CHAPTER 6
ENGINE AND AIRFRAME RELATED SYSTEMS
CHAPTER OBJECTIVES
After completing this chapter, you will be able to:
Recognize the operating principles of
Recognize the different types of ignition
hydraulic systems.
systems.
Identify the sources and prevention of
Identify the types and operation of jet engine
starters, and recognize the procedures for safe
operation of aircraft starting equipment.
Recognize systems using fuel for hydraulic
control.
Recognize the purpose of the bleed-air
systems.
Recognize aircraft power plant electrical
systems and their relationship to other aircraft
Recognize the use of the auxiliary power unit
(APU).
systems.
ADs deal with a large variety of aircraft
systems. Hydraulics apply to fuel and oils systems
systems. You need a knowledge of hydraulics and
too, so a knowledgeable AD must be familiar with
electricity because of these different systems. You
hydraulic principles.
must be familiar with such systems as ignition,
Pascal's law states that "any force applied to
start, bleed-air, and auxiliary power unit systems.
a confined liquid transmits undiminished in all
This chapter introduces you to basic hydraulics,
directions." This pressure acts at right angles to
electricity, and the related systems that the Avia-
the walls of the container and exerts equal forces
tion Machinist's Mate regularly maintains.
on equal areas. A 100-pound force will result from
5 pounds per square inch of pressure exerted
against a 20-square-inch area. Figure 6-1 shows
BASIC HYDRAULICS
a simple hydraulic mechanism that demonstrates
Hydraulics is the science of liquid pressure and
these principles in operation.
flow. In its application to aircraft, hydraulics is
the action of liquids under pressure used to
operate various mechanisms. All modern naval
aircraft use hydraulic systems and hydraulic
components.
The word hydraulics is from the Greek word
for water. Hydraulics originally meant the study
of physical behavior of water at rest and in
motion. Today the meaning includes the physical
behavior of all liquids. A liquid is any fluid whose
particles have freedom of movement among them-
selves but remain separate. In aviation, hydraulics
usually means the "red fluid" used to operate
Figure 6-1.-Simple hydraulic mechanism.
landing gear and flight control or propeller
6-1
