 se STARBOARD BEAM BEAM cm

PORT QUARTER sivo QUARTER moo !(.\ 090° RELATIVE ASTERN\____,

45.29(71)B 45.29(71)C Figure 3- 3. Relative bearings. Figure 3-4.Relative bearing change.

23 INTRODUCTION TO SONAR

j4T1VE BEARING BEARING 350 0 TARGET 340 CURSOR ECHO

45.29(71)K STERN EXPANDING NOISE Figure 3-5. Bearing andcourse indicator. CURSOR CIRCULAR INDICATIONS SWEEP 46.29(71)J but is aided by a videopresentation 360° in Figure 3- 6.- -Stern line indicator. azimuth. The presentation isa true picture of the area surrounding the ship,and, (with excep- tions noted later in the text) it doesnot change with alterations in ship's to course changes, so that he thencan be course. prepared to make adjustments to keep thebearing Although the video presentation isindependent cursor on target. of ship's heading, the .SonarTechnician needs When looking at the scope, it to be constantly aware of theship's course for is best to purposes of conducting search arcs; performing picture the ship as in the centerof a small segment of the ocean, with theocean always control manipulations, and reporfingsonar in- oriented to true north at the top of formation. Ship's course informationis provided the scope. in the form- of a stern line, The ship turns in the center, andits direction on the fade of the is shown by the stern line to indicatethe recipro- scope. The stern line, illustrated in figure 3-6, cal of the true course. is presented as an illuminated brokenline, which, as its name implies, indicates the directionof GYRO FAILURE the' 'ship's stern. If this' line ,indicatedthe bow Of the ship, it would be mucheasier tiiInterpret When the gyro is operating, the ship's course. Because mostsonar intormatiOn top of the comes from forWard, however, scope is north (000° true). When thegyro is : the'addition of inoperative, he top of thescope is 000° relative the stern, line. indicator in thatdirection would (ship's head). tend to alUtter the scope unnecessarily;:. The first indication ofa gyro casualty is NorMally, with the ship'sgyro operating, the erratic movement of the stern lineor the own ship's Movement 'does tot appreciablyalter illumination of the red GYRO OFF lighton the the 'presentation on the scdpeiOnly the stern sonar console. Any failure of gyro input to the line indiditdr 'shows ' whenthe ship is turning or if a course 'change'' lies` ocdurretL, sonar causes the sternline,to swing to 180° When relative, where remains as long as thegyro turning right, the stern line movesclockwise; inputs are cut off. If the ship is when turning left, itmoves counterclockwise. headed for a Movement of the stern line alerts target when the gyro fails,the target echo the operator moves to 000°relative. Thus, the shipmay 0

rrTri9r,..MP

Chapter 3BEARINGS AND MOTION 000

STERN_ BEARING 270 SUB 090 LINE CURSOR

TRUE PICTURE IGO RELATIVE PICTURE

A B Figure 3- 7. Effect of gyro failure. 71.4 be heading for a target bearing 090° true, butbearing is 029° and the ship's course is 027° the target echo- is presented at the top of thetrue, for instance, as in figure 3-8, you can see scope. that the true bearing of the target is 056°. The The effect of gyro failure is illustrated intrue bearing is obtained by adding the ship's figure 3-7. Part A shows the scope with normal course and the target's relative bearing. Thus, gyro input. The submarine is located to the by the formula we have: right of center. The stern line is at 270° and indicates that the ship is on course 090° true 027°T + 029°R is, 056°T. and headed for the contact. With a gyro casualty, the stern line will Now examine figure 3-9. The ship is on a swing 90° counterclockwise. The entire videocourse of 180° true, and the target is at 251° presentation will change a like amount in therelative. Again, it is easy to determine true same direction as shown in part B of the illus- target bearing by applying the formula as before: tration. To remain on target, the bearing cursor must also be trained,90° counterclookwlse. The 180°T + 251°R431°T. dials-below the kappa in the Illustration indicate , . the directIon, in wlIoh the bearing ;cursor is This time the bearing is greater than, 360°.. When trained coPtagt.. the answer exceeds 360°, you must subtract this figure to obtain the correct answer. Thus: CONVERTING TRUE AND.11ELA.TWE BEARINGS 180°T + 251°R =, 431°T360°T = 071°T.

Even though you lose gyro input to the sew, RULES FOR 'CONVERSION' you can easily .. determine the true bearing of the target if you know your ship'43, course and Certain rules are established for converting the relative_ bearing of the target. If ,the relative true and. relative. bearings. After each rule is

25 INTRODUCTION TO SONAR

SHIP'S HEAD

027° 071° , / 029° RELATIVE 4111 / \ee/TARGET e I 056° e 251° / RELATIVE ee o /1 e I/ . e / ee 180° /ooeee eee

OWN SHIP SHIP'S HEAD 45.29(71) F.2 45.29(71)G.2 Figure 3 -8. Target at 056° true. Figure 3-9. Target at 071° true.

stated, the mathematical formula representing If the true bdaring is less than the ship's the rule is given. The formulas are expressedcourse, 360° must be added to the, true bearing in firecontrol symbols. By means of thesebefore subtracting ship's course. Relative target symbols we avoid detailed explanations of thebearing equals true target baring plus 360° values or measurements. Following are theminus own ship's course. fire 'control' symbols used in these formulas. ByTruetarget bearing. B = By + 360° - Co BRelative target bearing. CoOwn ship's course. If the true target bearing is 045°T and ship's course is 270° true, for example, we find the True target bearing equals relative targettarget's relative bearing thus: bearing plus own ship's course. In formula, this rule is expressed thus: 045°T + 360° = 405° - 270° =-1 135°R By = B + Co If the true bearing, "as oomputed, is greater MOTION than 360°, that value must be subtracted from the total. Our rule now is: True target bearing As mentioned at the beginning of this chapter; equals relative target bearing plus own ship'sthe two types of motion are true and relative. course minus'360°. The Sonar Technician must have a thorough By.= B + Co-360° understanding of both types of motion in order to interpret target movement correctly and to If "you...know'your,course and the true targetgive assistance in making an attack. bearing, the formula may be worked in reverse to obtain the relative target bearing. RelativeTRUE MOTION target bearing equals true target bearing minus own .shipts course True" motion 10 the movement of an object across $he' earth, using true (geographic) 'north ?B Byx - Co is the reference point.

26 ' . 4e!...t . . I 17., Chapter 3BEARINGS AND MOTION

RELATIVE MOTION During the change in course, the ship also moves at right angles to the original course. Relative motion is the apparent movement The distance the ship moves at right angles to of an object in relation to another object. Dothe original course during the turn is called not confuse the concept of relative motion with transfer. The amount of transfer, as with advance, relative bearing. Relative motion is measured depends on the amount of turn, ship's speed, as a true direction of apparent movement. and amount of rudder angle. You may have been unaware at the time, Advance and transfer vary with each type but on many occasions you have witnessed theof ship, and even with ships of the same type. solution of relative movement problems. When Each ship, therefore, makes her own advance a baseball player races to catch a high fly ball, and transfer tables for various rudder angles or when a football quarterback throws down- and at different speeds. field to a receiver, the players are estimating As you can imagine, advance and transfer relative movement. As an example, assumewill affect target bearings during a turn. All your ship is on a course of 000° at a speed ofpossible, situations cannot be explained here 20 knots. You are overtaking and will pass because there are almost unlimited combina- close aboard aship that is also on course tions of target and attacker relative movements. 000°, but whose speed is only 10 knots. As If the target is on your port beam, for example, you close the ship, the' bearings to him draw and has the same course and speed you have, aft. Eventually you pass him and he falls further when you turn left to head for him, his bearing and further behind. His relative movement from will change to the right. Figure 3-11 illustrates you is approximately 180°, but his true move- the effect of advance and transfer on bearing ment is 000°. when the target is stationary, or nearly so. Following are three rules pertaining to relative motion you must remember when making an BEARING DRIFT attack on a submarine. Figure 3-10 illustrates these relative motion situations. When the sonar operator detects an under- 1. If range is closing and the bearings arewater target, he reports the bearing and range. drawing toward the bow, your ship will The conning officer then turns the ship to head pass astern of the submarine. for the reported target. As the ship turns, the 2. If range is closing and the bearing re- bearing cursor is trained back and forth across mains steady, the ship will pass directlythe target to check for bearing width, and the over thesubmarine.(If the submarine target is classified. - The operator then places were on the surface, a collision would the cursor in the center of the target pip. The result.) cursor shows direction of sounereception. Its 3. If range is closing and the bearings are length indicates range when the cursor line is adjusted to touch the target echo. With the ship drawing aft, the ship will pass ahead ofheaded for the target on a steady course, and the submarine. at a constant speed, with the cursor bisecting the echo, any change in target bearing results ADVANCE AND TRANSFER from target movement. If the target moves to When a ship changes course to head for athe right, the operator must train his cursor new bearing, she does not move as a car does to the rightin order to remain on target, on land. Water is a fluid substance, and itreporting "Bearing drift right." If the target does not allow the ship the advantage of goodmoves to the left, he must train his cursor to traction. As rudder is applied to a ship, athe left to remain on target, and reports "Bear- short period ensues before the rudder takes ing drift left." hold in the water. During the turn, the stern In an attempt to evade the attacking chip, of the ship actually slides through the water.the submarine will maneuver. The attacking As it slides, the ship tends' to advance in theship, in turn, changes course as necessary to same direction of her .origlnalcourse. Thereach optimum weapon firing positionwhile distance the ship moves in the orienal directionmaintaining sonar. contact. Regardless of the until she is on the new course is called advance. number of course changes of 'the ship, or maneu- / The amount of advance depends on ship's speed,vers by the submarine, the job of the operator amount of turn, and amount of rudder angleis to keep the cursor on the target. Correct applied. bearings, ranges, audio response, and other

27 Nen,. T.,114%

INTRODUCTION TO SONAR

31S°

SHIP SHIP

1 BEARINGS DRAWING TOWARD THE BOW. 2 BEARING REMAINS STEADY. SHIP WILL PASS ASTERN OF SUBMARINE. COLLISION COURSE.

13 BEARINGS DRAWING APT. SHIP WILL PASS AHEAD OF SUBMARINE.

71.5 Figure10. Relative motion situations. Chapter BEARINGS AND MOTION

directly at the target.) In this illustrative case, 0000T assuming a depth charge attack, additional lead TRANSFER is applied at 700 yards. This maneuver is called attack lead. The amount of lead depends on

DEARING target aspect, target speed, and the sinking ADVANCE TARGET time of the depth charges. As this final attack lead is applied to the right, the bearings com- SEARING 090°T mence to drift left and aft, down the port side, until contact is lost at short range. At this stage of the attack, the operator must train the 71.6 cursor rapidly aft so as to regain contact as Figure 3-11. Effect of advanCe and transfer the attacking ship clears the submarine. on bearing. In almost every depth charge attack, you will follow the same procedure, once you detect a target on the scope. The cursor is trained on target data can be obtained only when the cursor the target and adjusted for range. You continue is kept positioned properly on the target echo. to bisectthe target, tracking the submarine ATTACK LEAD movements until contact is lost during the final stages of the attack. For an attack using ahead- Once target movement is determined, the thrown weapons, the procedures are basically conning officer turns the ship to point the bowthe same, except that contact is not normally ahead of the target. This maneuver is calledlost. The sonar operator must be alert for thecollision lead.Ifthe proper amount of rapidly changing bearings at short range. leadis taken,the target bearing ceases its drifting movement and remainssteady. The amount of lead depends on the type of attack DOPPLER AND. TARGET ASPECT and the weapon used. Depending on the speed and maneuvers of the target, it may become When contactis made on an underwater necessary to increase or decrease the leadobject, these questions require answers:. (1) so as to maintain a steady bearing during the What is it? (2) Is it moving? (3) In which direc- approach phase of the attack. Drift may be tion is it moving? determined correctly only if the cursor is posi- Classification steps, when executed properly, tioned properly to bisect the target echo atgive the answer to the first question. Doppler all times. The following example should help helpstoanswerall questions. Doppler, an clarify bearing drift and attack lead. acoustic phenomenon, is explained fully in chapter Assume that you (the sonar operator) gain4. At this time it is enough to know that doppler contact on a submarine bearing 090° true. (The up means the target is headed toward you; submarine!s course is 180°.) The ship turns todoppler down means the target is headed away head for the targetand steadies on course from you; and no doppler means the target is 090°. This maneuver is apparent when the stern either broadside to you and neither coming line steadies on 270°. Noticing that the bearing toward you nor headed away, or it is stationary. is drifting to the right (caused by advance and Assume that you have contact with a submarine. transfer during the turn and target movement), It has doppler, so it must be movingbut in you move the cursor to the right to remain on which direction? By this time the ship has target, and report "Bearing drift right." There- turned to head for the target, enabling you to upon, the conning officer changes course to the arrive at the answer to the third question. If right to establish a collision lead. With colli-doppler is up, the target is moving toward the sion lead established, there. is no bearing drift, ship. If doppler is down, the target is moving relative movement of .the target on the scope away from the ship. is directly toward' the ship as. the ship' closes The operator's job is to determine the direc- the tirget, 'and .a true movement :in the direc- tion of target movement and report it. If the tion- of 180° ,(couise'of submarine), can be deter- submarine is headed directly at the ship, the mined from the video .presentation °mke scope target aspect will be direct bow and doppler by observation Of the target traces.(NOTE: will be up. If you are, headed at the target, and Remember that true bearing drift can be'deter- the target has bearing:. drift to the right with mined accurately only when the ship is headed no doppler, the target aspect is starboard beam. k a,

INTRODUCTION TO SONAR

SUBMARINE . Vi ill ta it

I I STBDPORT STBD BEAM I DIRECT PORT STBD DIRECT ASPECT I BOW I ------QTR. QTR STERN BOW PORT BEAM I I I I RIGHT I BEARING NONE RIGHT DRIFT I LEFT------LEFT I RIGHT NONE I LEFT I I

MODERATE MODERATE ). DOPPLER UP NO UP DOWN DOWN

-

71.7 Figure 3-12. Target aspect.

Figure 3-12 shows the five basic target aspects As the ship attacks, she makes minor course and theirassociated doppler. The degree ofand speed changes, but these changes have dopplerisdependent on target speed. Forlittle or no effect on target aspect or doppler. example: Doppler of a direct bow target with aIf the. ship circles the submarine, however, or high closing speed would be reported as "markedif the submarine makes a change in course, up." target aspect will change. A change in doppler Target aspect is best described as the relativeis the first indication that the submarine is position of the submarine with respect to thechanging course, and this change must be re- sound beam. Perhaps the easiest way of decidingported immediately. As soon as the new aspect which aspect the submarine is presenting is tocan be determined, it also must be reported. visualize it in the center of four quadrants and,During an antisubmarine attack (or series of by the process of elimination, solve for theattacks), aspect changes often. The sonar oper- proper quadrant. This proceduret gives a roughator'sJob is to detect, evaluate, and report aspect, and doppler and bearing drift will further each change as it occurs. define the exact aspect. Look at figure 3-13 to see how this solution is accomplished. Assume that your ship is headed for the target, and that initially you have a steady bearing with COMPUTING TARGET ANGLE high up doppler, which indicates that the ship and the submarine are headed directly for each Target angle,- which is ,e relative bearing, other. Next, you detect a bearing drift to thegives more precise informution on the course right, with . slight .up doppler. Quadrants A andof a ship' or submarine than does target aspect, B are eliminated because a target in eitherbut target angle is more difficult to obtain quadrant would have down doppler. A target inthan is -target aspect. In considering a destroyer quadrant C will hive up doppler, but the bearingmaking an attack on a- submarine, target angle drift will be to the left. ,Therefore, you wouldis the relative bearing of the destroyer from report "'Starboard bow aspect." the submarine.

30. A'

Chapter 3BEARINGS AND MOTION

DOPPLER DOWN DOPPLER DOWN

A B

BEARING DRIFT LEFT BEARING DRIFT RIGHT

NO DOPPLER NO DOPPLER

BEARING DRIFT LEFT TEARING DRIFT RIGHT

U. 0

C D

DOPPLER UP DOPPLER UP

OWN SHIP

71.8 Figure 3-13.Solving target aspect. Imagine that you are on board a submarinethe submarine changes Course, target angle looldng' 'at' an approaching destroyer. The rela-changesaccordingly. tive bearing of the destroyer is 090°, which Figure 3-14 illustrates several target angles. indicates it is approaching on the submarine'sAlso shown are angles on the bow (discussed starboard beam. As viewed from the destroyer, later) and related doppler. Notice that no matter the submarine's target, angle. is 090°, because in which direction the, shipis heading, the target angle is the relative bearing of the shipcourse of the ,submarine governs target angle. from the target, measured in the horizontal 'YOu. may be curioUs why. target aspect is so plane, from the bow.of the target clockwiselthportant. when target angle. provides, more accu- from 000° to 380°. Like target aspect, targetrate information. Aspect is given as a general angle depends 0n" target's heading. Whenindiaation and can 'be reported after only four

31

t. INTRODUCTION TO SONAR

angle, the submarine uses only 180°, specifying RE,ATIVE BEARING port or starboard side. To illustrate, a destroyer 40 SUBMARINE) TARGET ANGLE ASPECT DOPPLER has a submarine bearing 070°R. Aboard the 1 submarine the target angle would be reportedI ...... PORT BEAM as "Angle on the bow, starboard 70. A rela- A b 590 NO tive bearing of 345° from ship to target is reported on the submarine as "Angle on the bow, port 15.1' Figure 3-14 illustrates some angles on the bow. Target angle is not all guesswork. It can be computed accurately by using the formula: target angle equals true bearing plus 180° minus target course. Expressed in fire ,control symbols, the formula reads: Bts = By +180 - C, where STERN I47- Ab PI75 GOWN Bts = target angle. Bytrue bearing. C = target course. Assume that you are on a ship and tracking a submarine bearing 270°, course 135°. Find the target angle by applying the preceding for- mula. Thus: Bts = 270° + ItAle - 135° ..... zsi Bts = 450° - 135° 009 Bts = 315° IL STARBOARD FROM "T5. QUARTER I 3 SHIP An example of computing this target angle is Ab P95 SLIGHT seen in figure .3-15. In effect, the +180° in the DOWN OESTR OVER SUBMARINE FROM Sill formula allows the viewer to change places so that he may see his own relative bearing from the target. Compare the relative bearing of the destroyer from the submarine with the value 71.9 computed for target angle. Figure 3-14. Target angle. If the product of By + 180° is less than target course, 360° must be added to the equationbefore or five transmissions, based on doppler and subtracting target course. Example: A target the firstindication of bearing drift. Target is on course 270°, bearing 010°. angle, on the other hand, is derived from more precise data. It is necessary to know the sub- Bts = 010° + 180° marine's course, whioh can be determined only Bts = 190° + 360° by tracking the submarine for several minutes. Bts = 550° - 270° In many attacks, it is difficult to report an Bts = 280° accurate target angle because of radical maneu- Angle on the bow (Ab) may be computed in vers by the submarine or because of insufficient the same manner as target angle, with one time to determine target angle. In suoh in- exception. Because the answer is in degrees stances, target aspect information necessarilyof relative bearing, it must be converted to must suffice for the conning officer to, estimate degrees port or starboard. Referring again to the target angle, and adjust the attack leadfigure 3-15, you see that the destroyer bears accordingly. - 090°T and is on course 240°. .1n 'antisubmarine warfirei.there,is little time , . Ab , 090 190240° between, detection attack. :Target aspect thus Ab = 270°240° affords:. a: means: of reporting reliable informs- Ab = 030° or starboard 30. Lion quickly. f, . ,

Aboard a submarine, target ::angle,ie-deriVed If the answer is greater. than 180°, subtract by .a ,Method .knoWn. asangle;,on the bow, (Ab). the answer from 360° to obtain angle on the Whereas the ship uses 360° for computing target boW to port. ' , **.* 04,0 ,,,,,VM,...,...lt>...717311,5- Znr..l..2'tert.:Yfe?'-.."1tie.441F 7".r"P12,,,rA17;74.11:!.P,

Chapter 3BEARINGS AND MOTION

TRUE BEARING CIRCLES

RELATIVE BEARING CIRCLES

45.29(71)H Figure 3-15.Computing target angle.

Target course can be determined by thesubtracted from By. Conversely, if Ab is to formula C = By ± (180 - Ab). If Ab is to portstarboard, the solution within parentheses is the resultant of the figures in parentheses is added to true bearing. CHAPTER 4 PHYSICS OF SOUND

Sonar is an electronic device that utilizes sound energy as a means of locating submerged objects,such as submarines. The equipment may be either active or passive. Sonar of an active nature transmits the sound energy into the water and must depend on the returning echoes bouncing off the target to provide bearing 1111111111111INDIIIIWIAIVE111111111111 and range information. Passive sonar depends MED UM for bearing information on sounds originated by AIR the target (such as screw cavitation, machinery noises, and so forth). This chapter, then, deals with sound and its 71.18 behavior in sea water. Figure 4-I.The three elements of sound.

WHAT SOUND IS You may recall the experiment in which a Sound is the physical cause of your sensation bell was placed inside a jar containing a vacuum. of hearing. Anything that you hear is a sound. You could see the bell ringing, but you could Sound travels in the form of waves, whichhear nothing because there was no medium to vary inlength according to their frequency.transmit sound from the bell to you. What about A sound having a long wavelength is heard atthe third element, the detector? You may see a low pitch; one with a short wavelength isa source (such as an explosion)apparently heard at a high pitch. A complete wavelengthproducing a sound, and you know the medium is called a cycle, and the number of cycles(air) is present, but you are too far away to per second is the sound's frequency. Frequencieshear the noise. So far as you are concerned, are now measured in the Hertz system, 1 hertzthere was no detector and, therefore, no sound. (Hz) being equal to 1 cycle per second. Fre-For purposes of this text, we must assume quencies of 1000 cps or more are measured in that sound can existonly when an auditory kilohertz (kHz). Normally, sounds below 20 Hz vibration is caused by a source, is transmitted or above 15 kHz are beyond the human hearing through a medium, and is heard by a detector. range. Between these two frequencies is theFigure 4-1 illustratesthis assumption. The average human audible range. More information bell vibrates on being struck, thus acting as a on the characteristics of sound is given in thesound source. The vibrating bell moves the next section of this chapter. particles of airthe mediumin contact with it. And the sound waves travel. to the ear, which REQUIREMENTS FOR SOUND acts as the detector. Before sound can be produced, three basic Source elements must be present. (See fig. 4-1.) These elements are a source of sound, a. medium to Any object that moves rapidly to and fro, transmit the sound, and a detector to hear it.or vibrates and thus disturbs the medium around If there is no source to generate a noise, thenit, may become a sound source. Bells, radio there can be no sound. The same theory holds loudspeaker diaphragms, and stringed instru- true for the other required eleients. ments are familiar sound sources.

34 Chapter 4 PHYSICS OF SOUND

Medium RELATIVE POWER FOR AUDIBLE. SOUNDS Sound waves are passed along by particles of the material through which they travel. The 100,000 elasticity of the medium determines the ease, AVERAGE distance, and speed of sound transmission. The FREQUENCY 10,000 greater theelasticity, the greater the speed SENSITIVITY of sound. The speed of sound in water is about OF HUMAN EAR 1000 four times that in air, for example; in steel, 100 it is about 15 times greater than in air. 10 Detector 100 1000 10.000 The detectoracts as the receiver of the FREQUENCY HERTZ sound wave. Because it doesn't surround the source of the sound wave, the detector absorbs only part of the wave's energy, thereby neually 71.46 requiring an amplifier to boost' the signal's Figure 4- 2. Frequency sensitivity of the energy to permit reception of weak signals. human ear. THE EAR AS A SOUND DETECTOR ear at different frequencies. It is evident from The limits of human hearing are determined this chart that the ear is most sensitive to by two interacting phygical variables, frequency frequencies in the range from about 1000 Hz and intensity, and several other conditions that to 2000 Hz. The average person finds an 800-Hz are dependent on the individual variables (in- note a rather pleasant one to listen to for long cluding age, state of health, attention, and prior periods of time. In underwater echo ranging exposure). The limits of hearing, however, are equipment, the echo frequency commonly is normally between 20 and 20,000 hertz for young, converted to an 800-Hz note. healthy persons, provided the upper and lower Never turn up the volume on sonar equipment frequencies are sufficiently intense. For healthy, so that echo sounds are louder than necessary. middle-aged persons, however, the upper limit One reason is that the ear is not a sensitive may lie between. 12 and 16 kHz, the low-frequency detector of relative changes' in sound intensity. threshold 'remaining about 20 Hz. For purposes An increase or decrease of about one-fourth of this text, sounds capable of being heard are of the total power must take place before the called sonic*. Sounds below 20 Hz are called ear notices any difference. subsonics, and those above 15 kHz are known An intensely loud sound slightly paralyzes as ultrasonics or supersonics. The term "ultra- the ear, reducing its ability to hear low-intensity sonic" merely refers to acoustic phenomena sounds that follow immediately. This effect is above the level of human hearing. A 15-kHz similar to one you probably have experienced with vibration might be "ultrasonic" for the average light. If you look into a very strong light, your 60-year old person. eyes are blinded momentarily. Early active sonar equipments transmitted The ear is a sensitive detector of change in ultrasonic sounds through the water. Along with pitch. An average person can tell when sounds other sounds,. they received -echoes of these differ a few cycles in pitch, even though they ultrasonio'sOunda and converted them into audible cannot detect the change in intensity. This faculty ones.' Modern active sonars transmit soundsis known as pitch discrimination. It is a great within the audible range. Because these trans- help in selecting from a backgrotmd of reverbera- missions' are very high tones, however, thetions a submarine echo of slightly different equipment' converts theni into lowerones better pitch, that is, one with doppler. suited for liatening. Here's a summary of your ear's character- The 'human' -ear* is fr -good- sound' detector. istics: It can detect a wide 'range of frequencies, but does not respond -equally .vrell to all of them. 1. Your ear does not readily detect small Figure 4-2 illustrates the Variation in the amount relative changes in sound intensity. It is not of 'power that is barely audible to the average sensitive to high and low audible frequencies. . - . 0. WO. ,.,.%),11%,,,,,O,T .4 1,

INTRODUCTION TO SONAR

2. Your ear is sensitive to the 800-Hz note for which sonar equipment is designed. Your ear temporarily is paralyzed by very loud signals so that you may not hear the weaker signals that follow. RAREFACTION 3. Your ear hai the property of pitch dis- crimination. This characteristic will aid you in selecting an echo from the background of noise COMPRESSION and reverberation. TRANSDUCER Heavy gunfire may cause permanent deafness or other injury to your ears. Use ear protectors or cottun when near gunfire, and take every possible precaution to protect your hearing. As a Sonar Technician, you are essential to the successful fighting of your ship. Your ability to operate the sonar depends on the effectiveness of your hearing.

WAVES IN GENERAL Waves may be classified by types as trans- verse and longitudinal. A transverse wave is one wherein the particles of the medium through which the wave is passing move at right angles vertically to the wave's direction. In a longi- tudinal wave the particles move back and forth along the wave's direction 02 travel, resulting in compression and rarefaction of the wave. An example of a transverse wave is a water wave. Throw a stone, into a pool.A series of circular waves, travels away from the.. disturbance. In 4.221 figure 4-3 such waves are diagramed as though Figure 4- 4. Longitudinal waves. seen in cross section. Observe that the waves are a succession, of crests and troughs. The wavelength (1 cycle) is the distance from the SOUND WAVES crest of one wave to the crest of the next wave. The amplitude of a', transverse wave is half Sound waves are longitudinal or compression the distance, measured vertically from crest to waves, set up by some vibrating object such as trough, and serves to indicate the intensity of a sonar transducer. In its forward movement, the wave motion. the vibrating transducer pushes the water par- ticles lying against it, producing an area of high pressure, or compression. On the backward movement of the trans- ducer, ,.the water particles return to the area from, which they were displaced during com- pression and travel beyond, producing an area of lowpressure,,or a rarefaction. The com- pression moves outward by pushing the water particles immediately in front of the compressed = =, particles. The rarefaction follows the cbmpres- sion, transferring the,,,pull produced by the back- ward movement to the particles immediately ahead, The next forward movement of the trans- 71.19 ducer:produces . another compression and so on. Figure 4-S.Elements of a wave. In ligure 4-4 the compressions are represented

r1d? 36 mo-...xtvwsn.

Chapter 4 PHYSICS OF SOU,ND

substance is called density, and is defined as WAVELENGTH "weight perper unit volume." In the study of general physics, density of any substance is a com- Ct# parison of its weight to the weight of an equal volume of pure water. Because of the salt AMPLITUDE content (salinity) of sea water, it has a density greater than that of fresh water. Density is also an indication of the sound transmission characteristics of a substance, or medium. When a sound wave passes through a medium,itis transmitted from particle to particle.If the particles are loosely packed COMPRESSION RAREFACTION (as they are in fresh water as compared with sea water),they have a greater distance to move to transmit the sound energy. In so doing 71.21 time is consumed, and the overall result is a Figure 4-5. The sound wave. slower speed of sound in a less dense medium. Density and elasticity are the basic factors that determine sound velocity. The formula for by dark rings. As the sound waves spread out,determining velocity is: their energy simultaneously spreads .through an increasingly large area. Thus the wave energy becomes weaker as distance increases. C = Another way of representing the actions of P a sound wave is illustrated in figure 4-5.. Com- pressions are shown as hills above the reference line, and rarefactions as valleys below it. TheWhere c equals velocity, E equals the medium's wavelength is the distance from one point on aelaiticity, and p equals the medium's density. wave to' the next point of similar compression.Variations in the basic velocity of sound in the The change occurring in compression and rare-sea are paused by changes in water tempera- faction in the space of 1 wavelength is called ature, pressure, and density, as will be seen in cycle. the section on sound propagation. In fresh water of 65°F, sound velocity is approximately 4790 Frequency feet per second (fps).In sea water, velocity depends on pressure and temperature in addition The frequency of a sound wave is the numberto salinity. For all practical purposes, you can of vibratiOns per second produced bythe soundassume that sound travels at a speed of 4800 source. A sonar traniducer, for example, mayfps in 'sea water of 39°F. transmit On a frequency. of 5 *He; or 5000 vibrations per iecond. Motionis imparted .to Wavelength the sound wave by the backrand4orth movement of the, particles :of the Mednun, in ,effeCt Passing If a' sonar transducer vibrates at the rate of the wave along, althoUgh ,ther-partiolee them- 25,000 vibrations per second, and if the tempera- selves have very. actual movement. Theture is 39°F, the first wave will be 4800 feet Wave, hOvieier, may travel !great dietarioes-ataway at the end of the first second. Between the a high rate Of speed. transducer and the front of this wave there will

, be 25,000 compressions. Thus, the wavelength,

Density:: , that the...distance between ,pOints of similar "Perhapelyou'veheard People:speak ofheavycompression, mustbe '4800+25,000 or 0.192foot, ,fOg as being "thick as ,Pea souP.,', This murkybedatuie there are 26;000 compressions extending 'conditiOn irould' bi-' di .denee,.--fog :vaused-bY thethrough. a ;Clii3taiicie Of 4800 feet. The wavelength !atinospherei being 1:filbid *tb::.iniiitlVpititicles ofalways can be found if the frequency and the 'writer ; called 'VaPor.''Oendensation: .:forfilledvelocitf are known: Forinula: .atniosphere is heeler' -(becanse ,.theiVsreight 'of the thin a Oleg' atinos, WaVelength = . phere. The measUre' for this "thickness" --of' a Frequency INTRODUCTION TO SONAR

Suppose thewavelength is 0.4foot and the QUALITY frequency is12 kHz. What is the velocity? The quality of a sound depends on the com- plexity of its sound waves. Most sounds consist of a fundamental frequency (called the first harmonic), plus several other frequencies that are 12,000 exact multiples of the fundamental. The funda- mental is the lowest frequency component of the sound wave. By combining different fundamentals Expressed another way, velocity = 0.4 x 12,000 = in suitable proportions, a tone can be built up to 4800 fps. If the wave length and the velocity are a desired quality. Musical tones are produced known, the frequency can be found in a similar by regular vibrations of the source; when the manner. source vibrates irregularly, the sound is called noise. By sounding together the proper organ pipes, any vowel sound can be imitated. On the other hand, drawing a fingernail across a black-- - 4800. board creates a noise of a different sort. 0.4 rrequency- =--- DECIBELS Or, frequency = 4800 0.4 = 12 kHz. Throughout your Navy career as a Sonar Technician, you will be using decibels as an indicator of equipment performance. Power output CHARACTERISTICS OF SOUND and reception sensitivity of a sonar equipment are measured in decibels, which are used to Sound has three basic characteristics: pitch, express large power ratios. intensity, and quality. Together they make up In the decibel system, the reference level is the tone of a sound. With the proper combina- zero decibel (0 db), which is the threshold of tion of characteristics, the tone is pleasant. hearing. The pressure level, or signal strength, With the wrong combination the sound, quality of underwater sounds is compared to the 0 db degenerates into noise. level, and is given either a positive or a negative value. Sonar receivers are capable of detecting sounds having a signal strength below the 0 db PITCH level. In such instances, the signal is given a minus db value. An object that vibrates many times per second The reason for using the decibel system when produces a sound with a high pitch, as in the expressing signal strength may be seen in table instance of a whistle. The slower vibrations of4-1. It is much easier to say that a source level the heavier wires within a piano cause a low-has increased 50 db, for example, than it is to pitched sound. Thus, the frequency of vibration say the power output has increased100,000 times. determines pitch. When the frequency is low, The amount of power increase or decrease from sound waves are long; when 'it is high,the waves 'a reference level is the determining factornot are short. the reference level itself. Whether power output is increased from 1 watt to .,100 watts, or from INTENSITY 1000 watts to 100,000 watts, it still is a 20-db increase. (See table 4-1). Intensity and loudness Often are mistaken as, Examine table 4-1 again, and take particular having the same meaning. Although they are note of the power ratios for source levels of related, they actually are not same. Intensity 3 db and 6 db (also 7 and 10 db) . It can be seen is a measure of a sound's energy: Loudness is the that to increase a sonar's source level by 3 db, effect bf intensity on an Individual; in the sameit is necessary .to double the output power. As manner that pitch is the :effect of' frequency. .atypical example,. if the sonar source level Increasing the intensity' cause's as iner6ase indrops from 140' db to. 137 db, the sonar has lost loudness, but not in a directproportion. To double half ,its power. Any, 3-db loss, no matter what the loudness of a sound requires about a tenfoldthe source level, means loss of half the former increase in the' soUnd's intensity. power.

38 V. Chapter 4PHYSICS OF SOUND

Table 4-1. Decibel Power Ratio Equivalents BACKGROUND NOISE

Source Level (db) I Power Ratio L SELF I I AMBIENT]

1,3 ,,4 EQUIPMENT 1 I BIOLOGICAL 1,-' 3 2.0 5 3.2 6 4.0 CREW I I SEA 7 = 5.0 10 10 20 = 100 FLOW I MISCELLANEOUS I 30 1000 40 10,000 MACH1INERYI 'UNIDENTIFIED 1, 50 = 100,000 60 1,000,000=106 1" 70 cc 10,000,000101° =107 PROPULSION 100 110 1011 I AUXILIARY 140 1014

71.116 Now let's see what is required to increase Figure 4-6. Noise sources. a sonar's . range. To double the range of a sonar requires a source level increase of approximately 27, db. This power increase is equivalent to about across a wide band. Such a form of sound is 500. times, which . obviously is impractical. By called noise because it has no tonal quality. another method, suchas,increasing receiverThe source of several types of noises may be sensitivity, the range can be increased fairlyidentified easily, however, because of the standard easily, although it may not be doubled. . sound patterns of the noises. Ship noise, for So far we have disousted the decibel, mainly instance, consists of many different sounds mixed in relation to power. output, but the. decibel also together. You may be unable to distinguish a is used to determine receiver sensitivity. Re-particular sound, but, on the whole you could ceiver sensitivity- is measured in minus numbers, recognize the sound source as a ship. Some .which represent., the. number. of decibels below a noise sources are shown in figure 4-6. The referenoe level that a signal can be detected by sources, of many noises detected bysonar have the receiver. .The -largest the negative number, not yet been identified. Explanations of some the better the sensitivity. Although the,range kinds of noises that have an adverse effect on would not be doubled,, it is &ore. practical,. for a sonar Operator follow. instance, to . increase a receiver's ,sensitivity from 112 db to .115 db than it is to, double the Ambient Noise output power of the sonar transmitter. Also a itis, not always necessary to. .increase.. the Ambient noise, is background noise in the sea sensitivity :.of the receiver itself.,. An effective that is due to natural causes. Different phenomena increase of several, decibels may be achievedcontribute to the ambient background noise. if local noise levels can.be reduced, 'in -.such Many of the sources are lcnovni and their effects sources as machinery, flow .noise, .crew noise, are predictable, but many still are unknown. etc. . . From this unwanted,background noise, the sonar NOISE operator must be able.to separate weak or intermittent target noises. In general, theaverage The most complex sound wave., is, onein operator requires a target signal strezigth of which the sound.pOnsists of numerous frequencies 4 db above background noise,

r. INTRODUCTION TO SONAR

Thermal noise: The absolute minimum noise in the ocean is called thermal noise. As the name implies, it is a function of temperature. This noise is created. by the motion of the molecules of the liquid itself and is difficult to measure. Residual minimum: The lowest noise level-- that normally is measurable is called residual elmor''r "1r minimum. Different unknown phenomena un- doubtedly contribute to the minimum observable value. The point of interest, however, is that you are never likely to encounter ambient noise levels below the residual minimum. Surface agitation: For a sizable region above the residual minimum noise, the ambient noise 71.22 levels appear to be related to the surface agita- Figure 4- 7. Patterns of flow noise. tion.Usually, agitation of the surface of the ALaminar flow; BTurbulent flow. sea is measured as sea state. Surfaoe windspeed, however, ordinarily is a more reliable measure of expected ambient noise than sea state. As fluctuations of pressure will occur on its face, the wind rises, the surface becomes more andand what is called flow noise will be observed more agitated, causing the ambient noise level in the system. to rise. Normally noise levels in this region are As pressures fluctuate violently at any one associated with what is called sea noise to point within the eddy, they also fluctuate violently distinguish them from other noises, which really from point to point inside the eddy. Moreover, are not caused by the sea itself.. A heavy rain, at any given instant, the average pressure of the for instance, will add greatly to the ambienteddy as a whole differs but slightly from the noise. static pressure. Thus, very little noise is radiated outside the area of turbulence. Hence, although a Flow Noise ship7mounted hydrophone may be in an intense flow noise field, another hydrophone at some As an object moves through water, theredistance from the ship may be Unable to detect is a relative flow between the object. and thethe noise at 'all. Flow noise, then, is almost medium. This flow is easiest to understand byexclusively a self-noise problem. assuming that the object is stationary' and that Actually, not much information is known the water is moving Peat' the object. If theabout flow noise, but these general statements objeot ie reasonably 'streamlined and-its surface may he made about its effect on a shipborne is smooth, 'and if it .ief moving -very slowly,. ahydrophone: (1) It is a' function of speed with 'a flow pattern' 'known'. as 14211100 flew is set up. sharp threshold. At very low speeds there is Such 'a Patternis 'Amen in 7ii.eiviVin figure 4 -7, no observable flow noise. A slight increase *ere the lines represent- the Paths followed in ',!kieed changes the flow pattern from laminar by the water as it flowa around the object. Ifto! turbulent, and strong flow noise is observed the flow is laminar, all lines are smooth. Although iMmediately. Further increases in speed step laminar flow produces little, if any noise, it up' the intensity of the noise. (2) It is essentially (vents only at verY' low sneedsperhaPS lessa low-treqUency noise.(3)It has very high than 1.13r 2 knots: - Wield within the area of turbulence, but low theaPeed OfthiWitbir is increased,Avhorls leivele in the radiated field. In ;general, the and 'eddies begin "to -appear in the flow pattern, noise field is strongest at the surface of the as seen'part^R'infigure 4 -7, and the phenom- Moving body; decreasing rapidly as you move enon' lir called turbulent 'flow: Within' these eddies away 'from the surface. occur Pointe 'Where the.iiresitire 'IS widely dit= As the speed of the ship or object is in- ferent from thesitittic prensure' theinediuni. creased still further, the- local pressure drops Th40,'' are 'have,in off*, a: field:: If a low enough at soars points to allow the forma- hydrophone is placed Stith-a region, violenttioir*of gas bubbles. This decrease in pressure

40

`1, Chapter 4 PHYSICS OF SOUND represents the onset of cavitation. The noise associated with this phenomenon differs from flow noise. FREOUENCY 'HERTZ) spo. A000 .500C1 10.900 Cavitation DEPTSSSFT.

Cavitation is produced whenever a solid object p 40 moves through the water at a speed great enough to create air bubbles. After a short life, most .1ORPM of the bubbles collapse. The sudden collapse of ao the bubbles causes the acoustic signal known as cavitation noise. Each bubble, as it collapses, produces a sharp noise signal. 0 90 RPM Because the onset of cavitation is related to the speed of the object, it is logical that cavita- tion first appears at the tips of the propeller blades, inasmuch as the `speed of the blade tips is considerably greater than the propeller hub. This phenomenon, known as blade tip cavitation 71.24 is illustrated in figure 4-8. Figure 4-9.Sheet cavitation. As the propeller speed increases, a greater portion of the propeller's surface is moving fast enough to cause cavitation, and the cavitating represent any particular submarine. Note the area begins to move down the trailing edge ofgreat difference in . noise level caused by the the blade. As the speed increases further, theaddition of only 20 turns, from 90 rpm to 110 entire back face of the blade commences oavi- rpm.. At 90 rpm there is no cavitation; the noise tating, producing what is known as sheet cavita- level is due to flow noise and background noise. tion. This form of cavitation is shown in figure At 110 rpm cavitation has started, and the noise 4-9. Cavitation noise is referred to as hydrophonelevel has gone up many decibels, with a peak effects. amplitude at about 400 Hz. As speed is increased The amplitude and frequency of cavitationfurther, the amplitude peak tends to move toward noise are affected considerably by changingthe lower frequencies. The amplitude increases speeds.Cavitation noise versus speed at aat a lesser rate, but covers a broader frequency constantdepth is diagramed in figure 4-10.band. The curves are also characteristic of a The curves shown are idealized; they do notsubniarine on the surface and of surface war- ships, although the amplitude levels may be different. .

11/4

d

k2

WATER FLOW WATER FLOW10- 71.23 35.50 Figure 4 -8. -Blade tip cavitation. Figure 4 -10. Speed effect on cavitation noise. t.1

INTRODUCTION TO SONAR

generators, gasoline pumps, blower motors, and FREQUENCY (HERTZ) portable power tools. Any (or all) of the afore- 100 500 1000 5000 10,000 60 mentioned equipment may be operating at any 170 RNA one time, adding greatly to the noise radiated by the ship, and therefore entering the sonar ro. receiver.If thecombination of these noises 0 0 becomes too great for effective sonar search, 56 FT. 100 FT ask your watch supervisor to request the OOD 200 FT. to secure all nonessential equipment. Another 0- 20 az noise source is circuit noise, generated within the sonar equipment itself. This noise may be 300 FT. in the form of a 60-hertz hum, staticlike noises 0 from electric cables duea improper cable shielding, or leakage currents from other sources entering the receiver stages. Unlike ambient 35.51 noise, however, this type of generated noise may Figure 4 -11. Depth effect on cavitation noise. be controlled. Marine Life

Cavitation noise versus depth at a constant . A sonar operator may hear many strange speed (170 rpm) is shown in figure 4-11. Thesounds during his time on watch. He may have upper curve is the same as the upper curveto listen to (and try to identify) the source of in figure 4-10. As the submarine goes deeper,whistles, shrieks, buzzes, pings, knocks, crack- the cavitation noise decreases and moves tolings, and other weird noises not ordinarily the higher frequency end of the spectrum inassociated with the sea. Most of these noises much the same manner as though speed hadprobably come from different species of fish, been decreased. This decrease in noise is caused but only a few have been identified positively. by the increased pressure with depth, whichFollowing are descriptions of a few marine tends to compress cavitation noise. The curves life noises. are not exactly the same as those shown in Porpoises give out a whistling sound and figure 4-10, but the similarity is readily apparent. sometimes a sound like a chuckle. (Submarine hydroplanes and rudders sometimes also give Machinery Noise off a whistlingsound.)These mammals are found in all ocean areas of the world. Machinery noise is produced aboard ship by Snapping shrimp are common around the the main propUlsion machinery and by any. or world between latitudes 45°N and 45°S, usually allof a large number of auxiliary machinesin waters less than 30 fathoms deep. As you that may or may not be connected with theapproach a bed of snapping shrimp, you hear main propulsion system. Machinery noise usually a buzzing sound. As you go closer, the sound is produced by rotating or reciprocating machines. resembles fat sizzling on a fire, then becomes Most noise of this type. is 'generated by dynamici similar to thatgiven off by burning brush. imbalance of the rotating portion of the machinery Whales, which are found in all oceans, give that causes a vibration within the machine. Such off a. variety of sounds, including knocks, groans, a vibration may then be traiismitteiithrough the pings, and one resembling a swinging rusty gate. machine mounts to the hull, from where it is The knocking sound of the sperm whale resembles radiated into the water as acoustic energy. the noise of hammering. Sperm whales and other largespeciesseldomare heard in waters Shipboard Noise shallower than 100 fathoms. Blackfish, which are similar to whales, emit a whistling sound In addition to the machinery discussed solike a porpoise, but clearerin tone. far, there are many other shipboard noise sources The preceding examples of marine life noises over which you probably will not have anyare just a few that you will encounter. Do not control. Some of the noise sources are fire let_ the strange sounds mislead or distract you. and flushing pumps, air compressors refrigera- A valid target may be just beyond the whale you tion machinery, air conditioningsystems, dieselarelistening to.. Available tapes and films

42 Chapter 4 PHYSICS OF SOUND describe man. y. biologic noises. All Sonar Tech- loss is only half that of a sphere,or 3 db each nicians should- review these tapes and filmstime the distance is doubled. Spreading loss periodicallyto maintain proficiency in theirat close range is very high, but beyondabout recognition of sounds. 2000 yards the loss becomes less significant. UNDERWATER SOUND TRANSMISSION LOSSES Absorption Now that you know something of the theory In the topic on sound waves, you learned of sound, you are ready to take a closer lookhow a sound pulse moves through water.The at what happens to an underwater sound pulse. repeated compressions and rarefactions of the To gain the full benefit of echo ranging sonar sound wave cause the water molecules tomove equipment, you must be able to transmit'an back and forth, thus passing the soundwave underwater sound pulse and recognize there- along. An old saying goes: "You can't getsome- turning echo from a target.. Detection of the thingfor nothing." In our illustrativecase, echo depends on its quality and relative strength, energy is lost (in the form of heat) by the sound compared with the strength and character of pulsein itsefforts to compress the water. other sounds that tend to mask it. Energy lost to the medium in thismanner is Sonar Technicians must know (1) whatcan called absorption loss. weaken sound as it travels through water, (2) what conditions in the sea determine the path and speed 4 sound, and (3) what objects affect theScattering strength and character of the echo. When a sound wave travels through water, it Besides losses caused by divergence and encounters elements that reduce its strength.absorption, a sound wave losesenergy due Any signal strength lost in this manner is knownto the composition of the medium through which as a transmission loss. it passes. Composition of thesea, naturally varies from place to place, and from time to TRANSMISSION LOSSES time. In general; however, sea water contains large amounts of minute particles of foreign As a sound pulse travels outward from itsmatter and many kinds of marine life of all source, it becomes more and more weakened. shapes and sizes. Each time the soundwave Much of its energy is lost because ofsea meets one of these particles, a sma". amount conditions and distance. Three factors directlyof the sound is reflected away from its direc- related to sound transmission losses are diver- tion of movement and is lost. The reflection gence, absorption, and scattering. The latter twolossesto the water are knoWn as scattering are referred to as attenuation loss, and arelosses. Some of the scattered energy isre- dependent on transmission frequency. Divergenceflected back to the sonar receiver and is then loss is independent of frequency. . called volume reverberation (discussed later in this section). Divergence When a sound wave is projected froma REFLECTIONS point source, it assumes a sphericalshape, spreading equally in all directions. This spread- When a sound wave strikes the boundary ing is called divergence, and the further thebetween two mediums of different densities, wave travels, the more energy it loses. Thethe wave will be reflected, justas light is energy lost by a sound wave due to sphericalreflected by a mirror. Some of theenergy divergence is inversely proportional to the square will be lost, but most of it will be reflected of the distance from its Source, or 6 db eachat an angle equal .to the angle of incidence. time the range doubles. The angle of incidence is the angle, withrespect In shallow water areas,the surface- andto the perpendicular, at which thewave strikes bottom are boundaries that limit the verticalthe boundary. According to the physics law of divergence of the sound wave. Consequently,regular reflection (reflection froma smooth the expanding wavefront is cylindrical, rather surface) the angle of reflection equals the angle than spherical, in shape. Cylindrical spreading of incidence.

