NONRESIDENT TRAINING COURSE Aviation Machinist’s Mate 3 & 2 NAVEDTRA 14008 DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. PREFACE About this course: This is a self-study course. By studying this course, you can improve your professional/military knowledge, as well as prepare for the Navywide advancement-in-rate examination. It contains subject matter about day- to-day occupational knowledge and skill requirements and includes text, tables, and illustrations to help you understand the information. An additional important feature of this course is its reference to useful information in other publications. The well-prepared Sailor will take the time to look up the additional information. History of the course: • Sep 1991: Original edition released. Prepared by ADCS(AW) Terence A. Post. • Jan 2004: Administrative update released. Technical content was not reviewed or revised. Published by NAVAL EDUCATION AND TRAINING PROFESSIONAL DEVELOPMENT AND TECHNOLOGY CENTER TABLE OF CONTENTS CHAPTER PAGE 1. Jet Engine Theory and Design ............................................................................... 1-1 2. Tools and Hardware ............................................................................................... 2-1 3. Aviation Support Equipment.................................................................................. 3-1 4. Jet Aircraft Fuel and Fuel Systems ........................................................................ 4-1 5. Jet Aircraft Engine Lubrication Systems ............................................................... 5-1 6. Engine and Airframe Related Systems................................................................... 6-1 7. Helicopters and Turboshaft Power Plants .............................................................. 7-1 8. Turboprop Engines and Propellers......................................................................... 8-1 9. Power Plant Troubleshooting................................................................................. 9-1 10. Power Plant Inspection, Repair, and Testing ......................................................... 10-1 APPENDIX I. Glossary ................................................................................................................. AI-1 INDEX.........................................................................................................................................INDEX-1 CHAPTER 1 JET ENGINE THEORY AND DESIGN CHAPTER OBJECTIVES After completing this chapter, you will be able to: State the theory of jet propulsion. Identify the two types of engine designation standards. Identify the different types of engines and their Identify the common terms and variables major assemblies. effecting engine performance. Every rating or specialty has a language of the velocity of the water, giving us the term, its own. The Aviation Machinist’s Mate is no “a jet of water.” different. To be a good technician, you must learn and understand the language (terms and theories) Another example of the theory of jet propul- necessary for a thorough understanding of your sion is an inflated balloon. With the opening in specialty. With this basic understanding, you will the balloon closed (fig. 1-1) there is no action develop the skills to recognize, analyze, and because the pressure of the gas inside the balloon correct problems with jet engines. Without it, you is equal in all directions. When you allow the become a “parts changer” unable to recognize possible reasons for the problem and analyze them. This chapter explains the basics necessary for the Aviation Machininst’s Mate to build a strong foundation. You’ll learn the theory, terms, types of engines, and major parts of jet engines. BASIC THEORY OF JET PROPULSION Jet propulsion is the propelling force gen- erated in the direction opposite to the flow of a mass of gas or liquid under pressure. The mass escapes through a hole or open- ing called a jet nozzle. A familiar example is the nozzle at the end of a fire hose. The nozzle forms a smaller passageway through which the water must flow. The nozzle increases Figure 1-1.-Balloon example of restricting jet propulsion. 