ENGINE ACCESSORIES
All engine-driven accessories, with exception to the propeller tachometer-
generator and the propeller governors, are mounted on the accessory
gearbox at the rear of the engine. These accessories are driven from the
compressor turbine by a coupling shaft extending through a conical tube in
the center section of the integral oil tank. The propeller tachometer generator
and the propeller governors are mounted on the propeller reduction gearbox.
Oil Pump
Pressure oil is circulated from the integral oil tank through the engine
lubrication system by a self-contained, gear-type pressure pump located in
the low point of the oil tank. The oil pump is installed in a cast housing which
is bolted to the forward face of the accessory diaphragm, and is driven by the
accessory gear drive shaft. The body of the oil pump incorporates a circular
mounting boss to accommodate a check valve, located in the end of the lter
housing. A second mounting boss on the pump includes a pressure relief
valve.
Fuel Pump
The engine-driven fuel pump is mounted on the accessory gearbox at the 2
o’clock position. The pump is driven through an accessory drive shaft and
splined coupling. The coupling splines are lubricated by an oil mist from
the auxiliary gearbox through a hollowed-out section of the accessory gear
drive shaft. Another splined coupling extends the drive to the fuel control
unit, which is installed on the rear face of the engine driven fuel pump. Fuel
is routed from the oil-to-fuel heater into the fuel pump through a 74-micron
inlet screen. Then, fuel enters the pump gear chamber where it is boosted
to a high pressure and delivered to the fuel control unit through a 10-micron
pump outlet lter. A bypass valve and cored passages in the pump casing
allow unltered high pressure fuel to ow from the pump to the fuel control
unit, should the outlet lter become clogged. An internal passage, beginning
at the mating surface with the fuel control unit, returns bypass fuel from
the fuel control unit to the pump inlet, downstream of the inlet screen. A
pressure regulating valve is installed in this internal passage to accomplish
pressurization of the pump gear bushings.
tachometer-generator drive and mount pad is located at the 5 o’clock position
on the accessory gearbox and is driven from the internal scavenge pump.
Rotation is counterclockwise with a drive ratio of 0.1121:1.
Propeller Tachometer Generator
The propeller tachometer-generator produces an electric current which is
used by the propeller RPM indicator to indicate propeller RPM. The propeller
tachometer-generator drive and mount pad is located on the right side of the
propeller reduction gearbox case and has a clockwise rotation at a ratio of
0.1264:1.
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