AR INTRODUCTION TO SONAR

Reflection takes place whenever the soundMoreover, reverberation level is proportional hits the boundary between sea and air (seato source level and to pulse length. Another surface) and between sea and bottom, and when pointto remember is that when you are in ithits a solid object, such as a submarine.company with another ship, you may hear re- The amount of energy reflected depends on the verberation effects from her -sonar in addition object's density, size, shape, and aspect. More to your own. energy is reflected by a submarine broadside to the sound beam than by one that is bow on. From Mass of Water Reverberation from the mass of water is Surface Effect called volume reverberation, which was men- tioned in the discussion on scattering. Suppose Because the density of water is severala short pulse of sound is sent out from a station- hundred times that of air, practically all of aary underwater source, which is immediately sound wave is reflected downward when it strikes replaced by a listening hydrophone. As the the surface boundary. This effect is true onlypulse of sound travels through the water, it when thesurface is quite smooth, however.encounters various particles that reflect and When thesurface is rough, scattering takes scatter the sound. Because almost all of these place. particles are much smaller than a wavelength of the sound, they do not reflect the 'sound as Bottom Effect a flat mirror reflects light. Instead, they absorb energy from the sound wave and reradiate this The bottom of the sea reflects sound waves,energy in all directions. Some reradiated energy too. In deep water, this aspect need not befrom each particle returns to the hydrophone considered, but in waters of lessthan 100at the source location and is heard as a gradually fathoms, the sound may be unwontedly reflectedfading tone at the same frequency as the source. from the bottom. Other considerations being equal, transmission loss isleast over softFrom the Surface mud. Over rough and rooky bottoms, the sound is scattered, resulting in strong bottom re- Some of the sound energy from the source verberations. strikes the surface, the point of impingement moving farther and farther from the source .as the sound travels. If the surface were perfectly REVERBERATIONS flat, this sound energy would be reflected as though from a mirror, and would bounce away You probably are acquainted with the effectfrom the source in accordance with the laws in an empty room where your .voice seems toof reflection. But the surface is not perfectly echo all around you as. you talk.. After yousmooth, and each wavelet tends to reflect the stop talldng, the sound continues to bouncesound in all directions. Some reflected sound around the room from wall to .wall until itreturns to the hydrophone, adding to the re- finally is absorbed by the walls and the air.verberation. The sound level in the room while.. you are talldng is higher than normal beoause of the From the Bottom reverberation effects. ..The same effects can also be observed in the. ocean. Reverberation In general, reverberation effects from both in the ocean usually is divided into three cate-the mass 'of water and the surface are- small gories. They are reverberations from the masscompared. to .bottom reverberation. The bottom of water, from the surface, an_ d from the bottom.is usually much. rougher than the surface. Thus, The. following discussion on reverberationsmore of the sound is reflectectin other directions may ,seem like . a . repetition- of the topic on re-than those expected of a reflecting. mirror. If fleotions,. 'but the two phenoniena are not thethe water is fairly deep, no bottom reverberation same. Although'. reverberations are :reflections,occurs '...for. quite ..some time after the pulse, all reflections do not become ',reverberations.because the sound must be given time to reach All the processes; contributing to reverberationthe bottom and be reflected. Normally, a sharp are, -random- in nature, with the result. thatrise...eventually occurs in the reverberation level reverberation amplitudes vary. over, wide limits.after the source ik nut off. Chapter 4 PHYSICS OFSOUND

REFRACTION be detected by sound may be reduced to less than 1000 yards. This range may change sharply If there were no temperature differenceswith changing submarine depth. in the sea, the sound wave would travel approxi- mately in a straight line, because the speed of QUENCHING sound would be roughly the same at all depths. As indicated in figure 4-12, the sound would In strong winds and heavy seas, the roll spread and become weakened by attenuation atand pitch of the echo ranging ship make it a relatively constant rate. difficult to keep the sound directed on the target. Unfortunately, however, the speed of soundAdditionally, the turbulence produces air bubbles is not the same at all depths. The velocity ofin the water, weakening the sound waves. Occa- sound in !lea water increases from 4700 feetsionally this envelope of air bubbles blankets per second to 5300 feet per second as thethe sound. emitted by the transducer. Sonar temperature increases from 30° to 85°F. Asoperators can tell, by a dull thudding sound, will be seen later in the chapter, salinity andwhen the sound beam is being sent Out into air. pressure alsoaffect sound speed, but theirThis action is known as quenching. effects usually are small in relation to the large effects commonly produced by tempera- ture changes. Because of .the varying tempera- PROPAGATION OF SOUND ture differences in the sea, the sound does not IN THE SEA travel in a straight line. Instead, it follows curved paths,resulting in bending, splitting, and distortion of the sound beam. We have discussed the various basic phe- When a beam of sound passes from onenomena that cause power loss in transmitting medium in which its speed is high (such assound: divergence, attenuation (absorption, and warm water)into one in which its speed isscattering), reflections, reverberations, refrac- low (such as cool water), the beam is refractedtion(bending), and quenching. Now, we must (bent). A sound beam bends away from levelsconsider the structure of the sea as an acoustic ok high temperature and high sound velocity,medium, and learn the effects of this structure Ed bends toward levels of low temperature on the transmission of sound. and low sound velocity. Figure 4-13 illustrates Of the many conditions affeotint sound wave the refraction of a sound beam. As a result oftravel through the water, the .following factors refraction, the range at which a submarine caninfluence its speed.

71.26 Figure 4-12: Sound travel- in water of constant 71.27 temperature. Figure 4-13.A refracted sound beam.

45 - OP.

INTRODUCTION TO SONAR

CONTROLLING FACTORS Pressure Sound travels faster in water under pres- The speed of sound wave travel through the sure. Pressure increases as depth increases, water is controlled by three conditions of theso the deeper a sound wave travels, the faster sea. They are: temperature, which takes theit travels. Pressure effect on transmitted sound, form of slopes and gradients; pressure, caused although rather small in comparison to tempera- by increased depth; and salinity, or the saltture effects, cannot be neglected. The speed of content of the water. sound increases about 2 feet per second each 100 feet of depth. Temperature Salinity With presently operational sonars, tempera- Sea water has a high mineral content. Salt ture is by far the most important of the factorscontent is spoken of as the salinity of the water. affecting the speed of sound in water. DependingThe weight of the higher density sea water is on the temperature, the speed of sound increasesabout 64 pounds per cubic foot; that of fresh with increasing temperature at the rate of 4 to 8water is about 62.4 pounds per cubic foot. feet per second per degree of change. InasmuchThis variation is the result of the salt content as the temperature of the sea varies fromin the sea water. freezing in the polar seas to more than 85°F in The overall effect of increasing the salinity the tropics, and may decrease by morethan. of water is to increase the speed of the sound, 30°F from the surface to a depth of 450 feet,which means that when sound passes through it is clear that temperature has a great effectwater that varies in salinity, it travels faster on the speed of sound. Remember: The speedin thesaltier water. In the open ocean, the of sound increases when the temperature ofvalues of salinity normally lie between 30 and water increases. 35 parts per thousand. In the region of rivers

PRESSURE SALINITY TEMPERATURE (PSI) (0/00) (°F) 0 2500 5000 33 34 35 30. 45 60 COMPOSITE

2000

4000

CZ 6000 W.

8000

10,000

0 90'180 . 1421 46' 150 297404.551248004900 5000 VELOCITY CHANGE VELOCITY (FT/SEC) (FT/SEC)

.35.5(71) Figur4-14: Normal cloves for pressure, salinity, and temperature. Chapter 4 PHYSICS OF SOUND; and other fresh water sources, the salinity DEPTH AND TEMPERATURE values may fall tolevels approaching zero. The speed of sound increases about 4 feetper Except at the mouths of great rivers, where second foreach.gpart per thousand increasesalinity ma) be a determinant, the path &lowed in salinity. Salinity has a lesser effecton the by sound is governed by the water temperature speed of sound than does temperature, but its and the pressure effect of depth. effect is greater than that of pressure. The pressure effect is always present and always acts in the same manner, tending to Composite bend the sound upward. Figure 4-15 illustrates the situation when the temperature does not Figure 4-14 shows reasonably normal curveschange with depth. Even though the temperature for temperature, salinity, andpressure as adoes not change, the speed of sound increases function of depth in the Pacific Ocean and alsowith depth, due entirely to the effect of pressure, the resulting velocity structure. It should be and the sound bends upward. noted that the salinity variation playsa minor Figure 4-16 shows what happens when tem- part Fin the form of the depth-velocitycurve. perature increases steadily with depth. When This effect is almost entirely evident in thethe surface of the sea is cooler than layers first 500 feet below the surface. The tempera- beneathit, the water has a positive thermal ture curve also shows wide variations in the top gradient. Althoughthis condition is unusual, 500 feet. From 2000 feet, downward, the tempera- itdoes happen, and causes the sound to be ture is nearly uniform as the water approachesrefracted sharply upward. In certain areas of the maximum density point at about 40°F. The the Red Sea, between Africa and Arabia, tem- pressure effect is represented by a straight lineperaturesof well over 100°F have beenre- as the velocity increases linearly with depth.corded in depths exceeding 1 mile. Moreover, On the composite curve, it easily can bethe salinity of the water in those areas approaches seen that the velocity in the top 2000 feet is a30 percent, compared to between 3 and 4 percent somewhat skewed replica of the temperature in most ocean areas. curve. Below 2000 feet it follows closely the When the sea grows cooler as the depth straight line gradient of the pressurecurve.increases, the water is said to have a negative

RATERCOOL

71.29 71.30 Figure 4-15. PressUree tends to bend the soundFigure. 4-16. Positive thermal gradient tends beam upward. to bend the sound wave upward.

47, INTRODUCTION TO SONAR

layer of water is isothermal; beneath this layer the temperature decreases with depth.This temperature change causes the transmitted sound tosplit and bend upward in the isothermal layer and downward below it. Don't forget; When no temperature difference exists, the sound beam bends upward. When the temperature changes with depth, the sound beam bends away from the warmer water. Under ordinary conditionsthe sea has a temperature structure similar to that in figure 4-19.This temperature structure consists of three parts; a surface layer of varying thick- ness, with uniform temperature (isothermal) or a relativelyslighttemperature gradient; the thermocline, a region of relatively rapid de- crease in temperature; and the rest of the ocean, with slowly decreasing temperature down 71.31 to the bottom. If this structure changes, the Figure4- 17.Negative thermal gradient tends path of a beam of sound through the water also to bend sound downward. changes. Layer Depth thermal gradient. Here the effect of tempera- Layer depth is the depth from the surface ture greatly outweighs the effect of depth, andto the top of a sharp negative gradient. Under the sound is refracted downward. This commonpositive gradient conditions the layer depth is condition is illustrated in figure4-17. at the depth of maximum temperature. Above If the temperature is the same, throughoutlayer depth, the temperature may be uniform. the water, the temperature gradient is isothermalIf it is not uniform, a positive or weak negative (uniform temperature). In figure4-18the uppergradient may be present.

SEA SURFACE

TEMPERATURE UNIFORM OR SURFACE LAYER CHANGING SLIGHTLY ISOTHERMAL OR ISOTHERMAL "MIXED LAYER'. WITH DEPTH WHEN TEMPERATURE UNIFORM

TEMPERATURE DECREASING THERMOCLINE RAPIDLY

TEMPERATURE REGION 131:LOW THE DECREASING THERMOCLINE SLOWLY ,b4: 121AXAIstitartkiieTtattlitlbearalgAn

71.32 Figure4-18.Sound wave splits whentempera- 71.33 ture is uniform at surface and cool at bottom. Figure4-19.Typical layers of the sea. Chapter 4 PHYSICS OF SOUND

Layer Effect Layer effect is the partial protection from echo ranging and listening detectiona submarine gains when itsubmerges below layer depth. Sometimes a submarine, diving througha sharp thermocline while taking evasive action, loses the screw noises of the enemy ASW ship. Although usually the pinging can still be heard, itis as a low intensity signal. On the ASW ship, ranges on submarines are reduced greatly when the submarine dives below a sharp thermocline. Often, the echoes received 'are weak andmushy. Shallow Water Effect

Echo ranging is difficult in shallow water 71.28 because the sound is reflected from the bottom.Figure 4 -20. Shallow watereffect on trans- When the ship is in shallow water, andthe ocean floor is smooth, the sound bends down mitted sound. from the Surface to the bottom, then backup to the surface, and again down to the bottom.predict sound conditions, but he should under- When the transmitted sound acts in thismanner, stand why results are poor one day and good there are spaces empty of sonarcoverage into another day. He should know what is meant by which a submarine can pass and be undetected. shadow zones, and the reasons why sound does In figure 4-20 yOU will notice howa sonarnot travel in a straight line. He also should contact on a submarine can be lost when thebe able to distinguish between poor equipment submarine enters the shaded area. adjustment and poor sound conditions. The shaded spaces in figure 4-20are called Following are some general conditions for shadow zones: Contact is regainedwhen the hearing echoes. submarine enters the wave path again. As shown in the illustration, contact is madeat long 1. Usually poor, near coasts (50 miles)as range (point A), it lost (point B), and re- compared to sea conditions farther out. Condi- gained. at shOrt range (point C). Note,however, tions for hearing are particularlypoor at the that without the reflection, the maximumrange mouths of rivers. would have been the shortrange at which the 2. Better in winter than in summer. contact Was regained (point C). 3. Better at night than in the middle of the day, especially in spring and summer. The reason for .the loss of contact atshort 4. Better in morning than in afternoon, in range is shown at point D; where the submarinespring and summer, but little change if white- passes beneath the sound.. The distance at whioh caps are present. In many localities, however, contact is lost at short range dependson the,conditions are better in the afternoon than in depth of the submarine. Here, isa rule of the morning, because of the effect of prevailing thumb for estimating a submarine's depth: winds that freshen in the afternoon.

. The range, in yards,'yards, at loss of contactis DEEP WATER SOUND PROPAGATION roughly equal to the depth of thesubmarine in feet. A- contact lost at 300 yards would this From the preceding disoussions, itcan be be preowned to'be about 300 Teet deep. concluded that the behavior of the soundwave , is influenced' considerably by the structure of Once .the 'bohavior Of sound in sea mate& is the sea. Most of our.discussion so far has known, it possible to prettot. sound .condi pointed out the adverse effectson a sound tiona in the Sea. From` the temperature gradient beam,in comparatively shallow watersay 100. of the Water; an 44614000 person can judgefathoms or less. Now, let's examinesome of the nitUdniiiin range to mepeot. A' neatSonar the phenomena that takeplace in very deep Technician is not expected to know 'he* towater.

-Y. INTRODUCTION TO SONAR

Direct Path Theoretically, if the sound waves were not VELOCITY.. RANGE 30 MILES affected by velocity gradients, all the sound waves would be straight lines, and would travel in a direct path at whatever angle they left the a. source. In actual practice, however, the sound til beam follows a path, or paths, as determined by the sea condition at the time.

SoUnd Channel 51.8 Figure 4- 22. Convergence zone. Figure 4-21 illustrates a combination of two gradients of equal slope, one negative and one positive. Their junction is a point of mini- mum velocity. If a sound source transmits at Convergence Zone this depth of minimum velocity, all of the sound beams that start in an upward direction will be Another effect that is closely related to the bent back down, and those that start downwarddeep sound channel is called the convergence will be bent back up. When such a conditionzone effect. The convergence zone effect is occurs, we have what is called a sound channel. now applied to long-range active sonar, but this The depth of minimum velocity is called the effect long has been used by submarine sonar axis of the channel. In this symmetrical situa- operators. If the sound source is placed near tion, a beam that starts out downward will rise the surfaceinstead of near the axis of the as high above the channel axis as it went below sound channel, the path followed by the sound it, and then will be bent downward again. Sound beam looks somewhat like that in figure 4-22. will remain in the channel as far as the channel Sound energy from a shallow source travels exists, and will suffer very little loss as it downward in deep water. At a depth of several progresses through the channel. thousand feet, the signal is refracted due to Sound channels are a rarity in shallow water pressure, and returns to the surface at a range (under 100 fathoms), but are always presentof about 30 miles. The surface zone is from in the deep water areas of the world. The depth 3 to 5 miles wide. of the axis of the channel is about 350 fathoms The sound that reaches the surface in the in the central Pacific and somewhat over 500 first convergence zone is reflected or refracted fathoms in the Atlantic. In the polar regions, at the surface, and goes through the same where the surface water is materially colder, pattern again. It produces a zone approximately I the axis of the channel lies nearer the surface. 6 miles wide at 60 miles, and another 9 miles wide at about 90 miles. Experienced Sonar Technicians are familiar with this convergence zone effect. Often they have picked up strong noise signals from targets that appear suddenly, VELOCITY --ft RANGE show up strongly for a few minutes, and then disappear. A surface or near-surface contact detected a. in the first convergence zone will have about the same signal strength as a target detected at 3 miles when no zone is present. Minimum depth required along the path of the sound beam isabout 1000 fathoms. The _usual re- - quirement-is 2000 fathoms for conducting con- vergence zone searches. The minimum depth 11.34 required is related to the surface velocity of Figure 4-21.Strong negative and strongpositivelthe sound, and increases as the velocity in- gradients forming a sound channel. creases.

50 " Chapter4PHYSICS OF SOUND

can, however, be noted by the Sonar Technician if he listens carefully. Although a stationary receiverwas used for illustrative purposes, the same effectscan be observed if the receiver is moving towarda stationary source. a DOPPLER AND REVERBERATIONS Earlier in this chapter you learned that as a sound pulse moves through the water it loses some of its energy to the water particles. 51.7 The particles reradiate the energy in all direc- Figure4-29. Bottom bounce effect. tions. Part of the reradiated sound is returned to the sonar receiver, and the effect knownas reverberation is heard. The water particles Bottom Bounce become sound sources and, as your ship moves through the water, doppler effect is noticed. For long-range search in water depths overThe following example should helpclarify doppler 1000 fathoms, newer sonar equipment may operateeffect for you. in what is called the bottom bounce mode. The Your ship is underway at a speed of15 transducer is tilted downward at an angle soknots; sound velocity is4800feet per second; that the sound beam strikes the bottom and is. sound frequency is 12 kHz. The sonar is keyed, reflected back to the surface,as shown inand 1 second later it is keyed again. During figure 4-23. . the 1-second interval, the first pulse travels Because of the depression angle (15° to45°) 4800feet. When the second pulse is transmitted, the sound beam is affected less by velocityit is only 4775 feet from the first one because changes than are sound pulses transmitted inthe ship has traveled 25 feet. Using the formulas the normal mode. At great depths, howevergiven in connection with wavelength,you can (2500fathoms and greater), the sound beameasily determine that the apparent frequency usually will be refracted before reaching theof the reverberations from ahead ofyou is bottom, thus producing a convergence zone effect. approximately 12.1 kHz whereas those from behind your ship have a frequency of about 11.9 kHz. Reverberations from the beam will DOPPLER have the same frequency as the transmitted pulse, because the ship is neither going toward You probably are familiar with the changingthe particles nor away from them. The doppler pitch of a train whistle as the train passesneareffect of reverberations is illustrated in figure you at high speed. As the train approaches, 4-25.To determine echo doppler, the Sonar the whistle has a high frequency. As the trainTechnician compares the tone of a target echo goes by, the frequency drops abruptly and be-to the tone of the reverberations. comes a long, drawnout sound. The apparent change in frequency of a signal resulting from relative motion between the source and the receiver is known as doppler effect. Figure 4-24illustrates doppler effect. Low HIGH Each sound wave produced by the whistle is given an extra "push" by the motion of the 11 of« Imo 1 mton 111 train. As the, train comes toward you, the re- I DO sultant effect 16 an increase in pitch, caused by compression- of the *aims. As the train Moves ay/ay_ from you;. the. sound waves are spree -fir. apart, 'resulting ina lower pitch. Because doppler 'effect varies inversely with the velocity. of sound, the: effect is t much lesS 71.37 marked in the seajhan it lain the air.'Doppler. Figure 4 -24. Doppler effect.

51: INTRODUCTION TO SONAR

REVERBERATION-I3.5 W}DOPPLER UP REVERBERATIONS ThE SA E 14.0 MT SUB ECHO - 14 0 kilt

REVERBERATION -14.2 kHz IDOPPLER UP RAlopSION 1.1k R VERDE%%%tti Aran LOw 1.9 MHz SUS ECHO-14.3 kHz .411LWIM11111 1 GI 11100 MIR1111118. 1 )ONE 1 1 illi 111 ONE PARTICLE PARTICLE 4UNOERWAT +-UNDERWAY OUTGOING PING 14.0kH .1111110111011 OUTGOING PING 14.0 WO

71.39 Figure 4-25. Illustration of doppler. 71.41 Figure 4-27. Doppler up. No Doppler Doppler Up Consider the echo from a submarine that isneither going away from nor toward the Suppose the submarine is coming toward sound beam. It either is stopped or is crossingthe echo ranging ship. In this situation, it is as the sound beam at a right angle. If the sub-though the submarine were a train approaching marine is in either of these situations, it re-a car at a crossing. The sound transmission flects the same sound as the particles in thereflected from the approaching submarine is water, and its echo has exactly the same pitchheard at a higher pitch than the reverberations. as the reverberations,which means the submarine When the echo from the oncoming submarine echo has no doppler. Whenever the pitch of theis higherthanthe reverberations, report submarine echo is the same as the pitch of"Doppler up." When making this report, you the reverberations, therefore, you .know thatare tellingthe conning officer that the sub- the submarine is stopped or that you are. echoingmarine is heading toward your ship and making off its beam, and you would report "No doppler."way through the water. This form of doppler Figure 4-26 illustrates a "no doppler" situa-is illustrated in figure 4-27. Noticein the tion. illustration that the echo frequency of the sub- marine on the ship's starboard quarter is the same as the ship's sonar frequency, yet it has up doppler. Remember, doppler is determined BUB ECHO- 14.1 kHz susECHO -13.5 kHz by comparing the tone of the target echo and REVERBERATION- 14.1 kHz REVERBERATION-13311HE the tone of the reverberations. Doppler Down Just as the tone of a train's whistle de- creases in pitch as the train moves away from you, so does the doppler of a submarine moving away' from your ship. No matter where the submarine is located in relation to your ship, -4UNDERWAY if he is heading away from you, the tone of OUTGOING PINS 140 kHE his returning echo will be lower in pitch than the. tone of the reverberations, Figure 4-28 71.40 illustrates two sibiations when you would report Figure 4-26.; No doppler. "Doppler down" to the conning officer.

52 Chapter 4 PHYSICS OF SOUND

%, 2 KNOTS 441444111N66 KNOTS SLIONT UP N NO DOPPLER

-..4,44,, 4 KNOTS%\\\ SUORT.UP DOPPLER /./ KNOTS i)Kar.TNO fi,oirSLIGHT UP NO DOPPLER $

REVERBERATION-14.11'11z SUB ECHO- 14.0t4It REVERLII ETC110:13.1174, DOPPLER DOWN N 6 KNOTS ,:iite2 KNOTS DOPPLER DOWN V7 .IC AI 0 D DE RO AviT NE sperpsiT UP 4/4 KNOTS '4-UNDERWAY "MOTS \01/%14tODERATE DOWN *omitsPING-PLO MNt MODERATE UP \\N2t0 TI CKNOTS 'NED' suotrr DOWN \I\ OR ABOVE 71.42 MARKED UP Figure 4 -28. Doppler down.

DOPPLER REPORTS 71.43 To summarize what you have just learned Figure 4-29. Doppler conditions. about doppler: Doppler is the difference in pitch between the reverberations and the echo. When the. echo is higher than the reverbera- You now realize how important it is to give tions, you will sing out "Doppler up". If it's an accurate report of doppler to the conning the same as the reverberations, report "No officer. It tells whether the submarine is coining doppler."If the. echo is lower than the re-toward or going away from your ship, and verberations, say "Doppler:down." gives the component of the submarine's motion. When you becotne a really skilled operator, Remember that any contact that does have doppler you will be able to give the degree of doppler, must be moving in the water; if it is not a that is, how high or low it is. For instance, surfaceship, chances are that it is a sub- a submarine coming directly toward your ship marine or a large fish. Figure 4-30 gives an at 6 lmOts returns a higher echo than a sub- idea of the value of doppler. marine ooming, directly toward the ship at 2 knots. Also, a submarine coming direotly toward the ship at 6 knots returns ii higher echo than a HOW TO RECOGNIZE ECHOES 6-knot submarine that is heading only slightly toward the ship. Sonar Technicians learn to recognize one The importance of prompt and accurate re- echo from another' by listening to recordings ports cannot be overemphasized. Two "details of reverberations and echoes and by practicing count: how much speed the submarine is making,. with the sonar aboard ship. The following topics plus how much it is heading toward or away contain remarks intended to serve as helpful from the ship. The combination of these twohints, but they cannot take the place of actual considerations is spoken of as the component praotice. of the submarine's,speed toward or away from the ship. If the submarine's speed component TWO TYPES OF ECHOES is more thanknots,. report "Doppler marked, up (or down)." :When it is S to: .6 knots, in- Echoes are of two types: those with doppler Olnsivei report "Doppler moderate, up (or. down) and those without doppler. If an echo has doppler, If. less. than 3- knots, then call it "Doppleryou can assume that it is a submarine or a slight, up (or .down). ". (See fig. large fish or mammalperhaps a whale. 53 INTRODUCTION TO SONAR NI!

position, and movement of the target, and the conditions of sound transmission in the sea. You probably will hear a lot of different sounds while echo ranging. A stationary object near the surface produces good echoes, but ./../ NO DOPPLER there will be no doppler. (Once in a while, a strong current or tide will cause an echo to have a doppler effect, but such an occurrence is unusual.) A whale may have echo character- istics closely resembling those of a submarine. Echoes also may be heard from large fish, such as blackftsh. Schools of herring or other Small fish sometimes run large enough to re- DOPPLER DOWN e flect a strong echo. In shallow water, as along #49, the Continental Shelf on the eastern coast of oo * the United States, hulls of long-sunken ships may return a 'very convincing echo. Because Nazi U-boats were so effective in this area during World War II, the shelf is littered with dead ships capable of hoaxing the unsuspecting 71.44 sonar operator into believing his contact is Figure 4-30. Value of doppler. actually a submarine. Often you will hear strange chuckling and whistling sounds in an area abounding in por- If the echo has no doppler, it is from the poises or dolphins. If the water is shallow and beam of a submarine* from a stopped sub- the bottom is hard, rocky, or covered with Marine, from the submarine's wake, or it is coral heads, sound waves are reflected strongly. not from.a submarine. If an echo without doppler Often these reflections return as loud and clear is from the beam of a submarine, it will be as echoes from a target, but they have no sharp and clear, because the side of a sub- doppler. marine presents a large reflecting surface. From time to 'time, you may pick up strange sounds that are difficult to identify. Submarine Sharp, loud echoes, withoutdoppler, are hydroplanes and rudders frequently give off a received from any large, solid surface. The noticeable whistling sound: Submarine pumps larger the area of the target, the greater the and other machinery can be heard rattling or strength of the echo. thumping if the machines are not silenced. You A weak, mushy echo, without doppler, is also can hear a torpedo. heard from such objects as riptides, kelp beds Torpedo noise is distinct from all others. schools of small fish, and wakes that are breaking When a torpedo is fired from a submarine, the up. The weak, mushy sound is caused by the first indication might be the sound of escaping numerous small reflectionsthat combine in air, quickly followed by a sound like a propeller random fashion to form an irregular echo wave. noise. The rhythm is too rapid for the beats Often, you will .receive the worst type of to be counted (as you can count those of a ship's echoes from the stern of a submarine. The propeller), and it increases swiftly In intensity target area is small and is broken into multiple as it approaches, resembling the whine of a surfaces by the screws the wake, and the like, jet engine, but not as high-pitched. so that there its acombination of reducedpower and .interferenoe. Don't dismiss weak, poor- ARTIFICIAL TARGETS sounding echoes as nonsubmarine; Experienced sonar operators will tell you that although an Submarines are capable of putting artificial echo from dead astern of the target is hardest targets into the Water to confuse the tracking for an operator toidentify,it can be done ship. They are of two general types: targets with .a 'little perseverance. . that are self-propelled, which can return an Thb strength of the echo depends on the eoho with doppler; and targets that are sta- power' of the incoming wave. This power depends tionary,providingexcellent sound-reflective on the sound output of the transducer, the size; qualities, but usually without doppler. Practice Chapter 4 PHYSICS OF SOUND

and experience in recognition are the best in- surance in countering these artificial targets. Some of the self-propelled kind receive the ping of the echo ranging sonar, amplify it and give it a change in doppler, then retransmit it. REPORT EVERYTHING They also may be programed to simulate sub- marine movements. Usually the returning signal is stronger than the returning echo from the SURFACE VESSEL submarine, so it is easy for the inexperienced sonar operator to shift from the actual target to the artificial one. The stationary type also returns a strong echo, which often is more pronounced than that rA from a submarine. This type of target comes in several forms. SUBMARINE One form of stationary target is a "pill" of chemicals, which reacts with water to form bubbles of carbon dioxide gae.- The action is much the same as bicarbonate of soda in water. The pill dissolves, creating millions of bubbles of the gas, which, because they are grouped together, return a'strong echo.

Another target of the bubble type is pro- KELP SUBMARINE duced when the submarine releases a quantity SUBMERGED of air. A few moments are required for the air to rise to the surface, and while it is doing so, it provides excellent sOund-reflective character- istics. Like the pill, the echo returned is often 71.45 stronger than that obtainable from a submarine. Figure 4- 31. Report everything you hear. Similar to the air bubble released by a sub- marine is the knuckle, which is a mixture of air and water created by a submarine makingFurthermore, you must be suspicious of echoes a sharp turn. Although it is not in general usethat change suddenly from weak or mushy to by a submarine commander during an attack,clear and sharp. Such an echo may be a self- because it slows him down, he may have topropelled target leading you away from your make a hard, high-speed turn in an attemptquarry. to avoid a weapon. The knuckle can produce a clear, sharp signal upon which an inexperi- Electronic and mechanical jammers are also enced operator may concentrate while* the sub-used by submarines. The electronic type usually marine escapes. operates on one of several selectable sonar frequencies, acting as a screen by -overloading Stationary false targets do not affect thethe ship's sonar receiver. The mechanical type pitch of the echo. This characteristic meansof jammer releases a series of explosions that that a stationary target does not give a dopplerjam the sonar receiver because of their wide change except under very unusual conditions.bandspread of noise. The mechanical type is This unchanged doppler characteristic is anespediallyeffective in shallow water because important clue in recognition of 'a false target.of repeated reverberations from the bottom. When tracking a target, for example, an You must remember that doppler can tell abrupt change from doppler up (or down) to noyou considerably more about target motion than doppler may well be an indication that thesimply whether it is going toward or away from target has ejected a bubble to throw you offyou. You must practice to achieve the near- guard, which may result in your making anperfeot discrimination demanded of a good Sonar attack on the false target. You must, therefore,1Teohniciaa. To achieve thisgoal, you must be suspicious of any drastic change in doppler.-11. listen and concentrate on echoes.

55 4

INTRODUCTION TO SONAR

REPORT EVERYTHING Report every sound you hear, regardless YOU HEAR of whether you can identify the echo. Figure 4-31 illustrates a few of the many objects that may return an echo or emit a sound. Do not delay One of the Sonar Teohnioian's most important maldng your report while you try to determine tasks is to distinguish the target echoes fromwhat you have detected. By the time you decide other noises that tend to mask them. Sonarit's a submarine, it may be too late. Don't be operators hear. many kinds of echoes. Rocks, afraid to make a report that may turn out to be shoals, buoys, mines, surface craft, whales,nonsubmarine. The safety of your ship and the schools of fish, wakes of surface craft andlives of your shipmates are worth more than submarines, as well as the submarines them-the time spent or the ordnance expended on a selves, dan reflect sound. false contact. CHAPTER 5 BATHYTHERMOGRAPH

The travel of sound waves in the sea was ocean temperature at a given time can be used discussed in the preceding chapter. To interpret to predict what will happen to the transmitted correctly the information displayed by sonar sound as it travels through the water. equipment, Sonar Technicians must have a thor- As a result of knowing the temperature of ough knowledge of the factors affecting sound the water at various depths, we can arrive at wave travel in water. Because thermal conditions fairly accurate conclusions regarding the maxi- of the sea are of the utmost importance to Sonar mum range at which a submarine may be detected, Technicians, a means must be available for as well as the most favorable depth for the measuring water temperatures at various depths. submarine to avoid detection. These two funda- The measuring device ;Oiled is the bathythermo- mentals are important considerations in anti- graph, called BT. Use of the bathythermograph submarine warfare. They influence the types of enables the submarine hunter to determine the screens Used for convoys, and aid in determining layer depth and to estimate sonar detection the spacing of ships in the screen. ranges at various depths. By determining layer depth, an estimate can be made of the probable EFFECT OF TEMPERATURE depth the submarine captain will employ to escape detection. The submarine captain uses The speed of sound through water increases the BT to determine the best depth to avoid at the rate of between 4 and 8 feet per second detection. for each 1°F rise in temperature. This 4- to Much of the data used in conjunction with 8-fps change depends on the temperature range BT information for determining sonar detection of the water. At water temperatures in the ranges cannot be included in this text because 30° range, for instance, a 1° rise increases the of the classified nature of the subject matter. rate of travel differently than does a 1° rise in Sonar range prediction methods are presented the 70° range. in other publications, such as Sonar Technician Ships and submarines of the U. S. Navy operate G 3 & 2, NavPers 10131 and Mu Technician. in all sea temperaturesfrom near freezing in S 3k 2, NavPers 10132. the polar regions to the upper 80s in the tropics. Before proceeding to our discussion of the To provide accurate range data, sonar equipment BT and its use, acbrief review of the tempera- must be adjusted to the changes in sound velocity. ture effects on sound travel is appropriate. Under some conditions, a pulse transmitted by sonar equipment may travel easily through water that varies greatly in temperature. Under TEMPERATURE different conditions, the pulse transmitted may be unable to penetrate a 5° temperature change As explained in chapter 4, the conditions layer at all, because it is reflected and scattered that affect sound travel in water are pressure, instead. salinity, and temperature. Increases in pres- sure speed up the velocity of sound, making LAYERS the speed of sound higher at extreme depths. An increase in salinity also increases the velocity A pulse of acoustical power may provide of sound. The effects of pressure and salinity sonar reception out to several thousand yards are not nearly as great, howeVer, as are those' of range. The same pulse, if transmitted into a caused by changes in temperatureparticularly layer of water. (such as a sound channel that abrupt changes. Information obtkined about the tends to keep the pulse confined within it), may

57

vork )4. .1"

ie INTRODUCTION TO SONAR be able to provide sonar data on contacts many are the types of BTs that provide the necessary miles distant. data. Sound has a natural tendency to seek paths toward the cooler layers of the sea. Because the AN/BSH-2D temperature of the sea normally decreases with depth, the path of a transmitted pulse of sound The AN/BSH-2D is designed for use in all usually is in a downward direction. types of submarines. It indicates changes in If a cross section or a profile of the sea's sound velocity with depth, and shows direction temperatures were taken, a normal condition of buoyancy change. It can measure and indicate might show a layer of water of uniform tempera- temperatures between 40°F and 90°F, salinity ture (less than 1/2° temperature change) from content from 20 to 40 parts per thousand parts the surface to varying depths. This condition is of water, depths between 0 and 800 feet, and called isothermal. Next, there would be a region buoyancy from 0 to 100,000 pounds. Whenever of water in which the temperature decreased a change occurs in salinity, temperature, or rapidly with depth. Such an area is known as a depth, their new values are indicated within thermocline. Finally, for the remainder of the a few seconds. measured depth, the temperature would decrease The AN/BSH-2D consists of five units: two only slightly with depth. salinity-temperature elements (one On the peri- scope shears and one on the hull below the THERMOCLINES waterline), an amplifier computer, a recorder, and a switch for selecting a salinity-temperature The thermocline can play havoc with a pulse element. of acoustical energy. As the transmitted sound The selector switch chooses one of the salinity- pulse reaches the thermocline, one of two effects temperature elements and connects it to the is apparent. amplifier computer. Changesin salinity and First, the thermocline can prevent passage of temperature cause the element to change its the pulse, reflecting it back to the surf ace. Targets electrical resistance characteristics. The ampli- beneath the thermocline may possibly be un- fier computer converts the change in electrical detected. This possibility is one of the reasons resistance into corresponding voltage changes, submarine commanding officers seek the cover amplifies the signal, computed' the sound velocity of such thermoclines, thus hoping toevade and buoyancy changes, and transmits the informa- detection by surface ships or aircraft. tion to the recorder unit. This unit then displays Second, the thermocline can allow passage the data on a card. Accuracy of the AN/BSH-2D of the sound pulse but alter its direction con- is ± 8 feet in depth, ± 6 feet per second in sound siderably in so doing.This effect is called velocity,and 2-1/2 percent of the 'change in refraction. If a sound pulse enters a thermo- buoyancy. clineat,for instance, a 30° angle from the sea's surface, it is possible for the angle to be DEPTH-SOUND SPEED MEASURING altered to 70° or more while traveling through SET AN/BQH-1A the thermocline, and change again as it emerges. The result of this refraction can be a distorted The AN/BQH-1A is a completely transis- path of sound travel that affects the accuracy torized device used to provide accurate informa- of target presentationat sonar console. tion concerning sound ranging conditions in the

O surrounding water and buoyancy during diving operations. SUBMARINE BATHYTHERMOGRAPH The equipment is capable of measuring sound velocity in sea water over a range of 4600 to More information is required from a sub- 5100 fps. Accurate depth measurement is provided marine BT than from its shipboard counterpart. by a depth element and its associated circuitry. Because salinity, temperature, and pressure Velocity of sound and depth of the sensing element, affect the ability of a submarine to maintain which measures this velocity, are displayed on a desired operating depth, knowledge ofthese two-channel (pen and drum) servomechanism conditions and their effect on buoyancy is necesk recorder (fig. 5-1). sary so- that the diving officer can maintain Maintaining the trim of a moving submarine trim of the submarine. The AN/BSH-2D and thct is aided greatly by indicating on the recorder AN/BQH-1A (which is replacing the AN/BSH-2D) chart a 'series of isoballast lines. These lines Chapter 5 BATHYTHERMOGRAPH

BOUND .1411A0,

Lrr WO. SPAN ,?,1 T f , AOZ,':ii-0.16i.aal:P.:iticigaZirag

35.156 Figure 5- 1. Depth -sound speed measuring set AN/BQH-1A. are precalculated for various classes of sub- changing conditions of salinity, temperature, and marines. Charts must be selected with isoballastpressure, the AN/BQH-1A recording equipment lines printed for that particular class of sub-must measure these changes in terms of absolute marine. In indicating a trace that crosses the values of velocity of sound in water. Sensitivity isoballast lines, action of the pen and drum gives of the velocity-measuring portion of this equip- the amount of water to pump or flood in order toment is sufficient to indicate changes in sound maintain the submarine's trim. velocity of 1 fps when passing through a thermal Buoyancy changes, indicated by crossings of gradient. Equipment pressure circuits are capable isoballast lines; ray be related to submarineof indicating changes in depth of approximately depth and also to velocity of sound In Water. 1 foot. This measurement represents the mini- Both submarine buoyancy (upon which' trim de- mum readable definition of the recorder chart's pends) and velocity of sound in water are definite. pressure portion. functions of salinity, temperature, and pressUre, Isoballast curves are calculated in such away Inasmuch as a moving subniarine encountersthat individual curves pass through all points INTRODUCTION TO SONAR where a loss in buoyancy with depth exactly 3. Depth scale select: A two position switch equals any gain in buoyancy resulting from athat permits an operator to select either of two decrease in water temperature or increase ofoverlapping depth scales. One depth scale is 0 salinity. to 800 feet; the other, 700 to 1500 feet. 4. Press4o-set 4800 fps:A spring-loaded Functional Operation. switch, that, when depressed, applies a cali- brating signal internally generated in the partic- To measure sound velocity and to ascertainular sound head in use. The switch acts as a velocity gradients in the surrounding water, twosystem check of performance and accuracy of transducer assemblies (sound heads) are pro- sound velocity indication.Italso assists in vided with each depth-sound speed measuringproper positioning of new recorder charts. equipment. One assembly is mounted on the upper (or sail) portion of a ship. The other Repeater: The repeater unit is identical to device is mounted at the keel. the recorder unit,but therepeater has no To obtain accurate information concerningoperational controls. The only control on the changing gradients and subsequent effects on repeater is the power on/off illumination switch. buoyancy during diving operations, it is advis-The repeater cannot be operated unless the able to use the lower sound head while diving,recorder is also operating. and the upper sound head while ascending. By following this pattern, radiated heat from the Operating Procedures skin of the ship will wash away from the sound head. Radiated heat, consequently, will not inter- Because the AN/BQH-1A and its associated fere with measurements of gradients 'and indi- sound heads and depth circuitry are completely cations of corresponding buoyancy changes. transistorized, no warmup time is required for Sound velocity in water is measured in the proper operation. Following is the normal oper- following manner: The AN/BQH-1A transmits ating procedure recommended for the set. into the water a pulse of acoustic energy. This pulse travels. from a transmitting transducer 1. After lighting off the equipment and select- through the water and is received by a seconding the desired sound head, the recorder illumina- receiving transducer. The time required for ation control is adjusted to provide sufficient pulse to travel from transmitter to receiver is light to clearly view the chart. (NOTE: When measured by means of electronic timing circuits. surfaced, the upper sound head is not immersed. Thus, a direct measurement of sound velocityCare must be taken to avoid energizing this is made. This method of -direct measurementhead until the submarine completely submerges.) eliminates the need for correlating various factors 2. The depth scale select switch is set to of the ocean: salt content, density, and tempera- the desired depth setting (0-800 feet or 700-1500 ture, plus pressure corresponding to depth atfeet). The equipment is now ready for normal which velocity is measured. operation. 3. The press-to-set 4800 fps switch is de- Description of Controls pressed and held until the velocity indicating drum reaches a steady position. Indicated veloc- Operating controls of the AN/BQH-1A depth- ity position should be 4800 fps. (NOTE: For sound speed measuring set are described foreach sound head the absolute value of the 4800 - the recorder and repeater. Refer to figure 5-1. foot calibrate velocity varies slightly. Test data sheets supplied for the sound head In use should Recorder: Following are the major operating be consulted for exact calibrated readings.) control switdites on the recorder. 4. In the preceding step, when the drum steadies, the press-to-set switch is relea3ed. 1. Power on/off recorder illumination control: The drum should rotate and Indicate the sound This control. applies 400-cycle primary power to velocity in the water at the sound head in use. the recorder. It varies the brightness of the 5. When both sound heads are immersed, internal chart illumination. the sound head select switch may be rotated 2. Sound head select: A: two- position switch to select first one, then the other, sound head. that permits an `operator to select either theEach time the select switch is changed, the upper or lower sound head for displaying sounddrum should rotate to a position that Shows velocity on the recorder drum. the velocity of sound at the sound head selected. Chapter 5 BATHYTHERMOGRAPH

When shifting from one head to the other, the SHIPBOARD BATHYTHERMOGRAPHS recorder also indicates the difference in depth between the two sound heads. A surface ship is much less concerned with 6. The press-to-set 4900 fps switch is de- buoyancy and salinity data than is the submarine, pressed. When the drum rotates to a velocityconsequently the shipboard BT is required to reading of 4800 fps, the switch is released. make only temperature versus depth measure- The drum then will re.tete and begin to givements. Three types of mechanical BT are in a continuous record of yelxity and depth forgeneral use aboard ships. One type is used the, sound head in use. for measuring shallow depths (200 feet), another far medium depths (450 feet), and the third for Checks and Adjustments deep water (900 feet). The BT carries a coated glass slide on which is scribed temperature Minimeni front panel controls and adjustingchanges as the BT dives to its operating depth. knobs are !retained;le the AN/BQH-1A. Peri- Upon retrieval, the teinwatures are read by odically, the operato.;- should depress the press- placing the slide in a gridded viewer. Essentially, to-set *Mitch and verify that the initial calibration each BT is constructed 'the same, and eave one accurney cf the equipment t maintained through- operate: in the same manner. Differvmese will out an operui..ing period. be noted where applicable. Table be:. lists the various Ste h. use and gieee their designed operating c,.. u. ,A new type, the expendable BT, Emergency Use is discussed later in the chapter. 3, Because the velocity display and depth display DESCRIPTION OF UNITS on the AN/BQH-1A are indepeadent of each other, th, recorder is capable of emergency All three BT types use the ...Nene size slide operation on either independent ohannehtifailure for recording temperature and depth. To elabo- of the depth circuitry occurs, an operatormay rate, the elidelithiSttin the deep model shows continue to supply useful velocity information4-1/1 times more data than the one used in the by manually posit Toeing the depth pen to e.readable e; 'tam model. The information taken, by the deep portion of the chart. In the event of have in BT is compressed, in comparison to the shallow the eouni 'Asada or drum circuitry, depth 'informs- recording. Because of this compression, it shows tion may still be euppited independently. loss detail and thereby makes it more difficult to read accurately. Lowering a deep-type BT in shallow water to obtain arecording is impractical 71.113 because insufficient deka: is gleaned from the Table 5 -1. BT Series Designations slide to make accurate readings possible. The deep BT differs slightly from the other two in that it does not have a stylus lifter. The stylus litter on the shallower BTs lifts the Series No. Name Design depth stylus from the slide as the PAT comes to within 70 to 50 feet of the surface while being retritved. OC-1/S This action prove' ts double traces that would OC -1 A/S Shallow 0 to 200 feet complicate the reading of Surface temperature. OC -1 B/S Another difference 0 that the spring on the 0C-1C/S depth element is.outeido the bellows. Because 0C-2/8 the deep- 13t pressure islement 3.a sit:Plier (to OC -2A/S Medium 0 to 450 feetwithstand the premiere of deep water), the Nang OC -28/S cannot fit inside to bellows as it does in the OC -2C /S depth elements of shallower BTs. Some old models of the deep DT may further be Identified OC-3/S by a diving lug mounted just forward of the fin OC -3A /S Deep 0 to 900 feetguards. The diving lug allows for very deep- OC -3B/S angled diVes to enable the PT to. reach its OC -3C /S designed depth in a minimum amount of time. Figure 5-2 shows. atypical mechanical bathy- thermegraph. ti RI 6 6, O INTRODUCTION TO SONAR

tzreesia___ #I.,,-)irrtbif:i

71.72 Figure 5-2. The bathythermograph.

Except for the differences just noted, allThe tube assembly is wound in staggered fashion three ofthe BTs are constructed the same.on a six-sided frame that extends beyond the They consist of a thermal element, a depthbody of the BT. This staggered winding ensures element, a body tube, a nosepiece, and a taila flow of water around the capillary tubing. guard. An auxiliary nose sleeve is availableBreather holes in the body tube allow water to to aid the BT in diving. These units are shownrun freely in or out, thereby keeping the internal in figure 5-3. pressure eqtialized with the outside pressure. The Bourdon tube element has a bimetallic _Thermal Assembly strip, and any difference in temperature between The thermal assembly is the temperature- the water within the BT surrounding the Bourdon measuring element. The temperature readingtube and the water flowing past the capillary represents the average temperature of the capil- tubing is offset by the action of the bimetallic lary tube assembly, which is located in the tall. compensator.