1-1 opening to release the air (fig. 1-2) the balloon Obviously, propulsion depends solely upon moves, Its movements appear to be in all direc- internal conditions. The container does not “push tions. Actually, it is always moving in the opposite against” external air. In fact, a complete vacuum direction from the open end where the air is would produce greater force. This is the basic exiting. operating principle for all jets. The rocket Let’s look at the balloon example from the (propulsion unit) is one of the four main classes mechanics point of view. Igniting a hydrocarbon of jet engines. fuel (compound containing only hydrogen and Before we move on to the physical principles carbon) and oxygen in a closed container (fig. 1-3) of jet engines, let’s review the basic principle to releases heat. The burning fuel causes the trapped the three other types of jet engines. gases to expand rapidly. Since the force of the pressure is balanced, the container does not move. THE ATHODYD (RAMJET) ROCKET Suppose you attach a plain cylinder with open ends under the wing of an aircraft flying at high When combustion takes place in a container, speed. Air enters the front of the duct and leaves the expanding gases rush out at a high velocity at the rear. Nothing increases the force of flow (fig. 1-4). The release of internal pressure through the duct. There is a loss of energy because at the nozzle end of the container leaves an of skin friction and airflow disturbances at the unbalanced pressure at the other end. The entrance and exit. released pressure propels the container (rocket) If you add heat energy to the air as it passes in the direction opposite of the exhaust gases. through the duct, the air would expand and increase the jet velocity. (Figure 1-5 shows a duct Figure 1-4.-Principle of jet propulsion. Figure 1-2.-Balloon example of jet propulsion theory. Figure 1-5.-Thermal duct with heat added externally to Figure 1-3.-Combustion in a closed vessel. accelerate the airflow. 1-2 heated externally by burning oil sprays.) The THE PULSEJET ENGINE amount of heat you can add is largely dependent upon the pressure of the air treated. A simple The “intermittent impulse” jet engine (fig. 1-8), method of raising the pressure is to pass the air known as the aeropulse or pulsejet improves through a DIVERGENT entry nozzle. A divergent compression by sacrificing the principle of con- entry nozzle decreases the velocity of the air and tinuous power generation. The pulsejet is like the increases the pressure. This also provides a for- ramjet, but with a series of nonreturn shutter ward pressure wall for the jet to react. A valves. Fuel injection nozzles located just aft of CONVERGENT exit nozzle further increases the the shutter valves provide fuel. As the engine jet velocity. The simple gas unit (fig, 1-6) created travels through the air, pressure on the nose opens has little practical use because of the following: the valve and rams air into the duct, mixing air with fuel. Igniting the combustible mixture creates 1. Air compression depends solely on “ram a high pressure (from the expanding gases), clos- effect.” ing the valves. The violent ejection of the gases 2, A limited amount of heat is added. forms a relatively low-pressure area inside the 3. Considerable heat is lost by radiation. duct, admitting a fresh charge of air through the The next step is to improve the method of flat spring valves. Because of the temperature of adding heat, through internal combustion. the duct and the return of part of the flaming Figure 1-7 shows a divergent-convergent duct. exhaust gases, the rest of the charges burn without Fuel is injected and burned, releasing heat directly an igniter plug. This operating cycle or pulsations into the airstream. This simple “Aero THermO creates a loud buzzing sound. “Buzz bomb” DYnamic Duct” (ATHODYD) or RAM JET is described an early application of this unit, the used in remotely piloted vehicle (RPV) and cruise German V-1 flying bomb. missiles. We learned the basic principle of jet propul- sion with the rocket. The ram jet taught us that adding heat would expand the gases and increase velocity. It also showed the amount of heat that is possible to add is dependent upon the amount Figure 1-6.-A convergent discharge nozzle. Figure 1-8.-The aeropulse or pulsejet. Figure 1-7.-The ramjet engine. 1-3 of air available. The pulsejet proved that the more Air from the compressor section goes to the air an engine could compress the greater the power combustion chamber. This is the area where fuel (thrust) it produced. Now we will learn how a gas and air are mixed and ignited. The burning of this turbine engine increases air compression to fuel/air mixture produces hot, expanding gases develop the tremendous amount of thrust used in that rush into the turbine rotors. The turbine modern aircraft. rotors attach to the same shaft as the compressor rotors; so the turbine drives the compressor making the engine self-sustaining. Finally, the GAS TURBINE ENGINE exhaust gases exit the engine (fig. 1-10) as jet thrust. The compressor is the greatest single reason Now that you have a basic understanding of the gas turbine engine runs and produces the jet propulsion, let’s look at the physical principles thrust needed in modern aircraft. We will discuss of jet propulsion. compressors in greater