as a structural support between the combustor assembly and the reduction drive. The cylindrical,
contoured casting is open at both ends and is equipped with a wire mesh screen to cover the intake duct.
Intake air passes through the inlet assembly and into the impeller. The air then passes through the
diffuser to the combustion section where it flows between the outer walls of the housing and
combustion liner. At the end of the liner, the flow reverses direction and enters the combustion
chamber. After combustion, the gas exits at the forward end of the combustion liner through a nozzle
and the turbine wheel.
6.8.
FUEL SYSTEM
The T62T-2A and T62T-16A have identical fuel systems. The fuel system is illustrated in
figure 6.6. The system consists of an inlet filter, fuel control, six main fuel injectors, a start fuel nozzle,
main and start fuel solenoid valve, a fuel pressure switch, and the necessary plumbing. Fuel for the
APU is supplied from the same source that supplies the engines.
6.9.
FUEL SYSTEM OPERATION
The accessory drive gear drives both the fuel pump and the acceleration control assembly to
deliver fuel to the engine at approximately 300 psi. Fuel is directed through the inlet filter, in the fuel
pump, through the outlet filter with the fuel pump, and into the governor housing. A relief valve
installed in the governor housing bypasses excess fuel from the pump outlet to the pump inlet.
During engine starting, fuel is forced through internal passages to the fuel pressure switch.
Normally closed, the fuel pressure switch opens on increasing fuel pressure at 100 to 120 psi. When
open it actuates the start fuel solenoid valve and the main fuel solenoid valve to the open position, and
completes the ignition circuit. Combustion takes place in the combustor when atomized fuel from the
start fuel nozzle is ignited by the spark plug.
At 90 percent speed, fuel flow to the start fuel nozzle is cut off. The main fuel injectors
continue to supply fuel to the combustor. Fuel flow to the main fuel injectors is increased in direct
proportion to increasing air pressure, thus eliminating the possibility of over temperature or compressor
surge during acceleration.
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