PISTONHEAD PEN BOURDON TUBE TAIL IFTER PISTON SUDE H LDER

PR URE SPRING (STEEL) BELLOWS STYLUS STYLUS ARM PRESSURE UNIT THERMAL UNIT

71.74 Figure 5-3. The BT and its parts.

62 Chapter 5 BATHYTHERMOGRAPH

Depth Element 71.114 Table 5- 2. Maximum Towing Speeds The depth element, located in the body tube, consists of a piston device with an accurately wound steel spring. An envelope, made up of three metallic bellows soldered together, sur- rounds the spring and keeps the water pressure Maximum speed offthe spring and off the spring side of the pistonhead. In one type of BT, one end of the BT type Depth Without With bellows assembly is soldered to the solid nose- (feet) nose --nose piece, but in another type this end is soldered sleeve sleeve to the mounting base. In both types, the movable epd is soldered to the spring side of the piston- 0C-1B/S, 0C-1C/S 200 15 22 head. Increasing water pressure tends to collapse the bellows and compress the spring, causing OC -2 B/S, OC-2C/S 450 10 13 the slide holder attached to the pistonhead to move forward, that is, toward the nose. 0C-3B/S, OC -3C /S 900 3 6 Body Tube The body tube serves as the main support and the BT still can reach full depth. Table 5-2, and protection case for the depth element and based on paying out 1000 feet of cable, shows thermal assembly. The movable brass sleeve the maximum ship speeds that can be used with covers the slide , ports next to the slide holder. and without the nose sleeve. Note, for instance, The sleeve may be moved forward easily when that to get the BT down to 900 feet without the itis necessary to get at the slide and slide' nose sleeve, own ship's maximum speed would holder. When the BT is to be lowered, push have to be 3 knots. With the nose sleeve, the back the sleeve until it touches the forward speed could be as great as 6 knots. end of the tail fins, thereby enabling the auto- The other device is a towing block attached matic stylus lifter to be activated. This action well aft on the BT and used while lowering the .covers the slide ports and also releases the instrument. This attachment causes the BT to stylus lifter so that the stylus can write on the dive at a steep angle because the towing point coated glass slide inserted in the slide holder. is well aft. Nosepiece: Tail Guard A Lute eRercentageof theapproximately The tailpiece assembly consists of the fin 25-pound weight of the BT is concentrated in pieces strengthened with two tie strips. This nosepiecie.. This weight makes the nose aseembly protects the capillary tubing and stabi- sink first during a BT loweringc. if,the towing cable is payed out freely.. The nosepiece has lizes the BT during the lowering, towing, and an attached :towing fin,: etviirel,, and shackle raising of the instrument. where the towing cable may be attached easily. THEORY OF OPERATION Auxiliary Nose Sleeve The BT can be operated while the ship is On Vessels Moving. at high speedi, earlier underway at speeds up to 18 knots. It works models of the hydro bathYtherraographoftenfailed most satisfactorily, however, at speeds of 12 to diVe to the depths' from which 'information' knots or less. was `desired. TWo types of diVing attachinents The temperature element, corresponding to Ifs*. been added to overcome this: the mercury column in a' glass thermometer, One 'attachment' is heavy bronie consists of ,about '45 to 50 feet of fine copper slipPed.: over the 'nose: -Otthe instrument_ "'and tubing filled with xylene. The tubing is wound Bemired bk:tightening,..tini =looking screws. This -around' inside the tail fins of the BT and comes sleeve adds to the Weight of: the BT and increases into direct contact with the sea water. One end diving speed. The shipcanmove at higher speed of -the tubing 'is fixed; the other 'end is attached 3 INTRODUCTION TO SONAR

TEMPERATURE ELEMENT PRESSURE ELEMENT

STYLUS ARM GLASS BELLOWS SLID! 411101 41111 7 111- ri I STYLUS "LIFTER BOURDON HELICAL XYLEM PILLED PISTON SPRING TUBING 'ruse HEAD

71.73 Figure5-4.BTtemperature and pressure elements.

to a Bourdon tube. As the xylene expands ortoward the surface, the spring expandsthe contracts with the changing water temperature bellows to its original shape. Thus, the trace the tubing expands or contracts, Closing thescratched on the plated surface of the slide is Bourdon to inove. A stylus is attached to thea combined record of temperature and pressure. free end of the tube. The stylus records the Pressure, IS directli proportional to depth. movements of the Bourdon, as it expands or Each instrument must be calibrated carefully 'contracts with ()binges 2 of 'temperature, on aby the Manufacturer because external, pressure gold-colored, :metallic=cOiited- glassslide.The temperature range Is 28° '.to 90°F. The slightly affectsthe internal pressure of the slide is held rigidly. on the end of a coil spring,xylene in the.Bourdon,and because temperature enclosed in the copper bellows. Water pressure, changes alsoinfluence the movement of the which increases in proportion to water depth,bellows. compresses the bellows as the'BT A special grid is supplied with each instru- Figure !'34 Illustrates 'the-ST lenVeritOre ment: for converting the stylus trace, to, tempera- and preSSUreeletionte; The dOttëdllné drawingsture and. depth. re,edings., These grids are not in the lower portion of the illuitietiofilehOiv theInterchangeable. For.correct readings the grid action of the stylus :moving,,jleft, on the slide,Is constructed so that the temperature lines may with a decrease In temperature, and the bellowsnot always be exactly straight and vertical, but being compressed 'Ato thee right: (note arrow), asvary, slightly,: with Increasing depth. The depth . depth; increases: 'Increase in depth, pulls the -.lines, likewise, are not exactly arcs of circles, slide; toward .themOsesot the BT, at right angles With radius equal to the length Of the stylus.

to the :-directiOn- In Avhich the stylus,- Moyes. toInstead,, . they are calibrated to allow for thermal .. record, ;temperature.:.- When I the ,..13Tis.,fraised expansion of the bellows. Chapter 5 BA THYTHERMOGRAPH

At a temperature of 105°F, the recording are special sheets, issued by the National Oceano- stylus moves against a stop pin. U this tempera- graphic Data Center, for recording the informa- ture is exceeded, the calibrationof the instrument tion obtained by lowering the BT. These logsheets becomes ruined, perhaps permanently. For this are discussed later in this chapter. reason, the BT must always be kept out of the When a BT has been damaged, turn in the sun and away from the vicinity of firerooms, instrument to the nearest repair facility at the steampipes, and other sources of heat. An in-first opportunity, The BT repair facilities are strument that has been overheated may have located at the San Francisco, Pearl Harbor, and the stylus arm jammed by the pen lifter bar in Boston Naval Shipyards, the high-temperature position. U another BT is aboard, use it, and turn in the damaged instru- BT TOWING EQUIPMENT ment for adjustment. U a spare is unavailable, gently lift the stylus arm from the pen lifter Towing equipment required to operate the bar and let the arm swing baok toward the low- bathythermograph is described in the following temperature side. *Wit. The temperature calibration henceforth will be in error as a result of deformation of the 1. Hoist: The hoist has a drum with a capacity Bourdon. This information must be recorded on of 3000 feet of cable, an electric motor with con- the bathythermograph logsheet. The BT logsheets trols and reduction gears, a control lever for

is

71.75 BT towing equipment.

65

8 INTRODUCTION TO SONAR 4.# operating thebrake and clutch, and a drum revolution counter. 2. Boom: The boom should extend at least 8 feet and no more than 10 feet from the side of the ship, and it should be strong enough to withstand a force of 1500 pounds. A typical hoist and a boom are shown in figure 5-5. In the illustration the BT is suspended from the towing block and is ready for lowering. 3. Towing block: A small counterbalanced wheel that attaches to the end of the boom to 71.76 allow cable to pay out with minimum friction. Figure 5-6. BT cable hitch. 4. Wire rope: The wire rope is of 3/32-inch diameter, 7 x 7 stainless steel aircraft control type, and is 3000 feet in length. through the towing block at the end of the boom. This block is of a special counterbalanced design BT ACCESSORIES for BT use. The type of cable hitch used to connect the Each BT comes supplied with the followingBT to the wire differs slightly with various accessories:(1) a grid and slide holder, formodels. The instruction book accompanying each viewing the slides, (2) a box of slides, (3) aBT shows the method of attachment for that swivel for attaching the BT to the cable, (4) amodel. One such cable hitch is shown in figure pair of tongs for holding the slide to rinseit, 5-6. If the connection is frayed, rusted, kinked, and (5) a thermometer for takingbucket tempera-or doubtful in any way, cut off the faulty part tures. These accessory items are described asof the wire and make a new connection. Be this text progresses. sure to seize the hitch to prevent its coming free. Check the swivel carefully. On those models OPERATION OF THE BT that use a Fiege-type swivel connector, make sure the Fiege sleeve is screwed into the socket Personnel operating the BT at night andas tightly as possible. More BTs are lost be- during rough sea conditions should wear life-cause of poor connections than from any other jackets and use safety lines. For each loweringcause. of the BT the succeeding steps must be followed. Step 3Check Winch Step 1Determine Water Depth The hand lever on the winch serves as both Determine water depth in order to select the brake and clutch. It .has three positions. When proper BT. it is vertical, the .winch. is in neutral and the drum can be turned" in either. direction. When Step 27Examine Wire and Connection to BTitis. pushed outboard to the engaged (or hoist), position, the motor' turns the drum"; and spoold Whenever poSsiblei determine that the wire is on the Wire. When the lever is pulled. inboard hitched to, the wind' reel. in such a manner that(or,..toward the operator) to the brake position, it cannot pull_; liifeSe if all wire shoUld pay off thethe drum is looked and cannot be rotated. drum. As an additiOnal precaution, do not pay ...Nip' the winch leverla neutral, turn on the out the 'last laYer Of wire when biking theinciter to make sure power. is available. The BT. The wire should be :Wound on the drum so"shaft:_ bearings should be kept well lubricated that it...PaYs &it an:Creels in at the top. of the,accerding to the instructions provided with each drum. For, : eurvey, *ft; it recommended drum should turn freely. that bare*ire'be'lised4not plastic-coated'ifire. ...The winch,10stallatiOn should be such that If 900-foot dePth BTs , are to be usedc.:it least tlie:wire .passes. across the top of. the drum. 2000 feet of 3/32-inch, 7 x 7 stainless steelThe hand lever should move away from the wire should be used. The plastic-coated wireoperator to engage the motor, and toward the usually comes in 1200-fOot lengthS and cannotoperator to 'set the brake. On some earlier be spliced, hence it is not long enough for use.model winches, the hand lever operation is with 900-foot BTs. Run the free end of the wirejust the reverse; that is, the brake is away,

.66 Chapter 5 BATHYTHERMOGRAPH

and the clutch is toward the operator. Checkthe stop pin. The slide must be fully in, other- these operating positionsto make sure thatwise the temperature recorded will be fictitiously the installation is correct and that the drumlow. Check the grooves of the slide holder to revolves freely in neutral. ensure that they are Olean, free of glass chips, and that the spring holds the slide firmly against Step 4 Put Slide in BT the opposite groove. With the slide fully in, the stylus is brought against the plated surface when Remove the waterproof .cover from the box the sleeve is moved back to cover the opening. of glass slides and take out one slide ata time, To reduce extraneous scratches on the slide, holding the slide by the edges to avoid damaging do not move the sleeve back until the BT is the metallic film. Do not remove the waterproofready to be put over the side. cover from the box until actually ready to use the slides. Step 5 Put BT Over the Side Insert the slide into the hole on the side of After obtaining permission from the OOD to the BT as shown in figure 5-7 and push it intomake a lowering, pick up the BT and pull the its bracket. The edge of the slide with thesleeve down over the slide port. On the shallow beveled corners goes in first, the longer beveland medium depth models, pull the sleeve down toward the nose of the . BT. Make certain thattoward the tail as far as possible so as to engage., the plated surface of the slide is toward thethe catch of the stylus lifter, then push the sleeve ' stylus. Push the slide in all the way againstup toward the nose about 1 inch. This action leaves the port open enough for the catch .to release when the BT is retrieved. On the 900- foot model, the sleeve should remain all theway back toward the tail. Set the winch lever in neutral. With one hand, hold the BT at the rail; with the other, take up the slack in the wire by rotating the drum: Set the brake when all slack is in. When ready to commence lowering, set the winch lever to neutral and lower the BT into water to such a depth that it tows smoothly Just below the surface. Put on the brake and hold the BT there for 1 minute to enable the thermal element to come to the temperature of the surface water. Set the winch counter at zero. Step 6 Take.Bucket Temperature While the BT is being towed at the surface, take the bucket temperature of the surface water and record it on the bathythermograph log .sheet. Special bucket thermometers are supplied for U.S. Navy surveys by the Oceano- graphic Office. These special bucket thermo- . meters arc more accurate than thermometers issued with the BT kits, and are to be used in lieu of the ones in the kits. The thermometers are read to the nearest 0:1°F. A bucket can,.be made from a half-gallon can (obtained from the galley) and attaching a line to it. Attach the bitter end. of the line to the lifeline or rail. Throw the can over the side and let, it fill and empty several times before 71.77 . hauling a surface sample aboard. Assoon as Figure 5- Inserting the slide. itisaboard, set At on deck and insert the

67 so, INTRODUCTION TO SONAR thermometer into the bucket so that at leastStep 8Stop at Proper Depth 3 inches of the bulb end is immersed in sea water. Stir the thermometer with a circular To reach a given depth, the amount of cable motion for 20 to 30 seconds and then read itto be payed out depends on the speed of the ship, with the stem still immersed in the water.the type of BT, and whether the nose sleeve is Stir it once or twice more and check the reading.attached. Table 5-2 provides a rough estimate The buclultesample must be taken while theof speeds at which full depth may be expected BT is being towed. Make the temperature read-to be reached when using 1000 feet of wire. ing as soon as possible after the sample is on The observer should take data on the length deck. If the sample is allowed to stand for moreof wire payed out and the actual depths recorded than 45 seconds, the temperature reading noby the BT. He then should plot a graph showing longer is valid. It also is of importance to stircounter reading against depth for various ship the thermometer to bring speeds. it to temperature When the counter indicates that the proper more rapidly and accurately. length of wire is payed out, or when the last layer of wire on the drum is reached, the brake Step 7Lower the BT should be applied smoothly, allowing the drum to stop without a sudden jerk. An excessive Move the winch lever to the neutral positionjerk will part the wire. Now the BT will swim and allow the wire to pay out freely. Success inback up to near the surface far astern. Check reaching the maximum 'desired depth depe to see that the wire leads properly for hauling chiefly on two factors:(1) having the winchin. If it does not lead from the towing block to drum and towing Neck bearings. well lubricated e center of the drum, adjust the boom guys to minimize friction; and (2) getting the BTuntil it does. down below the ship's screw wash as soon as poslible. With practice, it is possible to raiseStep 9 Haul in the BT 1#--1 the BT slightly,after the surface .towing is completed, skip it Oft the crest of. a wave so Move the hand lever smartly from the brake that it swings forward, and then lower it rapidly.position to the hoist position. Do not pause while This method enables the BT to plunge into thegoing through neutral, otherwise more wire will water, and its momentum will Carry it morepay out. Guide the wire back and forth in even rapidly y past the turbulence of the wash, enablinglayers on the drum, using the stick. The end of it AO reach a greater depth, Thil technique isan old swab handle will do. Do not use a metal especially 'useful with the 900-foOt instrument.guide. If kelp or seaweed fouls the wire, ease It takes practice, but, to the experienced operator,on the brake and clear the wire with a boathook. this method is easy to use and is more effectiveHaul in at full speed until the BT is close astern than the diving lug assembly. attache to somebut still a safe distance from the ship's screws. of the Old models. Step 10Bring BT Aboard When the 'ship is making more than 12 knots, there usually ls .enough drag on the wire while When only about 100 feet of wire is out, the the 'HT: is diving to ensure that it will not slackenBT should be readily visible at- the surface. and backlash. At lower speeds,.and during heavyAs the wire is hauled in, the BT will reach a rolling,- the wire may slack betWeen ..the winchposition nearly under the boom where it will and the towing block. Slack. in. the; wire: maybegin to porpoise, breaking clear of the surface cause, backlash .ot the-Winch drum or: a kink atand swinging forward as the ship rolls or as the ,,towing block, The.operttor ,shbuld providewave crests pass: This' action is the most himselfwltli'.a round; stick., about ..15 -inches long critical point in the operation. To bring the for the purpose 'of. gently:slowing the drum whenBT alongside and. raise it without too much excessive slack appears. :Do. not apply too much swing requires practice. If the BT is brought pressure .:,to the drum...with -the., stick, becausein too fast, it may skip or swing forward of once: thtAiving motion' .of the BT is 'arrested, itthe boom, perhaps hitting the side of the ship Will not dive- farther regardless', of the' 'amount or swinging completely over the boom. If the of:Ay/ire': payed, out. DO not touch the wire withBT skips or swings forward of the boom, it your", hands when the ,' drum is in motion; youisadvisable to shift at once to neutral and may be injured seriously... ' allow the BT tosink freely until it passes

:68 Chapter 5 BATHYTHERMOGRAPH clear astern and it is safe to try again. The CAUTION: Never let the temperature of the operator must learn the feel of his own winch. BT exceed 105°F (40.6°C). If this . temperature is exceeded, the cali- With a littleprtoticethe BT can be brought bration of the instrument will be safely to within 2 or 3 feet of the towing block. damaged. Never leave the BT on The winch motor should be turned off at this deck without protecting it from hot point, eliminating the possibility of accidentally sun. Suitable protection tothe jamming the BT against the towing block. Some thermal element can be effected winches have a handorank, permitting manual rotation of the drum at this point. The BT can by keeping it covered with wet then be brought aboard in various ways, de- cloths. pending on how the boom is rigged. Step 12Check Slide With the standard gate boom, the use of a retrieving line and ring is recommended. This As soon as the slide is removed from the line consists of a metal ring from 1 to 1-1/2BT, examine it to be sure that a suitable trace inches in diameter through which the wire iswas obtained. If the trace is smudged or oblit- passed between the towing block and the. BT.erated in any way, lower the BT again with a To the ring is attached a retrieving line, whichfresh slide. is secured to thelifeline or rail. With the Once a suitable slide is obtained, rinse it off proper amount of slack, the ring rides freelyin fresh water, and label it according to the when the BT is being lowered and hoisted. By directions given later in this text under the topic hauling in on the retrieving line while easing heading "Marking BT Slide." the brake, the BT can easily be brought to hand. If a retrieving line is not used, it will be PRECAUTIONS TO BE OBSERVED necessary to rig in the boom by casting off the -To obtain the greatest accuracy and prolong after guy and swinging the boom in with thethe useful life of the BT, certain precautions forward guy. Two men can pull it in with amust be observed. They are discussed in the boathook one man on the hook and the other to slack the wire with the winah. If the boom ensuing topics. tops up, the BT can be brought aboard by one Disassembling BT man hauling in on the topping lift. Do not disassemble the BT. It is a precision Step 11Remove Slide and Secure Equipment instrument, with delicate internal mechanisms. Even with thegreatest care possible, it is As soon as the BT is in hand, move the sleeve difficultto avoid damage if disassembling is forward toward ,the nose to .lift the stylus off attempted aboard ship. the slide. This action prevents the upper portion If, for any reason, the BT fails to operate of the trace from being affected, by air tempera- satisfactorily, it should be turned in for repair, ture and becoming obscUred as the instrumentwith a report indicating the symptoms to aid is handled.. the repair facility in correcting the trouble. Slack off the' wire, place the BT in. its deck Standard failure reports also should be sub- rack, and set the brake. NOtffy the bridge that mitted in accordance with current directives. the BT. is On .deck. Partially eject 'the Slide. by pushing itgainot edge with the forefinger Maintenance of BT the wire slide "remover; or aPenoil throughthe slide-ejecting POO. GriP the slide carefully ,by The BT is an accurate measuring instrument the thuMb and forefinger. Hold. the elide only and, although the construction is reasonably

by the edges,-:being careful not .to obscure the rugged, the internal mechanisms are delicate. trace with smudges Or fingerprints. Careful handling is essential to maintain the If another lowering 16 to be made soon and accuracy of the measuring elements. there is no danger of -overheating the BT, it .After each period of use,the.BT should be may be left 'in the deck rack connected to therinsed with fresh water. Never store a BT wire. Otherwise, unshackle it and stow in aWitt is being withdrawn from use without first cool place: rinsing it thoroughly.

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1 Chapter 5 BATHYTHERMOGRAPH

1,

71.82 Figure 5-9. Grid mount assembly and slide viewer.

20 feet for the 450-foot model, and 40 feet foritems, needed for reading BT slides, appear in the 900-foot model; the BT slide shows doublefigure5-9. The grid mount assembly in the traces over the entire trace length; more than illustration is a bottom view and shows the grid 18 months have elapsed since last calibration.as it is mounted in the assembly. Patting it in as shown (backwards) allows it to be read correctly when viewed through the slide viewer. The BT BT SLIDES slide fits behind it with the etched side toward the grid, and is held in place by a spring clamp. To make proper use of information on the slide obtained by lowering the BT, an. under- Loading Slide into Grid standing of how to interpret the trace and its Mount Assembly meaning is of as much importance as the lower- ing and raising process. To read the trace To load the BT slide into the grid mount properly, two pieces of equipment are necessary. assembly, set the slide loosely in the holder. They are the. BTgrid and the slide viewer.It should be positioned with, the coated surface down and the beveled corners on the right side, GRID AND VIEWER just 'clearing the stop pin. Hold the assembly as shown'. in figure 5-10. 'With a thumb motion Notice in figure 5-8 that the grid has a blocklike that used in rolling a cigarette, push the in the lower right corner containing certainslide against spring until the slide drops information. Included are the BT serial number, flat against he grid:' Then push the slide to the type (OC-2/S, meaning that It is the medium,the right. firinly against the stop pin. The coated or 0- to 450 -foot depth model), fond the date ofsurface should lie smoothly against the grid. manufacture. The prescribed method prevents the grid The grid is mounted in a grid mount assembly from scratching or rubbing against the coated that attaches to a slide viewer. Both of thesesurface. When the holder and slide are placed

71 INTRODUCTION TO SONAR

peo05*V GP.* VIP go se go 0 25 50 75 100

125

15 175 71.83.2 61' I Figure 5- 10. Looking the BT slidein the 200 0C-14 grid mount assembly. 11-9-60

In the viewer, make sure that the slide is kept tight against both the stop pin and the groove opposite the spring. Otherwise, temperature and depth readings will be incorrect.. 71.84 If the grid becomes loose in the holder,Figure 5-11. BT slide as seen through the apply cement to the face of the grid. Check to viewer. see. that the narrow edge of the grid is tight against the stop pin, and that the long edgetrace and scales into proper focus. Handle the (the zero pressure edge) is tight against thegrid carefully to avoid scratching the grid or edge of the holder opposite the spring. The the slide. Each BT has three identical grids. spring is narrow and is placed in such a posi-Two are sent along with the BT, one of them tion that the grid fits behind it. As a result, theto be used as a spare. The third grid is retained spring bears on the slide and holds it snugly at the National Oceanographic Data Center. without pressing on the grid. HYSTERESIS EFFECTS Reading Accuracy The stylus etches information. while the BT The tracescratched by the stylus is a tem- sinks and also as it rises. If water conditions perature-depth .curve.Each,point on the trace. whereitrisesdiffer greatly from where it represents the. temperature, at a given depth. sinks,two distinctly different traces will be Temperature and depth values are read from theseen. Usually, however, differences in water curve on the slide. Temperatures, arereadconditions are negligible, so that, if two traces horizontallyand' should be read as close as appear, they may be caused by hysteresis. This possible to the nearest tenth (0.1) of a degree. condition is a lag in the movement of one of the Depths are read vertically and .should be read elements. to within 10 feet. or better on the. 900400t BT, Ifitis suspected that hysteresis exists, 5 feet or better on, the 45046ot BT,:. and 2 feet insert a new slide..in the BT and make a second on the 2004Oot models., lowering. A brief inspection of the slides will Whena BT., slide. seen through the viewer, reveal if water conditions changed during the the trace is superimposed upointhe grid for the two lowerings. If water conditions are the same, paiiicular., AT that made the temperature record- and the BT is affected by hysteresis, each of ing.. Figure "5-41. shows what a, Sonar .Technician the two slides will ehow two separate traces ..sees ashe, viewsa BT:Slide.,, following each other: If the traces are essentially ,Place thethe beak of thejx.ansparent,glass a Slight separation is negligible. ,.which, is tuled offtainperature and depth :lunges.: The slide should 'be held back .,of the READING SURFACE TEMPERATURE gild in the same pOsition it.had in thefm..The When the BT is on the deck, it usually has viewer's eyepieCe may. be adkieted to bring the different. temperature than when put into the 72 .'l

Chapter 5BATHYTHERMOGRAPH

water. The temperature element moves the stylus along the zero depth line of the surface water 60 65 temperature position during, the 30 seconds or 0 111.1"..mmommismAmMANNuma °11111:02111A6mmAmilmlismimiall11le SEA more when the BT is towing at the surface. 015gommmismoMMMIIMAnompiNVIRSURFACE Consequently,the top of most traces is an 00 NAM, nom:::::1:g: almost horizontal line. This surface trace should -Imo mmommompAimmoirkillimmow.gaft.111 fall along the zero depth line of the grid when elli:LAimmumEnr411111111111milli the slide is viewed. If it appears more than 3 :1141:::::::iii1:::!4:: feet above or below,, correct. the depth readings 100 mm by the amount of this error. Read cAurf ace mmmmmmmmmmmmmmmmmm UiR 150 m mmmmmmmm ft temperature by noting the point at which the e trace starts downward from the surface trace. It's a good idea to make a comparison from 600mmm:::!1mmmmmmmSmmm:mim:mg .! :..i.:l.22i:.i.i.2!i!.!i.i.!fti..ft.Iill!..1: time to time between the surface temperature iiift as read from the slide, and the bucket surface 250 temperature as read for thesame lowering. On a seriesof slides taken from the same 4 BT, the readings from the slide and the bucket thermometer should be about the same. If there 71.85 is a difference, and if the difference continues Figure 5-12.Graphing the BT trace. for later lowerings, the calibration ofthe BT probably has shifted.A shift in calibration, sometimes called a shift in thezero points, of theythermograph observation. It is from usually does not change the the sourpattern that an estimate of maximum accuracy of the BT. sonar range can be made. But, make a note on the BT logsheetshowing The variation of temperature with depth can the slide number and the time at whicha shift in calibration", was detected. be quite complicated. Many different conditions If the BT accidentally strikes either the may be represented by the different bathythermo- ocean floor or. an underwater object, the depth graph slides. It is convenient to consider the at which it struck can be determined by reading water as layers. In each layer the temperature the depth of the horizontal line across the trace, can change from top to bottom. Create a mental made when the stylus arm vibrated with the picture of the location of these layers from the shock. appearance of theslide. Visualizetoo, how the temperature is changing. Study the following READING examples until each kind of layer can be identi- BT. TRACE fied easily. The bathythermograph, as alreadypointed out, provides a continuous visUal record of the tem- Negative Gradient peratures froth the .surface .of the seaa depth to which it is lOwered.. The temperatures of A negative gradient condition exists when the various ocean 'depth*. recorded. on the Slide by temperature of the water decreases with depth.. the BT are represented'..ae egret:Oa' tempera- A loWered through a negative gradient, ture against depth when seen through,the grid proctdoes a slide with the etched trace sloping viewer. Figure 542 shows the. portion of. a to the left as depth increases. Figure 5-13

BT grid immediately eurrounding the . trace. represents a trace showing a negative gradient. In figure 512, the line marked"A"repre- This illustration, a -particularly sharp sents changes in temperature between the sea gradient, wiiiali`iecoMMon.' Negative "gra- surface and 'a depth of 250 feet. Little change dients spell trouble for sonar' operators because in temperature results until'a. depth of 50. feet they result in; hort seem*. ranges. is reached. At that point, 'the ; temperature of the Water,begins to -cool quite rapidly to a Positive Gradient depth of .145 feet. Below 145 feet, the water cools more slowly. Sometimes, layers are found in which the

From the temperature curve, one can dis- temperature increases . with depth. The BT trace cover the sound pattern of the seaat the time slopes to. the right. Although usually observed

:73 0%4 INTRODUCTION TO SONAR

71.87 Figure 5-13. Sou&l pulse travel through negative gradient. in coastal waters, this condition may be -found unusually long ranges to targets near the surface. anyyhire. In figure 5-14 a positive gradient is Little of the pulse's pov(er penetrates the nega- _shown to exist down to a certain depth, beyondtive gradient, however. The reason is that the which a negative. gradient is formed. Depending higher temperatures in the lower part of the -on the depth of the start (top) of the negativepositive gradient bend the pulse back up toward gradient, such a trace can also mean troublethe surface of the sea from which it is reflected for the Sonar Technician. As a result of thisdownward again, and so on, foiming a surface condition, the shipboard sonar operator observes channel.

POSITIVE GRADIENT ,UNUSUALLy LONG _ ii FtNES,Zi, .

71.86 ;Figure 5-14. Sound pulse travel through positive gradient. k

Chapter5 BATHYTHERMOGRAPH

4ni verfNitp 6% IA !!:1 1%.

ISOTHERMAL: ti NO 6 RAD I EN T LONGRANGES ';461,1t

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71.88 'Figure5-15. Sound pulse travel through isothermal water conditions.

Any energy of the pulse that does pass throughtemperature profile of the sea. Notice that the negative gradient is reduced greatly, andevery time a straight, vertical BT trace is the sound beam is bent sharply downward. Sub-*recorded, the layer of water between its limits marines operating 50 feet or more beneath theis known to be isothermal. top of the negative gradient are difficult targets to detect. The shipboard Sonar Technician- may DAILY HEATING get extremely long ranges on a submerged target near the surface (such as the underwater Daily heating of the surface water layer has section of the hull of another screening ship),a marked effect on sonar ranges. It produces a but he may be unable to detect a submarine condition MW men call afternoon effect. just a few hundred yardsaway. Should the When the surface is heated by the summer submarine enter the positive gradient, however, sun, and the winds are not strong enough to it probably would be detected. keep the surface water well mixed, the water ,close to the surface may be several degrees Isothermal Layer warmer thlui the water 20 to 30 feet down. This effect is maximum in the late afternoon, An isothermal layer of water is one of uniform. ornearly uniform temperature through- out. This condition is not confined necessarily near the surface of the sea, but often is found TEMPERATURE -. between layers or gradients of markedly dif- SURFACE ferent temperatures. An isothermal condition can be caused by Waters of two different tem- peratures mixing. In this respect, it sometimes is referred to as a mixed layer. Isothermal layers' are of importance in predicting the path the sound pulse will follow. For this reason Sonar Technicians must be able to read accu- (A) (B) rately the top and bolom depths of such a layer. Youare,shown anAspthermal condition in figure 5-15.Now look at figure '5-16 to see how iso- 71.89 thermal layers sometimes are located in a Figure 5-16. Temperature profiles. 'Is

INTRODUCTION TO SONAR .g mean time (0000 to 2359), giving the hour and minute at which the bathythermograph entered SURFACE the water. Draw a dash between the slide num- ber and the time. Slide number 5, taken at 2240, for example, is marked 5-2240. 2. Line 2, Date: Day, month, and year are 1600 entered as numerals. Use Roman numerals for the month. For example, 29 November 1950 is written as 29-XI-50. 3. Line 3, BT instrument serial number: The serial number of the BT is stamped near the J nose of the instrument. It is an important number, 2000 2400 0400 because thedata center that processes your slides has over ten thousand grids, only one of which is a duplicate of yours. Always include 71.90 any letter that precedes or follows the serial Figure 5-17. Effect of daily heating. numbers; for example, BT 1216A or BT AA-1257. Without the proper instrument serial numbers, the information on your slideis worthless. and usually disappears at night as the surface cools off and water continues to mix. Figure FURTHER USE OF BT SLIDES 5-17 is a simplified illustration showing how traces on a series of slides may indicate daily In addition to providing immediately useful heating or,cooling near the surface. data on the temperature conditions of the sea, An isothermal layer is seen at 0600 (localBT slides are used in compiling charts that time) on a calm, clear day. From 0600 to 1600 give the ocean's average thermal conditions for the surface is shown gaining heat from the suneach month of the year. These charts are pub- faster than it can dissipate the heat back intolished by the Navy Oceanographic Office in the the atmosphere. The surfaCe temperature in-form of an atlas.. Atlases give the average creases, and a negative gradient layer, repro-.thermal conditions and probable detection ranges sented by the crossed lines, is established.for various types of operational search sonar e**.\This layer deepens as the heat penetrates, andequipments. The charts are used by planning diffuses downward by conduction during the time the surface is gaining heat. .---7-After 1600 the surface cools off by evapora- tion faster than it receives heat from the declining sun. The cooler and denser surface water mixes and may destroy the -.megative gradient layer. Sdficient cooling may occur during the night to reestablish a single isothermal layer, as shown at 0400. MARKING BT SLIDE Immediately after the slide is removed from the BT, it must be marked as outlined herein. Use a sharp pencil,: and be ocreful that you don't obscure or touch the .temperature trace. Informs** on the slide and BT logsheet must agree. Figure 5-18 illustrates the information to be marked on the slide. 1. Line 1,Consecutive slide number and time group: Number the slides consecutively between:: ports.If 300 slides are used, they 71.91 are numbered -from. 1. to 800. .7.7se. Greenwich Figure 5 -18. Marking the BT slide. Chapter 5 BATHYTHERMOGRAPH

personnel to select safe convoy routes. Another The foregoing procedure is to protect your use is to estimate where the enemy might have slides so that NODC has the necessary informa- his submarines deployed. tion to process them. Fold and staple the BT In wartime, routes of each convoy must be logsheet so that the mailing format printed on planned carefully. If an area in the ocean hasthe _reverse side isdisplayed. Mail the BT consistently poorsonar,conditions, the convoy slides, lopheets, and recorder charts to escorts will have difficulty detecting subinarines, The National Oceanographic DataCenter so the convoy should stay clear. If the average detection ranges between two areas differ notice- Washington, D.C. 20390 ably; it. will- be necessary to vary spaIdng of the escorts. The atlases show these conditions and, OBTAINING ADDITIONAL LOGSHEETS because they-are available in: advance of. the AND SLIDES actual operation, they can be' used to estimate the number of escorts needed to provide ade- Bathythermograph logi3heets may be obtained quate protection. as follows: The dimes are prepared from the informa- 1. All naval activities in the Atlantic area tion contained; on, thousands of BT-slides, which, (including theGulf of Mexico, Panama for many years, have been forwarded by individual. Canal Zone, European and Mediterranean ships to the Oceanographic Office. Atthe Oceano- areas) submit completed Form DD -1149. graphic Office; the slides are analyzed, and to . average monthly thermal: -conditions,, for areas The Oceanographic Distribution Office of the ocean are 'plotted on ocean charts. The U.S. Naval Supply Depot result is a mixithlY series of :charts, showing 5801 Tabor Avenue average condition 'thernial belts. The belts can Philadelphia, Pa. 19120 be consulted to decide which are the dangerous 2, All naval activities in the Pacific area and which are the relatively _salevassage routes. (including Antarctic and Indian Oceans) To guarantee that the., slides arrive hi ',good submit completed Form DD-1149 condition, they -must be handled with utmost _The -Oceanographic Distribution Office care. They must not be iniudged, scratched, t.S..Neval Supply Depot or broken., '_TO c.be 'Useful; they must ; retain: alh Clearfield, Utah 84015 of the infOrmatiow: required by the National , . Oceanogrephic :Date Center, =where the slides: 3. Allother navalactivities may request now are prOcesSed,- w - - The Naidonai OceanOgrapnic Data Center MAILING SLIDES: 'AND: LOGSIIEETS2,,' shihgton;D.G.20390 . ' Bathythermograph slides are 1i:standard stock TO avoid breakage; and to ensure-eidO delivery ROM the' elecitrOnic system and are obtained Of the BT slides, !imake- Certain that you', carrythrough ; any 'normal supply.Support ;channel. out the folloticing :fireffitlittoiii-.befOre mailing the The ,StOck number and desoriptiOn is NS 6655- slides to the Oceanographic Office. 67-67-987, SlideSet, Metallic Coated: A set :consists of molded plastic box, 50 slides, and 1; :Futpacvz: .no,inittOrial.-betWeenfalides. ,.;teleiCoping box for shipping. the box welh,.usiiig the .same ?pox in' hitt reo,eited standard mailing,' Copies of tliis OpO=0107/ii4=0..)t-744it A: BT slidegmustbe .accompanied r`wobtained ;;tOiiit' . 3.%6a) en r(NO ^whensent-to the Oceanographic 9 :444 0,taii#464:0#40.Brid. `processiag'th& BT elides: .orin;.muo A,38igned standard radio mission tcf {rsynoptio° BT , ornionrere mess e''

INTRODUCTION TO SONAR

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INTRODUCTION TO SONAR

A sample logsheet is illustrated in figureItem 9 Air Temperature 5-19. Information pertaining to one BT drop is supplied on the form. The environmental half Record the dry and wet bulb air temperatures, of the lOgsheet requires completion of 14 items. to the nearest 0.1°, and check the appropriate The radio message portion has 7 data units,box for °F or °C. If centigrade temperature is less than 0°, add 50.0 to the actual reading (-2°C plus spaces for the necessary trace readings.is entered as 52.0). Enter a dash above the first ENVIRONMENTAL DATA ENTRIES (tens) digit to indicate Fahrenheit readings below In the heading of the environmental data section, record your ship's name and hull num-Item 10Barometric Pressure bercountry,sheet number, and sponsoring Use millibars, to the nearest tenth, to record activity.Spaces for cruise and station numbers barometric pressure, omitting the thousands and tre for special assignments.' If an apparenthundreds digits (1011.2 mb si 11.2). Table 5-3 malfunction of the BT wows, inolude pertinentis used in converting inches to millibars. information at the bottom of the sheet under "Remarks.'-" Successive logsheets are numberedItem 11Weather consecutively. Record present weather (WMO code 4501) Item 1 BT Instrument Number as follows: The number is stamped on the nose of the BT. Always include any letter used' as -a prefix 0 Clear (no cloud at any level). or suffix to the number.. Compare' the 'number 1 Partly cloudy (scattered or broken). stamped on the BT with the number on the BT 2 Continuous layer(s) of cloud(s). grid. The two numbers MUST agree. S Sandstorm duststorm, or blowing snow. Item 27.-Slide Number 4 Fog, thick dust, or haze. 6 Drizzl,e. Number ihe slides consecutively, starting with 6 Rain. number. 1for,the; first BT reading taken after 7 SnoW, or rain and snow mixed. leaving port. 8 Shower(s). Item 3.4. Date 9 Thunderstorm(s). Day :and month are given according to Green- wichdate. Record the last two digits of .the, 00 -Calm 20 195° 204° year. 4- 01, 5° 14° 21205°7214° Item 44 Time 02 15° 24° 22, 21 5° 224° 03 25 34 23 225°-234° RecOrd the GMT ;and.minute_at .which 04 35°+ 44° 24 235°-244° theST entered ,the.wate 05 45° 54°. 25245° 254° Items 5'1,,and 0,,÷1; 06 55° 64° 262556,-264° ; 07 850-- 7r 27. 265°=- 274° Record, thif Mispheie, 08 ,75° 84° 28 -275°.-284° IN or -E., E or l the BT. 09 ' 94° 29 '285°-294° Prefix ,`complete 10 95°-104° 31Y 2'95° -i=304° the ' degrees ,;1 id9-; 8° is.' 31 '105°7=314° recOrdedtas08;-- 6. reixirded, as 027 32. 315°7- 324°

m, 1,=== 34 344°

:36;;'355° 4° tion

gAviatAtiii Chapter 5-BATHYTHEFtMOGRAPH

112.78(71B) Table 5 -3. - Conversion Table, Inches To Millibars

Milli- Milli- Milli- In In In. M- In' In' Milli- In 51111- Milli- bars ban bars bars bars oars- In bars

27. 50 931.5 28.00948.228. 50 965.129.00982. 129.50999.0 30.00i.01&080. 501, 032.0 27.51 931.6 28.01948.5 28.51965.5 29.01982. 429.51 27. 52 999.330. 01 1. 011 330. 51 1.033. 2 981. 9 28.02948.9 28.52965.829. 982. 7211.5 999.7 31 021.018 630. 52 I, 033. 5 27.53 932. 828.03949. 2 28.53966. 129 03 983. 129. 53 1, 000.0 27. 54 80. 03 1, 018.930. 53 1. 033. 9 932.6 28.04949.5 28.. 966.529.04983.429.541,000.3 80.041,017.330.541,034. 2 27.55983.0 28.05949. 9 28.55966.829. 05988.7 27. 56 29. 55 1,600. 730. 051, 017.630. 55 I, 034. 5 983.3 28.06950.2 28. 56967.2 29.06984.129. 56 1, 001.080. 06 1, 018.030. 56 1, 034. 0 27.57983.8 28.07950. 6 28.5 967.529.0 984.429.51, 001.4 27. 5 8 80. 071, 018.330. 57 I, 035. 2 9 3 4 . 0 28.08 9 5 0 . 2 8 . 987.8 21 984.8 2 9 . 5 8 1, 001.7 3 0. I; 1, 018. 830. 58 1, 035. 6 27. 59934.3 28.09951..2 28.5'968.229. 985.129.5 1,002. 0 80.091, 019.030.591,035.9 . . 27. 60 984:628. 10 951. 628. 968.529. 1 i 985. 429. 60 1, 002. 480. 10 1, 019. 330. 60 1, 036. 2 27, 61 935.0 .28. 11951. 928. 61 968.829. 11985. 8 29.61 1, 002. 7 27. 62 80. 11 1, 010. 630. 61 1, 036. 6 935.328. 12 952. 8 28.6 969.229. 12986. 129.62 1, 003. 130. 12 1, 020.030. 62 1, 086. 6 27. 63935.728. 13 952 6 ; 28.68969.529. 13 27.84 986. 520. 63 1, 003. 480. 18 1, 020.330. 63 1. 037. 3 936.028. 14 952. 9 28.64969.9 2114 986.8 20.64 I, 003.7 30. 14 1.020. 730.64 1, 037. 6 27.65 986. 328. 15953. 828. 970.220. 15987. 129.65 1, 004. 130. 15 I, 021. 030. 65 1, M. V 27.66 936. 728. 16 953.6 28 970.529. 16 27.67 987. 529. 1, 004. 430. 16 1, 021. 330. 661, 038. 3 937.028. 17953. 9 28 6 970:929. 1 987.829.67 1, 004. 730. 171, 021.730. 67 1..038. 6 27.68937.4 281;954.3 28. 971. 229. 1:988. 2 27.69 29. 68 1, 005. 130. 18 1, 022'030. 68 I, 038. 9 987.728. I 954. 628. 971. 629. 19988.529. 69 1,005.4.30.191,022. 480.691, 039.3 27. 70 938.028..20955.0 ,28 971. 9 '29.20988.820. 7 0 1, 005.8 3 0 27. 71 . 201, 0 2 2 . 730. 71 I, 030. 0 988.4 28.21955. 3 28. 71972. 229. 21 989. 220.71 I, 006. 130.11 I, 023. 030. 71 1, 040. 0 27.72938.7 28.22955..628. 972.6 29.22989.529. 72 1, 006.4 30.22 I, 023.430. 72 1, 040. 3 27.78 . '939. 0 28 28958.0 28. 78 : 972 929.,23989. 829.78 1, 006.830. 23 1, 023. 730. 75 1, 040. II 27.74 .:939. 428. 24956. 3 .28..7 973. 2 .21124990. 229..74 1, 007.1 27. 75 30. 24 I. 024. 030.74 I, 041. 0 639. 7 .28. 25'956. 728. 75973..629. 25900. 529.75 1, 007..5 80.21, 024.480. 75 1, 041. 3 27.76940:1211. 26 957. 0 48. 7 973:11 '2946990. 920.'761; 007. 880. 26 1,- 024. 730. 76 I, 041. 7 27..77940.428: 27 .: 957.'328` 174:8 29.'27991..229. 77 1, 008. 130. 27 1, 025. 130. 77 1, 042 0 27.7:940.1 :28:28957.7 28.E 7 , 974.:629.28991.539. 78 1, 008. 580. 28 1, 025..430. 781, 042.3 27 7''941.128:29 , .958. 0 .28.7' .174: 9 29.29991.929. 79 1, 008 8 31 291, 025.730. 791, 042. 7 1 1 27.80,,:.;941:4 28:30 !' 958:3 W. 3 9 7 5 . 1 2 9 . 9 9 2 . 229. 1, 6 0 9 . I3 1 . ' iI, 028.1 3 0 . 1 , 0 4 3 . 0 27.,81 ',6,:941. 8 28.31 ' ...;,958,.728. 81 975.6 ;29.31992. 629. 81 I, 009,5 -81 81 1,026. 430. 81 1, 043. 3 27.82 942. 1.28 32 -659. 028: :v .971.0'29. 992. 929. 82 I, 009. 8, 30. 821, 026. 830. 821, 043. 7 27.88 942. 4 '411.. 88 '. '951:4 t 28. 976:8 '; 29:88993: 229. 88 1, 010. 280. 831, 027.130;981,04t0 ." 27.14942. 8 28:34 4 ,459:1 .`,28. 976. 6 ' 29. 84993. 8 ' 29. 84 1; 010.1 -.80. 84 I, 027.:430. 84 1, 044. 4 27.85-Y..948: 1 .,28: 85 !. 980:0 .' 2885, -; 977: 020 35903. 929. 85 1, 010. 880. 85 1, 027.830. 85 1, 044.7 27.86948. 4 -28,8611460,428.: 977:3 .19.16 - 994.229. 86 1, 011.2 80. 86 I, 028. 1 30. 86 1, 045. 0 27.87941 8 . 28. 87 ;.-660.1 ' 28 : ''.977. 7 29 "8 994, 629. 871, 011.5 30. 87 1, 028: 430. 87 1. 045. 4 ,27.88 ,',944.,1: 28. 88.961. 1'''. 28. : : 978. 029. 994. 929:88 I; 011.'9 27.89 .: 948'5 30. 381, 028. 880. ':1, 045. 7 . 28. 39 : 961. 4 , 28. ',,...' 978. 3 29:39995. 329. 89 1, 012. 280.391,020. 130. 89 I, 046. 1

27: 90 :.:644. 8 ,.28:40541...7 .28 ' . 978. 729. 1 9986 21 .01, 012.5 it 40 1, 029:530. II 1, 046. 4 X27.91 ';'945.1 '',18:41 ..'.9132 1 28_91 ',... 979. 0 '.29. 41995.' 9 ' 29:91 1; 012 9 '80:41 1, 029:880.91 I, 046. 7 .27i92 : 7 4 94IZ5 '.12&42 ; , ; 9 6 2 :. 4 2 8 . :.;979.;8 4 9 : 4 2 9 0 6 . 3 -, 2 0 . 92 1, 018:2 :. -80.421, 0 8 0 . . 1 .. 30 . 0 2 1 , 0 4 7. 27.- 98': 945. 8 '..2&;48 ;962:1 :.28.1 :. 979.7.7!29. 43 :..996i.6'29.68 1; 013..5 .:30. 43 I, 27:',94 :-; 030.5: 30. 03 1, 047. 4 946:2.' 28:44 ',- .96311 ,.... 28: 04 .: 980.- 0.29.. 44' 097. 0 . -21 94 1; 018;9 80.44 I, 080. 830. 941, 047. 8 27: 95 ,. :946.:5'28::45 '..968:4, 28:4, '' : 980.4 ...29:45 '. 997`8 ..MI: 95 I; 014:2' 80:45 1,631: 280. 951, 048. 1 ,: 27. 96 ,''..-,9418 ;:,28.'46 ';'4983.- 8 '1868 i 80.1 420:46 : 1 '1.29. 96 I, Olt' 6 a& 46 1, 081.580. 06 1; 04& 4 '. 27:1.97 '',"t447:`2,, 28..47 7-A'964:1 .....:!2&'. '..t:'.981:. 0 =..' 29.37 :-..998..029. 97 I, 014.. 9 '.30.47 1,981. 8 .,-. 30. 0 1,0488 27.68 ,cr447 46 `: 28: 48 /r664r4 '28:-i;"`. 981:4 -E29'48 .":.998.. 3 '... 20. 08, 015:.2 ,'. 30.48 I, 082: 230. 08 1. 049. 1 :., 27.19 ,-: ... :28.:49 ' .. 9(K 8 -,2W 99 ::.981:1 ,-;39:49 '2: 808.'8 19.69 I; 018'6 4140 1, 032 5 ;'30. op 1, op. 5 .:.-1,,,..1.? :1.,:.,',...;. ....:-..,::..' '....; -7...... '::::,',.,Y:j,'41.... , ,'. s' s ' '''''="-. '4".".4. ;o'.`.''. ''''' 1 '.'" , .r.

INTRODUCTION TO SONAR

Item 12Clouds TRACE READOUT 1. Type: Code the significant type of clouds Interpretation of the BT trace is necessary (WMO code 0500). to obtain the required values for making up the sonar message and for radio transmissionof 0 Cirrus. BT information. The observer must insert the 1 Cirrocumulus. BT grid and slide in the viewer and read off the 2 Cirrostratus. points for encoding where the BT trace changes 3 Altocumulus. direction. This procedure is in addition to read- 4 Altostratus. ing surface and bottom values. 5 Nimbostratus. No adjustment 'is made for discrepancy be- 6 Stratocumulus. tween reference temperature and BT temperature. 7 Stratus. Any bias in depth (trace beginning above or below 8 Cumulus.. zero line) must, however,' be adjusted visually 9 Cumulonimbus. before reading at any depth. Otherwise, the trace x Cloud not visible because of darkness,will be in error. fog, duststorm, sandstorm, or other A sample BT trace readout is shown in phenomena. figure 5-20 with the readout figures to the right. The arrows indicate points that should be re- 2. Amount: Record the fraction of the celestialported. Do not routinely read points at 50 or dome covered by clouds (in eighths) (WMO code100 feet unless the trace changes direction at these points. When the trace is in a straight line, 2700). only two readings are necessarya surface 0 Zero. reading and a reading at the deepest depth of the 1 One okta (eighth or less, but not zero).BT trace. '2' Two oktas. 3 Three oktas.. RADIO MESSAGE INFORMATION 4 Four oktas. 5 Fiiie oictas, The radio, or BATHY, message should contain 6 Six oktas, sufficient points so that the trace plotted by the 7 Seven.oktas. addressee isidentical to the original trace, 8 .Eight.oktas...:____ except for minor wiggles. Provision is made on 9' Sky obscured; -.'or ciciud amount cannotthe BT log for entering the readings inthe proper be estimated. order for radio transmission. The observer should not interpret the number of spaces pro- Item 13Waves vided for this infornudion to be a restriction on the number of points to be recorded. Use as Enter :the' mean height of the predominantmany Mies on the BT logsheet as requiredto waves: Check, the appropriate box to indicatedescribe the BT trace; accurately:: feet. or . Meters: Record the :period of the waves The radio message portion of the BT log- inseconds.'. sheet shown in figure 5-19 is completed as described in tke following itemizidion. Item 14i; Sea. .l.Siirfiee,,E,effirencse ,Temperature. Item 1Prefix Use the 'apPrOpriatef. code :from, the .ticoom-, panYinti; list ,to indicate the iiistkunient. used An. BT messages are prefixed by the word obtaikey:ea and inBATHY. -.which is preprinted on the. logsheets, which nearyesttenth of itdelgree;..::

h. Chapter 5 BATHYTHERMOGRAPH

aill 00647

14647 DISREGARD NIGGLE. 30694 40676

51619 54563

73552

90492

SELECTION OF SIGNIFICANT VALUES TO BE REPORTED

71.93 Figure 5-20. Trace readout.

Item 4Octant of Globe BT TRACE READINGS Record the octant of the globe as follows: When enterir.g, the depth-temperature read- ings, adhere to the following directions, North latitude Symbol 0 0° to90°W, ZZ Water depth in feet. ZoZo is the 1 90°W to 180°. surface, preprinted as 00 on the log- 2: 180°to90°E. sheet. Depths of subsurface temper- 3 90°E to 0 °. ature changes are recorded in tens of feet; e.g., 140 feet is recorded _South latitude as14.. TTT Temperature. T0T0 is the surface

.5 .0°. . to90°W. temperature. Subsurface tempera- 6 tures are symbolized by TsTzTz. 90°W to 180°. . 180° to90°E. Record the temperature to the near-

8 90°E. to '0%. est 0.1°F or C.

. . All messages must terminate with mes age

.Items 5 inifO4-Innition suffix figures 19991... --, Along.: the right edge of the radio message oor minutes of latitude;section, record the date -time group el the BT message,., 40ppectIve.,*::".iv Prefix 4ith. zeroes fnon .eedieert4eMeeeeP whenneoessary to;doniPlete.''Ule7:delIre! was rr 0,. Ocample ::- Latitude5318. is recorded as' :053 , YAK aleBT,radio .messageis..shown is hide 9%51 is entered fit:piljniii;the'fifeinintien.eontlined si:;:***OstigeA§9;4401::ftgiire 5=19. .9:nPir.egeAs jibt: Sent: tn; the bill)! the :ixarttp AoDC. The NAVAL MESSAGE OPNAV FORM 2110411 WT. 34113/N 01074034000

From:USS Fred T. Berry DD858

To: 1114mAFAerigavA

BATHY31230 03742 06527 XX686 00647 14647 306% 40676

51619 54563 73552 90492 19991

DISTRIBUTION: (P3os 0103 ONLY)

SEA SURFACE' TEMpERATORE..: ship's location. The message is sentinugassified, REPORTS with Upriority.precedenoti.,' Figure 5-22 illustrates the log on which to !In'connection'with the antisubmarine warfarereorct ;' the sea surgace ..,. temperatures. It is beiiii'iyStionir4(ASWERS);..a4'.:filled, into,:represent:the collective readings for ' ships:: of the.U.3;.:Fleiet,'-:Eir, aaingle day.' message OrPiat 4s:01m4ar ilrFAIY.1§ to maidlori i-BATHY, message. tff0dct' atngY tv: 'esseesti?vet:- Chapter 5BATHYTHERMOGRAPH

SEA SURFACE TEMPERATURE LOG

SHIP'S NAME.FRED 7: afilg Y HULL NoDDesaDATE.2.a. ...

I END . Of

MESSAGE

INDICATOR f . ...t C T E M I , D OM I IT a44I.le /Late1.1. 66T;T,T,' 1 999 1I CTENJ2B08?22123 1212a 0 12Do ,I.ZIEonErglEnDori BEGINRADIOMESSAGE )iarin WITHCTEM

2.21 I,ENTERTHE FOLLOWING ... 18 12°I° !5_,2 42 APPROPRIATELETTERAS I,TO INDICATEINSTRU- fii MENTUSED FORMEAS- 22o46i19460 72 /7 URINGSEA SURFACE - L.0 ElpFl L r_ i[1 Eip, TEMPERATURE.

z ' 2-2 ./6't4a 92. 2I. (03.E/ ENDRADIO ir,CE,_,i[[-_, L'.',,,;.i'L)LE:: 'MESSAGEWI ( N) INJECTION THERMISTOR .2102n ,iya..3:eIiiig 19991 (NSRT) RIgHOLIFIVELLIL1.115.3, ( B) BUCKET THERMOMETER 2201.2 1 te,05: - 10xX 7p,.7 AM_,....411-1 -.I.. Li r 1 ) INJECTION .,..b.1ri.....0 (J .:.D .,ii. 11.::, :kt. iz4L."., THERMOMETER 5 it4gii1ii6 1 2 44 4 ( 0) OTHER (SPECIFY) riFir,r,r, ro r7, 17,1,-.1 , . ia,rifiLt.i Li]. L, L.,-,_i L.,1 L.."L..3 , i.iiig947140 . 1r,..''-'t--.-' -: Mi F O]Ei[JL:iLl.:- Eil...ALffilit.L,,, , t 1. ,,,.. ,.. .. , 21930 iA4ii11'2232 FTilF.::Ei .. ., 'i:iiir2 i),i:k TRANSMITDATAONLy.-:::, rii -.1 ,,,-Hp Fi[--1 FROMUNSHADEDPORTIOPI; ;JO OF WO. i'4f 999 1 247)

3 gi4,114-4. .1,C1C7 iYfti4; e4 INTRODUCTION TO SONAR

Canister Loading Breech

Canister Wire Spool

Launcher Recorder Cable (4-wire LAUNCHER shielded) Stanchion

Optional Equipment

Terminal Board.

