CHAPTER 4
JET AIRCRAFT FUEL
AND FUEL SYSTEMS
CHAPTER OBJECTIVES
After completing this chapter, you will be able to:
Identify the types of fuels used in aviation and
Identify the types and operation of engine fuel
recognize the operational properties required
system parts.
in aviation fuels.
Identify procedures for troubleshooting
malfunctions in airframe and engine fuel
systems.
Identify the parts and recognize a typical air-
frame fuel system. Also recognize the safety
Identify the major safety precautions, and
precautions required in airframe fuel system
recognize the basic procedures for fuel cell
operation.
removal and installation.
The jet engine fuel system usually includes an
INTRODUCTION
emergency system to supply fuel to the engine in
case of main system failure. In some cases, the
The purpose of the fuel system is to deliver
emergency system is a duplicate of the main
a uniform flow of clean fuel under constant
system. However, in others the emergency system
pressure to the engine under all operating
is not fully automatic and must be controlled
conditions. To accomplish this task the fuel
by the pilot. With the nonautomatic type of
system must be properly maintained. The AD's
emergency system, the pilot must accelerate and
responsibility to maintain and troubleshoot the
decelerate slowly, or there will be danger of rich
fuel system include the following:
blowout, lean blowout, stall, or overheating of
the combustion and turbine areas.
1. Knowing the different types of fuels and
Both the airframe fuel system and engine fuel
their characteristics.
system, as well as the type, designation, and
2. Knowing the different types of aircraft and
requirements of the aircraft fuels, are discussed
engine fuel systems and their parts.
in this chapter.
In general, aircraft fuel systems are divided
into two parts:
FUELS
1. The airframe fuel system consisting of fuel
For many years it was popularly believed that
tanks, float-operated transfer valves, selector and
gas turbine engines could burn any type of fuel,
shutoff valves, and fuel tank boost pumps.
from crude oil to aviation grade 115/145 gasoline.
2. The engine fuel system includes some
Of course, this is not true. Because of the wide
combination of different parts. These parts are
range of operating conditions and high rate of fuel
filters, fuel control units, engine-driven fuel
consumption, jet engines require specific fuels to
pumps, flow dividers, pressurizing valves, drain
operate efficiently and maintain a reasonable
valves, afterburner fuel controls, and fuel nozzles
engine service life. Various grades of jet fuels were
or injectors.
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