Wire Spool

k' . : , PROBE (XBI;) f : - t '

4.- :;- ; E Adabl:er BT :pystenf...7.

1!: q' 4 1-4t 67,1 r'er'S`11.-4* th, . I, 214.1' "'V° . . , Chapter 5 BATHYTHERMOGRAPH

be in centigrade. If you have only a FahrenheitPosition thermometer, you can convert the readings to degrees oentigrade by using the formula: 5/9 Octant, latitude, and longitude are recorded (F°42). If an observation is missed, insertfor each reading. See items 4, 6, and 6 in the 200E in the temperature space for that hour.radio message section of the BT log forproper Do not try to extrapolate. method of making entries. Each entry is to be the position of the ship at the exact time of Identification taking the temperature reading. Enter your ship's name and hull number, and Observation the date at the top of the sheet. 6 Enter the GMT hour and the sea temperature Message Prefix to the nearest 0.1°C. When the temperature is below zero, add 60 to the absolute value. Each message contains the prefix CTEM, together with a code letter indicating the install,- meat used tomeasure_the temperature. The Ending code letters are: (N) injection thermistor; (B) bucket thermometer; (J) injection thermometer; The message must end with the numerals (0) some other device, which must be specified. 19991. Instrument preference is in the order listed, EXPENDABLE BATHYTHERMOGRAPH Date Many undesirable features are connected with Enter the day of the month, the month, andthe use of the mechanical BT and its associated the year. The day and the month will contain two equipment. The most unwelcome aspect is that numerals eaoh. Use only the last numeral for..the ship conducting it_ BT drop must maintain the year. a slow speed and steady course. The deeper INTRODUCTION TO SONAR A

O.

I'-

. ?, !1.

. .

. . . 71.127 Figure 5-25.Expendable components and launcher. the drop required, the slower the speed noose- eery. Thus, the ship is inoretceingly vulnerable to submarine attack. The BT is often lost be- ', cause of parting of the'. wire. It is subject to damage caused by striking the bottom or other objects, Because of 'faultt.Slides, or a faulty. stylus, several loweringe:*ay .be,srequiredbe- fore an acceptable traoeCan:be obtained, thereby prolonging the-.8hip'S.'expoeure.t0'Itttabli,-±ROugh-. weather may produce .'StokluiSfirdoUkotinditiOnnii;.:: for operating Personnel; that ,a lowering cannot be made at all. Additionally, the ''..OpOt;t4.0.44;Irti::.:41

Tiding each . ship -.with .three.:- different' typee',-.'ef.;,.-, BTs must be considered, :PlUs-spareeeaohEO.#0,-; reqiiirint its 'mini:grid-0* individUalealibratiOn.-:":i!'='!: For many years thn:::Navy-,has been seeking a replacement, for the mechanical BT that'Would'''..,: be cheaper, more accurate and reliable, and ' safer to use. After .óxtensive evaluation, an ...' expendable b eir o been accepted and1s being Intro- %I 941re&15 ; freitisorAtittieHijoot;., '7)03.0;icir.4'.:Ortfitt tzti.44-FA : Is considered reasonably low. coflsumed. in maneuvers required forrn a mechani- often icost8 more -than the 71.119 ntik;-017.1,400:1rBT;;;', Figure 5-26:BT recorder. XBT is more accurate and has a greater depthweighs about 1 pound and is spin stabilized. It range than the conventional BT. Moreover, itscontains a thermistor, which senses tempera- use removes speed restrictions on the ship.ture changes, and a reel of special wire. The Readings can be obtained at speeds to 30 knots.cannisteralf:o,contains a reel of wire, and holds the probe. The launcher is essentially COMPONENTS a tube for holding the cannister. It can be installed to provide through-the-hull launching The expendable bathythermograph system isof the probe, eliminating the necessity for sonar composed of a sensor probe, a cannister, aperepnnel to be on deck in rough weather. The launch mechanism and a temperature-depth re-recorder (fig. 5-26) plots .a track on a strip corder. The expendable portion of the system,chart of temperature versus depth in real time. consisting of the canister and the probe, isThe strip chart is synchronized to the probe's seen in figure 5-24, and figure 5-25. The proberate of descent.

Jil -T.:4, 4. 11',., ...1 IT 4. tii 611.1XIMP, _,4 P..? P."' : ig + iv.t }, ,V a fie> b ti,l'..%itPIO Ell 4--:.x,4,7., 41'.:..-;', Zey 1MCRi'Mli"ta4 pc. .lorK,4Z .z pie) ut Sr.* pdg Vp.t eJiteitirse ms, , If +71'.iNt, ,' ti.,4L rutStabeNk AA til W.:. 1. V, JR Li.,:;,. '7i:A tri;'.,1,1 N'r, lag a:1)1Q rt.-V*74;4W !i±i.&04.p7liatin:V;,..«.2r.-4,0,4c.,p, tZ pp:414B trai4rtiv-Q Ili,nyt' 's MI: Kit. '0' ..9 in pat vir,,,koour, : ,W g ."..2...... v: t. ..J ..0.extn,p.s-i.+1_ --hr'4 Z.444-A470!k5 fisivoza,tvi ityirrom,.in ;get vi 01.1 virniviii2 et 041'0144.:.hrifit *-.)..; , s '',: fr ',...V* la. pa,, 40,. 7 14...b,'../.nr- .....4k..47.,Uolli 'AV-tIl to ,z, VECZ's,,,,. iro4 4744kmezr,5$11,04pIrrogl:ef-i'vzpv ,,,,,..;:,,,, ...,,,, ; ,,,,10,c7, ....,1 kRi4rec'tnrriratir:42 , rs: isyci$3;t -ave sobV,pi.tztAig .1; 44 si 4 te..4,6) c ,7Z :v- '-' ..gi Ft fielZ. t. V;:%... ',,1'... is. ..,:,..p 44.13.!.(..,4 57 ,,.9).__. c. , ...w.aN- 41,i^ r zil Z=16 C.,0". callZ4. Edit .rdta't -, MARI (.1.,Z i 5:13Tc1.412iralipwila .1 4 .,v,,,,grima grviittit54,,svzeik,,gt;_:-),,,tgR:,,,,,.._.p r.,,,,,,,:s,,,. ,,, urA,:, ot r; 1 .1i,rvo to,-tprt,t7;t...- 2; ", m.VIV:4;r21.1r, ,r,g,','A'7.?.:§i'flPr.`.:4M4K,41All4 -, ' Fr...er,":1171%Tit....t1.Velp...,T Pec.rt!, 0 .,..),pr., -.4p$N,,,,,..,, tc....,}..:;.?"' - 1,...?..,,,,t;;;::,ly'self . ,C-4 Ir.,. r:1 ,12VilneVd;,$..Ttlt`Pi';':';gf..);!,%,-,"..,2,Arle?.,..,'#-:'/A.,;J7241447: 1 es EOvo.,411,4,11.111.,_i tA V tfilf;'{:., .,!,' %,,,'",, 4. ,,,,1:,:r*Nakvgc..#)",; A pr 11.,;)..14'.,,'0,,,I,Vc. 'Zgtalftnig --kiwtanopszo.i ...4...'tiyAW,01.4VPS.'71.44,V,16},..e.r %;.,-C. v.' ,An Mit. ft: r..., I.."Y '''.. ;b11.talint. i.CIAZ 1N4X" 4t1,1.,'toi,:,.'.....1.1.! 1 , -3.11E4A-,...4%; tv7,1 ii,:4^g.', 74) "..1V.4..VgG A r.: , ?,',,,',. t" , '-' .4" At watxmku,c4ri...,x(pi Kt,i,.27.,,v..... tm.t.1 tp c. v.: to - t ....,,',e. ,,; ,'. , 11`07.1.,'"IrCIV4',4PgrtigAt."10.7,.,40'4,1F:Voc''"r r' kr, 4IPS ;IWO 11 trti,Ptg 4%1. 4; WIN ,it qii Ai 7,,,, rit. w 01.i.: Np; $sTr. a > %,,1;}C.-3:',0&!ilaSetrWat Icts:pPo'rq Of Xl.q-',i .i.v , 'IN ut . I; vi,t,,,rztalr:,,ov riy 0 -..-.4; 41....% -,.. Akt $.41.7:010 '.1.(ct t r'74,1,.,c ccl in;-,,,ter.mrvel'S 9.-4i4t1,4,441,1Azkvais,h5.: '..M. 'SW ..= f:441.1.4 'A.. n, 1: l9,_,...r,,--",,..,:,,,,t..- .3,-,.-xv-tir,t'.:,-;-,,,tiv, tivh,,Aksr,1,4_,,r,I, f., .f.,:p.,,qrtmAnesmyizt,:e.ty,,l/f7lcv..4k1,,.ter,.:.iir, Ix^.' : ,1 ,, ,,,...v. SI reftz."wittgra4st11.1,-,izur., }V,til,., r4011-,,,j1V.,0,. ,_:_c e_ 4',1:1c.:,1-;.r.7:-,,,Es,-1?.=,..1.1-r,h:;.6 r.,,,,,,01:1:;..y-TrA ^ -,_,- ,,tr.r- -1,-.:' '.0 ; k Tall !I. , r ,,-;.;,,, 40,1,:04.1,,,z.,,.1,4 -p. .--pyl..^.:-,.,..Pt, --.CY .0" IiINTOVTepiriritAgritit,;:-N, /...P,,,`2;,i1C.41, .L1: k'''.: .. >- , ` e,'5.71'?:,/V` :-,4K,zia.10110..t ,./-"- it si emaSfig I3 ft vm ems :.;'.e.,%'zr t..s. Di x i 1,,,:,,,IP ",--v4-1$.':,_.t, ..',) ,,tprzw oza.,-st.,1-1-11 4 ,1 /.'k e.:"..4.' INt414MV1.1/4',01.31';') 21,:i?'' itc:'5'..,-"4, tr..": - ": , -0 tv,QM nt,i' tow MK:47._.° ?Mk' ;.1, tr, r,:tt.: , t -; , a; "Y-t 4 ....4,t.f J... '.. "Z' 0 'r ' r,''p, piv, ,.tt.c.Trqs- ,-, ,-. ',. Aw.,,,;vi.,c.,;:c,...1,3,''..ti c' `tt 111001. ,.14..7. 4 ,,.. .-,,,t.,,, ,....-.;71,., iglu I_. \. jk .4r,( ,,,,,- ., . 0.,, i,,,,icyiKy10,11,2;;;C',M.N116.1' ;. r',. 4"-1 "r4 CI,,.f. 4.. ::. 7 .' 5 " '' .7. ,'7:-.).a.."14410.11c ,,....,:,.E.i.taFriy4?r.r..7".L'1.0.`,.'R',..1-rr,, K''t IC,,:l..7;YSWN'Ast,e7,es."!^4.P'",': '7 - . .1r.',,,-..-..e ' -..q c'P',tstiAc' cerw, -,,,qz..-1- -.,.,r -NI INTRODUCTION TO SONAR

OPERATION When the probe strikes the water, an electrode When you place the canister in the launch triggers the recorder. The thermistor transmits tube, a watertight electrical connection is foimed temperature changes to the recorder, where they between the probe and the recorder, causing the are plotted on the strip chart by a stylus. At a recorder to run for 2 seconds. This action sets depth of 1500 feet, the piobe,s wire is exhausted the automatic starting circuits, which are acti- and the recorder stops. A complete readout is vated when the probe hits the water. The probe obtained in 90 seconds from time of launch. is. held in position by a pin protruding from the'Temperature range of the probe is 28°F to 96°F, latinoher. Pulling the pin permits the probe to with an accuracy of 0.4°F. Depth accuracy is fall 'free, of the cannister, into the 'water. (The 2 percent or 15 feet, whichever is greater. canister remains in the launcher.) As the Figure 5-27 shows a representative tem- probe starts its 'free fall, the wire commences perature-depth profile. Only 6 inches of chart unreeling from the probe and from the canister.paper are needed for each 1500-foot drop.'Pres- This double unreeling action allows the probe to ent plans call for the fleet to be completely sink straight down, and permits the ship to equippedwiththe XBT systemwithin 2 1 proceed unhindered. years. CHAPTER 6 PRINCIPLES OFSONAR

The earliest sonarequipment was a passive device, a simple hydrophonelowered into the water and used to listenfor noise created bya submarine. The only indicationof a targetwas an audio tone. Bearingaccuracy was doubtful, and ranges were strictlyguesswork. 6 IPS SONAR Today's sonar III CONTROL accurate ranges andequipments provide highly INDICATOR bearings. They present RECEIVER-0. information both visuallyand aurally. Both active and passive types ofequipment are used. Although specificsonars and related equip- ments (except a fathometerand a tape recorder) are not covered in this chapter, TRANSMITTER- of operation given herein basic principles all sonar equipments. are applicable to

SONAR SYSTEMS IN Two general types ofsonar systems are employed for the detectionof targets. Theyare referred to as soaveand passive sonars. The active typei ofsonar is capable of trans- mitting underwatersound pulses that strike targets and are returnedin the form of echoes. Echoes returned indicatethe range and bearing TRANSDUCER of the target. Passive sonars dO nottransmit sound. TheyFigure 6- 1. Simplified 71.47 merely listen for soundsproduced by the target active sonar system. in order to obtain accuratebearing and estimated range information. an amplifier. The transmitter Active sonar systemsnormally are associated feeds a short, With surface ships,whereas passive systems powerful pulse to thetransducer for transmission usually are associated into the water. The signal with submarines. Newer 360° of azimuth. is transmitted in surface ships, however,employ separate passive systemt in addition to their A transducer isa device used to convertone active sonars. Sub- form of energy intoa different form. In marines, althoughstill relying primarilyon set, the transducer a sonar passive systems, alsoemploy active sonars. converts electricalenergy into acousticalenergy and reconverts the sound ACTIVE SONAR echoes to an electricalsignal, thus actingas both a loudspeaker anda microphone. Just as important to the A simplified activesonar system is shown sonar system as the in figure 6 -1. In this transmitter and transduceris the receiver. It set the sonar transmitter/functions on the superheterodyne consists of a high- frequency audio Oscillator and principle. In this unit the small,high-frequency electrical 91

r. INTRODUCTION TO SONAR

signals resultingom the echo are amplifiedbright spots on the CRT, similar to the display and converted toaudiosignals that can beof a radar's PPI. heard through a loudspeaker or earphones. The Some of the data that you may learn from receiver also feeds the amplified echo signalthe CRT presentation are as follows: to the various video indicating devices, such as the cathode ray tube (CRT) on the control indicator. 1. The size of the target may be estimated from the size of the echo. Don't rely too heavily Searchlight Sonar on this feature, though, because echo appearance depends on such factors as target aspect, range, Early active sonars utilized the searchlight and equipment performance. principlefortransmitting sounds. Like the .2. The distance of the echo from the center searchlight, the transducer. had to be trainedof the CRT represents range to the object to a particular bearing in order to transmitfrom your ship when the CRT is used in the sound on that bearing. The sound beam wasship center display (SCD) mode. narrow in bearing width (about 50), consequently 3. True bearing of the object can be deter- the echoes were received from only a small mined directly on the scope. sector of the surrounding sea. An arrangement 4. Target movement can be determined from of this type was necessary at that time becauseits scope presentation... Fixed objects such as sufficient power for omnidirectional transmissionreefs and sunken ships will move in a direction could not be generated.. The scanning sonars inparallelto your ship'S movement and in the widespread use today develop tremendous power opposite direction.Moving objects may have enough to be transmitted 360° in azimuth simul-motion in any direction with respect to own taneously. ship. Late modifications to active sonars allow the 5. The wake of a submarine often can be selection. ofdirectionallytransmitted sonic seen. By examining the wake, you may be able pulses, somewhat related In prindiple to the to establish a submarings heading even before earlier searchlight sonars. This feature, calledits movement can be determined by tracking. rotating directional transmission, is discussed 6. Submarines thatare toofar away for later. detection by echo ranging May yet emit enough The .Main disadvantage of the searchlightnoise to be detected. Under these conditions, type of sonar. was the. length of time required a small segment Of the scope appears to be to scan the area around the ship.. Search pro- filled with a rippling pattern. The general direc- cedures called for the operator to transmit,tion of the noise source can be ascertained listen for echoes, train the transducer to aby taking a bearing to the center of the noise new bearing, transmit, listen, and so on, firstpattern. on one side of the ship, then the other. It was possible for a submarine to slip by undetected TRANSDUCERS on the port side, for example, while the operator was searching on the starboard side. Moreover, Knowledge of the design and function of the maintaining contact with a target that had atransducer is the key to understanding the prin- rapidly changing bearing required a high degree ciples 'of Omar, whether of the scanning or the of proficiency on the part of the operator. searchlight type. You already know that a trans- Another disadvantage was that searchlight equip- ducer converts outgoing signals from electrical ment had only an audio presentation, whereas to acoustical energy, and converts incoming today's- scanning sonars provide both a videosignals from acoustical to electrical energy. and an audio presentation. Signals are converted by the magnetostriotive, piezoelectric, or eleotrostrictive process. Scanning Sonar Magnetostrictive Process Modernsubmarines and ASW ships are Magnetostriction is a process whereby changes equipped with scanning sonar, which transmits occur in metals when they are subjected to a sound pulses of high energy in all directions magnetic field. If a nickel tube is placed in a simultaneously. One of the features of scanning.magnetic field, for example, its length is shortened sonar Is a cathode . ray tude (CRT) display of all as a result of the magnetostrictive effect. The underwater objects deteoted in the area sur- effectis independent of the direction of the rounding the ship. Target echoes appear as magnetic field.

92 Chapter 6 PRINCIPLES OF SONAR

In the searchlight type ofsonar, severaltransducer elements have nickel laminations :hundred nickel tubes are arranged ina circlepressed in a thermoplastic material. Each element and mounted on one side of a metal plate calledcontains a permanent magnet for polarizingthe a diaphragm. Each tube is wrapped witha coilnickel. Several elements are mounted vertically of wire to prevent frequency doubling.Whento form 1 stave, and 48 vertical staves an alternating current is applied to the coil, are 'the, tubes shorten and lengthen arranged circularly to form the transducer. A at the rate ofscanning transducer is shown in figure 6-3.An the alternating current. Each tube ib polarizedexploded view of a portion ofa stave is seen by. a constant magnetic field, usuallysuppliedin figure 6-4. by a permanent magnet. Duringone half cycle of the applied signal, the Many types of operational scanningsonar a-c voltage and thetransducers are magnetostrictive. Exceptfor polarizing field. add; during the next halfcycle,variations in dimensions, theyare similar in they oppose each other, and the magneticfield is always in only one direction. The design. The type shown in figure 6-3is a contractionscylindrical unit approximately 19 inches india- of the tubes thus are fixed to thea-c frequency.meter and 27 inches long, and hasan operating As the tubes contract and expand, thedia-frequency of 20 kHz. phragm vibrates and producesan acoustic signal of the same frequency as the appliedalternating current. A magnetostr,ictive transducerused in searchlight sonars is shown in figure 6=2. Transducers employed withsome scanning sonars also operate on the principle of magneto- striction. Instead of nickel tubes,however, the

I

`TA

71.48 71.49 Figure 6-2.Searchlight magnetostrictive Figure 6-3.Scanning magnetostrictive transducer. transducer.

93 INTRODUCTION TO SONAR

71.50 Figure 6- 4. Exploded view ofone scanning sonar transducer stave.

Electrically,the magnetostrictive scanningphase delay of the sound beam, which results sonar unit acts as two independent transducersin the top of the beam bending downtoward housed in a common container. Oue ofthe the delayed portion of the beam. The effect independent unitsis the search section. The resemblesrefraction. Transmission isata other is the maintenance of close contact (MCC) downward angle of approximately 30°. section, located above the search elements. Because the elements are so placed that The search section is madeup of 48 verticalthey can cover a 360° area, there isno need staves. Each stave consists of nickellaminations to rotate the transducer in scanningsonar. and a polarizing magnet. Electrically, thestavesSuch an arrangement provides videocoverage are independent of one another. simultaneously on all bearings. Audiocoverage is afforded by training a cursor to the desired As its name implies, the MCCsection isbearing. Most present-daymagnetostrictive used to maintain contacton a close-in sub-transducers are built along the same general marine. The MCC elements transmit ina de-lines. Physical dimensions vary according to layed sequence from the top down, causingathe operating frequency andpower output desired.

94 Chapter 6 PRINCIPLESOF SONAR

Piezoelectric Process that is amplified and convertedto visual and audible signals. The piezoelectric transducer'functions much Nearly all transducers like the magnetostrictivetype. An exception now being built are is of the ceramic type. Ceramiccompounds have that crystalsare used instead of nickel highsensitivity, laminations. Various kinds ofcrystals have high stability with changing been employed, but the temperature and pressure, relativelylow cost, most commonly usedand can be constructed in almostany reasonable type is ammonium dihydrogenphosphate (ADP). shape or size. The arrangement of thecrystals on a dia- phragm is similar to themethod used in the Eleotrostrictive Process magnetostrictive transducer. Oneend of the crystal is attached to a bakelite-covered steel The most commonly usedceramic compound plate, and the other endis allowed to vibrate is lead zirconate titanate. Such freely. The free ends of thecrystal block con- transducers are stitute the transmitting and receiving known as electrostrictive transducersyet behave elements.in a piezoelectricmanner, and now are more The entire arrangement ofcrystals is connected widely used in modern electrically to give the .effect ofa single large sonar systems.-Although crystal. The elements a ceramic material is essentiallyelectrostrictive, are housed in a chamber it can be made to behavelike a piezoelectric filled with castor oil, whichhas sound trans- material by polarizing it permanently. mission qualities similar tosea water. The oil Polariza- also protects the sensitive tion is accomplished byimpressing an extremely crystals from beinghigh voltage on the materialfor a period of damaged by exposiure to wateror moisture. several minutes to align the When an electric current ofthe desired frequenoy molecules. Once the is passed through the crystals, molecules are aligned properly,the compound they change size can be treated similarly to that usedwith a as a unit, causing a vibration.Vibrations are piezoelectric material. passed by the castor oil,through the "window" of the sonar dome, into the sea water. When MODERN ACTIVE SONAR THEORY outside energy is 'received inthe form of an echo, it exerts mechanicalpressure on the crystals, which produce The theory of modern activesonar operation an electrical current may best be understood by breaking itdown into

TRANSMISSION ENABLING PULSE

AU010 ECHO SIGNAL CONTROL VIDEO ECHO SIGNAL INDICATOR KEYING PULSE (TO RELAY)

I

AMPLIFIED ECHO SIGNAL RECEIVER 41.. OD =II '"") AF SCANNER OUTPUT SIGNAL AMPLIFIER

4 NS o. 4.2 21 wl

TRANSMITTER TRANSDUCER 1411-.ECH0,_ACOUSTIC I. SIGNAL

71.51 Figure 6-5.Sonar systemblock diagram.

95 loo INTRODUCTION TO SONAR

three basic functions: transmission,reception, and presentation. A block diagram ofa repre- sentative sonar system is seen in figure6-5. 4111. PULSE LENGTH The diagram shows only the system'smajor units and main signal paths. Transmission Transmission of the sound pulse is initiated in the control- indicator, which qcritains theneces- SOUND CYLINDER sary keying circuits. Pulse leitth is also deter- mined at the control-indicator by thesonar

operator. The keying pulse from the control- . a.m. a.m. indicator triggers the transmitter oscillatorin am. the receiver-scanning system assemblyand actu- ates the transmit-receive switch in theaudio- frequency (a-f) amplifier. In the receiver-scanner 71.52 the pulse is modulated to the equipmentoperatingFigure 6-6. Pulse length determines thickness frequency, amplified, and delivered to thesonar of sound cylinder. transmitter, where it is further amplifiedto the power level required for transmission. The output of the sonar transmitter is fed Presentation to the transmit-receive switch in the a-fampli- fier, then to the transducer transfer switch For the returning echo to be ofany value, where selection is made between NORMALorit must be presented in sucha manner that MCC operation. The signal thengoes to thethe sonar operator can interpret the informa- transducer where it is converted to acousticaltion it represents. The echo is presented energy, and propagated into the water. The shape to the of the transmitted signal resembles operator both visibly and audibly. that of a The manually positioned audio scanningswitch hollow cylinder (or sphere, dependingon thefeeds the signal to the audio portion of there- shape of the transducer), which expandsin ceiver, which is of 'the superheterodynetype. diameter as it travels outward. Thethickness Incorporated in the receiver audio circuits isa of the cylinder walls dependson the pulse control for eliminating the effect ofown ship's length selected by the operator. (See fig.6-6.) speed on the reverberation pitch. Thiscontrol is called the own doppler nullifier (ODN). It Reception removes own ship doppler effeCt from target echoes,greatly aiding the operator in target If the transmitted soundwave strikes an classification. From the receiver the audio signal object having sufficient reflective characteristics, is sent to a headset position at the control- a small portion of the signal is returned to theindicator, and also can be fed to loudspeakers. transducer. In the transducer the acoustic signal After the output of the video scanningswitch is converted to an electrical signalby the is processed in the video portion of thereceiver, piezoelectric effectof the receiving staves. itis displayed at the control-indicatoron a Each of the 48 staves has itsown preamplifier, cathode ray tube. The sweepon the CRT is a located in the a-f amplifier. After preamplifica- spiral scan, which is synchronized with the video tion the signal is sent to the videoand audio scanning switch. (See fig. 6-7.) scanning switches in the receiver-scanning switch One method of obtaining a spiralscan is to / assembly. rotate the field of the deflection coils around The video scanning switch rotatescontin- the CRT, simultaneously applyinga sawtooth uously, thereby sampling noise signals andechoes voltage to the coils to cause displacementof from all bearings: The audio scanningswitch the sweep with each succeeding rotation ofthe is positioned to any bearing selected by thesonar coil. For clarity of explanation, thecoil yoke operator. Signals from the scanning switches is mechanically connected to the videoscanning are fed to the receiver section of the receiver- switch. As the video scanner and deflection scanner where they are converted to suitablecoil' rotate, thesawtooth voltage causes the frequencies and amplified for presentation. sweep to spiral outward from the center of the

96

10/ . Chapter 6 PRINCIPLES OF SONAR

START ,11, A N

SAM/TOOTH VOLTAGE -fir APPLIED TO SPINNING CT ROTOR :stiff

!SI, rI si --1I 20 TURNS LATER 1-1_4 / I/5

ti -4i141( 40 YURNS LATER 2,3*

INE )1/1gtfAIh. 01.1 tIO 4.11, ''-t.:1 FI, SO TURNS LATER I OMPLET z =Mot 47:11741.:"."ZO. woo,* = ounolgi /1(1 RESTART -or 711/41( ESTAR A STEPBYSTEP GENERATION. OF SPIRAL SCAN SYNCHRONIZINGTHE SWEEP WITH THE SCANNING SWITCH

71.121 Figure 6- 7. Generation of spiralscan.

scope at a linear rate. On reaching the scope'stip touches the echo, the target'srange is deter- outer edge, full deflection is achievedand themined. sweep is then cut. off. . Also located on the sonar control-indicator Rotation of the scanner is at sucha speedare various switches and controls. Theirpurpose that you don't see a spiralsweep, but whatis to give a better target presentation.These appears to be an expanding circularsweep.switches and controls, together withcomplete An echo is seen on thescope as a brighteningoperating procedures, are explained in themanu- of the sweep, at a distance fromthe scopefacturer's technical manual supplied witheach center, and in a direction correspondingto the sonar system. target's range and bearing. Rotating Directional Transmission During the interval between the end ofone sweep and the beginning .of the next, thecursor Conventional scanning sonars formerlywere is electronically producedon the scope. Because of the type just discussed; that is,only omni- of the long persistency of the CRT,the targetdirectional transmission was possible. ,Modern echo remains visible fora short time,.allowingsonars have an operating feature called rotating the operator to .determine accurately'the target'sdirectional transmission (RDT), which operates range and bearing. Bisecting the .echo with theon a principle similar to the searchlight type cursor gives, the bearing of the target. Byof transmission. The RDT providesgreater adjusting the length of the cursorso that its transmitted power than the conventional scanning

97 INTRODUCTION TO SONAR

type, affording improved sensitivityand detection range. At any instant of RDT,the signal is the resultant of phased excitationof several con- tiguous transducer staves, resultingin a source =SOUND SOURCE level improvement that ischaracteristic of direc- tional transmission. E]qie tationof the transducer staves is caused by output 'of a transmit scanner, which operates much like thevideo scanning switch of a conventionalscanning sonar. Transmission is accomplishedin a sector (up to 300° wide), which is centeredon the bow or on a selected bearing, dependingon the type of operation chosen by the operatorat the control unit.

PASSIVE SONAR SOUND SOURCE

Passive sonar, as itsname implies, depends entirely on the target's noiseas the sound source instead of the returned echoes ofa trans- mitted signal. Target detectionis achieved at great ranges through the ,use of highlysensitive hydrophones. Although passivesonar is usually associated with submarines,many surface ships now have a passive system that utilizes theiractive sonar transducers. During the intervalbetween sound pulse transmissions, the transduceracts as a hydrophone, allowing the sonar operator to moni- -SOUND SOURCE tor a broader frequency spectrumthan normally .is possible. Passive receptiondoes not interfere with the reception of pulse echoes.During trans- mission, however, the passive featureis inter- rupted. Hydrophones A hydrophone isa device used to listen for underwater sounds. In operationit is similar to the transducer of activesonar equipment when converting soundenergy to electrical energy. Two general types of hydrophonesmay be em- ployedelectrostricilve and magnetostriotive. Modern hydrophonesare of the electrostriotive type, consisting of ceramic elementsthat operate 71.54 on the piezoelectric principle. When theelements Figure 6- 8. Operation of the RLI. are struck by a sound wave, the vibrationsset up are converted to an electrical signal,ampli- A typical early type fied, and displayed at theoperating qonsole. uses the megnetostricti . effect for sound detection. Thehydrophone, which Single Line Hydrophone is trainable through 360°, isa line type whose nickel tubes are arranged Knowledge of the single line type of horizontally in a line. hydro- It is divided electricallyinto 'right and left halves. phone, although it is not, in generalusetitoday, Weak signals from the will aid you in understanding howmodern hydro- hydrophone are fed phones operate. to an audio amplifier, then tobandpass filters that remove undesiredfrequencies from the

98 Chapter 6PRINCIPLES OF SOLAR

detected sound. A supersonicconverter is used to increase the spectrum ofdetectable frequen- cies. PRE. COMP. LAG AUDIO 14 Accurate bearing is determinedby training- -- IND the hydrophone back and forthacross the direc- AMP. SW. LINES AMP tion of the sound source.Outputs of the right and left halves of the hydrophoneare fed to a right-left indicator (RLI). Anyphase difference between the right and left signalscauses the iiunni meter to deflect. Operation of the RLI is diagramedin figure 6-8. In part A of theillustration, the hydro- phone is on target. Signals inboth halves (right 71.55 and left) produce Figure 6-9.Block diagramof an arrayrtype a phase difference equal to passive sonar. zero. No deflection is indicated bythe meter needle. In part B, the hydrophoneis trained off the target to the right, and the meter needleand then are fed to a preamplifierto be ampli- is deflected in the "trainleft" direction. Thefied to a usable level. There meter indication informs theoperator that he is one preamplifier must train left to obtain for each hydrophone in thearray. The output a phase difference offrom each preamplifier isconnected to a slip- zero. The hydrophone in part Cis trained toring in the compensator a position left of the target. A righttrain is switch. The slipring necessary to obtain the desired bearing. couples the preamplifier outputto a rotor plate. One side of the rotor plateconsists of an The majority of passivesonar systems areequal number of brushes andsliprinp, each equipped with the automatic targetfollower (ATF) brush riding on a slipring.On the other side feature. With the ATF feature,right and leftof the rotor plate, a set ofbrushes is arranged signals are fed back into thetraining system,in a scale model of thehydrophone array. causing the hydrophone tofollow the targetThese latter brushes couplethe rotor plate automatically. output to the stator plate. Thestator plate has two sets of bars inlaidon the plate, one set Array Sonar on each half of the plate. Brusheson the rotor facing the stator plate makecontact with the Modern sonars utilizea hydrophone array,bars as the rotor is trained,and the signals which is installed inone of two configurations. present on the brushesare picked off by the The conformal array is curvedaround the sub- bars. Half of the brusheson the rotor plate marine's hull, with anopen end aft. The circularare always in contact with thestator plate, array consists of a number ofhydrophones thereby utilizing half of thearray at any given arranged vertically ina circle and mountedtime. The center of the statorplate, being the in or under the submarine'sbow. reference point, makes it possibleto determine the exact bearing of the target. MODERN PASSIVE SONAR The arrangement of the hydrophonescauses THEORY the signals to be out of phase witheach other at theoutput of the preamplifiers.For the The theory of modernpassive sonar consists signals to be usable, they of two basic steps: receptionand presentation. must be placed in Figure 6-9 is a simplified block phase with each other, hence,it is necessary diagram of an to delay the signal. Each barin the stator plate array type of passive sonar. Thearray cannotis connected to lag. lines. The be trained physically. Instead,a compensator purpose of lag switch is added that, in effect, lines is to delay the firstreceived signals a trains the systemproportional amount until the lastreceived sig- electronically. nals can catch up. Reception Once the.. signals are in phasewith each other, they are additive. Asa result we have a strongsignal, Signals received in to feed 'to the audio amplifier. an array type of passive There the signal is amplifiedand then is fed sonar system are converted to electricalenergy to an indicator. INTRODUCTION TO SONAR

:1 0

1k 5 /11.

DISPLAY SELECTOR

35.10 Figure 6-11.Azimuth indicator of an array-type

gm. passive sonar.

RECEIVER-TRANSMITTER

35.9 Figure 6-10.Console of an array-type pasiive sonar. TRANSDUCER

Presentation The console illustrated in figure 6-10 is representative of the indicators used withsome types of array sonars. Target indicationsare presented continuously on apaper recorder and a CRT. They also are given audibly. The 62.9 CRT is not located on the console itself,but Figure 6-12. Echo sounding equipment.

100 IDS Chapter 6 PRINCIPLES OF SONAR r era is a part of a separate unitanazimuth indi- cator (fig. 6-11). the depth directly from the line. Chiefdis- The paper recorder (on the advantages of this methodare that its use is upper portion limited to very shallow water, and theoperation of the console) plots thebearing of all noise. is slow. Operating in synchronizationwith the paper recorder is the CRT. It indicates The use of sound is themore common method the location of measuring water depth. A soundpulse, directed of all noise-producing targets byinward deflec- tions of the circular toward the bottom, is transmitted, andits echo sweep. An audio channel, is received. The time betweenpulse transmission provided with each azimuthindicator, permits and echo reception is measured listening' (with the aid ofan external speaker) and, based to this continuously scanning beam. or the speed of sound in water, the depthis thareby determined. Such an echo soundingdevice More detailed informationon passive sonar is known as a sonar sounding systems is contained in SonarTechnicia set, called a 3 & 2, NavPers 10132. Also fathometer. Basically the fathometeris a navi- consult the manu- gational instrument; but because itoperates on facturer's technical manual suppliedwith each the sonar principle, it usuallyis given to the equipment. Sonar Technician for upkeep. One type of fathometer usedaboard ships FATHOMETER and submarines is the AN/UQN-1sonar sounding set, shown in figure 6-12. Severalmodels of Water depths can be measuredin several the set are in use. In our discussion ways. One method is to drop a weighted, the AN/UQN- distance= 1C is representative of all theequipment modifi- marked line (lead line) to the bottomand observe cations.

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,..,,,,,-.:=_7,1;',::.,t-!..r.:',-;t..77,0,.-:::= 4...tE.,-.2i,.-., t4 .T.a-;q,:t':,...... TRANSMITTED. PULSE. TRACES 1`.....:7:-. :471:44-1::::::., ..'..!..TrTrmelp 7%1=1C=1:1,1i.. ,.:.-- . Vrr...,-t-,._ r .1. . MA ;..--1.11 x.r..4.:1.X... lizrj&,,e..4m '''''''''',-...... ,.,...,:ii., '.'"=`.47.'W"'"'"'_...-1154. ., ...L.:A: it %,,Vatr.dalri.....4....,...im utmamt. L'IM:"'.4',-144' (1,v 7- a 1 4 ..:'!..i.2.-Srr41 ,,,,,5,,;.;;,--,.:27...... ,,,,c,_,, ..., "---F7....r1..-----ii'. ,:. .1. IS ....:;...744-. .-....r....,,--,,i..1,_,-.-,.-:::-. , .7 ,-...--../12.,:...-:',... :J.' .-:1, '2! ',-".1%,...1.1;-,; .r, 2/.7 A'-: .'2 ^...,.r.'": A.-1..^,..--__ _.," .:7:-..7,.-.'--n MIC-7:-...:.--...... ,....,.. -,2 -M..' .'; - 7r.,-. ,..:711., r ------i

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62.10 Figure 6-18. Depth recording showinga steady decrease in depth.

101

1060 1 INTRODUCTION TO SONAR

The AN/UQN-1C fathometer employs the hot Other false indications are multipleechoes stylus and sensitized paper method of recording and reverberations, both of whichusually are depths. It also has a visual scope presentationcaused by too high a gain setting. I for shallow depths. This fathometer is Multiple a compactechoes are the result of the transmittedpulse unit, capable of giving accurate readings ata being reflected back and forthseveral times wide range of depthsfrom about 5 feetto between the bottom and the 6000 fathoms. Three recorderranges are pro- ship's keel. In vided on the AN/UQN-1C. They shallow water a solid linemay be recorded, are 0 to 600making it impossible to read the depth.Both feet, 0 to 600 fathoms, and 0 to 6000 fathoms.multiple echoes and reverberation effectscan The CRT ranges are 0 to 100 feetand 0 to be reduced by decreasing the gain. 100 fathoms. The equipmentmay be keyed man- Visual indication is supplied bya &rcular ually or automatically. (NOTE: All depthsare sweep on the face of a CRT. Transmitted pulse measured from the ship's keel, not the water's surface.) and returning echo mark the sweep trace radially. The visual indicator, pointing toa depth of 82 Two styluses are used, but theyare spaced (feet or fathoms, depending on the scalesetting) so that only one stylus records at a time. When is shown in figure 6-14. the fathometer records,a stylus starts down the recorder chart simultaneously with thetrans- OPERATIONAL PROCEDURE mission pulse. The stylus moves ata constant velocity and marks the paper twiceonce at Following is a brief discussionon normal the top of the chart when the pulseis trans- operation, security operation, and e.latt.t.nozprc. mitted, and again on the depth indication whenoedures. Refer tofigure 6-15 wil!ti,ikieding the echo returns. A depth recordingmade bythis description. a fathometer of this type is seen in figure 6-13. The recording illustratedwas made from Normal Operation a ship sailing over a sea with steadily de- For simplicity,it may be assumed that creasing depth. The first part of the tracewas there is only one normal way of operating recorded on the 6000-fathom scale. Inasmuch the as the paper moves from right to left,you can see in the section of the paper shown that the depth decreased from 4000 to 600 fathoms. (Later depth information isto the right of the paper.) When depth was about 600 fathoms, the scale was shifted to the 600-fathom setting. 0 (See how shifting makesuse again of the entire 0 width of the rap, r.) BeCause depthdecreased still further, the scale was shifted to the 600- \\I foot setting when a depth of about 100 fathoms was recorded. The marking on the paper is downward(stylus motion is downward) in alternaterows printed from 0 to 600 and 0 to 6000. Marking the.chart paper in this manner allows the same paper to be used for all recorder settings. You must check which scale the eqtdpinent is recording on to make sure whether ttl marking is in thousands of fathoms, hundreds of fathoms,or hundreds of feet. Be sure the range Beale inuse is greater than the water depth. Otherwise,a false depth indication (or no indication) will result, depend- ing on the position of the styluses at the time of echo return. If water depth actually is120 feet, for instance, and you have.selected the 100-foot range scale, a depth of 20 feetwill 71,57 be indicated. Figure 6-14. Visual depth indicator.

02 17 PTHROW TO ON AND WAIT 30 SECONDS, OR THROW TO STANDBY IFINSTANTANEOUS OPERATION MAY BE REQUIREDIMMINENTLY

INDICATOR OR RECORDER AND PROPER DEPTH RANGE ADJUST GAIN CONTROL TO GET IQSELECT A GOOD ECHO

ADJUST ILLUMINATION CONTROL TO SUIT USE TO MARK VERTICAL LINE ON SURROUNDINGS RECORDER CHART FOR TIME IDENTIFICATION

fathometer. Deviations may be consideredas 100 feet or 100 fathoms. On therecorder the expedients for conserving electricalenergy, time, scale is 600 feet, 600 fathoms, paper, or for maintaining sonar security. or 6000 fathoms. 8. Set the ping switch to AUTOMATIC. 1. MO* poNVefswitch to STANDBY, wait 4. Turn the gain control clockwiseuntil a about 30 seconds, then throw the switchto ON. suitable echo mark is obtained. This prooedure prolongs the life ofthe keyer 5. Observe that both styluses attached to tube by allowing the filament toheat beforethe revolving belt mark thepaper from the applying plate voltage. zero line to 5 feet. Oh the range switch select theproper 6. Check to see that the properrange mark- range Mile. On the in the scale is eithering is indicated on the top of thepaper. vY

INTRODUCTION TO SONAR

7. Depress marker button. Observe that aequipment to make such recordings. Themost straight line is drawn down the full lengthofcommon installation is the AN/UNQ-7 recorder- the paper. This line should be straightfromreproducer sound set, familiarly knownas a top to bottom, otherwise the stylus isout oftape recorder. adjustment. The AN/UNQ-7 tape recorder ismore sophis- ticated than many commercial types. Itis a Security Operation two-trackrecorderand reproducer, and is responsive to all frequencies in the audible If it is not desired to place pulsed range. 2 energyBoth tracks may be recordedeither simulta- in the water periodically, the fathometermayneously or independently. Normally,track B is be operated as for normal operation,except that the ping switch is triggered downward used to record signals directly fromthe sonar toequipment. Track A is used for recordingvoice SINGLE PING, then is released. Thecircuitryinformation. is arranged to pulse the first time thekeying When a recording reproduced by the equipment contacts operate after triggering and thenre-is played back, both trackscan be heard, or only lease immediately. The ping switchmay be held down as long as desired without one track, each channel. having itsown volume damage. Thecontrol. In short, the AN/UNQ-7 actsas a com- result is exactly the sameas if this switchbination of two separate recordersthat are were in the AUTOMATIC position. capable of being coupled to allow superimposing Shutdown two audio information channelsupon each other. Figure 6-16 shows the front panel of therecorder. Later models, namely the -7B, -7C,and -7D, Put the ping switch to the OFFposition.are transistorized and have a somewhat different Throw the power switch to the OFFposition (center). This action disconnects bothsides of the 115-volt, 60-cycle supply fromthe equip- ment (except the service outlet). ROUTINE MAINTENANCE r ti

Routine maintenance as used here applies ee, to functions, besides operation, thatshould be performed by the operator. When theoperator checks out fathometer equipment beforea run, he should be prepared (if necessary)to make minor adjustments, and replace lamps,tubes, styluses, or paper. Moreover, he shouldbe satisfied that the equipment will rendercon- tinuous satisfactory performance duringthe an- ticipated operating interval. The manufacturer's technical manualthat accompanies the particular fathometer aboard your ship lists a step-by-step procedure for accomplishing . minor adjustments, replacing parts, and preventive maintenancerequirements.

TAPE RECORDER Sonar Technicians, particularly aboardsub- marines, must be able to in recordings of sonar echoes and of other sounds detected by the tramsduoet or hydrophone. Snobrecordings' are valuable aids in classifying sounds (deter- mining the nears and/or source). Allships 7.54 and submarines are supplied withthe necessary Figure 6-16.Tape recorder AN/UNQ-7.

104 I /09 Chapter 6 PRINCIPLES OF SONAR

appearance, but their operating characteristics are the same as the basic model. Originally the AN/UNQ-7 had recording speeds GAP of 3-3/4 and 7-1/2 inches per second (ips). Field TAPE changes permitted an additional speed of 15 ips. All subsequent models, beginning with the AN/ UNQ-7A, have the 15 ips feature built in. In general, the faster the recording speed, themore faithful is the sound reproduction. SPACER The standard reel is 7 inches in diameter, holding 1200 feet of 1/4-inch tape. At a re- cording speed of 15 ips,1200 feet of tape will last about 15 minutes. CORE OPERATING PRINCIPLES Magnetic tape consists f finely ground iron- oxide particles deposited upon a plastic backing (tape). The particles, too small to be seen with the naked eye, are deposited in sucha way that they are allowed, to move or line up COIL in an orderly fashion as a result ofsome force applied to them. Me force having such an effect on the iron-oxide particles is a mag- netic field. This magnetic field can be caused by a common magnet or by a temporary electro- 71.122 magnetic field. It results from passing an elec- Figure 6- 17. Typical magnetic head. trical current through a coil of wire. MAGNETIC HEADS reproduction head. The three heads are con- tained in a single housing. A microphone. contains a magnetic device that is capable of producing electrical energy Recording Head representative of the sounds spoken into it. In a tape recorder, the microphone-produced The recording head is composed ofa highly electrical pattern causes a magnetic field topermeable material, which means that the core represent the pattern about a wire coil to whichispeasily magnetized, and just as easily demag- it is fed. The coil is wound on a core that hasnetized, by a current passing through the coil. a gap in one side. Because the magnetic fieldHigh permeability is a necessity in order for is most intense at the gap, that is where thethe magnetic field to follow the fluctuations of signal is placed on the tape. The narrower thethe signal to be impressed on the tape. gap, and the sharper the gap edges, the better In reality, the signal cannot be put " as is" is the response. Figure 6-17directly onto the tape. It must be mixed with shows typical magnetic head. The magnetic another signal for strength and linearity, that tape passes over the bead, and the electrical is, without distortion throughout the signal band. pattern is reproduced upon the tape in the The bias signal with which the original signal form of regular patterns of iron- oxide particles is mixed is of very high frequency too high to that line up in accordance with the signal passed be heard. Electrically, it has unchomging, steady- through the coil. strength characteristics. The a-c bias assures The recorder has three heads. The devicebetter acceptance by the tape of the signal to in the recorder about which the magnetic fieldbe recorded, and helps reduce distortion of is produced by the microphone 16 called the strong signals. recording bead. Another head, called the erase head, eliminates the magnetic pattern from the Erasb Bead particles on the tape. A third head is for play- Tape passes from the erase head to the back of the recorded signal and is called therecording bead, and then to the reproduction 105 INTRODUCTION TO SONAR

head (in that order). Theerase head demag- netizes both channels simultaneously. Other parts are on theupper section to guide It is un-.the tape and to pull it throughthe head device. necessary to erase a tape individually before When the tape unwinds from theleft reel, itis it is re-recorded, because whena tape is being threaded around the guiding used for recording, the erase head isenergized assemblies, fed so that a new recording cannot be ruined by through the head assembly, aroundthe capstan (which actually pulls the tape through),and then superimposing itover an older one. Thus, tapes it is taken up by the right reel having recordings that no longer . A pictorial diagram are needed for of the path followed by the tape fromreel to reel retention can be used directly. Themachine simply is set to record, the old tape is printed on the face of thehead assembly. By is put on, adhering to. the diagrim,you will have no diffi- and, after it passes the erase head, itis "cleaned" culty threading the equipment properly. of the earlier recording. Itnext passes the recording head, which putsa new magnetic Recording pattern on it. Reproduction Head After the tape is threaded, the taperecorder is energized by turning thepower switch to the ON position. Wu must wait fora short warmup The reproduction head, which is nextin line, period. is similar to the recording head in That is, construction. Next, select the speed at whichrecording is it has a broken ring of permeable desired. As mentioned earlier, thereis a choice material wound with wire coils. Whenthe re-of 3-3/4, 7-1/2, or 15 inches corded tape passes over thegap, the permeable per second. Select the faster speed for critical recordings,during material is affected by changes inthe tape's which the pitch of the echo magnetic field, and an electric current may have an important is induced part in later evaluation. A recordingmade at in the coils surrounding thering. The induced a higher speed can be studied more completely signal is amplified and fed tophone jacks for audible presentation. by reproducing it at the lower speed. (An800-cps tone, recorded at 7-1/2 inchesper second, is heard at 400-cps when reproduced at 3-3/4inches OPERATING THE EQUIPMENT per second.) Hence, recordings thatmay require lateranalysis. should be made at thehigher The top half of the tape recorder, speed. The divadvantage of the higherrecording as seen in speed is that the tape is used twiceas fast as figure 6-16, is the actual recorderan repro- when operating at the next slower speed. ducer. The lower portion is the amplifier Informa- section. tion on speeds to use for recordingand playback It includes controls and indicatorsthat directly are contained in the technical manual supplied affect the recording and playbackof the tapes. with each recorder.- Each recording track has a separate channel. Although the higher speed provides thehighest On the equipment they are labeledchannels A y and B. Channel A is used for voice , diffe rneont c s recording mqadeat poned detected and reproduction; channel B, forsonar informa- easily. tion. Both channels have separate Only when a critical analysis of therecording controls for is made does the faster speedprove its worth recording and reproduction. The recordingcon- trols are to the left of the amplifier over the slower one. section. The recording level is selected next,and Playback controls are at the right of theamplifier section. each channel's level must be adjustedindividually. An indicator on the amplifier assemblyis labeled Threading Tape record level indicator. Directly belowit is a two - position toggle switch labeledchemnel selec- tor. The position of the switchare marked A The roll of magnetic tape to beused for re- and B, each representing cording purposes is placed on the left a channel. Set the reel-hold toggle seiton to either channel, andobserve the assembly on the upper section of therecorder.vertical amplitudeon the face of the indicator. It is placed in stash away that, when the equip- ment is in operation (recording The record level controls, belowthe channel or reprodhcing), selector switch, are marked for channelsA and the reel rotates in a ootmterclockwisedirection; B. Adjust the level control for and themagnetic tape leaves the reel from the the channel bottom. chosen until the &pal peaks (shown in thelevel indicator) mem the Space betweenthe upper 101 . - Chapter 6 PRINCIPLES OF SONAR

and lower horizontal lines.Next, select therecord again. Thus, a tape being reproducedon other position on the switch and make thesamethe recorder proper can be ruined (bythe adjustments for the other channel. The equip-automatic erasure process during recording) if ment is now ready to record on both channels.the switch at the remote control twit is set to To start the recording process, an unlabeledthe record position during playbadc. Covsequently, button to the right of the record level indicatorthe switch on the remote control wit roustnever is held to the left, and the tape recorder controlbe moved from the standby position unless the (record section)is moved up to the No. 1standby light is glowing. position. A light (indicator No. 1) glowsas the When the machine is recording, the SECORD equipment begins to record. light on the remote control unit glows. When The unlabeled button is called the recordapproximately 5 minutes of recording timere- safety interlock switch. Its function is to preventmains on the tape, the RECORD lamp lashes accidental or inadvertent recording. To record,to warn that the end of the reel is approaching. you must place the record switch in the No. 1If the recorder outs out (this feature isauto- position, and simultaneously turn the recordmatic when the tape reel is exhausted), the safety interlock switch to the left. RECORD light goes out. When the tape recorder To stop recording, set the record switch toreturns to a standby condition, the STANDBY the neutral (middle) position. To start recordinglight glows again. again, move the safety interlockonce more to the left as the record switch is returned to theReproducing No. 1 position. The other position of the record switch is To play a recording, thread the tape, turn labeled AUX (for auxiliary). This position ison the power switch, allow for warmup, and provided foruse if an auxiliary recorder -choose the tape speed. reprod eer is added to the system. Next, place the REPRODUCE switch inthe No. 1 position (it has the same positionsas the Recording Remote Location RECORD switch).This setting actuates tape motion, and both channels are reproduced simul- A device that allows some control of thetineously. assembly from remote locations is included Finally, adjust the reproduce level controls with the tape recorder. A single operatingcon-for both channels to the desired output of each trol and two indicating lamps (labeled STANDBYof the headphones (if used) or the loudspeaker. and RECORD) are on the remote controlunit. The single operating control is a two-position To stop the playback, simply return the toggle switch that parallels the record switchreproduce switch to the neutral (middle) position. on the amplifier section. Preliminary adjust-This stoppage may occur at will throughout the ments, such as tape threading and level control,run of the reel. The equipment returns to the must be set before using the remote controlstandby condition whenever the neutral position unit. The standby light indicates thatpower hasis selected. As in the rewording mode, the tape been applied and that tape is threaded. It doesmotion stops automatically when the end of the not signify selection of the proper speednorreel 18 reached,. adjustment of the level controls. It does not Remember that the switch on the remote light when no power is applied, when the tapecontrol unit must not be set to record during is threaded improperly, nor when the equipmentthe reprodaation mode of operation. Otherwise, is used to reproduce a previously recordedtape.the recording will be ruined. The positions of the toggle switchare STAND- BY and RECORD. The standby positioncorre-OTTER USES sponds to the neutral. position of the record switch on the recorder proper; Therecord The tape recorder allows simultaneousre- position takes precedence at both locations,cording and reproducing of sounds. By tide meaning that if RECORD is selectedon the re-means, you can monitor what is being recorded mote control unit, the equipment will recordas it is recorded. Steps to set the eqtdpment one though the record switch on the equipment,to tide mode of operation are 'nobbled In the proper is in neutral. If RECORD is selected on the instrument proper, but STANDBY is setequtPment instruction book IMMO& MEWL on the remote control mit, the equipment willBisigaz-ligantimNmanips swan. III lead. AN/UNQ -7, .,r

INTRODUCTION TO SONAR

A switch on the upper section ofthe instrumentsonar can use either its hull-mounted allows rapid rewind and fast forward or its operation.towed transducer, or it can transmiton one and Instructions and procedures for using theswitch,receive on the other. Either transducermay as well as those for erasing and splicingthetransmit an RDT beam. Received tape, are also included in the signals are instruction book.presented in the normal manner at themaster consoles.

VARIABLE DEPTH SONAR Figure 6-18 shows the VDS transducerready for lowering. The transducermay be towed at Thermal layers, as you know,reflect oralmost any speed and at depths to refract the sonar beam, makingit difficult to several hundred detect and maintain contact feet. To stow the towed vehicle,the boom is on a submarinerotated so it faces forward and thetransducer operating below the layer. Toovercome thisis lowered onto a deck cradle detection problem, the variabledepth sonar where it is (VDS) was developed. securely fastened down. Modifications were made to existingsonars to permit them to transmit and receive signals SONOBUOYS through a transducer contained ina towed vehicle. Two current VDS systemsare the AN/SQA-10, used in conjunction with the AN /S(-29 and -30 The sonobuoy is an expendable devicedropped sonar sets, and the AN/SQ -11, used withthefrom an aircraft into thesea. It detects under- AN /S( -23 sonar set. water sounds or echoes (dependingon the type of unit) and transmits the detectedinformation Mad cations included the additionof a VDS to the aircraft by means ofa self-contained transmit scanner, receiverscanner, a-f ampli- fier, and a relay-junction box. radio transmitter. Some surface shipsare also The shipboardequipped to receive the transmittedinformation.

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81.63 Figure i48. Via briived vehicle readyfor lowering. "V".."""""!'"'".11''''',4^"%""Fr.v.,,IrtitYrrTMIT ),4,.Treeor,c,,;,,ort it;

Chapter 6PRINCIPLES OF SONAR

Sonobuoys are used primarily by ASWunits, but they also are employed in harbor The directional type of sonobuoyprovides defensebearing information on detectedunderwater installations. The three methods ofdetectingsounds. The submerged unit rotates ata slow underwater targets are echo ranging,directionalrate. Sounds detected by the hydrophone listening, and nondirectional listening. are amplified and frequency-modulated forradio The echo ranging type of sonobuoyuses atransmission.The transmitting frequency is miniature transducer for transmittingsounddetermined by the heading ofa magnetic com- pulses and receiving echoes. Operatingdepthpass at the instant of sound reception. is down to 200 feet. Received echoes are trans- The nondirectional type providesonly detec- mitted to the aircraft or ship inthe form oftion information. Range and bearing ofthe sound range information only. source are unknown. CHAPTER 7 BASIC FIRE CONTROL

Although the overall objective ofall SonarShipboard Antisubmarine Weapons Technicians is to aid in destroyingenemy sub- marines, the manner in which the taskis accom- Aboard ship, several kinds of plished varierWith the individualbranch of the antisubmarine rating. The shipboard Sonar weapons are available. The principalone is the Technician, forhoming torpedo. Others includedepth charges, example, tries to maintain continuouscontact through echo ranging hedgehogs, and rocket-propelledordnance. sonar and aggressively Figure 7-1 shows a Mk 32torpedo tube enters the submarine/ship duel,using everymount used for launching homing available means to hold contact. Thesubmariner torpedoes of has a tendency to sneak the Mk 43, Mk 44, and Mk 46types. The usual up on the target, gather-destroyer installation hasone triple-tube mount ing attack information from thenoises produced by the target itself, perhaps on each side of the ship. making one sonar Homing torpedoes are of two typesactiveand transmission just before firing. In eachinstance,passive. The active type transmits the ultimate goal of the antisubmarinemilt is sound pulses destruction of the enemy submarine. and homes on the echoes reflected fromthe target. The passive type is guided to thetarget by noise The system by which informationis collected and translated into weapon firing emanating from the target itself. data (including Early antisubmarine torpedoes had two positioning of trainableweapon launchers)is serious called fire control. drawbacks. First the enduranceor active period was relatively shorta matter of minutes.The second concerned their speed capability.Com- pared with speeds ofmany modern submarines, UNDERWATER FIRE CONTROL the homing torpedo was slowand could be outrun by a submarine. These drawbacks Fire control is definedas the technique by have which weapons are directed to been eliminated for the most partin modern a selected target.high-speed torpedoes. Thenewer torpedo also It consists of the material,personnel, methods, communications, and organization is quite maneuverable, in contrastto the sub- necessary tomarine, and has a tighter turningcircle. Except destroy the enemy. Underwater firecontrol includes all of the foregoing for attempting to delude thetorpedo with a components, withdecoy-type device, one of the bestdefenses the added difficulty that the selectedtarget isthe submarine skippercan provide spinet a a submarine, capable of moving in threedimen-modern antisubmarine torpedo isto call for sionsin range, bearing, and depth. an available power inan effort to clear the WEAPONS area at maximum speed. Modern torpedoes, however, normally are faster than thesubmarine. Some of the antisubmarine Inasmuch as the primary missionof an A/S weapons controlledescort vessel is to prevent the submarinefrom by underwater fire control equipment andused bymaking an attack, causing ships and submarines againstenemy submarines the submarine to are described in the topics 'that follow. Theevade a torpedo and rim from the.area would discussion also points up accomplish the escort's mission. some of the problems When conducting an antisubmarinetorpedo that must be overcome by theundernater fireattack, the ship must maneuver into control system to realigesuccess. Not all weapons a favorable are discussed because of the nature of theirOng position. A typical homing`torpedo runs classification. tiIn helical patterns while seekinga submarine. Once contact with the submarineis achieved,

110 '/5. 1 I11i INTRODUCTION TO SONAR

they are not considered effectiveas antisub-is established, the next phase (tracking)can be marine weapons. These torpedoes are used chief- initiated. ly against surface targets at fairly shortranges. Detection also can be made by radar. Ifa They are noisy and thus are detected easilyradar contact suddenly Disappears, there isa but are difficult to counter because of theirgood chance that the echo was the return from high speed. a surfaced submarine and that the diPaupearance Acoustic homing torpedoes available to sub-was caused by diving. If sonar comalso is marines have features for homing passively,held, it can be assumed the contact iba sub- actively, or a combination of the two. marine. Most surface-search radars can receive Wire-guided torpedoes are a variation ofa radar indication from a periscope. Hence, it the acoustic homing torpedo. Theyare guidedis possible to track a submarine that is operating to the target submarine's vicinity by signalscompletely submerged except for its periscope. sent over the wire by the launching submarine. The radar method goes hand-in-hand with visual After the target is acquired by the toipetio,detection because radar frequently provides the it homes on the target without further guidancefirst indication, directing eyes to the location from the launching submarine. of the periscope, snorkel, sail, or hull of the The submarine also has a rocket-propelledsubmarine. weapon, containing a nuclear warhead, called The sonar equipment aboard your shipor SUBROC, which was described in chapter 2.submarine is designed to detect and track the submarine, and feed computing devices with DETECTION-TO-DESTRUCTION PHASES tactical chita to achieve the destruction phase of the problem. Theoretically, the fire control problem begins when a target is detected and ends with its Tracking Phase destruction. In practice,- though, the fire control problem starts well after initial detection. It After detection, the contact must be tracked. commences after the initial classification and Aboard a submarine, a graphic display of target when target tracking is ordered. bearings is made during this phase. From infor- Like all other fire cdatrol systems (anti-mation furnished by this display, target motion aircraft, sttrface-to-surface, and the like), theis established. Normally, the submarineuses antisubmarine fire control system solves theonly passive sonar for tracking, because active problem in the following stages:(I) trackingsonar may disclose the presence and even the the target; (2) analyzing target motion; and (2) location of the tracker. computing ballistic solution. Shipboard Sonar Technicians track the target Detecting a submarine is no easy matter.with active sonar, depending largelyupon the Neither is it a simple task, oncea submarinestrength and quality of the echo of the trans- contact is established, to carry out thesucces-mitted pulse for target information. Antisub- sive phases mentioned here. Although fire controlmarine ships have fire control systems that systems are capable of performing complicatedincorporate automatic tracking features. Once tasks, such as predicting future positions, sub-the contact is established firmly, the automatic marine hunting is subject to errors caused bydevices keep the sonar on the target, andcom- human judgment. Training in Praiser operationpute the course to be steered so that the ship of the equipment for =dna= A.SWeffectivenesswill arrive at the best firing polition for the is a must for Sonar Technicians. weapons selected for use. Because the same equipment often is used in Basically, establishment of relative rates of detecting a submarine as in traria' it, detectiontarget motion is all that is desired from the is contddered as a phase, even though in timetracking phase of the problem. The trading strictest sense itmaynotbeapartof the problem.phase sets up the pattern for the next phase target motion analysis. It is from the relative Detection Phase rates that actual target motion is determined. A submarine may be detected inseveraiways, Target Motion Analysis Phase the most positive being visual siglding. If the submit** is seen to dive, classification is The target motion analysis phase isadynamic evident; there is so question about the positiveproblem because both the attacidng unit and the nature of the cestact. ones suet a claasificatioetarget usually are in motion continuously, and all Chapter 7BASIC FIRE CONTROL

CA related factors change constantly. Asa result ofballistic the target motion analysis phase, solution phase, for example, practi- we can establishcally coincides with that of the trackingphase. the true motion components of the target(course and speed). There are several An antiaircraft fire controlsystem presently ways of arrivingin use provides a solution in only2 seconds, at a course and speed solution. Adiscussion of the methods follows. once the target is acquired by radar. Yet, during that time, the target is tracked, itsmotion is The .target's true course and speedcan be established on the dead-reckoning tracer analyzed, and the ballistic solution is computed. (DRT) Most underwater fire controlsystems, however, plot maintained in CIC by Radarmen frominfor-take longer to develop mation supplied by the sonar operators a solution. The reason overis that certain inaccuracies in targetinforma- sound-powered telephone circuits. The DRT uti-tion are provided by underwater sound.Addi- lizes own ship's course and speed inputsto causetionally, range limitations of theweapons require a lighted "bug" to follow own ship movements.the attacking unit to be ata definite point to Sonar target ranges and true bearingsare plottedlaunch nontrainable weapons, and withina specific from the bug, thus establishing the subniarine'sarea to fire its trainable weapons. position. Course and speed are then determined After determining the target'scourse, speed, by the plotter. The DRT plot is usedby the CIC and depth, two items must be consideredin order officer to aid him in conning the shipwhen CICto complete the problem. One is howto close the has control of the attack, and tosupply search arcs to the sonar operators whenever contacttarget. The other is when to fire. is lost. To close the target, the course to steer for the optimum firing point must be lcnown.In the A maneuvering boardmay also be used tofire control problem the course tosteer is indi- determine contact course and speed, butthiscated as a correction to own course. Own ship's method is not so rapid nor so accurateas thepresent course must be changed by theamount DRT. The direction and distance ofcontactof correction necessary to interceptthe target. movement are transferred to a vector represent-The best intercept course isa collision course, ing own ship's course and speed, thus establishingwhich means the target is closingon a constant the target's course and speed vector.Another drawback to the maneuvering board bearing. Computing course correction isan auto- method ofmatic process in underwater fire controlsystems. plotting is that the target's plotted trackshows only apparent movement (relative motion). The second considerationwhen to fireisa decision reached from a compilation ofmany Target true course and speed alsocan beitems. If you use two different types ofweapons read from Beals on the attack director(discussed later). in the same attack, one of them to be firedahead and the other to be dropped astern, itstands to On surface ships the underwater firecontrolreason that the ahead - thrown weapon must be systems usually have to computea horizontalfired first. What the problem developsinto is a sonar range from the measured slantrange andcalculation of two time periods: the time of estimated target depth information. Thiscomputa- explosion and the time to fire. The problem is tion is necessary because the fire controlsystemsolved by computing the time of explosion after solves for target course and speed in thehori-the initial classification of the target,then sub- zontal plane on the surface in whichown shiptracting (I) dead time (bow long it takes,after operates. Slant range is transmitted to the attack the command to fire, to actually firethe weapon), director from *the sonar console. Depth isset(2) time of flight (the time required,after manually into the director. firing, for the weapons to strike the water), The attacking amine mayuse different and (3) sinking time (length of time forthe weapon, 1 methods to determine true direction of targetafter strildng the water, to reach Usedepth of motion. One method is by direct observation,the target).. When these subtractions when possible, of the angles as the bow. Angle are made, you have the time to fire. The values subtracted It on the bow was discussed in chapter 3. have been calculated from testingweapons and from previous agserienoe. Ballistic Solution Phase Assume that, after detecting a target, explo- sion time of 3 missies is calculated. Ifthe It is difficult to say When one phase orWeapon used has a dead time of 5 seconds,a solving a fire control problems ads and smothertin* of flight of 7 seconds, anda sinking time begins. One phase usually overlaps another;of 18seconds, then a total of 30 seconds cites they are concurrent. The start of Um(5 + 7 + 18 = 30) is subtractedfrom the 3 /iv113 INTRODUCTION TO SONAR

minutes to the time of explosion,leaving 2-1/2 REFERENCE PLANES minutes as the time to fire theweapon after the decision to fire is reached.Bear in mind that time to fire and time of Assume that a gun, rigidly fixedto a ship's explosion aredeck, fires while the deckis level, and its individual items. Although theweapon will beprojectile hits the target. The fired in 2-1/2 minutes, it willexplode in 3 same gun, if fired minutes. at a time other than whenthe deck is level, will miss the target. If thegun is free to train Destruction Phase (rotate) and elevate, however,compensation can be made for the ship's roll and Destruction of the target is the ultimategoal pitch. The gun of the submarine hunter. During then will remain reasonablysteady, this im- this phase theproving the chances of hitting the target,regard- computed ballistic solution is usedso that theless of the ship's motion. A fire ordnance may effectively be firedon the target. control system, Although the surface ship's in conjunction with a stable element,attempts primary A/S weaponto make the necessary adjustmentsto keep the is the homing torpedo; the methodsof submarineweapon steady. destruction by surface shipsare many and varied. Included are ramming, directldts Deviations from the level attitudeare meas- withhedgehogs,ured by a gyromeohanism (the stableelement), hull-rupturing near-misses with depthchargeswhich transmits to a computer in the and depth bombs, and damage ofless serious fire control nature that forces the submarine to system signals that indicate variationof the the surfaceposition of the deck with respect to thehorizontal. where it can be finished off with gunfire.Anti- Based on signals from the stable submarine submarines, ofcourse, use their A/S element, torpedoes on their submarine targets. the fire control system computesvalues of In short,train and elevation for theweapons launchers the destructive phase includesaction on the partto compensate for deviation from of the attacking unit that leadsto a killdirectly the level or indirectly. attitude. The various attitudesare measured with reference to flat, 6 ensional surfaces called planes. (See fig. 7-2.) Anunderwater FUNDAMENTAL PROBLEM fire control system computessolutions in the horizontal, deck, and vertical planes. The fundamental problem of firecontrol is to deliver fire on the selectedtarget. A direct hitHorizontal Plane is not required with someweapons. A depth charge, for example, can cause thedestruction of a sub- marine if the charge explodes A horizontal plane is tangentto the surface close enough to it.of the earth. Visualize thiscondition by laying All attacks are made withthe intention of hittinga playing card on an orange. The card the target, but withsome weapons, a near-miss represents is good enough. Solving the fundamental problemis no easy matter. difficulty is doe to suchfactors as target speed, maneuvers,range and speed of the weapon, all of which play importantroles in delivering fire on the selectedtarget. The solu- tion to the problem variesgreetly with given situations. A amok hunter, *srexample, "leaches the deck along the path of Bight.If the hunter aimed directly at the deckas be fired, the shot would pass through thearea at which he aimed; but, because the du* is moving;it no longer would be at that spot when the shotrew3hedthere. Compequeatly, the baster makes anestimateottbe fotare position of the amk,aims for that spot, and fires his gum. if heestimated oarreatliy; both the shot and the deck willarrive simulta- neously at the predicted position.The firecloatrol problem is similar to the dashhunter's problem, bat on a Satoh larger 71.123 Figure 7 -2. Reference planes.

114 Chapter 7BASIC FIRE CONTROL

the horizontal plane, the orange symbolizes the and purpose of the firecontrol quantities and earth, and the point of contactbetween the two their symbols. is the point of tangency. Everyplane parallel A compilation of the to the horizontal plane is likewisea horizontal nomenclature used in the plane. older antisubmarine fire controlsystems may be found in ordnance publicationOD 3447 and in Deck Plane Sonar Technician G 3 IA 2. The deck plane represents thelevel of the Old System ship's gun mounts. (Referencesto guns include similar weapons systems.) Whenthe ship is level, the horizontal and deck The older system of fire controlnomenclature planes coincide, is made up of cupital lettersthat represent basic but when the ship rolls andpitches the deckquantities, and lowercase letters, plane deviates from the horizontal. Thestable numerals, the element measures the amount of Greek delta (A), and theprime mark (1), used as angular devia- modifiers to expand the meaningor function of tion and transmits the informationto the firethe basic quantity. The control system. The fire controlcomputer com- capital letter C, for pensates for deck tilt by computing example, is the basic quantityfor true course. a solutionOwn ship is represented bythe lowercase letter in the horizontal plane, thenmakes train ando; and the target is identified by the elevation corrections. iVhat thesystem does, letter t. By in effect, is bring the deck adding the modifier to thebasic quantity, own plane back to theship's course becomes Co,and target course is horizontal. Ct. Vertical Plane Further expansion of theapplication of the basic quantity is provided by A vertical plane is perpendicularto the hori- adding more than one modifier, and placing them bothbefore and zontal plane, and is the referencefrom which after the basic quantity. Thus, bearings are measured. Relativebearing, for B (for bearing) example, is measured in the can be modified first to become Br(relative horizontal plane bearing), further to cBr(generated relative clockwise from the vertical planethrough own bearing), and finally to A ship's centerline to the verticalplane through °Br (increments of the line of sight. generated relative bearing). -4 The prime modifier(') signifies that the The system of planes makespossible thequantity is measured with respect to the deck -74 design and construction of mechanicaland elec-plane of the ship. Because tronic eqtdpment to solve the fire guns and directors control problem. are fastened to the deck ofa ship, Br can be Theft lines and planesare imaginary extensions measured only at the instant of some characteristic ofthe ship or target, the deck is hori- or of the relation in space between them. zontal. .Actual values of directortrain (angles measured in the deck planeare an fndication of FIRE CONTROL NOMENCLATURE train, not bearing, in the languageof fire control) consequently include a prime mark,signifying that Fire control nomenclature the quantity is measured withrespect to the deck provides a briefplane. As a result, B'r isdirector train and and accurate means of expressingquantities that represents the angle measured from otherwise would require extendeddescriptions. the vertical Two systems of expressing plane through the fore-and-aftaxis of own ship fire control quan-to the vertical plane throughthe line of sight tities presently are effective.The older of the two in the deck plane clockwise systems remains in use becausesome of the from the bow of earlier fire control equipment, own ship. such as the Mk 105, The Greek delta (A) also is used still is in service. With theappearance of new as a modifier. weapons, the old system was found to be It is placed before the quantityit modifies, and inade- signifies a change in that quantityduring some quate for expressing the firecontrol quantities specific time. It is an increment for such ordnanceas missiles. All new weapons of a quantity. systems (such as ASROC), therefore,use the new fire Control nomenclature. New System The entire nomenclature is too lengthy and Ordnance pamphlet OP 1700has established detailed for inclusion in thistext, but brief and standardized the nomenclature explanations of -the two systemsare provided used in de- do that you may better understand the scribing fire control problemsand their solu- meaningtions for the control ofguns, underwater weapons, INTRODUCTION TO SONAR

arid missiles. Volume 1 contains the nomenclature position indicated on thesonarscope, but at for the quantities applicable to solutions of the some other location. This difference in target gun fire control problem. Volume 2 covers the positions is due to curvature of the sound beam nomenclature for underwater related quantities. and to target movement during echo return time. Volume 3 has the standard nomenclature for The determination of actual target position ntssile related quantities. requires the application of corrections to the The plan of the OP 1700 system follows sonar measurements. These corrections, which the general pattern of the previous system, withare computed in the underwater firecontrol modification to permit introduction of newquan- system, consist of twoposition quantities: tities. It has greater flexibility- and -wider appli- apparent target position and past target position. cation to advanced fire control problems. (Target course and speed also are considered In some instances, quantities in thenew in the problem.) Sonar position quantitiesare system have different symbols than they do inillustratedin figure 7-3. The quantities are the old system. True target bearing, for example, expressed in the new fire control nomenclature. uses the capital letter B in the old system, but Two class quantities, range (R) and bearing in the new system it is symbolized as By. Target (B), are shown, together with the modifiers course in the old system is represented by Ct,necessary to express the appropriate measure- whereas in the new system the modifying letterment. Quantities related to apparent target posi- t is omitted. tion are represented by the lowercase lettera; The geometrical quantities used in naval firethose related to past target positionuse the control are those quantities involved in the letter p. The modifier h means the measurement mathematical solution of the general fire controlis in the horizontal plane; the modifier v refers problem. Hence, the geometrical quantities fall to the vertical plane. into certain main classes of quantities. Each of the main classes of quantities is represented by Apparent Target Position a class name. In each class, other geometrical quantities, besides the basic quantity,are ex- Apparent target position is the point from pressed by applying modifiers to the basic which the sonar echo appears to come. It differs quantity, as in the old system. The modifiersfrom present target position because of refrac- express the way in which the quantity is meas-tion of the sound beam, and because of target ured. travel during the time required for the echo to To illustrate, a class of quantities forex- return to own ship. The dotted lines in figure 7-3 pressing present target position is linear distance represent apparent position measurements. The between own ship and the target. This class ofquantity Ba is apparent target relative bearing, quantities is called ranges. The basic geometrical and Rim is apparent target range measured in quantity in this class is the linear distance betweenthe horizontal plane. own ship and the target, measured along the line of sight. It is expressed by the capital letter R.Past Target Position Another quantity in this class is the linear distance between own ship and the target, measured in Past target position is the location of the the deck plane. This quantity is symbolized bytarget when struck by the sound beam. In other applying the modifier d (meaning measured in the words, it is the position from which the sonar deck plane) to the basic range quantity R, formingecho actually comes. Past target position differs quantity Rd. from apparent target position because of refrac- The nomenclature assigned to represent thetion of the sound beam. It differs from present basic geometrical quantity in each class, and target position because.of target movement during the letters and numerals used as modifiersarethe time it takes the sound pulse to return to listed (ai mentioned previously) in the threeown ship. volumes of OP 1700. Extracts of Volume 2 of OP 1700 (underwater fire control nomenclature) Present Target Position are contained in Sonar Technician G 3 & Present target position is where the target SONAR POSITION QUANTITIES actually is located when the sonar echo reaches own ship. It represents the distance traveled When a target echo is received by a sonarby the target during the time it takes Um sound transducer, the target actually is not at thepulse to return to own ship from the target. VIVA ONFO.1.11.1.

Chapter 7BASIC FIRE CONTROL

N

..... S.

...... ,...... w....%.1.1o.. . =1...... 0.MR.. ...

owsftsso PRESENT TARGET ...... POSITION /) TARGET TRAVEL OURING ealmwleea. TIME OF SOUND PULSE . TRAVEL FROM TARGET TO SHIP iRvoj PAST TARGET

SOUND SEAM NI POSITION . APPARENT' TARGET POSITION

71.124 Figure T=3. Sonar position quantities.

- As shown in figure quantity B Is the target's made when conducting a DASH attack. Parallax relative bearing at the time the echo. ii.Teceisied. is the apparent: displacement of an object when Target depth. (Rv) s. and horizontal --range ..(Rh): seen from two different points. combine,;;thr;"prOduee': actual 'tariet'...,..range! (R). The ',CU, quantities used to express , " .... l . 'inear displacement between the computing ship NAVIGATIONAL PARALLAX *. anthassisting ship reference points is called *tigational .,parallax- (symbolized Pn), and is Two '.'eldPi)soliietiMeikicilierate::-Eiff,:a unit to lkOsnred:Slong the navigational parallax base- solve the tinderViate*: Oe:00#61:0;01ileni; One :. shiP-..metienre4'411di00400e1c;*iticerfdata. and ; rarauax 0Oireotions, to a :basic quantity, transthitsthe Information to Its assist ship, tuaccount for displacement, are symbolized widolf:inakee,theittitikWhen tiVO;ships'oPerate by lowercase lettere pn, and precede or follow in thii,:liitinier;i'COrrieetioir:f61:Parellax.MUst be, the basic quantity, which, is enclosed in paren- made: ;.CorreetiOni.:afOr?.-.piirsalaiirMist' algid' theses. ToAllUstrate: Relative target bearing

...... - ' . INTRODUCTION TO SONAR from the assist ship, as determinedby the com- puting ship, is expressed B system compatible with futureweapons. One + pn(B):::(B)pn, where modern fire control systemmay be used with B equals relative target bearingfrom the com- puting ship, pn(B) is the correction several weapon types. Regardless ofthe system, to be made it serves only onepurpose: the destruction of toaccount for displacement betweenthe twoenemy submarines. ships, and (B)pn equals relativetarget bearing from the assist ship after After target position is determinedthe basic correction is madeproblem for the system is to predictfuture for displacement betweenthe computing shiptargetposition,calculate the required attack and the assisting ship. course and firing Urns, and transmit the data Another type of parallax correctionis Pdo,to weapons and control stations. which accounts for displacement of the weapon Because most underwater fire controlsystems launcher from the reference point(the sonar are of a classified nature, they cannot be included transducer), measured in the deckplane along own ship's centerline. in this text. Certain conceptsare discussed, however, to give you some basic knowledgeof how a fire control system operates.

EQUIPMENT BASIC COMPUTING MECHANISMS An underwater fire controlsystem usually is designed to operate with The purpose of the computer ina fire control a particular weaponsystem is to solve the problem ofdelivering a system, although effortsare made to make theweapon on the target. Available information is

SPIDER. CROSS SHAFT

11R /49 --"11=,

Chapter 7 BASIC FIRE CONTROL

fed into the computer. If theinformation isfollow the rotation of the two sufficient and correct, the computertells how end gears, turning to get to firing position and the spider shaft a number ofrevolutions propor- when to fire. Thetional to the sum or differenceof the revolutions electromechanical computer solves theproblemof the end gears. by means of a maze of interconnecting machinery. Assume that the left side ofthe differential Taken as a whole, the computer iscomplex and is rotated while the right side difficult to comprehend. Basically,however, the is held fast. The components are simple machines moving end gear drives the spidergears, making consisting ofthem rotate on the stationaryend gear. This gears, levers, cams, springs, etc., that performmotion rotates the spider in the mathematical functionsmore rapidly than man same direction could possibly do. as the input and turns the output shafta number of revolutions proportionalto the input. If the right side is rotated while theleft side is held Mechanical Computing Devices stationary, the same resultoccurs. When the two inputs rotate in thesame direction, the Of the many deviicea forcomputing firedifferential adds; when they rotatein opposite control data,the easiest ones to .understanddirections, the differential subtracts.The output are mechanical devices that perform basicmathe-of a gear differential equalshalf the sum or matical operations. difference of the inputs. Another type of differential is Solving the trigonometric fractionsof a right the lever triangle is an .important mathematical differential, shown in figure 7-5.This device operationperforms the same functionsas the gear dif- beoause fire control computationsare based on ferentialit adds and subtracts, the right triangle. Threeof the six naturalis and the output functions of an angle in trigonometry proportional to the inputsbut themotion enter intoused in accomplishing the jobis linear. The the fire control problem. Theyare the sine,upper left drawing in figure 7-5 cosine, ands tangent. The remainingfunctions shows the secant, coseoant, and cotangentseldom lever differential receiving equalinputs. If both are used.inputs push upward one-fourthinch, the output Other mathematical computationsperformed byshaft also moves upwardthe same distance. mechanical computing instruments includealge-The drawing in the lower left braic functions, simple addition,subtraction, and shows unequal multiplication. inputs, and the triangleon the right represents the values entered on the lowerleft drawing. Mechanical computingdevices depend on (When comparing the drawings,remember that rotary and linear motionin solving problemis.none of the joints are anchored. Theentire When an electrical signalis received by aassembly is capable of moving.)In the lower synohromotor, for instance,/ the motorturnsleft drawing, consider input Ato be zero and a shaft, providing an output of rotarymotion. This motion is then transmittedalong .various shafts end through gear trainsto some other

point in the computer. As longas the pith of. motion is along shafts and gears, themotion is :rotary. If the rotary motion,is used as an input to a Component suchas a lever multiplier Or lever differential, the rotary motionis con- verted to linear Motion. Linearmotion is trans- mitted.' by Peehrodsand links, and may be /-ZERO INPUT reconverted to rotary motion. e = +4 INPUT. Figure 7-4 shows the parts ofa bevel gear C =+2 OUTPUT differential .which combines two,inputs into a INPUT single output that is either thesum or the differ- ence of the.. inputs. Around the center of the INPUT OUTPUT MOVEMENT:EQUALS 1/2 THE mechaniam are four bevel gears meshedtogether. E DIFFERENCE BETWEEN THE INPUTS Bevel gears on either sideare called end gearii; . those above and'.below are called,spider gears. The .:spider gears niesh =With theend gears to 71.103 perform the actual additionor. subtraction. They Figure 7-5. Lever differential. 119 r. INTRODUCTION TO SONAR

OUTPUT RACK INPUT SLIDE INPUT RACK \kr., MULTIPLIER PIN OUTPUT GEAR INPUT GEAR TO RACK C B

STATIONARY INPUT GEAR PIN TO SCREW

A 71.105 Figure 7-7. Flat cam and cam follower.

GROOVE differentials) and two outputs. When solvingfor 12.91 own ship movement, for example, the inputsmay Figure 7-6.Screw multiplier. be own ship speed and target relativebearing. The outputs are own ship's horizontalmotion along and across the line of sight. input B to have a value of 4. If Bmoves ahead a value of 4 and input -A remains stationary, Mechanical Noncomputing Devices then the output value C, is 2. ,.input A were -1, and input B were +4, then output C would In all types of computing instruments, certain be +1-1/2. For the type of leverdifferentialvalues or quantities must be limited insofaras shown in figure 7-5 the output equals halfthethey pertain to minimum and. maximum algebraic sum of the inputs. values. A mechanical multiplier Some computing components must havea limit commonly used is stop to protect them from too largeor too small the screw type, shown in figure 7-6. Ittakes two an input value. Limit stops are mechanical safety constantly changing input values, and .producesdevices that prevent shafts from rotating farther a single output that is the product of the twothan they should. Friction drives, overrides,and inputs. If the input to thescrews: (point A) is overdrives also are used to protect components. weapon time of flight, for example, and the A. input to the rack (point B) is mechanical stop is shown in figure 7-8. range rate, thenNotice that rotation in the type illustratedis the output (point C) is predictedrange. limited to about. 90°. Rotation A cam is a device that produces is halted when a mechanical the shafts 'come in contact with the fixedblock output that has a nonlinear relation to itsinput. at the top of the device. Cams usually converta rotary. motion into ,a A friction drive absorbs the shook that linear output. Figure 7-7 shOws other- a flat cam mounted wise could damage a computing component.If on a rotating shaft. A cam follower rideson thea motor overruns enough for the output to hit outer edge of the cam, converting the rotarymotiona limit stop, Or a handerank is turned with too of the input.; to a linear output. much force, or the line driven by the crank hits Other mechanical computing devicesused ina limit stop and the crank still turns, the fire control ..systems include suchmeohanisms friction drive 'slips andeases the strain on the as integrators and component solvers. Integrators mechanism. solve problems pertaining to time Saidmotion, A hunting tooth limit stop keeps valueswithin having two inputs and One Output. One inputmay.speoified computation limits. It has twogears. be elapsing time, for instance.,. andthe other input range rate. ;the One is connected to the input shaft,and the 'Of ',the' integrator other functions when the hunting toothengages will be.total change ,Ofrangev any instant ofas 'a . result of the quantities .'set on the input . time.. . gear. :. A component solver provides.'sobitions to An override allows a computing mechanism problemiqn*OlVing movement in relStionto theto accept larger quantities than the designspeci- target. The Solver haw: tWo inputs. (usuallyfromfies: The override permits acceptance of only Chapter 7 BASIC FIRE CONTROL

71.106 Figure 7-8.Mechanical stop. ry the maximum safe quantity limit,however. In from the electromagnet, thus allowingthe shaft other words, it allows the full valueto be used to turn freely. When the current isturned on, by some components, but still protectsothers from accepting unsafe values. the electromagnet exerts a force greatenough to overcome the effect of the springwasher Electromechanical Devices and pulls the cap tight against theelectromagnet, thereby locking the shaft .in place. Electromechanical devices combine two dif- ferent types of actionelectrical and An electromagnetic clutch is usedto engage mechanical. and disengage a line of gearing. Anexploded These devices; such as the magneticbrake and magnetic clutch, have wide view of a magnetic clutch is shown infigure usage and applica- 7-10. When current is fed to theelectromagnet, tion in fire control 'computing components. the friction plate assembly andcap assembly The magnetic brake can stop andbold a are in contact with each other, and the output shaft at a given value when certainconditions line transmits input rotation. When currentto are met. The magnetic brake is used to prevent the electromagnet is cut off, the frictionplate a line of gearing from turning. When thecurrent assembly and cap assembly separate by spring is off, no magnetic action takesplace. In figure action,losing contact with each other. The 7-9, an exploded view ofa magnetic brake, output line does not rotate or transmitany input notice that the spring washer holdsthe cap away to the clutch when these components are separated.

RETAINING RING Ne.V FRICTION PLATE ELECTROMAGNET ASSEMBLY SHIM WASHER BUSHING ASSECAPMBLY

SPRING HOUSING WASHER

BEAR114

71.69 71.60 Figure 7-9. Magnetic braket7exploded view.:. Figure .7-10. Magnetic clutch exploded view.

121 INTRODUCTION TO SONAR

Another device that should be considered STATOR here, although it is an electrical assemblynot COIL electromechanicalis the electrical resolver. The resolver is a computing device, and functions much like a transformer. It is capable of separat- EXCITATION E E cos a ing an electrical input vector into two right angle components. The resolver has a stator and a rotor, each part consisting of two separate ROTOR coils wound at right angles to each other. Volt- COILS ages induced on the stator coils by excitation of the rotor coils depend upon the displacement E sln of the rotor with respect to the electrical zero reference axis of the resolver. In solving for 12.105(71) a single vector, only one of the stator coils Figure 7-11. Electrical resolverschematicis connected electrically and represented on a symbol. schematic. Figure 7-11 shows the schematic symbol of an electrical resolver.

.. CICOS COMAE MECHANISM lis INMECHANICAL INTIORAl'OR C)CAM MECHANICAL CAM GI NC HUMANE OR 10108

QMN SINE MECHANISM COD GEAR DIFFERENTIAL toOF FRICTION DRIVE 1:1; FRICTION TO run cc)CAM ilarA.A.1.00CSA 0MUL LEVER MULTIPLIER 1103L UNIT STOP -LO IUSTRACTIVE LEVER 4. OLD ADOITIVE LIVER -gg- OL UEDA OVERRIDE DIFFERENTIAL DIFFERETTIAL I . C MECHANICAL COUNTER MECHANICAL COMPUTINGSYMBOLS OR ROTARY OVERDRIVE 0 Of.DIAL 40 MS SERVOMOTOR (M 0V VACIXACIVSE ferNICALIMOMNICALMNNEriOrMATICI (0)DL DIAL CROUP MECHANICALCONNECTION WA, itRESISTOR x\i- itrust MECHANICAL NONCOMPUTING IT R THYMTE RESISTOR SYMBOLS ilb L. LAMP

cr--.W SW TIMMY. SWITCH -I(- C CAPACITOR Ititi L INDICATOR LAMP 3:1CE MAGNETIC CLUTC11 OR til SW MKROSWITCH rsm SC SIMMIND CAPACITOR o a A AMPUFIER 041/4. SW ROTARY IMITCH QMT TIME MOTOR yiltIII mom RD RECTIFIER SO MINCHNO DIFFERENTIAL MOTOR 4 . auu:SdriaineN0OVIRENTUC NEW . ..V. T TRANSFORM MS SERVOMOTOR SCT MOOD CONTROL INNISFORMER ACT MC11/10 UnoA TIMNS/CRIMICTICIL tialliiin' MAY SW ommosvniaf

-- titirmirsammcctsacmeacwciuma 401 IMICHIM MOTOR MilOR ammo arm= 4 11111 C1 SWCAM-ACTIMO ELECTRICAL cowiecnos Vivo so ammo UMW= mcmoswntw

ELECTRICALSYMBOLS ELECTROMECHANICALSYMBOLS

13.5(71) Figure 7-12. Identifirtng symbols' and their abbreviations.' Chapter 7BASIC FIRE CONTROL

When the resolver is zeroedelectrically, the rotorcoil clamped to the stator coilis called the cosine coil. The other alI rotor coil, NC 2 Di IASI at right angles to it, iscalled the sine coil. Gra AI As the rotor rotates from 0° to360°, the voltage ALL MANUAL 1401.14 Se qsks, induced across the cosine coilfollows the cosine AUTOMATICb 001D-- function of the excitation voltage.Similarly, the era voltage induoed across thesine coil follows the to I- MUL P5 - a ON OPIN 'N sine function of the excitation oveRA SC11 0 voltage. INPUT

Schematic Identification of System °LIT Components -IDI OL1 S ORA I II I:I In the maintenance publicationsfor fire control NCI2 SL10 systems, the devices described 51.21 MILS in this section 01 are identified by standardizedsymbols. The identifying symbols and theirabbreviations for -1.02 ARIL 9 system componentsare reproduced in figure 7-12. Usage of some of the MT 1 in a sectional diagram component symbols may be seen in figure 0 IN 2 7-13. D2S OF2 SLR CAM1 DS UNDERWATER FIRE. CONTROLSYSTEMS A .modern fire controlsystem, as mentioned 71.61 earlier, is tailored to therequirements of a Figure 7 -19. Use of symbols particular weapon system. Aboardsubmarines, in a sectional .the. weapon is the torpedo.Aboard ships, the diagram. weapon system usually consists of severaltypes, such as AfS . torpedoei, DASH, hedgehogs,and depth charges. Despite thetype of fire control

RELATIVE TARGET POSITION MOTION KEEPER ANALYZER

TARGET TARGET SPEED COURSE

BEARING TIME TO FIRE FIRING FIRE RANGE PANEL WEAPONS DEPTH BALLISTIC. RANGE COMPUTER WEAPON' CONTRA. CIRCUITS (TORPEDOES, (BEARING ORDER, TILT ORDER, ETC.)HEDGEI4OGS,WEAPON A, DEPTH CHARGES)

SONAR ROLL EQUIPMENT

LEVEL STABILIZATION STABLE COMPUTER 'CROSS LEVEL ELEMENT4 r f B1

51.101 Figure 7-14.?TypIcalunderwater fire control system. rAr123 INTRODUCTION TO SONAR system used, each one has the same purposeto Submarine System direct fire to the target. Torpedo fire control on the surface is rela- Shipboard System tively simple. When the submarine is submerged, however firing torpedoes ata surface target A shipboard underwater fire control systembecomes complicated. When the target is another (representative of the Mk 105) is illustrated insubmerged submarine, the firecontrol,problem figure 7-14. The system performs the followingis even more complicated. The equipmentused functions: to solve the submariner's fire control problem is the torpedo data computer (TDC). It isillus- 1. Integrates associated fire control equip- trated in figure 7-15. ment with own ship components. The TDC consists of three sectionsposition keeper, receiver, and angle solver. Target infor- 2. Computes sonar and weapon stabilizationmation from sonar (usually passive) is fed to data, analyzes target motion, and providesathe receiver section, along withown course and solution to the ASW fire control problem. speed. Sonar bearing and targetcourse and 3. Provides ballistic control data for stern-speed are manually set into the position keeper. dropped depth charges, hedgehogs (both fixed The position keeper serves thesame function and trainable), A/S homing torpedoes, and train- as itscounterpart in the Mk 105 shipboard able rockets (weapon A). system. The output of the position keeper is sent to the angle solver section of the TDC, which continuously computes the correctgyro Target location information is supplied by the angle for the type of torpedo used. The TDC sonar to the ballistic computer (such as the Mk 5 then transmits this information togyro angle attack director). The same information is fur- indicator regulators located in the forward and nished to the position keeper, whichuses the data after torpedo rooms. The indicator regulators to track (dead reckon) the target. Target track automatically set the torpedo gyros to the ordered information is fed to the analyzer, which computes position.If computed target information iscor- target course and speed. rect, the torpedo, after being fired, willcome Target motion data from the analyzer, andto the course set by the gyro angle indicator target location information from thesonar, are regulator and proceed to hit the target. combined in the ballistic computer, whose output is weapon control orders. To compensate for roll FIRE CONTROL SYSTEM TESTS and pitch motion of the ship, the stabilization computer provides correction orders to thesonar Certain transmission, computing, and rate and to the weapon mounts. tests must be performed in order to ascertain that the fire control solution is correct, and If sonar contact is lost, the position keeperthat values are received correctly at remote continues to provide target track information.stations. Also, frequent operation of a system As long as the target does not changecourse orexercises servosystems, power drives, and com- speee. during lost contact time;. the resultingputing networks, thereby bringing attention to weapon control orders will be valid. any existing trouble. The latest shipboard. underwater fire control system is the Mk 14, Which was designed for Transmission Tests use with ASROC. The system 'also can be used with fixed and trainable hedgehog. projriutors, Transmission tests are held to check the DASH, and the Mk 43, _Mk 44; and Mk 46 A/S accuracy of automatically controlled devicesat homing torpedoes. remote stations, and to check their response . to changing signals; When running these tests, The Mk 53 attack console is' the datapro-the first ,.step is .to establish voice communica- cessing center for the system. It receives tatgetlions between stations. Next, theman at the position information from sonar or radar. Rd.,'transmitting station must read the combines it with own ship and ballistic dials' to exact output !hide of the quantity being checked. In turn, the f produce weapon orders. Aided tracking and posi- Man at the receiving station must adjust the qpn keeping 'are also functions of the attack'receiver to correspond to the reading from the console. . transmitting station. Chapter 7BASIC FIRE CONTROL

ti

4.191 Figure 7-15. Torpedodata computer Mk 4.

Computing Tests motion rates are integratedwith time to generate computer changes in target position, As sonar tracksa moving target, constantly the problem changing inputs are fed to the becomes dynamic. To test thecomputer's accu- computer. In-, raoy, consequently, both static stantaneous values of theieinputs are used *y tests are run. and dynamic theft computer to solveballfstio computattofirt and to predict future targetpositions. The com- Static tests: Static tests puter's solution is therefore basedon an infinite check the overall number of static (still) problems.' operation of the computingsystem in a stand- As relative still condition. In this type oftest, appropriate i7

INTRODUCTION TO SONAR

test values are inserted manually, and the problem assigned to relative motion rates by manually is stopped at a fixed point. Input test quantitiessetting inputs to the relative motion group. The are thus of a constant value and produce fixedtime system of the computer is then moved, answers, which do not change with time. Theseeither manually or by the time motor, an amount fixed answers indicate whether the static portionequal to the test interval. Readings are then of the fire control equipthent is performingtaken to ensure correctness of the solution. properly. Rate Tests Dynamic tests: Dynamic tests are run to check the computer's generation of bearing and Rate control tests check the functioning of range for specified time intervals against athe rate control system. Mechanisms of this mathematicalsolution whose answer containssystem correct values, such as target angle correct amounts of change in quantities for like and target speed so that computer target motion conditions. During the test, fixed valuesarerates agree with actual rates of the target. In

A

vf, 4

d 16, "1;"'"I prolidor -JD Iv 'r I

51.85 Figure 7-16. Tactical range recorder.

126 , ...r AS Chapter 7BASIC FIRECONTROL

other words, this testdetermines the time re- quired for the computer toarrive at correct RANGE relative motion rates. Timerequired must be small, but smoothne-s oftracking must also be considered. The rate control system is a com- - promise between these two factors. ; 91.! . ;ow.. 1. Rate control tests consistof tracking a . hypothetical motionless target with set for a selected sensitivitythe computer . ,,it of rate error ...P...., a/. detection. Sensitivity is controlled - TARGET ._ by the time ECHOES: constant input to the rate controlsystem. Initially TIME - a large error is introduced and the time motor ..N...;-, ...we, ..- is started. Time requiredto reduce the error . . :...me mOrioN. by a preselected percentage PAPER is timed by a stop- - - 411110 ,. . watch. This stopwatch readingis a measure of tihGEdo AO,. t the actual time constant . -RATE-1:..."" or sensitivity of the 11,e, system. It is compared againstthe theoretical , !:rJv value for the test. tititir Ire.1", TACTICAL RANGE RECORDER 71.64 Figure 7-17. TRR target The tactical range recorder(TRR) shown in traces. figure 7-16 is among theoldest underwater fire control instruments in the Navy.In the event of a casualty to the primary extension match the slope ofthe traces, then fire control system, read the speed on therange rate scale. When the TRR is a fairly reliableawdliary means of measuring range rate, directing depth charge and hedgehogattacks. The use only the latest 200 introduction of newer fire yards of traces, thatis, only those traces control systems and nearest the top of thepaper. Refer to figure such weapons as ASROC,however has resulted 7-18. in a deemphasison using the TRR as an aid in firing weapons. The TRR Because range rate isa clue to target aspect, still is a useful aid, which gives an indication of the though, for classifyingsonar contacts as sub- target's heading, marine or nonsubmarine,and for deterrojning you may wonder about the reliabilityof range. rate. For the greatestaccuracy in determining target motion. Because of thebroad scope bf the range rate, you must know subject of classification, onlya brief discussion your ship's speed, of the TRR is given here. and the ship must beheaded at the target. More detailed informa- Meeting these two conditions tion on the use of the TRR iscontained in Sonar is not always Technician CI 3 & a, NP 10131. possible, consequentlyyou must have some other means of determining aspect. Range Rate

The.traces on the recorderpaper show target range versus time. From. thetraces you can determine range rate and targetaspect. Range rate is the relative speedat which your ship is closing the target. -Target aspectis the target's heading in relation toyour ship. . The recorder papermoves downward at a constant rate, representing' time.The. stylus is eynchronizekwith the sound pulsetransmissions,. and moves swims thepaper from left to right. When a target, cho isreceived, the stylus burns a trace on the paper thatrepresents, target range, as illustrated in figure 7-17. To determine range rate,turn the plotter bar until the parallel lines 71.65 on the plotter bar Figure 7-18. Determiningrange rate.

L..)/ 122 1.12- .- r.. n ci.+w wwwmn.. r, vw. wvRw^` Rvyr' N1I. Vert rd' Xr' rrl wMVer..i+...rrVrm.v..wvrwv...r +,,.

INTRODUCTION TO SONAR

You learned in chapter 3 how to determinetraces. Thusdoppler up means a bow or direct- aspect from doppler effect. Whenyou can alsobow target; doppler, down means a quarteror observe an echo indication at thesame timestern-on target. you hear it, you can learn more about the target than you can from audio responses alone. Amore Individual Echoes reliable method of determining targetaspect Suppose a pulse of sound hits a submarine than that based on range rate alone is tocompare that is beam-on to the sound signal. All parts the recorder traces with the dopplereffect. of the outgoing pulse strike the submarine at Naturally, this method takessome practice andapproximately the same time. All parts of the requires a knowledge of how the tracesappear pulse are thus reflected and startedon their for different target aspects. return Journey simultaneously. In figure 7-19 you can see that parts 1, 2, 3, and '4 start back Doppler and Recorder, Traces together. These echoes hit the transducer simul- taneously, and when the returning echo reaches Doppler and recorder traces work together the receiver, it is transformed intoa short, dark in serving as a checkon each other. That isline on the recorder paper. A beam trace is the why it is essential to useyour eyes and ears same length as a recorded pulse length. simultaneously. When operating the recorder, The beam trace has no doppler, but it hasa look at the traces and listen to the doppler. Ifdefinite "smack" as you hear it. It sounds short you hear no doppler, you have either a beamand sharp, and it appears on the papervery much trace or one from a motionless target. (Doppler as it sounds. Both edges of the trace are sharp is a function of target motion. Ifa submarine and distinct, and the entire trace is solid and well is dead in the water, there isno doppler indica- defined. Because it is easy to recognize, 'it is the tion, but the traces will record the target inits simplest of the recorder traces. Study figure 7-19 proper aspect. Thus, traces for a stern-onuntil you can recognize the trace easily. target, which is dead in the water,are recorded Consider the quarter aspect target in figure as stern-on, but instead of having doppler down, 7-20. The stern of the submarine isnearer than you will have no doppler.) the bow, so that portion of the transmitted pulse For purposes of this text,assume that the marked 1 hits the submarine first and starts back target is in motion. This assumptionallows first. It is followed by the portion marked 2, and simple comparison of dopplOr andrecorder so on.

2 3 4

SIGNAL ECH- O S ONAL ECHO

51.29(71). 51.30(71) Figure 7 -19.Beam.aspect traces. Figure 7- 20. Quarter aspect traces. Chapter 7BASIC FIRECONTROL

SIGNAL. ECHO STERN-ON BOW V,00:4,1=1' 1 *""117*.i.1",i.4171.°qiX,Vg'IX 4V-14...%. ",,Ai, $. %.1.4... ''f S,Vi7:tggiC,;.:074, 11.17:11:'7. 4.7::::::::1711.?1,21H.A..0:1tr!"-i. -rk ...:.-.-;.-...14;yeli7, fir; - vziy,t-t ; i9., f. .:t 411V0-647;14,45,"?`:.4 A it;

51.31(71) Figure 7-21.Direct stern 51.31(71)A traces. Figure 7 -22. Bow aspecttraces. As you can see, part 1returns to the rans- ducer sooner than part 4,hence the echo is ranges from various parts ofthe submarine. recorded as ,a long trace.Because the trace is The traces may be drawn out, it is notas clear as a beam trace. very weak until you are at The ends are not clearly. short range, when theybegin to appear more defined. At longrange clearly. Because of the the trace may be weak,but you can distinguish wake effect, direct-bow it by the low doppler that traces are fairly irregular,especially at the accompanies it. right edge. But the wake If you-have a stern-ontarget, the trace is is not as prominentas similar to a quarter trace.(See fig. 7-21.) On a stern target, however,some of the echo re- turns from the wake, somefrom the stern, some from the conning tower,and some possibly from the bow. This characteristictends to make the echo even longer than thequarter target. It is not as solid as thequarter trace, but is quite long. Stern traces alsoare irregular, and they may vary in shape and length fromecho to echo. If the target is moving,doppler is down and the left edge of the trace maybeparticularly irregrd ar DIRECT BOW because of the wake. . m I ....r.w. .A, to ipo .0 ! The baw target traces, 4....ar 3 .T: P shown in figure 7-22.. '0.- 7-.40: ol:'? 1:. are longer than beam traces. The :-';'',.."".0"lP -,....i.ihk..i., 4 ..1: portion of the .4 1. I 14144 ..... PI' sound pulse that hits the bowreturns ahead of '4!,' ler;:e.,t the part that hits the stern.The resulting echo. 13if. is lengthened. Doppler from-amoving bow aspect. target is up. 1.,=er.1:144.4..,. Mti.+`,..71= . .CDs t;, Ni s'.96, If the submarine iscoming directly turd ...-... ..;...... 4... re./. your sound pulse, the traceis direct-bow, as it appears in figure 7-23. Again thetrace is long, because the echoes are returning 51.31(71)B at different. Figure 7-23. Direct bow aspecttraces. INTRODUCTION TO SONAR in stern traces, inasmuch as it is fartheraway than the submarine itself; doppler is high. One of the best ways to identify a TRR trace is to decide whether it is a beam trace. Normally, a good look at the trace is all that is necessary to resolve this question, but you should also listen for doppler. If doppler is low, the target aspect is either quarter or stern-on. If high, the target is either bow or direct-bow. Remember, though, that doppler depends on motion as wellas aspect of the target. Sonar echoes also are returned from other submerged objects besides submarines. Usually nonsubmarinetracesare recognized easily. Echoes returned from a wake, for example, ordinarily are not accompanied by doppler, the traces are quite long, and the entire series of traces consists of irregular waves. Stationary targets, such as nonmobile counter- measures (a bubble is an example) are very sharp and regular in the series of traces, but there is no doppler, and the range rate equals own ship's speed.

INTERPRETING DIAL. READINGS Sonar Technicians must be able to interpret, and sometimes interpolate, sonar and fire control equipment dial settings. Information to be read from these dials includes such valuesas range, range rate, target course and speed, and many other fire control values. Normally, two types of dials are used. They are disc dials and ringdials. A disc dial is simply a flat, circular plate 51.108 secured to a shaft, and inscribed with values of Figure 7 -24. Own ship and target dial groups. the function it serves. A ring dial is circular- shaped also but has a hollow center to permit placing a disc dial within it. An example of the use of these dials is shown in figure 7-24. read on the outer dial against the zero graduation of the inner dial. The top dial group displays target informa- tion. The bottom dial group showsown ship data. Own Ship Dial Group The counters between the two dialgroops show horizontal sonar range. The dial to the left of the The own ship dial group consists ofan inner range counters indicates horizontal range rate. disc dial, an inner ring dial, and an outer ring dial. The two inner dials are graduated in 5° Target Dial Group increments and are numbered at 10° intervals. The outer dial has only a diamond marker and Two concentric dials make up the target dial the words COURSE ORDER inscribed. The inner group. They are a ring outer dial and a disc inner disc dial shows relative sonar bearing (002°) dial. Both dials are graduated in 5° incrementsand against a fixed index at the top of the dials. The are numbered at 10° intervals. Target angle (144°) inner ring dial shows own ship'scourse (032°) is read on the inner dial against the filed indexat against the zero graduation of the inner disc the bottom of the dials. Targetcourse (072°) is dial. Course order (039°) is readon the inner Chapter 7BASIC FIRE CONTROL ring dial against the diamond indexon the outer ring dial. Of particular importance is theability to inter- polate (to "read between the lines")and to note Range Dials direction of change of the dial readings. Our discussion of the fire controlproblem, 1 and of the equipment used to solvethe problem, The counters between the target andown ship dial groups show generated horizontal was necessarily restricted to fundamentals. Com- sonar puter mechanisms, fire controlnomenclature, range (870 yards). The dial to the left of the antisubmarine weapons,' and recorder traceswere range counters indicates range rate (2 knots), only briefly covered, serving to acquaintyou with which is the rate in knots at whichhorizontal range is changing. the problems involved in making attackson enemy submarifies. You need to studymany technical The dials just discussedare only a few ofmanuals, and other trainingcourses, to fully the many that you must be ableto interpret.comprehend the duties of a Sonar Technician.

: CHAPTER 8 COMMUNICATIONS

The main essential of communication between (loudspeakers) circuits, sound-powered phones, two persons is that the language theyuse must be and automatic devices. These devicesare remote understandable to both. Not only must one personindicators, and are used to transmit bearings, be able to express himself clearly, but the otherranges, course orders, firing orders, and other man must be able to nomprehend what is communi-data. cated. Realizing that many problems are encountered When sonar contactis made, the bridge in communications, the Navy has adopted certainusually is informed over an MC system. By standard methods and practices to minimize this method, all stations concernedare alerted, errors and misunderstandings in message trans-and sound-powered phones are then manned to mittal and reception. Many of these standardeliml.nate excessive noise levels caused by the procedures are used by other allied services.constant use of loudspeakers. The ASW officer They are invaluable in conducting Joint inter-isdirected to make theattack. His course national operations. The phonetic alphabet, has orders to the bridge are relayed by automatic been adopted by all allied forces for combinedelectromechanical devices to direct the helmsman operations. in maneuvering the ship to the firing position. In this chapter you will become acquaintedAs the ship reaches the firing point, signals or with some of the internal and external communi-verbal instructions to fire must be transmitted cation systems used aboard ship. Additionally,to the weapons stations for firingweapons at you will learn correct operating procedures forthe correct time. radiotelephone and underwater telephonecom- munications. Because the phonetic alphabet and SOUND-POWERED PHONES sound-powered telephone procedures are covered in Basic Military, Reauiremente, NavPers 10064, they are not included in this text. The shipboard voice communication systein used most extensively is the sound-powered INTERNAL COMMUNICATIONS telephone (S/P) network, It consists of primary battlecircuits JA to JZ, with auxiliary and Most men in the Navy, regardless of rate,supplemental circuits for useif a primary are familiar with internal communications.Sonarcircuit is damaged. The degree to which these Techniciansespecially, have occasion to usecircuits are manned varies. Few circuitsare several types of systems available for trans-used under normal peacetime cruising condi- mitting sonar information, It IS almost impossible tions., During general quarters, when all battle to conduct attacks on enemy submarinesor shipsstations are manned, all circuits may be used. without some method of internal communications. Of primary concern to the Sonar Technician On a destroyer, sonar control may be locatedare the JA, JP, and as circuits. The JA, the below decks, on .the bridge level,or in somecaptain's battle circuit, is used for transmitting other section of the ship (depending on the typeorders to key, control stations and exchanging and class of ship). Because it is remote from'vital information with those stations. Weapons the bridge, some means of communication mustcontrol information 13 passed over the 8JP be established between_the--bithge andsonar circuit. The other S/P circuit you will probably control.-This-reitalle is accomplished by Oi,..man isthe 61JS. It normally is used as a Hang one or more of the internal communibakone-way system to provide contact range and Lion systems. Shipboard, circuits include MC.bearing and other data to UB plot, MC, and the .' 132

'4 ) 44(49./.9.7 a

Chapter 8 COMMUNICATIONS

bridge. The 1JS circuit is the main antisubmarine directly into the speaker grill. Release theTALK attack team control circuit.It connectsthe bridge, switch to listen. When your conversationis com- CIC, and sonar control, and is usedprimarily forpleted, depress the release button atthe far left conning .orders when sonaror CIC has control ofend of the row of station buttons to an attack. Normally, the 1JS is mannedby officers remove your in charge of the various stations. intercom unit from the circuit. Whenyou are called, the CALL light illuminates. It isunneces- Circuit discipline must be maintained atallsary to depress the button of the station calling; times when you are wearing phones.Personalmerely use the TALK switch as describedherein. conversations with friends on the same circuitmay cause a delay in the transmissionof vitalinforma- Despite its many advantages, when theMC 4 system is used' the noise level isincreased g tion, resulting in a delayed or missedattack. With greatly. This condition occurs because ofits the high speeds of modernsubmarines, such aspeaker-type output and the fact that it picks delay could result In the loss ofyour ship or the ship you are trying to protect. up background noise from the transmitting station. Because of the high noise level generatedby operating the 21Mb, it should be usedonly when MC SYSTEMS absolutely necessary. Although sound- powered phonesare the most REMOTE INDICATORS common Means of internalcommunications, there are other methods, one of which is theMC (ship- The fastest means of communicatinginforma- board announcing) system. The MC system is antion Is to transfer it electrically. Throughthe use electronic speaker-type system,similar to anof electromechanical and electronicrepeaters, office-to-office intercommunicationsystem, andsonar infOrmation is displayed at remote loca- is designed to provide amplifiedvoice communi- cation. ' tions aboard ships and submarineswithout delay. One type of display, an eleotronio azimuth- Sonar and. CIC underwaywatohstationsusually are not fully manned under normal cruising range indicator, shows bearing andrange of a condi- contact on, a cathoderay. tube. It duplicates audio tions aboard ASW ships. Whena sonar contact isand video information present at thesonar gained, the 29MC (sonar control andinformation) operator's console. is used to .alert CIC,- UB plot,and the bridge. Another type . of remote indicator displays Contact information Ouchas-; ranges, bearings, and doppler reports) is passed -sonar information electromechanically. Contact over this-circuitrange and-bearing ire shownby counters similar (a-one-way system) until the contact is.Classifiedto an automobile's mileage indicator. There as nonaubintrine or until ASW. stations is also can be an electroMeohanical order transmitter.In this fully manned. Submarinesutilize the 27MC.(sonarunit, a moving pointer (indicating firing and:radar control) sYstem. bearing) is matched by the' operator ata weapons station. Ariother :communication., BYsteinfount aboard Another moving pointer (Indicatingcourse to steer Most ships and subMarines'18 the2IMC (captain's during an attack (is matchedon the bridge by the 'Command syStem);' a two -way system, With helmsman. .. each intercOMmUnioatifie,-Unit capableof calling As you can see, electrical/electronic repeaters either '10 or '20 stations,depending on the-. type of roan:* the time required to transmitinformation ship in which it installed. the essentialeliminate noise-producing transmissions, and components:. are la. reproducer,. Amplifier;and'reduce the volume of trafficover S/P phone controls necessary, for .oper atiOn.,Thoreproducercircuits. acts as a microphone In the Callingunit and as loudspeaker in -the unit called.Amplification :takes :-place in,:the 'calling- unit., Thecontrols EXTERNAL COMMUNICATIONS consist of .the. telk,SWItoh.P3184100:se.enligh busy light,. call light, volume and dimmercontrols; 'During antisubmarine operations (and,forthat and a microphone or bandset-jankboSi.. matter, all werations),. it, is imperativethat . , . TOOperate 4 A bOinnulnioations between ASV units,such as ships the 2IMCi'dePreiis the pushbuttonMid* airtraft,- be conducted 'smoothlyand effi- of the 'station deidie&If the station isbOty;:thsCientlyeandlfree of confusion; insofar.aspraotic- :red BUSY light Will fInsh: If the BUSY-lightdoes not' fiabh, depress the' TALK .'7ableL' 'IV-faulty, microphone switch of:a sound - Sitfitcih- rind SPeak powered phone, frequently cutting out (acommon INTRODUCTION TO SONAR failure), can prevent vital information fromHeading getting through just as effectively as if it were not reported at all. The basic format of a military message consists of the heading, text, and ending. The Poorly trained or inattentive operators canmessage form isin plaindress,abbreviated cause confusion, delay, and mistakes, and mayplaindress, or codress. Codress is an encrypted even create a dangerous situation. message, with which a Sonar Technician normally is not concerned. Plaindress is used for radio- RADIOTELEPHONE telegraph and teletype communications, as well as for radiotelephone administrative messages. Radiotelephone (R/T), commonly called voiceA plaindress message usually has a complex radio, is a rapid means of exchanginginformationheading, consisting of call, transmission instruc- between ships, aircraft, and submarines. Voicetions, precedence, date-time group, address, and radio usually is amplitude-modulated. A con-other elements. The type of radiotelephone mes- tinuous-wave radiofrequency carrier has an audiosage you will use most, however, is the abbre- signal impressed upon it, varying its amplitudeviated plaindress, in which the heading includes in accordance with the audio variations. A handsetonly the station called and the station calling. or a carbon microphone is used to key the trans-In some instances, after communications are mitter. established, the heading contains only the station .Although voice radio is a fast means of corn-calling. An example of a typical heading is: muniOation, speed without accuracy is more thanFARMERBOY THIS IS ISLAND QUEEN. worthlestiit can be dangerous. When ships are Operating together at high speeds and in closeText formation, a mistake or a delay in coinmunioa- tions can cause a collision. The text of the message is the basic thought In antisubmarine operations, voice radio isor idea, the originator wishes to communicate. used toexohange contact and tactical informationIt follows the heading, and is separated from between the CICs and bridges of the shipsit by the word BREAK. Quite often radiotele- participating in the operation. The captain or thephone messages, particularly those of a tactical OOD mans the bridge radio circuit, used pri-nature, are coded, There are several reasons marily to ekOhange tactical hkorthation. Thefor coding messages. The first is obvious: so CIC officer and the Radarmen handle the Combatthat the enemy will not know your intentions. information (CI) net to 'exchange contact informa-If,for instance, you were. ordered in plain tion between CICs. Contaot information betweenlanguage to commence a sonar listening sweep, CIC's Is evaluated by the' CIC evaluator andand the message was intercepted by: an enemy pertinent information is relayed to the captainsubmarine, he could rig for silent running to and OOD on the bridge by 'use of sound-poweredreduce his noise output to a minimum, making phones.. your job all the more difficult. If the message Because radiotelephone procedures are usedis sent in code, however, chances of interpreta- with the underwater telephone, and beoause Sonartion by the enemy., are reduced even though he Technicians may be assigne&CICwatohes duringshould intercept it. Another purpose is brevity. normal cruising conditions, it is. necessaryforThe less time on the air the better, for both you to be familiar with proper radiotelephonesecurity and practical reasons. procedures. Signal codes are contained in communication publications knovni as .signal books (of which RADIOTELEPHONE PROCEDURES there are several), each having a particular application. One signal book consists of two Whenever you use a radioteleplvseyourletters; or a combination of letters and numerals, speech must be clear andslovi,SpeffilEame sagethat usually are used for tactical signals. (Mem- by natural phrases--not in stilted, word-b-rdbers of NATO use this book, as well as the fashion. Use a> normal tone; don't shout.. standard phonetic alphabet, for combined opera- nounoe each word dely, and clistinotly, p mgtions.) As an example, a certain two-letter and at intervals. Think what you 'are, toa numeral signal tells all ships to make oil fog say, then say. it. Keep the ssage as briasand smoke. From his signal book, the captain possible. ; . of on Italian ship can read and understand the

134 Chapter 8 COMMUNICATIONS

meaning of the signal as quicklyas the captain of a U. S. Navy destroyer. receipt. It merely means thatyou have received Two letters and athe messagenot thatyou understand it or will numeral thus overcome the languagebarrier carry out any orders contained in it. and make a brief messageas well. WILCO is the answer to the prowordACKNOWLEDGE, and Another means of reducing transmissiontime, means that you will comply with any instructions and providing a degree of security,is through or orders contained in themessage. For this the use of brevity code words.In general, these reason, the proword WILCO mustnever be used code words are used toconvey contact andwithout specific permission froma person having related information. Communicationpublication the authority to grant such permission. ACP 165 contains the operationalbrevity code. Following is a list of themore common At the end of the text, the word prowords, the meaning andusage of which you BREAK is should memorize. This list is notcomplete, as used again to separate the text fromthe ending. are the ones in communication publications. It consists mainly of the prowordsyou are most Ending likely to hear and use on theunderwater tele- phone. Should you be interestedin seeing a more complete list of prowords, check DNC5 The ending of a radiotelephonemessage con- or ACP 125. sists of one of two wordsOVERor OUT. When Proword Meaning OVER is used, the sender is tellingthe receiver ALL AFTER. to go ahead and transmit, ..All after. or "This is the end ALL BEFORE. ..All before. of my transmission toyou and a response is BREAK The text is separated at necessary." With the use of OUT,the sender this point. Do not con- in effect is telling the receiver:"This is the fuse theseparated end of my transmission to yoUand no response portions. is required." In motion picturesand television CORRECTION....An error in my transmis- productions, you are likely tosee military sion has been made. I personnel say "Over and out,"but there is now correct it. never a need for their combineduse in this DISREGARD This entire transmission is manner. THIS in error. Disregard it. TRANSMISSION FIGURES Figures or numerals follow. CALL SIGNS FROM This message is originated by I SAY AGAIN. . I repeat the entire trans- In radiotelephone procedure, shipshave call mission(orportions Ague that are common, easilypronounced words indicated). or expressions.' The radiotelephonecall sign I SPELL I shall spell the next word of one ship, for example, isBLUE STAR; another with the standard phone- is BEANSTALK; still another is tic alphabet. EL.TORO. All OUT U.S. Navy ships are assigneda voice call sign. This is the end of my If you need to know thevoice call sign of any transmission.No re- Navy ship, you can find it in the ceipt is required. communication OVER..., Go ahead with your trans- publication JANAP 119. mission at this time. (Or, This is the end of PROWORDS my transmission for whicharesponse is required.) RadiotelephOne procedurealso reqUires the ROGER I have received your last use of standard procedural words, calledpro- transmission satisfac- wordii. Although Reword!: are net code words torily. as such, they say a 084 deal with' the IllAY AGAIN Repeat all (or portions in- utmost dicated) of your mes- brevity. The words OVER. and OUT,,mentioned earlier, are prowords. Besides .' sage. OVER and OUT, THAT IS . You have repeated my mes- two other Proivords that are neverused together , CORRKCT are ROGER sage 'or have given in- . and:WILCO.. ROGER is,:used as formation correctly.

136 V51-0 INTRODUCTION TO SONAR

Proword Meaning mind. Go through the alphabet several times to get the feel of the sound of the dit-dah com- THIS IS This message is from- binations. TIME What follows Is the time or date-time group of this The Code message. TO, This message is for action In the pronunciation guide for the sounds of by and is directed to WAIT I must pause for a few the characters in the accompanying list, the seconds. sounds are written out phonetically insofar as WAIT OUT I must pause for longer than. possible. The short sound "dit" actually takes a few seconds. on the sound The 4,1,, is very short and WILCO I have received and under- the "t" is dropped. stood your message, and you have the assurance of the command that it Letter Pronunciation will be complied with (This type of answer re- A di-DAH quiresCO's permis- B DAR-di-di-dit Mon. ) WORD AFTER.. . Theword after (word) C DAH-di-DAH-dit (word) is . D DAH-di-dit WORD BEFORE .The word before (word) (word) is. E dit 'WRONG Your last transmissior F di-di-DAH-dit was incorrect. The cor- rect version follows. G DAH-DAH-dit H di-di-di-dit I di-dit INTERNATIONAL MORSE CODE di-DAH-DAH-DAH The international Morse code is a telegraphic K DAH-di-DAH alphabet, which is :another way of saying that it L di-DAH-di-dit is a dot and dash communication system. The M DAH-DAH code is pronounced by, saying 4%10and ,,dah," not "dot" and lidash,!' so forget about dots and N DAH-dit dashes and think only in terms of dits and dabs. O DAH-DAH-DAH The group of , dits j and dabs representing each character must be made as one unit, with a P di-DAH-DAH-dit clear break between each dit and dah, and. a Q DAB-DAH-di-DAH much more distinct break between characters. R di-DAH-dit Never try to 'identify a character by counting dits and dabs. Don't let yourself get into this di-di-dit habit., It's ateniPtation at first, butyou won't T DAR be able to -min* fast enough when the code speed U di-di-DAR picks up. .Learn 'sound - patterns instead. To understand. what :this, requirement means, rap di-di-di-DAB out the pattern beginning ,,Shave and a haircut." W di-DAR-DAR You recognize this ditty: from its characteristic rhythin'i,nottecauSe it has a certain number of X DAB-di-di-DAR. beats in it. You niUst learn code.the same way. Y DAH-di-DAH-DAH Each character haS, its Own dittinOtive sound si DAB-DAR-di-dit pattern. 'With' Andy iind drill,.***01: learn to ramp.* each Pattern as -last asyou.. I_ now Number Pronunciation recognise and e haircut." -The accent , always falls on dabs, and you should pronounce 1 di-DAR-DAR-DAH-DAH each rhythmical oenibination with that rule in 2 di-di-DAH-DAR-DAH

4 . 136 . . 141.'t4t. Chapter 8 COM hiUNICATIONS

Number Pronunciation Study and Practice 3 4 di-di -di-di -DAR If you have any troublelearning code, the following method 5 di-di-di-di-dit may be helpful. Go through the three groupings of short,medium, and long 6 DAB - di-di- di-dit pounds with their accompanyingpractice words. 7 %lake up words ofyour own if you wish further DAB - DAB- di- di-dit practice. Speak the 8 practice words in code. DAB -DAH-DAR-di-dit Say "Tee: DAH dit dit;Mine: DAH-DAH di-dit 9 DAB- DAR -DAB- DAR -dit DAH-dit dit." **0 If you can speak wordsrapidly and distinctly DAB-DAM-DAR-DAR-DAR in code, you'll havean easy time of it when you *Zulu is written as Z to avoidconfusion learn to receive code, becausethe spoken code with the number 2. and transmitted code soundsare similar. Practice the figures in evengroups: 11, 22, 33, 44, 55, **Zero is written as 0 to avoidconfusion with the letter O. 66, 77, 88, 99, etc.Learn each letter by overall sound. Never count the ditsand dabs.

Short Sounds Practice Words Long Sounds Practice Words E dit TEE, ATE, EAT, TEA, MEAT, MEET T DAH MINE, TIME, MAINE,. B BAT, BALL, BEAT, TEAM GLIB, GAB, JAB A di-DAR AIM, NITE,. TAME, C DAR -di- DAR -dit CUT, CAM, COAT, TEA, MATE CODE, CALF Idi-dit TAME, NAME, MITE, F di- di- DAB -dit FIVE,FAT, FUSS, MIAMI FEET, EFFECT M DAH -DAH MAMA,.MEAN, MAN, di-di-di-dit ACHE, HUSH, HAVE, MAT, EMIT HOLD, HOT N DAH-dit MINT, MANE, TAN, J di-DAH-DAH-DAH ITEM,. Tan JERK, JIM,JAR, JAM, JAB Medium Sounds L di-DAR-di-dit D DAH-di-dit LIKE, LAG, JELLY, MUST, SAME, MAMA, LOVE, LATE SUIT, AUTO P di- DAB - DAB -dit G DAR - DAR -dit MUSS, OUST, MUSE, PUSH, PAIR, POLE, PART, HAPPY. MUTE, ATOM . K DAH-di-DAR TAUT, MASS, MAST, DAB-DAR-di-DAH QUAY, QUEBEC, SUET, SAM, WIND QUEEN, QUIZ, O DAB-DAR-DAR SEA, TUM, SAW, OAT, QUIT SUE,SAT, WED di -di-di -DAB VIM, VERY, VETCH, R di-DAR-dit SUM, MUD, IOU;USE, VAT, EVE SEAM, DARK X DAH-di-di-DAR Sdi-di-dit GEORGE, :DOWN, WAX, XRAY, LYNX, SIX, EXAM . KIND,. , SORT, MASK U di-di-DAH y/ORK, GROW, URGE, .2 DAB -di4DAR -DAH YOUNG, YOKE, YAK, TUG, PULL JERKY, YAM W di-DAR-DAH WIGS, WORN, WET, Z DAli-DAB-di-dit WAKE, WALL. ZERO, BUZZ, FIZ- ZLE, QUILL, LYNX

187 INTRODUCTION TO SONAR

The only way to learn code is by practicecon-produced by keying an oscillator resembles UMW practice. (Practice makes perfect.) The thesound ofcode from the sonar trans- value of practice cannot be overemphasized,as you mitter. will learn when you test yourself, with the help After you learn the sound of each character of your shipmates, to find out how muchyou have at a slow rate of speed, it is not difficult to learned through practicing by yourself. reduce the time between characters and thus to If you have carried out the recommendationscopy at a much faster speed. But don't strive made up to this point, you are ready to receivefor speed before accuracy. Be a competent code transmitted to you on a hand key. The shipoperator. Make every transmission and recep- or station to which you are attached has practicetion accurately. Accuracy is much easier ifyou hand keys you can use. learn the fundamentals well. Some code practice Find a Radioman who will key codegroups exercises that will help you are included for to you to help you ni your training. The soundyour convenience.

CODE PRACTICE

1. EEE TTT AAA NNN I I ISSSHHH RRR MMM 000 EEE TTT AAA NNNI I I HUH MMM RRR 000 EEETTT I I I TTT EEE TTT III NNN 13E18000 AAA NNN EEE AAA NNN TTT 000III SSS 2. UUU. VVV DDD BBB KKK CCCWWWJ J J PPP UUU VVV DDD BBB KKKCCCWWW JJJ PPP VVV UUU BBB CCCKKKWWW DDD KKK BBB CCC WWW UUUVVVJ J J CCC WWW KKK PPP DDD VVVd J JUUU 3. RRR LLL FFF GGG Z Z Z XXXYYYQQQ RRR LLL FFF GGG QQQ ZZZYYYRRR QQQ GGG ZZZ LLL YYY RRRFFFLLL YYY QQQ RRR XXX ZZZ YYYLLLGGG LLL QQQ YYY UUU ZZZ XXXRRRLLL 4.1 1 1 2 2 2 3 3 34445 5 5 6 8 8 77 7 88 8 9 9 9 000 1 1 12223 3 34445 5 58 8 6 7 7 7 8 8 8 9 9 90001 2 3458 7 8 9Apo 1133 4 42 2 55776 8 88009 9 22 2 0 1 2 34 5 6 7 8 9 0 1 23 4 5 6 7 8 9 0 55 9 9 5. VUI YQZCXGRSLKJ PQXZRI FC VB WF K D.S HQZALKFBV RS T UO T M E G Y ZX V EGNIWSLHMUA EVUAE WQG HV I 3 Z LNRYUK VUWS XEDCRFVTGB ilIN UJMI.KOLPQ.AZWSXED C RF VT

138 Chapter 8 COMMUNICATIONS

CODE PRACTICE-- Continued 6. E8 Y 7 B6 X1 WO Z2A3 C5 34 I2 FU 1 F 5 D 8 Q 4 T 6U9Q 2 EO S 5 U 1 YG E 5 T 7 Z8 KE 3 J 4 S 3 M9 R1A2 RE 7 W 8 E9 R 2 A 3Z3 X6U8B7C6TE 8 Y7 B6 YnFl W4 Fl A 7 I 5 R8SO M6C 2 K 3 A 9 Z 3Z 6 D 2 7. WI. AN TY SXEC LV OD OZ SP TZ EC NU VA EHLM DQ BM ZS CD QA W SD PQ OWIE UR YT LA KS JDHF GM ZN )(B CV QZ WX EC W(j TBYN UM IL OP AESR DT FY HU JI .K0 LP ZS XD CFI, VGBEI NJ MK SW XE CRVT BY NU MI LO PS DOFI GY BUIN JU HA XR TV 8. DE FT BY 72 VA TV YB NU 54 98 IMHT BT 1134 66 CV VF TG 62 84 QA WS RF 64 2$ BY77 GY AA YF UHLT VD BK KK 99 2556 83 25 LA KSJD CY BU IN EB QVQV ZZ 22 $$ TT 75 44 VY 53 VSCW MC WH 86 FS SSER EE 26 CG PL IA LE FGQY 85RI 39 NF JE SI25 37 AR 9. WNT AGR DTS ELY BFC UZXREH KCE HIJ AQERNG TCV EPL ZSW QAH SRL GET VRTGUK GYO DCM XSD ZAUYER DLN ARG VNB EDX EWS UTARHI KTZ HEY ALKRDC TOC ESX RIP PKJ NYH GHT DFRVED SWN VET XFZRDA FUO NYH OLX RWH MKY ATANWSRGU SKZ KDG OKL OIX 10. OLVHM GLM YELURXOHIZ OVICT FINXC X.SHTY VIZNT UBLMQABLEEJNCYZ BZWCN JNCDUTLZKLABDEFZVNUW KFREO LMXMVNHUWQRNVUTKUXFC DEHLy HEDIP AZQWI ZYSKQ IQAW M 11; NWZI1,1 ZXCKADBTGWWNLIP WBUOX ADXFR JIQCA UTHAVNCHRFDEEDC XVIIRW QIMNJ FSTROTNBLUJHKNI 0Q.JUY RGBNS VCXTRJTUBD CGFH 5 VXH7G 2JI9 Y TX 38 6 Ti 4 8PBTOZX

PEOSIONS sent as one character,that is, without the pause between letters. normal Proceduralsignals, called prosigns, . by radidelegraph.operators aroused for the samereasonSENDING that prowordsare .used-by radiotelephonetalkers. bidet prowords have:anequivalentprosign,Whichi) in ,cevottal instancetis Your Ability to sendcode depends mainlyon abbreViation.of the".two 'considerations.. prowOrd.- noticein the accompanying First, you must knowthe net. of *wipe that some correct sound of thecharacter you are attempting of them are oversoored.'to:transmit. Second, Overcooling means that,the, letters; -are; to you must know the correct hemethod for keying.,Practicing the code aloud,

139 ."NV INTRODUCTION TO SONAR

Prosign Proword Meaning Remarks AA ALL AFTER All after Used to identify AB portions of a ALL BEFORE All before transmission WA WORD AFTER Word after when requesting a repetition. WB WORD BEFORE. ...Word before K OYER Go ahead and Every transmission transmit. ends with one or AR OUT End of trans- the other of these mission; no prosigns. reply expected or desired. Xi WAIT I must pause fora few seconds. AS AR .. WAIT OUT I must pause longer than a few seconds. ST BREAK Long break Separates text of message from heading and end- ing.

II Separative Used for all other sign. separations in messages. Write it as a short dash. DE FROM From EEEEEEEEE. .CORRECTION I just made Corrected version an error. is sent immedi- ately.

EEEEEEE . Ail DISREGARD THIS TRANSMISSION

... SAY AGAIN Repeat

R ROGER I have received all of your last transmission. as well as receiving it by Oscillator should givemuch tension. forces the key button up before the you a good. knowledge of code sound. The properdabs are completely formed; spacing between method for keying is your next concern. characters is irregular, and dits are not clearly Probably..,the-iiist key .yoU,11; -.encounter. isdefined. If the spring tension is very weak, the unshielded telegraph key,- 'normally used euicharacters run together and the space between practice oselliators .on shipbOard 'Lind on stationcharacters is too short. . circuits, The .key lutist- be adjUsted properly. The gap.... between the ,contacts,. regulated by before you can transmit clear-cut characters.the ....space -:adjuSting. screw -.at the back of the

MAO rkey, r- With parts - =labeled, is ihOwn Inkey, should. be set. at one-sixteenth. inch. for figure. 8.7,1, ,:v: : ..; 'beginners.::'.This. 'measurement. does not apply A sPieing 'tension licreW;lbehini the key to;'.every key and operator; :it' is a matter of controls .the 'ilineinitiofiupward tension' On the kiY::1)ersonal. ;preference.. SOme operators like a The ` tension desired` varies With...operators,' ToooksedAtey,..others, an Open key. .Closeds! and Chapter 8COMMUNICATIONS

SPACE ADJUSTING BINDING LATERAL Conditions of the water have SCREW POST BLOCK a bearing on TRUNNION SCREW the speed at which you will be ableto transmit. LOCK NUT At times you can transmit rapidlyand your SPRING TENSION signals SCREW will be clearly audible. Other times LOCK NUT you may have to go very slowly, otherwiseyour dits and dabs cannot be distinguishedby the BINDING KEY LEVER receiving operator. POST UNDERWATER COMMUNICATIONS For many. reasonsit is necessary for a ship and a submerged submarine tocommunicate with each other. Of paramount importanceis the TRUNNION safety of the submarine and itscrew. During SCREW exercise periods the shipcan advise the sub- LOCK NUT KEY BUTTON marine when it is safe to surface.Should an LATERAL BLOCK emergency arise aboard the submarine, the ship TENSION SPRING CONTACTS can be so informed. Exercises can be started and stopped, or one in progresscan be modified, 76.8A by using the underwater telephone.Attack accu- Figure 8-1. Hand key. racy can be signaled by the submarine tothe attacking ship. Sonar Techniciansmust be pro- open" are terms fora short and a long gap.ficient in radiotelephoneprocedures because As the student progresses, furthergap adjust-those techniques are used forunderwater voice ment may be made to suit hissending speed.communication. When CW (radiotelegraph)is Contacts that ars too close havean effect similar used, you must be able to send andreceive to weak spring tension. Contactsthat are spacedMorse code without causing delayor misunder- too far have the same effectas too much springstanding. tension. The most widely used underwatertelephone The final adjustment of the keyis .theside-installation is the AN/UQC-1.(andmodifications) wise alignment of the contactpOints. This align- sonar set, commonly called Gertrude. Although ment is controlled by thetrunnion screws at intendedf...r use by sonar controlpersonnel, either side of the key. If theyare too tight, thesome lustallations provide remote voiceopera- key lever binds, If theyare too loose, thetion from the bridge and fromCIC. It operates contacts have sidewise play.Usually, when theas a single sideband suppressed carrier trans- sidewise alignment is correct,no further adjust- ceiver, with a modulated frequency of 8to 11 M. ment is required. It has a microphone for *doetransmission and From the beginning you should a hand key for sending CW signals. Mounted learn theon the front panel of the control unit (fig.8.-2) correct way to grasp the key.The followingare a speaker, microphone, and earphone jacks,' instructions, in the. order listed,constitute the on-off and receiver-transmit switches,a tele- proper prooedure for, becomings . proficientgraph key, and three neon glow operator: Do not hold the key tightly,but let lamps indicating output, plate voltage, and filamentvoltage. . your fingers rest lightly on the key knob.Your When you wish to transmit: by voice, thumb rests against the side,your forefinger set the rests on top of the key; toggle switch to VOICE 65 CW RECEIVE,plug your third finger isin the niicrophone, and depressthe microphone bent and -relaxed with theremaining two fingers.button. For CW transmission,. Speed and. accuracy: of, transmission set the toggle :depend, switch. to a large extent, on acquiring to CW TRANSMIT anduse the hand key. the proper move-(CAUTION: Do not operate in the CW mode ments of your wrist, and handwhile ,operating for the key. To close the -key, longer than 30 minutes ata tinie..Operation for your wrist moveslonger periods causes excessiveheating of the Upward and your hand rocksdownward towardtransducer.) ,yOur fingertips. Toopen the key,. these two movements .The range of transmission varies withwater are reversed your wrist coinei-conditipne, local noise level, and down and your hand rooks back.A dab should reverberation be about three times effects. Under normalsonar conditions, however, as long as a dit. . . communication between shipsshould be possible

141 INTRODUCTION TO SONAR

sent, but indicate pauses the operator makesso that his transmission can be understoodmere easily. LONGSHOT THIS IS' WEASELOVER WEASEL THIS IS LONGSHOT OVER With communication established, WEASEL sends his message: LONGSHOT THIS IS WEASEL BREAK .1 AM READYAT REQUIRED DEPTH SPEEDAND COURSEBREAKOVER LONGSHOT gives a receipt, using an abbreviated call: THIS IS LONGSHOT ROGER OUT 71.71 Following is an example of a related series Figure 8-2. AN/UQC-1 control unit. of messages between ships conductingan ASW exercise. at ranges out to 12,000 yards. Under thesame DOUGHBOYTHIS IS BIG BEN BREAK conditions, submarinei achieve a greaterrange. CEASE ECHO RANGING DURATION MY Ifthe submarines are operating in 'a sound ATTACKBREAKOVER channel (described in chapter 4), the communica- BIG BENTHIS IS DOUGHBOY ROGER tion range may be many miles greater than that BREAK INFORM DOUGHBOY THIS CIR- achieved by shit*. CUIT WHEN ATTACK COMPLETED Local noise, caused by ship's movement OVER through the water, machinery,screws, etc., can DOUGHBOYTHIS IS BIG BEN ROGER reduce the range to less than half the normal OUT range. Severe reverberation effects may also cause a reduction in range, but you canovercomeCorrecting an Error them by speaking slowly, pausing after each word to let the echoes die out. At very shortranges it If you make an error in transmission, send may be impossible to reduce the receiving gain the proword CORRECTION immediately. Go back to a comfortable speaker output level. Then,to the last correctly sent word, repeat it, and you must speak softly, holding the microphonecontinue with the correct version. Example: away from your lips. WEASELTHIS IS LONGSHOT BREAK VOICE PROCEDURE ALL HERECORRECTIONALL CLEAR SURFACEBREAKOVER As mentioned earlier, you will use the same voice procedures for underwater voice communi-Waits cation' as fOi radiotelephone transmissions.In other words, yOu call the -station for whichyou When an operator finds it necessary to delay have a Message, identify yourself, send yourtransmission momentarily, he sends the proword message, and .end the transmission with eitherWAIT. Ifthe delay is for longer than a few OVER or OUT. moments, the transmission is WAIT OUT. Anew call is made when communication is resumed. Calling and Answering Repetitions Here .an example of a ball from -a sub- marine (call 'sign: WEASEL) to an ASW ship (call The request for a repetition is SAY AGAIN, sign LONGSHOT), Dashes shovin are not actually .not ,,Repeat." Used alone, SAY AGAIN means

142 7 Chapter 8 COMMUNICATIONS

"Repeat all of your last transmission." Fol- Underwater telegraphprocedure closely lowed by identification data,it means "Repeatparallels underwater telephone the indicated portion ofyour transmission." procedure. Con- The answer to SAY struction of messages is thesame, and so are AGAIN is I SAY AGAIN, principles of calling, receipting, correcting followed by the repetitionrequested. Example:errors, waiting, and obtaining repetitions. WEASEL asks LONGSHOT torepeat all of his You last transmission, and will notice two importantdifferences, though: LONGSHOT complies.Instead of using voice calls,you will use the THIS IS WEASELSAY AGAINOVER international call signs of the ships.Also, in- stead of prowords, you willuse prosigns. THIS ISLONGSHOT I SAY AGAIN WEASEL THIS IS LONGSHOTBREAKCall Signs CHANGE BASE COURSE TO ZERONINER ZEROMAINTAIN PRESENT DEPTHAND Call signs are letters SPEEDREPORT WHEN READYBREAK or letter-number com- binations. They are used chiefly foridentifica- tion of a communication activity.By international agreement, the United States hasthe use of the first half of the A block(assigned to Army and If WEASEL missed only theword PRESENT, Air Force units) and all of he would frame his requestas follows: the K, N, and W blocks. You are already familiarwith the K and W calls. They are assigned tocommercial radio THISIS WEASELSAY AGAINWORDAFTER MAINTAIN OVER stations. Your concern here is withthe N calls, assigned to the Navy, MarineCorps, and Coast Guard. Naturally, your primary interest When WEASEL has the completemessage, he is with sends a receipt. U.S. Navy ship calls. The Navy assigns a 4-letter callto each of its ships. Should the need arise,you can find the international call ofany Navy ship in ACP 113, ca Sian Book ForShips. Following are a few examples. To cancel a message inprogress, cease sending immediately and transmit the proword Ship Call Sipu DISREGARDTHIS TRANSMISSION.Example: LONGSHOT'S operator beginsa message, then is ordered to delay it. USS Cony (DD 508) NILX 'US$ O'Bannon (DD 450) NUJC USS DuPont (DD 941) NTIR WEASELTHIS ISLONGSHOT TAKE STA- USS Seawolf (SSN 575) TION DISREGARD THIS TRANSMISSION NBWY OUT Call Once a message is receipted for, tit cannot be The call is a transmissiondirected to the canceled by means of theproword DISREGARD station with which you wish to THIS TRANSMISSION. Instead,a new message communicate, must be Berg. requesting that station toanswer. Begin the transmission with the call sign ofthe station you are calling.Next, give the prosign DE(from), UNDERWATER TELEGRAPHPROCEDURES then the call sign ofyour own ship, and finally the prosign K. In the followingexample the USS Cony, a DD (call sign Knowledge of the Morse coae itselfwill not NILX), calls the enable you to send submarine pitfilh (call sign NJRV):Call: NJRV a correct message. You also DE NILX K; reply: NILX DENJRV K. gait now must have a workingknoviledge of simple radio- repeats the call: without the telegraph prOdethire: YOuwon't need to master prosign K and pro- all the .details because ceeds with\theiext Of themessage. sonar communications are After. comziumication is established,further kept to a." bare mininnun,land-Merniageatent arecalling or answering incident to in brief, 'Plain style.' If you:learn the procedure transmission of a message usually. given herei, Yon Will be able to. is handled by abbreviated handle any under- calls. The abbreviated call omitsthe call sign water metisage'. you are likelyto encounter.of the ,station called: If 'there.is a possibility

1.4s . .vAA-S> INTRODUCTION TO SONAR of confusion, however, a full call should beletters DE (from) and the four letters of your used. Example; full call: NJRV DE NILX; abbre-ship's call sign, ending with K (over). If the viated call: DE NILX. contact is a submarine, and he decides to answer you, he will transmit his call letters. You then Text can look up his call sign in ACP 113 to obtain his name and coantry. The call is followed by the text, which is Many search sonars can be used to transmit the main part of the message, It is the basicCW signals. This usage puts a power drain on idea or information that the originator (stationthe equipment, however, causing it to heat up. with information to send) desires to communicateBuilt-in overloads are provided to reduce power to the addressee (station receiving the message). output before damage occurs to the equipment, The text may be sent in plain language or it may resulting in reduction of range with the lesser be sent coded, Inaddition to regular codedpower output, Thus, under normal conditions, signals, Sonar Technicians use a special 3-letter CW transmission is not recommended for search code with meanings that cover most of the in- sonars. formation sent or exchanged in underwater com- munications. This code is contained in FXP 1. The 3-letter code sometimes is referred to SUBMARINE COMMUNICATION METHODS as the "short signals," Use of short signals shortens the time required to exchange informa- The AN/UQC underwater telephone is the tion. Even so, you will handle many underwatersubmerged submarine's primary means of com- messages with plain language texts. municating with surface ships. For this reason, The heading and text of a message areduring exercise periods ships are required to man separated by "ET, Likewise, the text and ending the UQC continuously. In addition to its required are also separated byTT. use for safety purposes, the UQC isused through- out qen exercise by ships and submarines for Ending sending attack signals, obtaining range checks, transmitting sonar short signals, and for several The ending marks the conclusion of the other purposes. Subject to equipment limitations, message. In underwater sound communications, keyed sonar is the secondary means of underwater the ending consists of the prosign K or Mccommunications. Many submarine sonars do not depending on whether a reply is required. have .CW capability. Emergency communication equipment carried Challenging by a submarine include a radio and a telephone. The radio is battery-powered and floats to the In some situations the use of CW, rather surface upon release through the signal ejector. than voice,is highly desirable. Here is anOnce on the surface it automatically traramits example; Your ship (or submarine) is on a on emergency radiofrequencies. routine patrol. You have a "probable" sonar The emergency telephone, designated AN/ contact, The captain wants to know its nation- BQC-1A, is also battery-powered, and is portable. ality, and orders you to challenge. One methodIt has the same voice frequency characteristics is to use voice transmission: as Gertrude, with a range of, about 5000 yards. The usual installation provides one set in both UNKNOWN STATIONTHIS IS (your ship's the forward and after torpedo rooms. In addition international call sign)IDENTIFY YOUR- to its voice transmission capability, the AN/ SELF --OVER . BQC-/A can emit a 24,26 kHz continuous tone for homing purposes. Submarine rescue vessels You. couldalso tellthe unknown station its have equipment capable of detecting and homing bearing and range from. you.,. He may not have on the tone, With all batteries in good condition, an underwater telephone installation, however. 72 hours of continuous tone transmission is Even though equipped with telephone, if hepossible. Range of the homing signal is 2000 to is from a..foreign nation he may not understand 5000 yards,, you. By using CW, you can transmit an. inter- Colored flaresand smoke signalSafford national interrogation signal. This signal is another means of communication. Black or green (two di-dabs sent. as. a single group: di- signals are used. by the submarine to indicate dah-di-dah). The challenge is followed by .thethe simulated firing of torpedoes and to mark Alt

Chapter 8 COMMUNICATIONS her position. A yellow flare or smoke signifiesassistance. You must makeevery effort to the submarine intends tosurface. Ships mustmaintain sonar contact and establish then clear the area and keepother shippingtions by any means possible, communica- away. A designated ship notifies thesubmarine but preferably that the signal was sighted, and by voice. informs him Detailed pyrotechnic,sonar, and explosive when it is safe to surface.A red flare denotes signal information is contained trouble. It means thesubmarine is carrying in FXP 1. All out emergency surfacing Sonar Technicians must becomefamiliar with procedures. If the flares the signals in thatpublication. The rescue of are repeated, or if the submarine failsto surface a disabled submarine's crew could within a reasonable lengthof time, it can be depend on assumed he is disabled and your ability to establish and maintainreliable requires immediatecommunications.

145 r

CHAPTER 9 MAINTENANCE

Any piece of machinery or precision equip- program known as the StandardNavy Maintenance ment requires some type of care to keep itand Material Management System, more famil- running efficiently. Proper upkeep of an auto-iarly called the 3-M System, which will be mobile, for example, includes changing the oildiscussed later in the chapter, as will the POMSEE at certain mileage intervals. The windshieldprogram. must be kept clean; headlights and brakes must be adjusted every once in a while; andan OPERATIONAL MAINTENANCE occasional engine tuneup must be obtained. Sonar equipment also requires periodic upkeep, but in Operational maintenance is the elementary more detail and at more regular intervals thanupkeep performed by the operator to keep his does an automobile. Aboard your ship or sub-equipment in good operating condition. It consists marine you will assist in carrying out scheduledmainly of proper operation of the equipment, maintenance on the equipment to which youare such as starting, stopping, calibrating, andmanip- assigned. ulating controls in the prescribed manner. At Various publications are available to assisttimes, operational maintenance may also include you in carrying out a maintenance program.inspection, cleaning, and lubrication of equipment, The manufacturer's technical manual for eachand replacement of minor parts, such as indicator piece of equipment is an invaluable aid. These lamps. books describe the components of the equipment, operating standards, and required maintenance. PREVENTIVE MAINTENANCE Other publications include the Naval Ships Tech- nigg Manual and Electronic Information Bulletins Preventive maintenance is work done that is (Ems). intended to forestall equipment failure. Com- prising this category are inspection, cleaning, testing, and lubrication. It also includes minor TYPES OF MAINTENANCE adjustments and replacement of minor deterio- rated parts (if no high degree of technical skill Maintenance is divided into three categories,or internal alignment is required) which, if left according to their complexity and purpose. Theuncorrected, might lead to equipment malfunction three typesof maintenance are operational,or part failure. preventive, and corrective. At first glance it may seem that preventiveInspecting and operational maintenance are synonymous, but there is a good deal of difference between All electronic equipment should be inspected the two. Operational maintenance is confineddaily for such defects as broken meter glasses, to acts that can be performed by an operator loose control knobs, burned-out indicator lights, while he is on watch, and usually is furtherloose cable connections, and the many small items confined to one component, such as thesonarthat may be checked with or without the equip- console. Preventive maintenance is a systematic'ment actually being energized. On units that progrant .coverinrithe. entire sonar system, andutilize ventilation for cooling, the intake and requires several Men-to carr,eut. outlet areas should be inspected to see that they The Navy's operational, and preientiVe main- are free of obstructions. tenance program 'fortnerly was called POMSEE. Many items can be inspeated daily, weekly, Ships and .stations today,hditiever, utilize aand monthly to help maintain the equipment in

146 /1=111. Chapter 9MAINTENANCE

serviceable condition, but theyare too numerous to mention in detailhere. In some instances CORRECTIVE MAINTENANCE these routine checksinclude electrical measure- ments to check individualunits for malfunctioning Corrective maintenance isanother name for circuitry. Technical manuals repair, and is necessaryonly after equipment furnished by thefailure. Corrective maintenanceusually calls manufacturer include lists ofchecks to be con-for replacement of internal ducted at regular intervalsand the desired petits or alignment reading or measurement of electronic componentsrequiring technically required for peak per-trained personnel. Some of formance of the specificequipment. this work is per- formed by operatingpersonnel while assisting 7 Cleaning the technician. Asyou advance in rate you will perform more highly technicalmaintenance on your own. Cleaning is an importantpart of preventive maintenance.External surfaces of electronic units and the surroundingspaces should be cleaned daily. This dailyroutine reduces the MAINTENANCE AND MATERIAL amount of dirt and dust thatenters the equip- MANAGEMENT SYSTEM ment through circulating air blower intakes. Reliability of electronic Some dust and dirtnaturally will work their equipment depends on way in, hence the interiors of thequality of the preventiveand operational units should bemaintenance received by the cleaned carefully at leastonce a week with a equipment. As equip- soft cloth. If possible, ment becomes more complex,the maintenance a vacuum cleaner shouldprobleni becomes evergreater. be used. Avoid using blowers,bellows, or cleaning In the past, many solvents, because theytend to push or wash programs evolved that often dirt into inaccessible were uncoordinated and sometimesunworkable. corners. If it becomesThe lack of well-trained necessary to use a cleaning solvent,use only technicians, together methyl chloroform. See with the large numberof reports required by NavShips,Technicalsome programs, seriously hampered Manualarticle 67.306 for safetyprecautions. the main- Air filters shouldbe cleaned at least tenance effort. Overloadedbureaus, moreover, once acould not properly correlatethe mass of informa- week. Climate andoperating conditionsmaytion in the reports. require cleaning more often.Overheating due to clogged air filters often is To alleviate these conditions,the Standard a prime cause ofNavy Maintenance and equipment failure. Neglectin cleaning filters is, Material Management (3-M) therefore, inexcusable. System was implemented.The 3-M systemre- places all other maintenanceprograms. It pre- Generators must be givena careful cleanli-scribes standard maintenance ness check while the equipmentis Inoperative. procedures and Brushes and commutators provides a feedback reportsystem that enables should be cleanedthe program to be updated, frequently. Be careful notto bloworbrushcarbon and corrects errors dust and other foreign and deficiencies. matter into the windings Procedures for managing and or bearings. When cleaninggenerators, ensure reporting the that the brushes slide freely maintenance program arecontained in Main- in their holder andtenance and Material Management exert proper pressureon the slipring or com- (Eiji Manual, mutator surface. Basic elements of the 3-Msystem are the Lubrication Planned MaintenanceSubsystem (PMS) and the Maintenance Data CollectionSubsystem (MDCS). The PMS provides Electronicgear has many partssuchas a uniform system of planned preventive maintenance. TheMDCS provides a motors, hoists, gears, andspringsthat requiremeans of collecting necessary regular lubrication. Themanufacturer's technical maintenance and supply datain a form suitable formachine manual should be followedto ascertain where,processing. A man-hour how often, and how muchlubrication is needed. accounting system also Use caution when lubricating is used aboard repairships and tenders in the parts of anyconjunction with the MDCS. Asa third class piece of equipment, andfollow the instructionpetty officer, you will be in the book: pertaining tothe individual type of concerned with the equipment, Too muchlubrication can be justPlanned Maintenance SubSystemand certain por- as harmful-as too little. tions of the MaintenanceData Collection Sub- system, The degree ofequipment readiness, 147 ti

INTRODUCTION TO SONAR effectiveness,and reliability depends on how The frequency code is: Ddaily, W weekly, well you perform therequired maintenance.Mmonthly, Qquarterly, Ssemiannually, A annually, Coverhaul cycle, and R situation PLANNED MAINTENANCE SUBSYSTEM requirement. Frequency codes for daily, weekly, monthly,quarterly,semiannual,andannual Preventive maintenance, when properly car-planned maintenance actions are self-explanatory. ried out, reduces casualties and associated costsCode C designates certain planned maintenance and equipment downtime required for majorre-actions performed in a specified quarter (i.e. pairs. The PMS is designed to simplify main- once) during the operational cycle between ship- tenance procedures (insofar as possible)byyard overhauls. Code R identifies planned main- defining the maintenance required, schedulingtenance actions that are to be performed before its performance, describing the tools and methodsgetting underway, after a specified number of to be used, and providing for the detection andhours of operation, or to meet other require- prevention of impending casualties. ments that arise only during specific situations. In establishing minimum equipment mainte- Figure 9-1 shows a maintenance indexpage nance requirements, theNav Ships Technicalfrom a typical PMS manual. Information entered Manual, manufacturers' technical maiii saw on the MIP includes the system or component, applicable publications are reviewed criti-a short description of each maintenance require- cally. If planned maintenance requirementsarement, maintenance frequency code plus a consecu- found to be unrealistic ,Jr unclear, theyaretive number starting with numeral 1 for each modified or completely revised before incorpora-frequency code assigned, rate(s) recommended tion into the PMS. to perform the maintenance, average timere- It is possible that the planned maintenancequired to perform the maintenance, and related specified in the PMS may differ from thatmaintenance requirements. Related maintenance prescribed in other documents. Shouldsomerepresents additional planned maintenance that variance become apparent, remember that, inso-can be completed before, in conjunction with, far as preventive maintenance is concerned, theor immediately after a scheduled maintenance. PMS supersedes and takes precedenceover Shipboard application of the PMS varies slight- existing requirements set forth in various tech-ly from one ship to another. Clarification isre- nical publications. quired, therefore, of information found on MIPs regarding rates recommended to perform main- Planned Maintenance Subsystem Manual tenance and the average time required for the task. Actually, maintenance tasks are performed A master Planned Maintenance Subsystemby personnel available and capable, regardless Manual (OpNav 43P1) is tailored to each ship.of the rate listed on the MIP. As listedon the It contains minimum planned maintenancere-MIP, average time required does not consider quirements for each maintainable componenttime required to assemble necessary tools and installed in that particular ship. Normally,appro-materials, to obtain permission to secure equip- priate sections (engineering, electronics,weap-ment, nor to clean the area and put away tools ons, etc.) of the master manual are kept in theupon conclusion of a task. Always remember that office of the department concerned. Respectiveno maintenance is complete until all tools and sections are used by department heads in planningequipment are put away aad the area is cleaned. and schedulingall maintenance requirements in their departments. Scheduling Planned Maintenance The departmental PMS manual containsa section for each division or maintenancegroup For each division or maintenance group,a within a department. Each divisional sectioncycle schedule that provides a visual displayof includes a table of contents and a maintenanceplanned maintenance requirements (based on the index page (MIP) for each system, subsystem operational cycle of the ship between shipyard or component. Applicable portions of the PIAoverhauls) is exhibited in the departmental office. manual are kept in the working space for theInformation supplied on a cycle schedule forany equipment to which they pertain:, These portionsparticular division or maintenance group includes serve as a ready reference to.the requiredthe MIP number from the PMS manual, a listing planned maintenance. Each MIP containsa briefof all- equipment within that particular group for description of maintenance r requirements andwhich planned maintenance is ..required, and the the frequency with which theyare to be effected.specific quarter in which the semiannual, annual,

148 Chapter 9 MAINTENANCE

System. Subsystem, tif ComPollent Reiman Publications DATE 1 October 1965 AN /SQS -29B, 29C Sonar Detecting-Ranging Set

Somme Cord Compel N.. IINAtmense Iteueltoment N.R. Res Men ROOM N.. Riled Noun Nointosonce - J201000000ASAESH 14 1. Measure noise level (hull equip- M-13 STG2 3.0 M-11 meat). STGSN 3.0 2. Compute ship and sea noise level.

J201000000ASAESJ 14 1. Calculate AN/SQM-2 voltage attenus- M-14 ST1 1.0 None tion factor. STGSN 1.0 2. Measure and observe transmitter output pulses.

J201000000ASARSEQ1. Test hull and VDS receiving system Q-1 STG3 0.8 None noise. STGSN 0.8 2. Test hull own doppler nullifier circuit. 3. Test VDS own doppler nullifier cir- cuit.

J201000000ASAESL S1. Clean and inspect sonar set. S-1 5103 9.0 R-1 STGSN 9.0 J201000000ASAESMA1. Calibrate sonar test set. A-1 STG3 0.4 None STGSN 0.4 J201000000ASASSN 1. Lubricate high-voltage motor C gen- C-1R STG3 1.5 None erators after 3000 hours of opera- tion or at 3 year intervals. J201000000ASAESPIt 1.Test operational readiness of R-1 STG3 1.8 None equipment prior to getting underway. - STGSN 1.8 J201000000ASAESQR 1.Replace commutator brushes in high- R-2 STG2 1.5 None voltage motor-generators. STGSN 1.5 These maintenance. cards were prepared for this equipment in which the fol- lowing field changes have beenac- complished: AN/SQS-29, 29A-1 through 9, 11, 12, 15 through 17, 19, and 20. Ofthese, the following field changes affect the maintenance actions: AN/SQS-29, 29A-19 and 20 NON,maintenance requirements cards and maintenance index pages will be made available as future field changes are accomplished that affect the pre- scribed planned maintenance.

, . (Page 2 of 2)

NAINTINANCI iNDlx PAO, OPNAV FORM 4700.3 SURBAUPAGICONTIOLNUMBIN 80-9/2-A5

98.171 Figure 9- 1.- Maintenance indexpage. .1

INTRODUCTION TO SONAR

and overhaul cycle planned maintenanceactionsleading petty officer circles themaintenance are to be performed. A cycle schedule also listsrequirementnumberand reschedules it for 4 quarterly and situation requirement planned main-another day. Current status of scheduledmain- tenance actions that must be scheduled,as welltenance is readily available by looking atthe as monthly planned maintenance requirements.weekly schedule. Cycle schedules are utilized by department heads, in conjunction with their division officers and leading petty officers, toprepare quarterlyMaintenance Requirement Card plannedmaintenanceschedules. A quarterly schedule is displayed in a holder, knownas the A maintenance requirement card(MRC) is a maintenance control board, adjacent to the cycle5 by 8 inch card on which a plannedmaintenance schedule to which it pertains. A quarterly sched-task is defined sufficiently to enableassigned ule gives a visual display of the ship'semploy-personnel to perform the task. (See fig.9-2.) ment schedule and the planned maintenanceto beA master set of MRCs is maintainedin the performed during that particular quarter. Adepartmental office. Cards applicable tothe quarterly schedule has 13 columns,one forequipment in which Sonar Techniciansare in- each week in the quarter, for schedulingmain-terested are maintained in the workspace. If tenance throughout a 3-month period.

At the end of each week, theleading petty a r corraremr N. N. NUNOCP officer of a division or maintenancegroup up- AN/S(28-2911, 29C Sonar Detecting- ASW-U/V SO-9 M-14 dates the quarterly schedule by crossingout Ranging Set (with an X) the preventive maintenanceper- SUOSTST Sr NCI. AT CO IAN. Cults MM formed. If a planned maintenance actionis not None ST1 1.0 Sonar SWAN 1.0 completed during the week it is scheduled,the EIC-J201000 leading petty officer circles the actionon the IS P. OCIICROPTION 1. Calculate AN/SUM-2 voltage attenuation Mn, quarterly schedule. Uncompleted maintenance factor. is 2.0 then rescheduled for another week withinthe 2. Measure and observe t itter output flAII0TOW pulses. same quarter. 1.0 At the close of each quarter, theapplicable A UT IONS 1. Observe standard safety precautions. quarterly schedule is removed fromits holder 2. Shove across all terminals of 19D terminal board to and retained on board as a record of theplanned electrical ground, using a shorting probe. maintenance completed. This recordmay be TOOLS, PARTS, IALS. TIST COY discarded at the beginning of the secondquarter 1. Electronic multimeter (VTVM), ME-6 ( )/U or equivalent 2. Audio oscillator,, TS-382 ( )/Uorequivalent after the next shipyard overhaul. 3. Oscilloscope, AN/USM-105 or equivalent A quarterly schedule also isused by a 4. 1/2" Open and wrench 5. Sound-powered phones (2) 8. Warning tags leading petty officer to arrangea weekly planned 6. Sound Measuring Set, AN /SQM -2 9. 4' Jumper lead maintenance schedule for posting inan appro- 7. Shielded test lead (2) 10. Shorting probe priate workspace. The weekly schedule of M planned it. maintenance should not be considered Voltage attenuation factor for AN/SO4-2 Serial as the a. total of all work for a given week. Thisweekly is . work covers only scheduled plannedmaintenance NOTE 1: Above factor is obtained by performingMR 1 of this MSC.After this factor has beenobtained, N. and is in addition to other routine work,upkeep, subsequent accomplishment of this MRCwill with MR 2. o and corrective maintenance to be accomplished. .... The weekly schedule providesa list of com- illillaillEX 8 ponents in the working area, appropriate a. Turn OFF and tag both equipment POWER switches. page b. Turn OPP and tag both voltage regulatorswitches. number of the PMS manual, andspaces for the c. Turn OPF and trig bullhead power switch. leading PO to use in assigning planned t main- 1. Calculate AN /EOM -2 Voltase Attenuation Factor. tenance tasks to specified personnel. Dailyand a. Removecoveron terminal side of hull relay and weekly planned maintenance actions Junction box. (Cable stuffing tubes are on right p are pre- when facing terminal side.) printed on the forms, and the other maintenance (Cont'd on Page 2) actions are written in by the leading POas re- LOCATION OATS quired. When the leading Pd to assured that 1 October 1965Z a MONT MASCO It OMR II maintenance task is completed, hecrosses out 0/NAV /ONO 11/061 MM. "NI the maintenance requirement numberon the weekly schedule. If for some reasona task 98.176 cannot be completed on the day scheduled, the Figure 9-2. Maintenance requirementcard. 180 f 1,16 Chapter 9 MAINTENANCE

a card in the workspace becomes lostor muti- lated, a new card may bemade from the master INSTRUCTIONS ON BACK OF GREEN PAGE set and can be used until Inom.,et39E a feedback report is sum sr, sent in and a new card obtained. TO1 NAVY MAINTINANCI MANAITIMINT NM MCI DATE l0.'sly 1967 A maintenance requirementcard is one of San :leger!tl,fora,.r.TY.!A the principal components of the PMS with which IAA. Coltul Pao Sonar Technicians are concerned.Suppose that on a Monday morning an individual looks SUBJECT: PLANNED MAINTENANCE SYSTEM FEEDBACK REPORT at the svrOginu.ications tut cr7RMS,2C weekly schedule and finds thathe is assigned Control i. onar Li staring C et the maintenance action identifiedas M-14. The 5UIS4VITRM M. R. NURSER r - f' -2 weekly schedule indicates thatthis particular sonaroysters TCf>A T: .,(73Ci maintenanoe action is listedon page SO-9 of DISCREPANCY, the PMS manual. The MRCthat describes the TA O. Diecription task assigned is identified by ETiniPmonl Cilhilli ITToraPilkol the number com- Wel Precoulions Winkel bination SO-9, M-14 in theupper right corner. ittinlaro nINIP) Publkolions In preparation for performingthe assigned task, Took Etc. Technicai Milcellareevs MRC number SO-9, M-14 isselected from the rquirl am'arrhog EiProcedure set of cards in the workspace. An MRC identi- lecommend proceduree. be changed to read:riling fies each component;gives the rate and time a noncor.ducting nozzle,vacuun equipment to pick required to perform themaintenance; gives up loose dust andirt. a brief description of maintenancerequired; cites safety precautions to beobserved; and lists tools, parts, and materialsneededto accom- plish the task. This informationis given to enable personnel to becompletely ready to perform all prescribedmaintenance before actually working on equipmentauthorized. The procedure described on, the MRCis standardized, and is the best known method ofperforming that particular task. Forpurposes of time conserva- tion, any related maintenancerequirement in- cluded on the MRC should bedone at the same time or in conjunction withthe assigned task. 11110NATU a The 16-digit numberon the lower right side MS COPY TORS ORWW 46) of the MRC is the bureaucard control number. ADDRESSES This number alsoappears on the MIP. Each 1 MRC has a bureau card number, which must 40.101 be referred to in anycorrespondenoe concerning the card. Figure 9-3.PMS feedback report. In some ships, twoor more divisions may have identical equipment.When duplication Fleet ships use the Norfolk occurs, each divisionretains separate (but identi- address; Pacific cal) MRC cards for the Fleet ships send reports to the SanDiego address. equipment. When submitting a feedbackreport, be sure Feedback Report it is filled out completely andlegibly. If the purpose of submitting a feedback report isto correct a discrepancy, for example, A PMS feedback report,OpNav form 4700-7 on a main- (fig. tenance requirement card, besure the discrepancy 9-3) is designed for reportingany dis-is clearly identified, and that the crepancies or suggested improvementsin the recommended PMS as installed aboard change is correct and readilyunderstood. In- ship. This report isstructions. for preparing the reportare listed to be filled out by theman who discovers aon the baok of the form. -discrepancy Or suggests animProveinent., It is signed by a designee of thecommanding Officer, MAINTENANCE DATA COLLECTION and is mailed via the typecommander, to anSUBSYSTEM appropriate field office listedon the reverse side of the originatar'i copy of the The Maintenance Data, CollectionSubsystem form.Atlintia isintended to providea means of recording

161 INTRODUCTION TO SONAR

maintenance actions in substantial detailso thatimmediately after it is overhauled. a variety of information may be collected A minimum con-value is set by the cognizantcommand for certain cerning maintenance actions andperformanceperformance characteristics that must of equipment. In addition to the foregoinginforma- be obtained tion, MDCS furnishes data before the equipment is consideredsatisfactory. on initial discovery of a Maintenance Standards Books providemethods malfunction, how equipment malfunctioned,how many man-hours were expended for measuring the performanceof a specific on its repair,equipment. These books havespace for recording equipment involved, repair parts andmaterialsthe measurements, and givea preventive main- used, delays incurred,reasons for delay, andtenance schedule for the equipment. the technical specialty or workcenter that per- The Main-.; formed the maintenance. tenance Standards Books do nottell how to locate trouble in the equipment. Theapplicable In recording maintenance actions,codes musttechnical manuals must be consulted be used in order to convertinformation to a for methods ?, language that can be read by and practices of troubleshooting.Maintenance automatic dataStandards Books are in twoparts:Part I processing machines. Codesare listed in theReference Standards Tests, and Part equipment identification code (EIC)manual. Third IIPre- class petty, officers are required to prepareventive Maintenance Checkoff. numerous maintenance forms, using appropriate Part I contains itemizedstep-by-step pro- EICs. These forms are sent toa data processingceduresfor making tests, enabling theperson center where coded information ispunched onto making the test to record significantoperating cards, which then are machine-processedtovalues taken while the equipment isoperating at produce various reports foruse in maintenance peak efficiency. Upper and lowerlimits or and material management. tolerances are given so thatan indication is I Reports coming from theautomatic dataimmediately apparent if performancefalls below processing machines are accurateand usefulthe prescribed limits. Illustrationsare included only if information is enteredclearly and cor-to show test point locations. rectly on maintenance forms. Allcodes supplied on the, forms must therefore be accurate Part II contains maintenance stepsthat must andbe performed at regular intervals.These steps clearly written. include tests on circuits and The MDCS requires that coded components, and entries bethey specify what and when otherroutine main- made on OpNav forms 4700-2B(shipboard main-tenance (such as lubrication) should be tenance action), OpNav form 4700-2C(work re- mom- quest), and OpNav form 4700-2D plished. Part II enables the operatingpersonnel (deferred action).to perform checks and preventivemaintenance Detailed desoriptions of entries forthese formsin a systematic manner. In general, appear in the EIC manual and in chapter3 of the steps the I-M Manual, OpNsiv 43P2. outlined in part II are thesame as those used in part I to establish the. valuesrepresenting equipment operation at peak efficiency. Allchecks should be performed by the operatingpersonnel POMSEE PROGRAM insofar as possible. Although the 3-M system A distinction between performancestandards has been imple-and reference standards should bepointed out mented in all MOO type commands,some shipsat this time. do not yet have the system in operation, or only Performance stanelards set forth in the part of the system. Aboardships that do not per- have any part of the 8 -M system in formance standards sheets muste.be...met .when operation, the equipment is installed. When it is establishedthat old POMSEE program 'still must becarried (AM The short title POMSEE 16- &tined the equipment meets the performantiestandards, from thereference standards are taken bya qualified underlined letters of the terns'Iberformatioe, Deraticitt; and Maintenance Standards person and are entered in ink inthe reference 'for. EleO- etandard odium in .part I of theMaintenance trafficEquipment.This tide is.. an accurateStandards Book. self-description of the dOistente of POMSEE publications. The POWEE;.pAblioationn Upon completing each preventive maintenance includecheck prescribed, results should be enteredin the Performance Standards Sheets andMaintenancetime schedule table accompanyingeach chart. Standards Books for elecitrOuloequipment. . Performance Entries in these tables are of primeimportance, sheath are filled out .because they indicate by tiohnioline wheis equipteetit whether the equipment is is inatalled andPerforming at maximum efficiency.Comparison 152 Chapter 9MAINTENANCE of a given reading with readingsobtained pre- progressively in the same directionevery time viously, and with the initial referencestandardthe check is made, it is an indication that the test indications (part I), will revealany signifi-equipment is not in top condition, that a failure cant change. It is expected that from timeto may be about to occur, and that corrective time readings will showsome changes. Minor measures should be taken. At such times the variations do not necessarilymean that thetechnician should refer to appropriatemanu- equipment is not operating properly. If, however, facturers'instruction books for service and a particular step shows a reading that variesrepair procedures.

163 CHAPTER 10

SAFETY; TESTEQUIPMENT; TESTMETHODS

Sonar Technicians mustassist in the upkeep and repair of thesonar equipment aboard theirGENERAL SAFETY PRECAUTIONS ship or station. Consequently,you must become familiar with the types oftest equipment, test Whenever possible, deenergize themain power methods, and safetyprecautions to be observedinput to any equipment beforeyou work on it. when using or workingon electronic equipment. Remember, though, that there stillmay be power Naturally, a knowledge ofelectronics is requiredin the equipment from suchexternal sources as also. Information relatedto the electronics fieldsynchros, remote indicatorcircuits, and stable can be found in Introduction elements. When youopen the switch in the main to cElec Jtronics supply line (or any other NavPers 10084; Basic Electronics,NayPes-1011117 power switch), indicate and Basic Electricity.NavPers 10086, Informa- the switch is open by attachingto it a tag reading; tion on the selection,care, and use of hand and"This circuit was orderedopen for repairs and portable power tools iscontained in Basic Hand- shall not be closed except by directorder of (your tools, NavPers 10085. name, or name of person in charge ofrepairs)." If you musi workon an energized circuit, observe the following safetyprecautions. SAFETY 1. Never work alone.Have another man, Maintaining electrical and electronicequipmentqualified in first aid for electricshock, present is a dangerous business.Every year, lives areatll times. He should alsobe instructed in how lost aboard ship due to electricshock. Severalto secure the power. oases of fatal shook have beenrecorded from 2. Use insulating rubbermatting. The matt- using such equipmentas portable drills anding must be, kept clean anddry. Wear rubber grinders,. fans, movie projectors,and even coffeegloves, if possible, anduse insulated tools. Re- pots. In most instances, deathwould have beenmove rings and watches. avoided by observing appropriatesafetyprecau- 3. Use only one hand Wheneverpossible. Keep tions. Most men will treat withextreme cautionthe other hand behindyou or in your pocket. a circuit containing several thousandvolts, but 4. Do not indiscriminatelystick your hand into will act With indifference .4 toward the commonan enclosure. houbehold variety. Yet, 116 voltsa-o is the prime 5. Have ample illumination. source of death from electric shook.You must 6. Never short out, tamper with,or bypass an continually be alert whenworkingwith eleotricity,interlock. and you must adhere strictlyto all pertinent safety precautions.. Before working on a deenergizedcomponent, discharge all capacitors in the unit.A capacitor is a device for temporarilystoring .electrical AlthoUgh some safetypractices are given inenergy. Sticcessive small charges this .chapter, you should become are built up the safety astrUctions familiar within the capacitor for later release.Sonar trans- contained in the followingmitting equipments utilize thisfeature by building publications: Naval ,Shins TeOhniOalManual, chap-up electrical energy in the ter 9870; Vandbook ofTest Methods and Practices, equipment's capacitor Nav8hips 0987-.000-0130; bank between each ping.A trigger pulse then and Safety Precautionsreleases the energy ina single high-powered for Shore Activities,aVS0 P-2455. An index of Navy DepartMent dociiinents pulse. Nearly all types ofelectronic equipment containing Safetyuse capacitors ofvarying sizes and types. precautions applicable to theoperating forces is contained in OpNav Notice ,Normally, the larger the capacitor,the higher the 5100. electrical charge it will hold fora greater length 154 Chapter 10SAFETY; TESTEQUIPMENT; TEST METHODS

HANDGRIP foreign matter, suchas dirt, grease, or paint, (INSULATOR) that might interfere with therequired metal-to- metal contact at the groundconnection points. Fuses are another source of potentialdanger to the careless Sonar Technician.The purpose of a fuse is to protect electriccircuits and com- ponents. A fuse blows becausemore current than the fuse can handletries to pass through it. The cause of the current overloadmay be a momen- GROUNDING GROUNDING CABLE CUP tary surge in ship'spower, or it may be a short circuit. Whatever thecause, two precautions must be observed when replacing fuses.First, use a, fuse puller, even if power is 1.1(71) secured. (Although Figure 10-1. Shorting bar. it is desirable to securepower to the affected circuit, it is not alwaysnecessary or practical of time. On many electronic equipments, chargesto do so.) If you were touse a screwdriver, pliers, or your bare fingers, great upwards of 14,000 volts are present.Usually, harm may be such large charges are discharged by mechanicaldone if you contact adjacent livecirouits.Second, means when the equipment is opened. Many'always replace a fuse withone having the same other capacitors, however, must be discharged rating. Substituting a higher rated fusemay cause 4 manually by the man working on the circuit.serious damage to the equipment. Ifthe circuit 4 To drain capacitor charges, the does not burn out, dangerous potentialsmay exist device you willthat normally would not be present,thus endanger- I use is the shorting bar, shown in figure10-1.ing servicing personnel. The shorting bar usually consistsof a copper rod, which has an insulated grip on one end. A heavy Cathode ray tubes (CRT) are used in all braided cable is soldered to the rodnear the grip. sonar On the free end of the cable is equipment. They are of ruggedconstruction, and a battery clip.normally have a long life. They do requirereplace- When using the shorting bar, firstsecure powerment from time to time, however, and to the equipment, clamp the cableclip firmly to a few pre- the frame or other good ground, cautions must be observed in handlingthem. A then dischargeCRT must be handled gently to prevent breaking each capacitor by holding theinsulated handgripit and to avoid displacing its internal and touching the terminals of thecapacitors with elements. the copper rod.Always ground the capacitor atAlways place a CRT face downon cushioning material. If the tube is broken,don't handle the least twice, because the capacitor'scharge mayglass with bare hands because the tube's not be completely drained byone application of inner the shorting bar. surface is coated with a toxic material.Gloves and special face masks are available forwear by Practically all electronic equipmentshave apersonnel handling CRTs. metal grounding strap Connectingthe equipment chassis to the ship's hull. The purpose of theSAFETY WITH POWER TOOLS grounding strap is to Plane theequipment's frame and the hull at the same electrical potential, thus Hazards associated with the use of portable permitting perionnel to touch theequipment with- out danger of receiving electric power tools include electrical shock: an electric shook. Asbruises, cuts, falls, particles in the you know, a difference in potential iswhat causes eyes, explo- current to flow.If a component shoUld developsions, and the like. All 'Sonar Technicians should a short to the chassis, the short-circuited become 'familiar with the 'safety practicescon- pdwertained in Navahios Technical Manual, chapter will bleed off to. ground throughthe :strap.If there is a faulty or open ground 9600, section II. Following aresome of the gen- strap connection,eral safety precautions you should observe when however, a potential. difference isestablished.working with power tools: Should you then come incontactwiththe.equipment, you become the grOund strap. 1n .otherWords, 1. Ensure that the toolsare grounded in the current passes from the equipmentthrough accordance with articles 60-25 through 60- yoit ',to ..ground,' resulting in, an electric shook 27 and 60-29 of the NavShipsTechnical possibly (Chita One. . 'YOU Manual. that all grOUnd tonnetitidtia are tightand free of 2, Avoid, if possible, using splicedcables.

155 . INTRODUCTION TO SONAR

3. Carefully inspect the cord and plug. If the The following care is prescribed when theman is cord is frayed, or the plug appears damaged,breathing. replace them. 1. Lay victim on his back, with his he ad lower 4. If an extension cord is used, connect the than his feet. Loosen the clothing about his cord of the power tool into the extension neck and abdomen so he can breathe freely. cord, then connect the extension cord into Keep him warm, but not hot. SUMMON the power receptacle. When your work is MEDICAL AID. finished, unplug the extension cord from the 2. Keep the man still. Electric shock weakens power receptable, then unplug the cord of the heart, and any muscular activity on his the power tool. part may cause the heart to stop function- 5. Wear safety goggles for protection against ing. particles that might strike your eyes. 3. Normally, no liquids should be given. Never 6. See that the cables do not present a trip- give stimulants nor sedatives. ping hazard. 4. U the necessary materials are available, apply a small amount of vasoline to his ELECTRIC. SHOCK burns, and cover with a sterile dressing to prevent infection. Electric shock is a jarring, shaking sensation. You may feel as though someone hit you with aResuscitation sledgehammer. Although usually associated with high voltage, fatal shocks often are received from If the shock victim is not breathing, immediate 115 volts or less. If your skin resistance (whichefforts must be made to revive him, even though varies) becomes low enough, a current of 100he may appear to be dead. (Victims ofsevere milliamperes (.100 ampere) at 115 volts, sus-electric shock sometimes appear as though rigor tained for only a couple of seconds, is sufficientmortis. has set in.) The effort must be continued to cause death. until medical personnel can take over,or until a competent person declares the victim to be dead. Symptoms and Effects Speed in beginning artificial respiration is of the utmost importance. Figure 10-2 shows thatthe The victim of an electric shook is very palervictim's best chance of survival dependson his skin is cold and clammy. His breathing (ifbeginning resuscitation within 5 minutes. he is breathing) is irregular, shallow, and rapid. He may sweat profusely, and his eye pupils will The mouth-to-mouth method ofartificial be dilated. In some cases he will be unconscious,respiration is preferred. Next inpreference is the and have an extremely weak pulse, or no pulse. In severe cases he will have no heartbeat. Vital organs in the path of the current may be damaged I I I I (usually due to heat) and nerves paralyzed. CURVE SHOWING POSSIBILITY OF SUCCESS PLOT TED AGAINST ELAPSED TIME BEFORE - START OF RESUSCITATION Rescue and Treatment . The first thing to do for a victim of electric shook is to remove him from contact with. the circuit' The best method is to open the switch, if you Can do so withoUt.tob much delay. If an ax is handy and the power cable is toccissible, the eo cable can be cut,:.:asSuMing that it would take, too long to find' the proper switch. If there are no ready means for cutting the power, use any dry 5 10 IS 25 nonconducting material to. pull "the:Man free; a TIME IN MINUTES belt, clothing, a piece of lima wooden stick, or a sound powered phonb aord. Be extremely careful that *4-don't become a 'vicitirkyOUrSelf... 71.101 The treatment. to givea shook victim depends Figure 10-2.Importanoe of speed incommenc- On his OtsditiOn-whetherhe is breathing ornot. ing artificial respiration.

.156 . Chapter 10 SitetF:TY;TEST EQUIPMENT; TEST METHODS

back-pressure, arm-lift method. Detailed 'afar- and plug. A firm connectionto the power recep- matlor, on administeringartificial respirationcan tacle. is all that is needed be femri, in Standard First AidTrainingCo: tree, to ground such equip- NavPers 10081, kvici in Handbook of ment so that it will be safeto the touch. Other Test Methods equipmentperhaps olderor repairad test equip- and Practies section 1.Whichemr method you mentmay not be equipped use, the important ob;eotive 4a tostart immedi- with the three-wire ately. cord. If it is not so equipped,the test equipment should be grounded, witha separate cable running TKIIT 14,UIPMENT from its chassis or housingto the frame. Aiwa:* check to see that theground connectIOn !a firm Electrical equipnamt is designe:1 tooperate and that it is sufficieLtto take any electrical at certain efficiency levels-Technical kvitruc- load supplied to it. lion books and sheets contf.':.ingoptimum per- VOLTMETER form ance data--such as voltagesand resistances --are prepared for each Navy equipment.The Thecltage of a circuit, instructions aria intended to aidthe techniCian or the voltage drop in maintaining the equipment. across part o. a circuit,is measured witha As a Sonar Technician, voltmeter. Various voltageranges :ire obtained you will work with by adding resistors ofdifferovalues ammetere, voltmeters, ohmmeters,and electron watt thecoil of the meter% zeries tube analyzers. You alsoInv have occasion to movement. The we such equipment as wt.,11.noters, voltmeter 8....tir.!ly isa current-measuring instru- power factorme3t, but it :ndicates voltagethrough measure- meters, capacitance-resistance-inductance ment of the current flow bridges, oscilloscopes, signalgeneratox., and through a resistor of other types of test equipment. Imovn value. When usinga voltmeter, the following Busic movements precautions must be observedto prevent damage and construction of measuringdevices are dis-to the meter; cussed in Basic Electricity . 1. Observe proper polarityin connecting the meter to the circuit. GROUNDING TEST EQUIPMENT 2. Always connect themeter across (parallel to)the circuit componentbeing tested. Equipment that measureselectrical values of 3. Use a range (scale) component parts mustnever assume. a ground large enough topre- level different from that of vent full-scale deflectionof the needle. the chassis of the The accuracy of the voltagereadings depends component. One reason ill thatmeasurement ofon the sensitivity of the mete:. an electrical value of a component, byan equip- Sensitivity is the ment having its own ground level meter's internal resistance,measured in ohms value, wouldper volt. A low-sensitivityme'.er will indicate possibly reflect the differencein potential be- erroneous values when used in tween the component and thetest equipment. a higik-resistaroe The other reason is that if circuit due to the loadingeffect of the metal. the ground level ofBecause the meter is connectedir. parallel, the the test equipment differsfrom that of the com-total resistance of the circuit ponent being measured,a condition of electrical 1.:8 reduced and the hazard may result, and amount of current is increase:.The following maintenance personnel examples show how metersensitivity affects may be shocked. For the groundlevels of the test accuracy. equipment and component parts to be the same, Figure 10-3 shows a seriescircuit. The value all electric and electronictest eqUipment must of resistor R1 is 50,000 be grounded. Self-contained test ohms, that of R2, loo.goo equipment, suchohms. Source voltage is 150volts. The circuit as niultimeters, havetwo test probes andone grounding cable. When the has a current of .001 ampere,as determined,by grounding cable is Ohm's lavi, whici, means that50 volts is dropped attached to the componentbeing tested, it isas though the test equipment, tomes RI, and 100 volts is droppedacross R2. were part of the chassis When.yOu puttee a voltmeter of the component.Touching the. teat equipment across R2, will it in one hand and. the chassis read 100 volts? Maybc,Asinnne the meter hasa Of the component in sensitivity rating of 1000 Ohms the other does not, itritilelt,result in electric per volt, and you shook If the grounding cable is tuts the b- 100 -Volt scale. The meterresistance attiobedeourely.id 100,000 ohnia4' Whenyou connect the meter Externally powered eqUipMent,such as a tube across R2, you have two 100,000-ohm tester, is groundedAO the: frime.. of theship resistors through'a standard three-Wire electrical in parallel, 'and the equivatentresietancebecomes cord 50,000 antis. (The total resistsmik. of twOparallel

157 INTRODUCTION TO SONAR

MEGOHMMET ER RI i000.rt./V An ordinary ohmmeter is incapable ofmeasur- 50,000A 75 V ing resistance of millions of ohms,as found in conductor insulation. To test for insulation break- Z.= i50 v 0-100 SCALE down requires a much higher potential thanis i00,000/1. furnished by an ohmmeter. An instrument known as a megohmmeter ( calledmegger ) is used for these tests. The megger supplies 20p00.n./V the required high potential by means ofa handcranked d-c 1 98 V generator. Meggers usually are rated at 500 volts, although higher rated typesare available. To avoid excessive test voltage,the megger is 71.125 equipped with a friction clutch between the hand- Figure 10- 3. Effect ofsensitivity on meter crank and the generator. When the generator accuracy. is cranked fast enough to exceed its ratedvalue, resistors equals their product divided by the clutch slips. As with the ohmmeter,power theirmust be removed from the circuitunder test sum. It ie always less than the value of the small- before connecting the megger. est resistor.) The total circuit resistanceis no longer 150,000 ohms, but 100,000 ohms,and the MULTIMETER total current flow is .0015ampere. By applying Ohm's law you can see that the meter willread The multimeter is a multipurpose meter that 75 volts. (If the meter hada 0-500-volt scale, can measure resistances, a-c and d-c voltages, you would get a reading of about. 90 volts.) and d-c milliamps. Its versatility and portability Now use a more sensitive meter,one rated eliminate the need for carrying several meters for at 20,000 ohms per volt. The internalresistance test purposes. The usual precautions must be of the meter is 100 times 20,000or 2,000,000 observed when making resistance and voltage ohms. The equivalent resistance of R2 is approxi- measurements. When measuring d-c voltage, pro- mately 95,000 ohms, total circuit resistance is per polarity must be observed. The face of the 145,000 ohms, and total current is ,00103ampere. instrument has separate graduated scales to indi- The meter will now indicate about 98 voltsacross cate the three values that can be measured. Be R2. sure you read the proper scale. OHMMETER TUBE TESTER The ohmmeter is used to measure resistance, check circuit continuity, and test for grounds. Electron tubes often are the cause of equip- It has a self-contained voltage source. Because ment failure. They may burn out, or their elements the ohmmeter is a resistance. measuring device, may become shorted or broken owingto vibration. you must deenergize the circuit under test before Even new, unused tubes are subject to damage, so you connect the ohmmeter, otherwise serious you should always test a tube before inserting it damage wIllresult.to the meter, into a circuit. The test instrument you willuse The resistance measuring capabilities of the is the tube tester. Its usual application is to ohniMeter are, controlled by fixed resistors of measure the mutual conductance of a tube, which different valUes connected in series With the is an indication of how well the grid can control Meter's MO/intent On 'sonic) ohinthetere, scale plate current. The tube tester also can measure selection is accomplished with a selector switch; the emission of rectifier tubes, test for shOrts, on others, separate test lead jack Connectors are and tell if a tube has become gassy. used toolkain the deeired scale: 1 To ensure, an accurate reading, the meter must OSCILLOSCOPE be .zeroed to the 'Scale vied. Zeroing is accom- plished by diaiktiiiethe tiat,fericia together and The oscilloscope is one of the most valuable adjusting; 'the; 'variable radiator labeled 4fohmti pieces of test equipment available to the Sonar zero adju00..10,:align. the Pointers With. the ter() Teanician. With the oscilloscope you can deter- Mark. on the dial. WheileVet ,ycik. Change. sissies, mine a signal's frequency, pulse width and amplia the Meter must be zeroed again. tulle, Measure voltages and phase relations, and

158 Chapter 10SAFETY; TESTEQUIPMENT; TEST METHODS

TRY TO LOCATE THE TROUBLE BY OBSERVING THE CIRCUIT'S FAULTY OPERATION

NOWNTAL DOILSOION 111 AW11.1111 TRY TO LOCATE THE TROUBLE BY USING EYES AND NOSE 1

VFAV 'LOCALIZE THE TROUBLE AT THE FAULTY SECTION BY POW TESTING TECHNIQUES TINNUN ii OWIp NOW I WINATOI NUN WUW !LOCALIZE THE TROUBLE AT THE FAULTY IRK BY SCK TESTING TECHNIQUES 'M SY.NCAW I INPUT BITICAL VERTICA1DIPLICTKIN !LOCALIZE THE TROUBLE AT NE FAULTY CIRCUIT OR Lau rag A11.111111 BY TESTING TECHNIQUES

REPLACE OR REPAIR THE DEFECTIVE PART Is .0/ TEST THE IRCUIT'S OPERATION-4 ADJUST CIRCUIT 20.324 Figure 10-4. -Block diagram ofa CRT oscillo- 12.259(71) scope. Figure 10-6. Troubleshootingprocedure. Observe signal waveforms. Thelatter use is par- ticularly helpful, inasmuch asmany technicalcondition.' The means by whichyou will find the manuals include (in their servicing blockdia- faulty component is called troubleshooting,which grams) waveforms at various test points. consists of logical testing methods.Troubleshoot- The oscilloscope (fig. 10-4) consists ofa ing aids you will use are troubleshootingcharts, cathode ray tube, vertical,and horizontal beaniservicing diagrams, and voltage andresistance deflecting, circuits, sawtooth Voltagesweep cir-charts. cuits, and necessary: power 'supplies. Thesignal Troubleshooting charts list various equipment to be observed(asine wave, for instance)ieApplied malfunctions, their probablecause, and the neces- to the vertical deflectioUplitii.,Ifthat were the sary corrective action. Servicing diagramsshow only .signal applied, all youwould see °lithe scope test points, desired waveforms,proper voltages, would be a straight, vertical line.To have the and other related servicing information.Voltage sweep conform to the sine wave voltage.on the and resistance charts show the normalvoltage and vertical deflection plates. a sawtooth(linearly resistance values at the pins of connectorsand tube increasing) ,voltage is applied ;simultaneously to sockets. the horizontal deflection plates. The; resultis that Although much of the equipmentyou are the sweep moves, across the scope' ata uniform required to maintain is quite complex, andyou may rate, following the fluctuations of the signalapplied feel that it is beyondyour capability to keep it to the vertical platOs. When the sawtoothsignal operative, the job usually becomes mucheasier if reaches its cutoff point,,thesweep returns' rapidly it is first broken up into successive,logical steps. to,its starting. point, to Await the- next sawtooth Figure 10-5 shows a generaltroubleshootingpro- signal:: The measurement .:of frequency,calibra-(*dun. Steps 1 through 5 are to be followedin tion, and: other: special situations reqUiresthe use locating the trouble. Steps .6 and 7are carried out of synohroscopei which is an oscilloscopeWith in making repairs. Sometimes steps 2,3,4, and 5 special circuits added, such as sweeptriggers andmay be eliminated, but never steps 6 and 7. marker. generators. The. sWeep,comnyonoesonly when a signal Ir. received. Oscilloscopes andsyn.- OhrosCopes are explained in detail in HendbookOi TERMINAL DESIGNATIONS Twit- Methods and' Practices, and BodoBloc- tranico. When carrying out your troubleshootingpro- cedures, you will find thatmany test points are TEST METHODS located:pion terminal' boar"Wiring diagrams, ; which aid you "in tracing Whenever., a piecej,of sonar equipment breaks a bitoultfromone unit to another, indicate the terminal connectionsof each down, it may be your .jobto. locate the trouble andcircuit in each unit, You must restore understand, there- , the faUltyi circuit to4te,proper. operating fore the system used for markingterminal boards INTRODUCTION TO SONAR and conductors, as set forth in Dictionary of Stand- ard Terminal Designations for Electronic Equip- ment, Nav Ships 900,186, Terminal Boards Terminal boards are marked with a 3- or 4-digit number preceded by the letters TB. The first 1 or 2 digits of the TB number represent the unit number in the equipment. This number is assigned by the manufacturer in a logical order. The last 2 digits represent the terminal board UNITNA I.T11401 number in a unit, starting with 01, 02, 03, etc. TERAINA/ BOARD UNIT 411 SPAGHETTI 0 Thus, terminal board TB 1003 indicates the 3rd LEEVING terminal board in the 10th unit of the equipment. TRIO CONDUCTOR' 0 2A Z2DitUiK37B CABLE Terminal Markings TERAINA/ 0 TERMINAL Markings of terminals on terminal boards 0 indicate a specific function for the following circuits: (1) common primary power circuits, (2) ground terminals, (3) common servo and p 70.6 eynchro circuits, (4) video circuits, (5) trigger Figure 10-6. Conductor and terminal markings. circuits, and (6) audio circuits. The breakdown of these categories into specific functions, with the terminal designation of each, is listed in portion of the illustration, for example, showsa NavShips 900,186. They are called rigidly assign- conductor running from terminal 2A on TB101 ed designations. to terminal 'TB on TB401. The spaghetti sleeveon the conductor attached to TB101 is marked 2A- Terminals whose functions do not fall under the 401-7B, indicating the other end of the conductor categorie5 listed are assigned designations by the is attached to terminal 7B on TB401. The sleeve equipment manufacturer in accordance with Nav at terminal 7B of TB401 is marked 7B-101-2A, Shilx. 900,186. They. are manufacturer-assigned indicating the other end of the conductor is designations. Only terminals that are connected attached to terminal 2A on TB101. If you must together externally haveexactly the same desig- remove a conductor from a terminal, the first nation within any given equipment. set of letters and numbers tells you to which ter- Conductor Marking minal it must be reconnected. On the conductor lead, at the end near the point Cable Marking of connection to IL terminal post, spaghetti gleam- ing is used as a marking material end insulator. When doing maintenance or repair work, you The sleeving is 'engraved with indelible ink, or may have to trace a cable from one section of the branded with identifying numbers and letters bya ship to another, examining the cable for damage varitype/ machine, and slid over the conductor. that might be the cause of equipment breakdown. The order of marking is such that the first Cables are identified by 'metal tags that give in- appearing set of numbers and letters, readingformation on the cable's use. Tags are attached from left to right, is the designation corresponding to the cable as. close as practicable to each ter- to the terminal to which'. that end of the wire is minal connection, on both sides of decks andbulk- ortmected. A dash follows the terminal designa-.heads, and at intervals of about 50 feet. Colored tion, and then the number (without TB) of the ter "tags formerly were used to classify the necessity minal board to which the other end of the conductor of the cable, and you may still see some of them. is attached. There is another dash and the designa- Red indicated a vital circuit, yellow a semivital tion of the particular terininal .towhich the otWr circuit, and gray ,a'nonVital circuit. end. of the wire is connected. The cable designation information is acombi- nation of letters and numbers, consisting ofa Figure 10-6 shoWshow terminal boards, ter- semis:* letter, circuit letters, andoable nUmbers. minds, and conductors. are' 'marked.' The, lower A typical cable designation is R-8K3. The service

1 CA* Chapter 10 SAFETY; TEST EQUIPMENT; TESTMETHODS

letter (R) means the cable supplieselectronic. Table 10-1,Standard Color equipment; the circuit letters (SK) denotescanning Code for Resistors sonar; and number 3 means it is the third cable in the scanning sonar circuit. A completelist of Significant cable designations may be found inchapter 9600 Color of NavShips Technical Manual. figure or Decimal Resistance number ofmultipliertolerance CABLES zeros

Black.... Insulation resistance tests (ground tests) 0 --- Percent * mustBrown.-. 1 be made periodically to determinethe cable's ------condition. Tests also should be made Red 2 ------when theOrange... cable sustains physical damage, whencables have 3 --- -- been disconnectedforcircuit or equipmentYellow... 4 ------changes, after shipyard overhauls, Green... 5 ------and when theBlue... cable has been subjected to oilor saltwater, The . 6 --- .. 500-volt megger is used for makingthe tests.Violet... 7 .1.. ... - -- Gray.... Following, are the recommended testprocedures. 8 --- .. White.... 9 ------1. Disconnect the cable from.the equipment.Gold. .. 0.1 5(J)* Silver... 2. Measure the resistance betweenthe cable ------10(K)* armor and ground. A zero reading should beNo color.. ------20(M)* obtained. 3. Connect all Conductors in thecable together, *Symbol designation alternatefor color. and simultaneously measure theirresis- tance to ground. If the reading isat or above 20.373 the acceptable minimum,.no other readings need be taken. (Usually 10 =gamsindi- carbon resistors are rated at 1/2to 2 watts. cates an acceptable condition, butmini-. Wire-wound resistors usuallyare rated above 2 mums vary according to cable type, length,. watts. and temperature; consult theappropriate Resistance value is indicated by coloredmark- instruction, book for the equipment.)U the ings on the resistor. The standardcolor code reading is below the acceptedminimum, the given in table 10-1 is used to interpretthe resis- conductors must be separated andtested tor markings. With only slight effortyou should be individually to isolate the faultyconductor. able to memorize the color codein a short time. RESISTORS A resistor always has three (sometimesfour) resistance value indicators. Two methodsare used A resistor is. a to color Code fixed resistors. Infigure 10-7, the device used to limitcurrent axial lead type is shown to the left; flow. It is. of either the fixed variable type. the radial lead Resistors. are tested with is shown on the right; Resistancevalue is deter- an ommeter after the mined as follows: color A indicates resister .. is disconnectedfroni. the circuit. This the first sig- nificant figure, color B the secondsignificant action prevents 'damage tothe meter from circuit figure, color C gives the voltage, and ensures that only theresistor being multiplier (number of zeros), and color D is the percentage oftolerance. tested gives a readingon the meter. Before con- If there is no fourth color the ducting the test, set the meterto the proper scale, tolerance is 20 touch the ends of the metertest leads together, percent. Assume that an axial lead anda radial and adjust the meter to obtain lead resistor each has the followingcolor code a zero reading. marking: Ared, B---green, Corange, and D Fixed. Resistors gold. Referring to table 10-1,you find that the first significant figure is 2, thesecond significant figure is 5, and the multiplier is 1000 Fixed resistors may be made ofwire, wound' (three zeros). on a core and Coated with ceramig; The resistance value is 25,000ohms, or 25K as or they -away it sometimes is marked be . on a schematic diagram. made of Carbon. Theyhave either axial or The tolerance is 5 percent. radialleads; and have:a Wattage,rating according to the amount of 'heat- they dissipate. .4%. fixed resistor is tested by placingan ohm- In general.; meter lead on each resistor lead.For the resistor

1R1 14, 1 + INTRODUCTION TO SONAR

RESISTANCE' IPER ELEMENT C A S ado, medial Weds eolor leads

Band A Indicates Arm siplAcem Spurs of resistance value In ohms. Body A

Bond 11. he:Scales sewed mignilicont figure. End B

Bond C Indicales decimal multiplier. Band C or dot

Band D If any Indicates tolerance in percent oboes nominel reilmatice Band D voles. II no color °upsets In this position, tolerance le 20%. Nam loam**. lewlatd vokewead masa Awe deed lads ad an ado, coded team to as Idlbad fade okra woo* Oast tad A is data walk TERMINAL TERMINAL 20.374 Figure 10-7.Color code for axial-leadand TERMINAL 1 radial-lead fixed composition resistors.. WIPER (TERMINAL 2) used in our example, a reading of 24K to 26K would be acceptable. Low-power, wire-wound resistors have axial leads, and are color coded similar to the regular 71.94 axial lead resistor, except that band A is double width. Figure 10-8.Meostat.

Variable Resistors potentiometer customarily refers to any adjusta- ble resistor having three terminals, two of which Variable resistors are of two general types. are connected to the ends of the resistance element They may be rheostats or potentiometers. and the' third to the wiper contact. The potentio- A rheostat normally is used to adjust the cur-meter is illustrated in figure 10-9. By positioning rent in a circuit without opening the circuit. Some the sliding contact, any desired voltage within the rheostats, however, are so constructed that the range of the potentiometer may be selected and circuit may be opened also. In general, a rheostat used where needed. As a rule, potentiometers are has two terminals. One terminal is connected toconstructed to carry. smaller currents than rheo- one end of the resistance element; the other, tostats. the sliding contaot..' As seen in figure 10-8, the Potentiometers are measured in much the resistance element is circular' in shape and is same way as rheostats. When disconnected from made of resistance wire wound around aninsulatm the circuit, they may be tested with an ohmmeter ing form that usually' is of a ceramic material. by measuring-for total resistance between termi- The resistance is decreased by rotating the wiper nals 1 and 2. Applying one lead to terminal 3 and toward terminal 1. the other lead to either terminal 1 or 2 and moving TO test a rheostat, you first must disconnectthe wiper results in a smoothly increasing or it from the circuit. An ohMmeter is used to mest; decrealing variation in resistance. sure the resistanow betIVe-en `.teiniinalii 1 and 2 (refer to fig: 10-8), withithe'viiper rotated all the COILS way to terminal 2. This action gives totalresis- tance: Moving, the wiper ilOwly back toward ter- Coils used in electronic circuitry are of many minal 1 ihoWs an evei=deoreeeing resistancetype's. Among the types are the inductance coil, until a reading of zero; is Obtained. If a reading ofwhich is used to oppose changes in current or fre- maximum shOwi on the'inetei during this phase quency; field and armature coils, as used in motors of rotating the wiper toward terminal 1,. it means and generators; and solenoid coils, which are used the wiper is not 'maldng Witter Contact at thatin electromagnets. Point:: "' ' '- 6. All types of coils have one characteristic in The potentiometer (Often'Oalled a pcitu) isa common: They are made of varying lengths of wire, control instrument used for vitying theeinotmt oftherefore gin. ohmmeter may be used to makea voltage apPlied to an electriaal device.The term continuity teat to determine if there are any opens,. Chapter 10 SAF ET Y;TEST EQUIPMENT; TESTMETHODS

WIPER RESISTANCE ELEMENT 110 V DC SOURCE T 10

TERMINAL 2

TERMINAL 3 TERMINAL 1 TERMINAL 1 71.95 Figure 10-10. Inductancein a-o and d-o circuits. WIPER (TERMINAL 3)

The alternating currentis accompanied byan alternating magnetic field.around the coil, which cuts through the turnsof the coil. Thisaction induces a voltage in thecoil that alwaysopposes the changing current.When the switch is in 33.75(71) tion 1, the lamps burn posi- Figure 10-9.Potentiometer. !)rightly on direct current. In position 2, althoughthe effective value ofthe applied a-c voltage isequal to the d-o value,the or breaks, in thewire. This lamps burn dimly becauseof the opposition devel- continuity checkis the oped across the inductor. simplest test for coils.Other tests for measuring Most of the appliedvol- the currentflowandvoltage (Aube made tage appears across coilL, with little remaining ous kinds of test equiPment, with vartn.for the lamps. An electromageet Direct current andalternating current work is another device thatuses a differently when there isa coil in the circuit: When coil. The electric bell isone of the most common a circuit containinga coil is energized Withdireot instruments employingan electromagnet. A sim- current, the .coil's effect ple electric bell isdiagramed in figure 10-11.Its in the circuit is evidentoperation is explained only at the instant thecircuit is energizedor deen- as follows: ergized. For instance,.ivhenthe.switch in figure 10-10 is pliced'inpositiOn1;the inductance ofcoil L causes a delay in thetime required for thelamps to attain normal brilliance.After they attainnor- Mal:brilliance, the inductancehas no effect on the circuit so long as theSwitch remains closed.When the switch: is: opened,an eleotric spark jumps across the opening switchcontacts. The spark is -caused by the collapsing turns of the inductor. magnetic field cutting the When the inductivecircuit is supplied withal- ternating current, however,the inductor's effect is continuous. Forequally applied voltages,th% current through the circuitis less when 'alter Ling current is appliedthan whendirectourrentis applied and is allowedto reachits steady 71.96 state. Figure 10-11. Electricbell. 103 A

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INTRODUCTION TO SONAR

TRANSFORMERS Transformers ordinarily are tested by check- ing for shorts, measuring resistanceof the indi- vidual windings, and measuring voltageoutputs of each winding. 1. Descriptions of transformers are contained in the technical manual for theequipment wherein the transformer is used. Themanual spedifies the terminals to test for eachwinding and tells what the measurement should read.Small power transformers, of the size usedin electronic equipment, usually are color codedas shown in figure 10-13. In an untapped primary,both leads 71.97 are black. If the primary is tapped,one lead is Figure 10- 12. Magnetic circuitbreaker. common and is colored black, the tap leadis black and yellow, and the other leadis black and red. 1. When the switch is closed, current flows On the transformer secondary, from the negative terminal of the battery, the high-vol- tage winding has two red leads ifuntapped, or two through the contact points, the spring, the red leads and a yellow and red two coils, and back to the positive terminal tap lead if tapped. of the battery. On the rectifier filamentwindings, yellow leads 2. The .cores are magnetiied, and the soft- are used across the entire winding, andthe tap lead is yellow and blue. If thereare other fila- iron armature(magnetized,by induction) is ment windings, they pulled down,: thus, causing the hammer to may be green, brown, or slate. The tapped wire is yellowin combination strike the bell. . with one of the colorsjust named; that is green 3. At the instant the armature is pulled down, and yellow, brown and yellow, the contact is broken, and the eleOtromag- or slate and yellow. net loses its magnetism. The spring pulls the armature up so that contact is reestab- lished, causing the operation to be repeated. The speed with which the hammer is moved NIGN up and down depends on the stiffness of the VOLTAGE spring sad the mass of the movingelement.,

, The magnetomotive forces:Of the twocoils are RECTIFIER in series aiding, therefore the, magnetismof the FILAMENT core is increased over that produced byone coil alone. Safety devices also utilize coils for theiroper- FLAMENT ation. A circuit breaker, likea fuse, protects a 110.1 circuit 'against short circuits and overloading.In the circuit breaker, the windiagigan electromag- net is connectedin series with thelaidcircuit to Nat be protected and. With the. switoh.contactpoints. The principle of Operation,is illustratedin figure . t 10 -12.: Excessive current throUgh themagnet winding causes the switch to be tripped, . .11 FLAMENT and the. NO.3 circuit to both breaker 'and `14d: is openedby 'a SLATE spring. When the circuit faultqleared,:the di- quit is closed again by resetting thecircuit breaker manually. Coils have,many more applications and 20.379(71) canbe, Figure 10-13.Color coding ofsmall power studied more thoroughly in Basic::Electricity: transformer leads.

164. - Chapter 10 SAFETY; TEST EQUIPMENT; TESTMETHODS

The easiest way to checka suspected. mal- functioning transformer is tomeasure its voltage output. This test can be madeby using a volt- meter to measureacross the proper terminals, and comparing the reading obtainedwith the proper voltage, as indicated in thetechnical manual. If only one reading is inerror, it indicates that only that winding is at fault. Ifan windings read in error, the trouble could possibly bethe fault of either high- or low-inputvoltage. Consequently, it always is necessary tomeasure the input voltage as well as the output voltage. If improper voltage ismeasured at any of the 17.1 SO CPS output windings, the next stepis to measure the 117 VOLTS resistance of eaohwinding. For thismeasurement, the connections to the terminals 20.344 must be dis-Figure 10-14.Simplified schematic of connected first. Power to theequipment must be capacity secured in order todisconnect a transforme. checker. Once the leads are freemeasure the resistance across each winding with an ohmmeter set to the leak bias and lowers the platecurrent of V1, proper scale. Check each windingoarefully,includ-reducing the shadow angle. ing any center taps. Next, set theohmmeter to. a high scale and test for shorts In the basin Wheatstone bridge circuitusing between windings d-o voltages and simple resistances;the balance and between windings and ground. is obtained when the If no faults are discoveredin the voltage or voltage drops are equal resistance readings, or in. the across the ratio arms. In the a-c capacity bridge, tests for shorts, it is insufficient tO have equality ofvoltage drops the transformer is assumed to be inproper operat- in the ratio arms. The phase angle ing condition. It thencan be connected back in the between current circuit: and voltage in the two arms oontainingthecapaci- If a replacement is required, tors also must be equal in orderto obtain a use as the balance. When a balance is obtained,the current replacement only the one indicated inthe manu- is equal on both sides of the facturer 's teOhnioal manual. Itis always good bridge circuit. policy to test for The capacitance-inditotanoo-resistancebridge, a short and make a resistance type ZM-11/U, shown in figure check on a new transformer beforebetallingitin 10-15, is widely 'the circuit. used .to measure capacitance,resistance, and inductance values in addition to specialtests, CAPACITORS such as the turns ratio of transformersand capa- citance quality tests. It is a self-containedinstru- ment, except for a source of line Capacitance, inductance, andresistance are power. It has measured for precise accuracy its. own source of 1000 -Hz bridgecurrent with a by alternatingsensitive bridge balance indicator, current bridgei. ,These bridgesare composed of an adjustable capacitors, inductors, and source of direct .current for electrolytic capacitor resistors in a wideand insulation resistance testing, variety of combinations: Thebridges operate on and ameter with. the principle of the Wheatstonebridge, in whichsuitable ranges for leakage currenttests on an unknown resistance is balanced,agaiust electrolytic capacitors. known Many. capacitors have. their value resistances: The Unknown resistanceis oaloulated printed on in terms of the them, butsome,types use a color node systemto resistance after the bridgeindicate .their value. The is balanced. One type ofcapacitance bridge circuit color code used is the appears in simplified ScheMatioform in figuresame as that used for resistors, but the methods 10i-14. When the bridge is of marking the capacitorsvary greatly. The balanoed by adjustingMethod used for fixed mica the two variable resistors,no a-c voltage is de- capacitors is shown in figure 10 -16. . veloped across the'input ofindicator tube. VI, and A blaok dot in the the shadow angle is maximum. (v1is a:!'magio upper left corner signifies that the capacitor.has a mica dielectric. The eye" 'tube; commonly Used as..a radio receiver center. 'dot in the upper tuning indicator.) AO slightimbalance produces, row indicates the first an a-c voltage, which; in turn,.develops eigS141oanti ; figure, andthe upper right dot indi- i grid- cates' the second significant figureof the capitol-

165 /70 INTRODUCTION TO SONAR

zero to the value 25, giving the resultas 2501.4. The red center dot indicates that the T1ST actual capaci- CORO. tor value may be greater or smallerthan the 250 tud by plus or minus 2percent. The left red dot means it is a bypass or silver mica capacitor. Some mina capabitors have only threedots, indica- ting the first and second significantfigures andthe multiplier. Their tolerance is 20 percent,and they have a 500-volt rating. Try readingsome of the ,,ungfrsom values of the mica capacitorsyou see in electronic equipment when they are exposed to view.Learning to read capacitor values is a matter ofpractice, much like reading resistor values.

Powto collo, TUBES 3oT6woo) Electron tubes are essential components of electronic equipment. If the average tube isnot overdriven, nor operated continuously at maxi- mum rating, it can be expected to have a life of at least 2000 hour6 before the filamentopens. Tubes do fail,, however, before achieving their full life expectancy. Some of the more importantcondi- tions affecting the life expectancy ofan electron tube are (1) the circuit function for which the tube is used; (2) deterioration of the cathode (emitter) coating; (3) decrease, with age, in emission of impregnated emitters in filainent4ype tubes; (4) STRAP defective seals, which permit air to leak into the RINGS envelope and oxidize the emitting surface; and (5) CARRYING internal short circuits andopen circuits causedby .HANOI' vibration or excessive voltage.Because of the attendant expansion and contractionof the tube elements during the process ofheating and cool- ing, the electrodes may lean 20.345 or sag, causing exces- Figure 10-15. Capacitance - inductance- resist-sive noises (microphonios) todevelop. Other ance bridge, type ZM-11/U, electron tube defectsare cathode-to-heater leak- age and nonuniform electron emission ofthe oathode. The defects, of whichonly the most tance value in micromicrofarads (AO). The right common are listed here, contribute to abort dot in the lower row indicates the decimal 50 multi- percent of all equipment failures.For this reason plier that determines the number ofzeros to beit is good praotice, when added to the right of the two significant figures. you are troubleshooting the equipment, to eliminateimmediately any tube The center dot (lower row) specifies the tnlerance,that may have contributed tothe equipment's which is the possible deviation of the actual capaci- failure, but avoid blind replacement tor value from that given byitri dot markings. of good tubes The by fresh spares. In a glass envelopetube, visible left dot on the loiver row deals withtemperatureevidence of a tubs defect coefficients, may bi3present when the and applications. filament is open, when the platecurrent is exces- By way of explanation, a capacitOr withupper.; sive, when the tube becomesgassy, or when arcing row dots colored black, red, and green (readingoccurs between electrodes. When metal-enoased . from left to right, according to the directionaltubes are warm to the touch, itis an indication that indicator). would mean a mica capacitor withthethe heater is operating. A tubemay be tapped significant figures 2 and 5. The lowerrow adoinlightly with the finger while operatingin aparticu- (reading from right to left) are brown, red, andlar circuit to providean aural indication of loose red. The brown dot requires the addition ofoneelements or microphonios.

166 Chapter 10SAFETY; TEST EQUIPMENT;, TESTMETHODS

CAPACITANCE BLACK DOT IDENTIFIES DIRECTIONAL MICA CAPACITOR . INDICATORS COLOR TOLERANCECHARACTER- ISTIC Rif SIGNIFICANT DECIMAL SIGNIFICANT FIGURE MULTIPLIER FIGURES OF CAPACITANCE BLACK 0 2ND 1 20 PERCENT A IN Rd BROWN 1 10 B CHARACTERISTIC RED 2 100 2 PERCENT C CAPACITANCE TOLERANCE DECIMAL MULTIPLIER ORANGE 3 1,000 0 CHARACTERISTICS YELLOW 4 E A - ORDINARY MICA BYPASS GREEN 5 F B - SAME AS A-LOW LOSS CASE BLUE 6 0 VIOLET 7 C - BYPASS OR SILVER MICA ( ±200PARTS/MILLION/C) GRAY 0 D- SILVER MICA WOO PARTS/MILLION/C) WHITE 9 E - SILVER MICA (0 TO +100 PARTS/MILLIOWO GOLD 0.1 5 PERCENT F - SILVER MICA (0 TO +50 PARTS/MILLIOWO SILVER 0.01 10 PERCENT 0 - SILVER MICA (0 TO -S0 PARTS/MILLIOWO

20.376(71) Figure 10-16. Color code for fixed mica capacitors.

Several types of tests may be conducted to multigrid and diode tubes are tested for cathode determine the condition of a tube. The mostemission. common test is substituting a good tube for the Multigrid tubes: For a test of the emission of suspect one. Other tests, requiring theuse ofa multigrid tube, the tube is connected asa a tube tester, are emission,transconduotance,half-wave rectifier. (See fig. 10-17.) Theplate gas, short circuit, and noise tests. and all the grids of the tubeare connected together. A milliammeter anda variable resistor Substitution Test are placed in series with the tube, and the entire circuit is connected across a transformer second- Substituting a tube known to be in goodcon- ary. Because of their common connection, the dition is the most reliable method of, decidingplate and all of the grids are at thesame poten- the quality of a questionable tube. In high fre- tial with respect to the cathode. Asa result, the quency circuits; tube substitution should be car- tube functions as a diode rectifier,conducting ried out carefully one at a lime; noting the effect of differences in intereleotrode 'capacitancesof the substituted tuba on'timed (aligne4 circuits. The substitution' Method' of testing cannotbe used to advantage to locate more thanone faulty tube in a single circuit. U both an'a-f amplifier tube and an i-f amplifier tubeare defective in a receiver, replacing either one does notcorrect the trouble. If all Ahe,tubes,are replaced, there is no way of knowing which tubeswere defective. Under these or similar conditions, theuse of test equiPment designed for testing thequality of a tube saves valuble time. Emission Test An important indication of the condition of a tube is obtained by a comparative check of the cathode or filament emission. In most instancen% a pronounced` lower-than-normal emission, or a 1,73 complete loss of emission,- indkiates that the tube Figure 10-17:Basio circuit used for emission has reached the end' of its, useful life. Both test.

167 INTRODUCTION TO SONAR

current only on the alternate half-cycleswhen the plate and grids are positive withrespect to TUBE UNDER the, cathode. The amount of current thatflows TEST indicates the condition of the cathode- emitting surface. On tube-testing equipment, themeter scale usually is calibrated by dividingthe total pointer arc into three areas, whichare labeled GOOD, WEAK (or FAIR), and BAD. Diode tubes: The emission test for diodeand rectifier tubes and the diode part ofmultisection tubes is similar to the emission testused for multigrid tubes. The tube filamentor heater is FIXED PLATE operated at the rated value, andan a-c voltage is BIAS VOLTAGE applied to the test circuit consisting ofthe diode, a d-c milliammeter, and a variable resistor.A tapped secondary is utilized' insome circuits to vary the amplitude of the test signal. The variable Figure 10-18. Basic circuit 1,76 resistor limits the tube current toa safe value. used for gas test. The amount of current flowing throughthe resist- ance and the meter depends on the electron If the amount of gas in the tubeis appreciable, emission within the tube, and thereforeindicate; the collisions between the the emission quality of the tube. numerous gas molecules and the cathode-emitted electronsrelease many secondarily emitted electrons, and theresulting Transconductance Test flow of grid current is high.The baste circuit used for the gas test is shownin figure 10-18. With switch S set to position 1,a certain, value of The term transconductance (also calledmutual plate current is measured by thed-c milliam- conductance) expresses the effect of gridvoltage upon the plate current of a tube. By meter. If there is no gas (ora negligible amount) measuring present in the tube, throwing switch Sto position the transconductance ofa tube, it is possible to 2 does not change the plate evaluate the tube's ability to amplifya-c signals current reading. If much more accurately than by gas is present, current flows throughthe large measuring its value grid resistor, causinga voltage drop to cathode emission, beoause this testmore closely develop with the polarity approximate, aottialcirouitconditions.Transcon- as shown. The net effect is to reduce the negativebias voltage on ductance is expressed mathematicallyas the the grid of the tube, resulting in ratio of a change in plate current an increase in to a small change plate. current. Small plate currentincreases are in control grid voltage, with allother electrode normal; large increases indicate voltages held constant.Transconductance is excessive gas. measured in units of conductance In some circuit's a neon light isSubstituted for called mi- the milliammeter and glows toshow the presence cromhos. of excessive gas.

Gas Test Short Circuit and Noise Tests In all electron tubes, exceptsometypes of rectifier and regulator tubes, thepresence of any appreciable amount of gas is' extremely The test for short-circuited elements must be unde- applied to a tube of doubtful. quality_ beforeany sirable. When gas is present,the electrons other tests are made. This procedureprotects emmtted by the cathode collidewith the molebules of gas. As a result of the meter (or any other indicator) fromdamage. these collisions, electrons Also, it follows logically, if a tube under testhas are dislodged (secondarily emitted)from the gas molecules, and positive elements -that are short-circuited, thereis no gas ions are formed. further need to apply additional tests tothattube. Because the contra grid isnegatively 14Iesed, Short .oircuit tests usually are sensitive enough the positive gas ions are attractedto it, aM-they to indicateleakage resistance less than about 1/4 absorb electrons from the ,grid.circuit' in. order to revert to a more stable condition megohm. The 'proper heater voltage is appliedin (notionized), order to detect any tube elements that mightshort

168 Chapter 10SAFETY; TESTEQUIPMENT; TEST METHODS

111

1.75 Figure 10-19. Basis circuit usedfor short circuit and noisetests.

as a result of the heatingprocess. The shortnot loose enough to Indicate circuit test is similar to thetest for detecting on the neon lamp noisy (microphonic) or loose loud crashes of noise (or static),over and above elements. Becausethe normal amount of noise thatis present, are the only difference betweenthe two tests is in theheard from the receiver. The sensitivity of the device usedas an indicator, the noise test also may noise test is discussed as be made without theuse of the high-gain amplifier a part of the short cir-merely by inserting the leads froma pair of head- cuit test. phones into the noise test Figure 10-19 shows a basic circuit receptacles. The latter used for check, of course, is notas sensitive as the test detecting shorted elements withina tube. With the made with the amplifier, but plate switch set to position 2, the plate ordinarily is more of the tubesensitive than the short circuit testmade with the under test is connected to theleg of the trans-neon lamp as an indicator. former secondary containingthe .neon lamp. All the other elements are connectedthrough switches to the other leg of thesecondary. If the plate of SEMICONDUCTORS 'the tube is touchingany other element within the tube, the a-o circuit of the secondary is completed Semiconductors have been used inelectric and both plates of theneon lamp glow. If no shortcircuits for several years. exists, no indication willbe present, or only one Copper-oxide and Nita of the neon lamp will glow. selenium dry-disc rectifiersare two of the more Each of the otherfamiliar types. The outstandingcharacteristic of elements is testedAymeans of the 'switchinga dry-disc rectifier is that it will conduct arrangement 'shown. Resistor R2limits. the cur- current rent through the neon lamp' easily in one direction, butvery little or no cur- to a safe value.rent in the opposite direction,thus acting like a Resistor -R1 bipassegVany smallalternating our- rents in the circuit that might vacuum tube diode. Dry-disc rectifiersare too be caused by straybulky and heavy, however, formany moderneleo- capacitance, thus preventing theneon lamp from indicatiLg% erroneously. Tapping tronio requirements. Experimentsinnonconductr the tube lightly is ing materials led to the developmentof the tran- recommended to detect looseeleMents that might touch when the tube is vibrated. sistor, making possible themicrominiaturization found in modern electronic equipMentsuch as The-noise test is, in effect,no more than.acomputers and missiles. very sensitive short:aro:snit test.In figUre 10-19 . two leads are taken from Transistors are constructed Of semiconductor either side;Of theneon materials. The most widely used semiconducting lamp and brought to externalreceptacles labeled . "noise, test". A high -gain amplifier (with speaker) elements are germanium and, silicon.In their regular forth, these substancesare nonconductive. is connoted to the receptaoles.Perhaps the hand- iest amplifier for this test When impurities are added to them,however, they is an ordinary'radio ,behave as, 'conductors., AddiAgarsenic to Prnia- receiver. The antenna and groundterminalSofthe receiver:are connected to the instanoe, -results inthe presence of a noble test jacks, and large amount Of free electrons (negativecharge). anormarshortnircuit.testis madewhile tapping the tube. If tube elements.areloosebut The material ip then asertgoonduoterof the N-We perhaps withnegative current. When indiunt is addedto INTRODUCTION TO SONAR

3. Absolute maximum ratings ofvoltages and collector current. These ratings mustnever be exceeded. 4. Collector power dissipation factor. 5. Beta (gain) of the transistor. P-TYPE N-TYPE CRYSTAL CRYSTAL 6. Collector out-off (leakage) current. -1111.1- You should know the semiconductor specifications before attempting quality tests. Transistors normally are more rugged than electron tubes, and do not often require replace- 20.23:71.98 ment, Their life expectancy is 40,000 hoursor Figure 10- 20. Junction diode. more. Should it become necessary foryou to replace a transistor, however, certain precautions must be observed. Before removing the oldtrand sistor, note the orientation of the transistor's germanium, P-type material is formed, which base, emitter, and collector leads toensure proper produces the flow of positive (hole) current. (The insertion of the new device. Cut the leads ofthe theory of operational semiconductors, which is too new transistor to the proper length to prevent involved for this :text, can be found inIntroduction undue stress. When soldering thenew transistor to Electronics, NavPers 10084.) into the circuit, use the proper solder,soldering When .N- and P-type materials are combined, iron, and a heat sink. Transistorsare very suscep- they form what is called a junction diode, shown tible to heat, r-f radiation, and electric shook.One with its schematic symbol in figure 10-20. Because of the most frequent causes of damageto a tran- a diode Will not amplify asignal, athird semicon- sistor is the electrostatic discharge fromthe ductor section is added, forming alimotiontran- human body when the device is handled.Such sistor, which acts like a vacuum tube triode.(Other damage may be avoided by dischargingyour body transistor types include' the tetrode andthepower to the chassis before handling thetransistor. transistor.) The transistor actually is two junction Detailed information on how to replace atransis- diodes platted back to back, with the centerelement tor, handling precautions, and transistorlead common to both junctions, and are Of either the codingmethods is given in Servicing Techniques PNP or the NPN type. Internal ourrentflow is the result of hole Conduction:in the PNP type,and of electron conduction in the NPN typo. Externalcur- rent in itransistordirouitis always eleotronflow. COLLECTOR The elements transistor are called the PLATE OUTPUT IC emitter, beim; and collector; They cOrrespOnd GRID BASE respectively' to a vacuum tube's cathode,-control grid;' and plate; Figure' 10-21 ShOiti the' two types IN= of transistors, their aOheMitidayMbols; and their EMITTER relation to 'the triOde. The primary different*be- hi/ea.-the operation' of.vacuum tithe. and 'a tran- sistorthatthetibeis voltage!-cyerated andthe transistor is ourrent-oPerata4'resulting in low power requirements for transistors', Transistors, like vacilizit'-ltibes;come in a variety Of types, each With itsown characteristics. FollOwing are:some Of the data foulitaa tran sister specific:141On sheet pUblished by, themanu- B facturer. PNP 1. The kind cd eeinicoaduOtor (PNP,NPN, diOde, eta:), type of materialused, MA tYPe of caoastruotiofi "- ' 1.280A(20A) COMMOIXPplioationslaUdiciainplifier,roc". 'Figure 10-21.Corresponding elements intriode Adler; eta.): and transistor. Chapter 10SAFETY; TEST EQUIPMENT; TEST METHODS

for Transistorized and Printed Circuits,Nav Ships 93394. Four main failures are associated with tran- sistors: (1) opens, caused bya break in the leads PHP or a break in the emitter-base di-Colleotor-base junction; (2) shorts, caused bya rupture of the crystal through the base material; (3) high leakage current, caused by contamination buildingup on the emitter -base or the collector -base junction; and (4) low gain, oausedbyexoessiveheator mal- treatment. Before testing a transistor, first determine the type, whether PNP, NPN,or diode.Groand all test equipment to the ohassie under test. If removalof the transistor from the circuit isnecessary, use a lows-wattage soldering iron (35 wattsor less), use proper. heat sinks, and ground the soldering iron Up to the chassis under test. Two basic units of test equipment oan, be used to test transistors. The TS-1100/U transistor tester is designed to test the beta (gain) ofa transistor while in the oirouit, the ICO (collector leakageaura 71.99 rent), and shorts with the transistor removedfrom the circuit., Figure 10-22. Transistor leakage current test. If the TS-1100/U test setts not available,any good multimeter orvacuum tube voltmeter A general statement can thus be made:The (VTVM) may be used after first observing certain front-to-back ratio must always beat least 10 precautions, To. avoid loading the circuit,the to 1, multimeter MIS have a sensitivity of atleast 20,000 ohms per volt on all. voltageranges; the ohmnieter circuits must notpass a currentTransistors exceeding 1 mlillimPere. The VTVM shouldhave an input resistance of 11 megohms ormore, and Three tests can be accomplishedon the tran- must have an isolation transformer betweenthe sistor by using the multimeter. Thetransistor meter and, the powerline. must be removed !roil' the circuit fortesting. Determine the type of transistor,whether PNP or NPN. The same resistance testcan be per- Diodes formed on the transistoras on the diode. The . . transistor hastwo,junctions, the emitter -base and Before lasting a diode, its polarity mustbe the colleotor-base. Because each junctionoanhe deterniined. The diode usual/y.18 markedwith atreated as a diode, the same readingshold true. phis (+) or minus (-s,) sign. Confect thetest leads When teetiagpOwer transistors,the same ratio to the diOde in a forward bias aondition;that is, (10 to 1) holds ,true, except that thereverse resist the ,positiVe ,tead to the Positive sideof the.diode anoe must be in excess of only 1000 ohms. and the negative' lead toi the negative side.Cur- To perform the. leakage current test,the man-, rent will now flow easilys'ind ifareading of 1000 ufaoturer%.1Pecificationa should be 'Consultedto ohms or less is obtained, this part ofthe test is isoertain the allowable limits.Determinethe type gOod. If a higher reading is obtained,the, diode is of transistor and set upone of the tests shown in open. figure 10-22, using a 6 -volt battery andmioroani- Connect. the test leads, to. the :.diodein ameter. reverse .bias Oenditie rtie positive lea&tothe U the leakage current is twioe as muohas the negative side of.the diode and the negatiielead tospecification sheet calls for, replace the transis- the positive side. Cwient,w111not fkAy, readily, tor. if. no 'specifications are available,use the and,a reading in eiweis ef 10,000. cameshould, be followiag rule 'of thumb: obtained. ig,A, iN000:, ohms, is obtained,. the ..diOde is 'boiled. 1. Hillard transistorless than 1 mioroamp, .1 INTRODUCTION TO SONAR

resistor, and the like) prevents the flow ofcur- rent. Before conducting the test,secure power and disconnect the circuit to be tested. An ohmmeter normally is used to test forcon- tinuity on those parts of a circuit whereinresist- ance is low. An open circuit is indicated when the meter reads very high or infiniteresistance. When testing for circuit continuity, theohm- meter should be set on the lowest scale.If a medium or high scale is used, the needlemay indicate zero ohms, whereas the actual resistance could be as high as 500 ohms. Occasionally, you may have to makea contin- uity test of a circuit whose endsare in different spaces. Several methods can be used to testa circuit from one compartmentto another. (Always make sure the power is secured beforeyou dis- connect the circuit.) The following means oftesting are accomplished more easily by twomen. 71.100 1. Attach a jumper from one end of thecircuit Figure 10 -23. Transistor gain test. to ground. At the other end, connect theohm- meter in series between ground and thecon- ductor. A very high resistance reading 2. Small germanium transistorlessthan 10 indicatis an open circuit. mioroamps. 2. U an ohmmeter is not available,a pair of 3. Medium germanium transistorless than sound-powered telephone handsets with 100 mcroamps. alligator clips on their leadsmay be used. 4. Power transistorsless than 1milliam- Connect the handset leads between the cir- Pere. cuit and ground at each end of the circuit. If the circuit is open, communicationis The beta test can be acoomplishedbyinserting impossible. a 10,000-ohm resistor betweenthe collector-base 3. A battery-powered test lamp enocan be .junction and connecting tile meter tothe emitter used. Ground one end of the circuit. Connect and collector as shown in figure 10-23. the lamp between the other end andground. Once the resistance is obtainedon the meter, If the lamp does not light, the circuit is use the following formula to figure the gain: open. B .1* 1200+R. The letter B represents gain,1200 is a constant, and R is the resistanceread on the Intermittently open circuits sometimesare meter. encountered. These breaks usually are found in Check the manufacturerle Speoificationforthe cables or wrapped multiple wiring. When thcitest- gain of each transistor. If the specificationsare ing equipment indicates_ an open circuit, the cable not available, use the following ruleof thumb: or wiring can be Handl Any momentary contin- uity of the circuit is apihrent by in indicationon 1..Silicon transistors 5 timesor more. the test equipment, and the location of the break 2. High-frequency transistors-10times or more. is then known. 3. All other transistors -x-16 timesor more. Grounds

. circuits are caused by some part of CONTINUITY TESTS the circuit making contact, either directlyor The purpese of the continuity test:it. indirecitly, with the metallic structure of the ship. to . GreMid.s Lave several causes the two most ensure that a circuit is ocUnPlete-Or continuous:common being frayedor worn insulation that An open circuit is one inwhich a,breakin the bir- allows bare wire to come into contact withthe ouit (a broken lead; defective Switch., Winedoutequipment's chassis Or ships structure; and Chapter 10SAFETY; TEST EQUIPMENT;TEST METHODS

moisture-soaked insulation that providescurrent a leakage path to ground. (a-43 or d-c) to bemeasured and that the scale Usually, a ground is-indicated by setting is set to theproper range. Because defec- a blown fuse tive elementsmay cause higher-than-normal or tripped circuit brepker. A highresistancevoltages to be present ground; however, mayoccur where insufficient in the circuit, the highest current can .flo* to rupture the fuse voltmeter range should beused first. Oncea read- or open theing is indicated, adjustthe voltmeter scale circuit breaker. gressively pro- An ohmmeter is used in, testing for downwarduntil the lowest scale grounds.appropriate to the actualvoltage may be used. By measuring, the. resistance.to ground at anyThis system gives the point incircuit, 'it is possible. to determine most accuratemeasure- ifment and avoids damageto the meter movement. that point is grounded. Beforeconducting this test, Many schematics indicate it is necessary to Study the associatedwiring dia- proper voltages at grams for the, presence' of intentional various test points. Ifa certain stage is suspected, groundi.the voltage can bemeasured by placing the These..grounds must, bedisconnected before theleads at the designated test circuit can be tested accurately.&zero, or very test points. The voltage reading obtained by themeter should be thesame low,. 'reading indicates thecircuit is grounded.as that givenon the schematic.

Shorts CURRENT Current, expressed in A short circuit is similar toa grounded one, amperes, is measured except that it is between two in much the sameway as voltage except that the or more. conductorsmeter must be connected in seriesin the circuit and usually has a greater tendencyto blow fuses.being tested. The ammeter is Two conductors with frayed insulationmay toach. a low-rebistance each other, short- circuiting: the, current instrument because,. if it offeredmore than a Toominute .amount of resistance, itwould reduce the much solder On,the pin ofa cOnnecter May causeamount of Current flow in the a shert circuit An adjacent pin: Again, the test circuit and result instrument used is in an erroneous measurement. the ohroineter. Isolate the two ' When the ammeter is connectedin the circuit, suspectedcircuits.and connect the ,meterto them.it is used in the manner prescribed A high. resistance 1readingindicates the circuits for the volt,- are said_ meter. In other words, start withthe higher scale . ; . . : and, progressively: adjust the Shorte may ocipitriii Ooictuoionisiesiaesthose scale used until a 14 in cables. or.. in, the, wirbit, reading ,is obtained on the lowestscale that gives in, chassis: CoMponentsa meter. indication... such as .traniforMers,.motorWindings, and cepa- If a circuit:is disconnected . citais ,to name .A.few or opened to insert SM are also, susceptible tothe meter for.nmeasurement, be sure and restore A short cireuits.:1.These :iooMponenta ,r. sholildbe checked for a resistance that. -part 41f.,..the circuitbefore further testing. reading, and this reading. Because.: of 'the Urns and compared with the figure given the component effort ,expended in in the schematic or eqUipment connecting an'. ammeter.. into-a circuit,-it usually is technical manual.more advantageous to measurethevoltage across a resistor of known value and calculatethe current ' -. : . ' , 1 by using Ohm's law. VOLTAGE ....:';'...

Jr )The4oltage!.,,tetiC isaccomplished only with . .- RESISTANCE power:applied to the equipment, Prescribedsafety piabot4os:,nuist be :obeerved,: therer.:,..., Usually fOretepre*ent injury 7te: personnel the, resintance of a circuit, portion of i :CrciaMage.to....:":.Circnit, ,OrCircuit elementis measured with the tligi',.4,4*R0*,: . Iiit4 tAii:iii:'44-oilliri,.:.Ohninteter.. Firsti'Power iii') V must .beseonred to the , i0014 .#4...,*ij?q '..., faiocr.':.;01.17ciiit and. Met:meter 1*? zeroed before connecting ?. .... : '000* el**-.1.;the*eter.:intext.heCircUiti.,.,.:,.,. .,.: , .. -,....:. .: or.0.1.niel:43 1 ,a' ..k Selection ' of, ...the.PrOper scale is animPortant at,stt,is m e. .-..4.,i Ps ;,..,k);,,,)::-: ,...,...1 : vs --,,A.?,,., 3; n.:iii.fnii, resistance measurements.To ce, ..:Inormv c .,,sii? ,.., .: :. kusing' t,, low resistance, . use ..the lower ,..... ,,.., a ,,,., isz : vi Ifit.0;h1i440'1**sad:ithe:, toe Y.N meter. e r ,Inere;:eien sennresiitr Ifor gas ex'of;,volti riSliiiii .'[0 , , -f to ;1'. i.. ..:.., - ,

$7,

vy tr .5- 54, 1;;,Ckt.401rjf:. INTRODUCTION TO SONAR

check a circuit with high resistance, select the high I. Clean commutators of dirt, oil, scale, because the low range scale may indicate or grease with a lintless cloth moistened witha safety- infinity when actually the resistance is less than 1 type petroleum solvent. megohm. Clean scratches and rough edges from While conducting resistance tests, take into the account that other circuits containing resistance commutator bars by pressinga very fine and capacitance may be inparalielwith the sandpaper against the surface witha block of circuit wool that has the same contouras the com- tested. To obtain a correct reading, the circuit mutator. A piece of canvas is tested should be isolated from other parallel oir- sometimes cults. adequate for this purpose. Thesandpaper or When measuring a resistor, remember that canvas should be moved back and forth most resistors have a tolerance of approximately acroma the surface, parallel to the shaft. Remove all grit cater this operationby 10 'percent. If the measurement of aresistor falls means of a lintless cloth. Under no circum- within this tolerance, it usually is considered to stances should emerricloth beused for meet requirements and need not be replaced unless cleaning. the circuit calls for a critical value, 3. Clean high micafrom betweenthe commuta- tor bars. This procedure consists of GENERATOR MAINTENANCE remov- ing the mica protrudingfrom the commuta- tor slots, so that. there is no contact Minor routine maintenance of generators is between the mica and the brushesas the performed by the Sonar Technician toensure a commutator revolves. Thisprocess, called proper voltage supply to the associated sonar undercutting, equipment. This part of the text is notintended accomplished by sawing or to scraping the mina from the slots.An ideal teach the methods of generator repair; only those tool for this purpose isa hacksaw blade procedures required as, normal maintenanceare that has been ground down toremove all discussed. teeth, so as to prevent -burringof the commutator bars. For small commutators, a slotting file 'may be used to file and Commutators scrape outtha mica. Caremustbe takennot to undercut too deeply. Although thesquate The first iequirement for good commutation is shaped slot usually Is preferable, continuous, close contact betweenthe commutator the V- shaped- Blot maybe more satisfactorywhere and the brushes. Successful ,commutation isnot a 'the- alas are 'likely to 'collectdirt. After function of the electric circuit, or the bkush,or the undercutting is completed,' oommutator, alone. It dePende- emove all burrs 01.1' all of those fao- and polish 'the commutator. Do not: useany tors; and ban; be maintained only prOughproper:- lubricants when Undercutting.: inspection, cleaning, and maintenance. Inspection; Proper inspection of the commutator SliPriolto 001431filts the' following steps: The principle of close electrical :contact 1. Cheok the :bara on the commutator for flat applies to the sliprings as well as to thecommu- spots, bUrned condition, andlooseness indi- tator. With few minor exceptions, the procedure cated '-'hyirregular': high or low bars. for inspecting, cleaning, or minor resurfacing of 2. Chedk for 'striaks and grooves:: sliprhIgs: is identical to that for commutators.. 3. Clock for:dragged Copperon the leading . edges,of .tirit bars) and torlilied Biotacaused yrt,he: dragged: cCpperii,.*:-. Entities -4.:Cheok4110:4400:1':,. Connections: for;:;thrown.) 80140:_ ..,=The'' brushes 'of 'a' generatorare the:points of 5. Check the', Mt() ifiika pitted condition and the5: contact;. between.the external .cirOuit conductors 41 TresP)106'... SO. 0;,: dirt,and particles yv of carbon ,1414410comMutatOr:,.Thess,po:nts 6.'brush*!:, the : commutator 13o:.;:as:Ito.'take off thee. generatedwar INr hes .ride:On the :itirfao8 of, thecon-. , mutati iiie:,,halt.4n,p1sioe by brush hOlders: .conuitv... ° Bras lie:Mad&Of. ,:higbiride CarbOn.' rare:. , froralthe:. frame;and are free, Chapter 10SAFETY; TEST EQUIPMENT;TEST METHODS

to slide up and downin the holders so that may follow irregularities in they brush on a generatorwhile the armature the surface of the turning. Residual still is commutator.. 4flexiblebraided-copper conductor, magnetism may causeagenera- commonly calleda pigtail, connects each brush tor output, even thoughall power is securedto the to the external unit. If the brushdoes not slide freely circuit. A spring forceseach holder, sand its sides in the brush to bear on thecommutator with from 1 1/2 with a medium-coarse to 10 pounds of grade of sandpaperuntil the sides make pressure for every square inchof but free fit. a close brush surface ridingon the commutator. Thole springs ordinarilyare mounted so that brush After the brush isfitted in the holder,fit pressure is adjustable. it to the commutatorby sandingitwith coarse grade of sandpaper. a medium- Brushes should be inspectedperiodically to see Sand in the direction that proper spring of commutator rotationby placing the. sandpaper tension is applied, thatthe strip between the brush brushes ride free in" the :brushholders, that the oontaot surface and the . brushes are of ..adequate length,. commutator, with the roughside of the sandpaper .and that they toward the brush. make proper maximumcontaotwith theoonimuta- tor, Apply pressure to thebrush and pull thesand If brushes becomeWorn to an' extent paper through the contactarea. Repeat this length is reduced 'where process until the brush face considerably, the ability ofthe the commutator makes agood at with spring to exert properpressure is affected. Fail- curvature. ure at the brush to ride free After all brushesare replaced inthis in the holder has the blow the :Nub= dust manner, same result. When theseconditions .obour, brush away from thecommutator replacement is necessary. and toward the outsideof the generator. To replace., a brush, firstsecure all power to After replaoement ofbrushes and cleaning, the generator, wait until power may be restored and the shaft.has stopped,, the generator turned remove the defective brush, on. Watch the brushes forproper operation and then place thenew possible excessive brush in the holder.Never attempt to replacea sparking. If sparking isexces- sive, some additionalfitting may berequired. APPENDIX I TRAINING FILM LIST

Certain training films that are directly relatedto the infor- mation presented in this 'trainingcourse are listed below under appro- priate chapter numbers and titles.'Unless otherwise specified, all films listed are black and white withsound, and are unclassified. For. a description of these and other trainingfilms that may be of Interest, see the United. States /au Film Catalog,NavWeps 10-1-777 and supplements thereto."

Chapter 1 .1. THE SONAR TECHNICIAN MN-10319. The Sonar Technician. (29 color.)

Chapter 2

SUBMARINES AND ANTISUBMARINE UNITS MC-10232A Dash. '(30 min.color.)

-- -Chapter 4 PHYSICS OF SOUND

MN-8998e . Phykics "oi Underwater SoundPart 1Basic Principles. (20 min.) MN-8998O Physics of 'Underwater Sound, Part 2Velocity Profiles. (25 Min.)

MN-8998H .Physics.. of Underwater Sound Pert 3Absorptionand

Saittering..07 mln.) .

.Marine BiologySounds in . the Sea. (30 min.. color.)

.Chater5

sATiFr ERMOCIAAPH..

f;=litatloytheo,'Oicigraph Observations. -1111,-

vY

te(V110.1.0.*S Nimmoren wr*e*u~wr..etsn.rnmrmrtabKsVQVBVPir*P'XRPreltIqrlfAgr'er,"15PtRrifrtlret%"""'

Appendix I TRAININGFILM LIST

Chapter 8

COMMUNICATIONS MN-2621B Radio Operator Training (9 min.) The Technique ofHandSending.

Chapter 10

SAFETY; TEST EQUIPMENT;TEST METHODS MA-7812B Circuit Testing With Metersand Multimeters Practical Application. (33 min.) MN-9655 Printed Circuits and theirRepair. (28 min.) . 4. MN-10384 The JunctionVransistor.(28 min.color.)

Classified training,tapes are availablefor use by Sonar Tech- nicians to develop Airoftoiettoyin the. detection and classification of and underwaterAtargets..The AcoUstic SensorTraining Mate- rials Catalog,: NavPers987904, ,.with the SECRET lists the tapes. available; as supplement thereto Menfeif these sonar . well :as procedures to follow for procure- tr aining aids. ,

,. INDEX-

A towing equipment, 85 towing operation, 88-89 Active duty requirements, 4 trace readout, 82 Active sonar, 91 theory, 95-98 Advance and transfer, 27 C Advancement in rating, 2 Aircraft, MN, 19 can signs, 135 Ambient noise, 39 Capacitors, 185 Ammeter, 173 Cavitation,. 41 AN/BQH-1A, 58 Coils, electronic .circuitry, 182-184 QN /BSH -2D, 58 Collision lead, 29 Angle on the bow, 32 Communicational introduction, 132 Antisubmarine units, 14-19 emergenCy, 144 Antisubmarine weapons, 110-112 pyrotechnic, 145 Armament, submarine, 13 Commutators, 173 Array-type passive sonar, 99 Conductor markings 180 Artificial respiration, 156 Continuity.tests, 171

Artificial targets, 54 . Convergence zone 50 ASROC, 18 Conversion table,Anches to millibars, 81 Attack lead, 29 Converting true and relative bearings, 25 CorrectiVe maintenance 147 CRT oscillOscope, block diagram, 159 CTEM lcig; 84-87 B Basic computing mechanisms, fire control, 118 D' Basic coursos /Wig fire' Joni:roll introduction, 110 Decibels, 38 BATRY message information, 82 Deep water sound propagation, 49 -51 Bathythezziograph DeteCtion4o-destruction Phases, expendable 88 fire. cOntrol, 112-114 ship)Oard, Development Of submarines, 9-12 submaiine,18 Dial readingsl.fire control, 130 Beiringdrift; 27. DivergenCelraound wave, 43 Briring measurement, 20 Doppler, 29,51,128 Bearing1;.2248' Duty ,assigninents,:2 Brushes, generatok 173 calibration, 70. E logi .;77,83,, 10044.4Cncetr0 message,84 fiwVISN30.7.0., ...... nonoroncoma4woomeffirerme7441,no '17',,,,11014,110..7Nryhritt.!IVVVVVIMIFTN&Irt,OVITI"

INDEX

Electromechanical devices,fire control, 121 Electron tubes, 166-169 Mailing precautions, BTslides, 77 Electrostrictive process, 95 Maintenance, introduction, 146 Enlisted rating structure,1 Maintenance requirementcard, 150 Environmental data, BT log,80 Manual of Qualificationsfor Advancement Equipment, underwater firecontrol.-118-131 in Rating, 3,6 Expendable bathythermograph,87 -9b Marine life noises, 42 External communications,133 Marking BT slide, 76 MC systems, 133 Mechanical computing devices, F fire control, 119 Megohmmeter, 158 Fathometer, 101-104 Mines, 14 Fire control Military standards, 3 computing mechanisms, 118-123 Missiles,14 detection to destructionphases, 112-114 Modern passivesonar theory, 99-101 dials, 130 Morse code, 136-139 nomenclature, 115 Motion, 26-29 reference planes, 114 Multimeter, 158 symbols and abbreviations, 122 system tests, 124-127 Flow noise, 40 N Frequency of soundwave, 37 Fundamental problem, firecontrol, 114-118 Navy Training Courses, 7 Noise, 39-43 Noncomputing devices, firecontrol, 120 G Normal .curves forpressure, salinity, and temperature, 46 General ratings, 1 Nuclear submarines, 13 Generator maintenance, 173 Graphing the BT trace, 73 Grounding test equipment, 157 0 Gyro failure, 24 Occupational standards, 3 Ohmmeter, 158 H Operational maintenance,146 Oscilloscope, .158 Hydrophones, 91-98 Hyiteresis effects, BT72 P Parallax, 117 Passiire:sOnar, 98 Inactive duty reqeirementi,5' theory, 99 -101 Internal communications, 132 Piezoelectricprocess, 95 PMS feedback.report,151. pOMBEE'program, 152

potentionieter; . Power tools, safetyprecautions,, 155 Preparation for advancement,3 P17,10,ek*itintenanCe, 146-152

stAv41.-, :- ''45-51 INTRODUCTION TO SONAR

Publications-continued Sonar information, 20 Military Requirements for Petty Sonar position quantities, 116 Officers 3 & 2, 6 Sonar system, block diagram, 95 Training Publications for Advancement Sonar Technician rating, 2 in Rating, 3, 6 Sonobuoys, 108 List of Training Manuals and Sound Correspondence Courses, 7 audible range, 34 Pulse length, 96 characteristics, 38 description, 34 propagation, 45 Q speed, 46 waves, 36-38 Qualification for advancement, 2 Sound-powered phones, 132 Qua ls Manual, 3, 6 Sound wave reception, 96 Quenching, 45 Stern line indicator, 22 Study methods, 7, 8 Subject matter courses, 7 R Submarine armament, 13 Range rate, 127 antisubmarine weapons, 111 Radiotelephone, 134 bathythermograph, 58 Rating courses, 7 communication methods, 144 Reading BT trace, 73-75 general characteristics, 12 surface temperature, 72 f history and development,. .9 Record of Practical Factors, 2, 6 locating requirements, 20 Reflections, sound wave, 43 propulsion, 13 Refraction, sound wave, 45 SUBROq 13 Relative bearings, 22 Relative motion, 27 Remote indicators, 133 T Resistance 173 Resistors, 161 Tactical range recorder, 127-130 Resuscitation, 156 Tape recorder, 104-108 Reverberations, sound, 44 Target angle, 30 Rheostat, 161 Target aspect, 29 RLI operation, 98 Temperature effect, 46, 57 Rotating directional transmission (RDT), 97 'Temperature profiles, 73-76 Terminal designations, 159 Test equipment, 157-159 Test methods cables, 161 Safety capacitors, 165 precautions, general 154 coils, 162 power tools, 155 c9ntintdty tests, na Scanning Sonar, 92 current, 173 Searchlight sonar, 92 esistance173 Sea surface temperature reports, 64. resistors, 181' . Semiconductors, 169 -171 seMiconductors 171. "finding code;"139=.141 transformers, 164 ervice Tatingt,4*:-; tubes, 166469 "'allow watereYec on transmitted sound 49. voltage 173J Board antisubmarine weapons, 110 Therniocline0; 48,58 ytheimographs, 61 -71 3 -M system,;: equipment 147 T000004.;13 de.:8 4:1 col:2.066,q7;

r r ' ry, /s , INDEX

Training Publicationsfor Advancement in Rating,.,3,6 Underwater fire control,110-114 Transducers, 91-95 systems, 123 Transformers, .164 Underwater sound transmissionlosses, 43-45 Transistors, 171 Transmission losses, soundpulse, 43 Troubleshooting procedure, testmethods, 159 V True bearings, 22 Tube teeter, 158 Variable depth sonar,108 Noltmeter, 157

U

Underwater communications,141 telegraph procedures, 143 voice procedures, 142 Wavelength, 37 Weapons, antisubmarine,110-112