Fuel Control. The fuel control, which is secured to
PURGE VALVE ASSEMBLY. A start fuel nozzle
the forward face of the governor, contains a minimum
purge system is used to prevent the buildup of varnish
fuel flow orifice, an acceleration needle adjustment, a
resulting from fuel evaporation. The purge system
ported fuel metering valve assembly, a governor
consists of a purge valve assembly and rigid tubing
adjusting plunger, a governor tension lever, a bearing
connected to the start fuel nozzle. The purge valve
and valve assembly, and an outlet port. The aft end of
assembly is threaded into a special fitting that is installed
the fuel metering valve extends into the fuel control
on the compressor discharge pressure port.
housing. The spring retainer, which fits over the end of
During an APU start, the start fuel solenoid valve
the fuel metering valve, is held in position around the
opens and fuel pressure forces the piston in the purge
metering valve by flanges on the spring retainer and the
valve to one side in the valve chamber. This allows fuel
bearing and valve assembly. The piston of the bearing
to flow through the start fuel nozzle. At approximately
and the valve assembly fits into the center of the fuel
65 percent of engine speed, the start fuel solenoid valve
metering valve assembly.
closes to cut off fuel pressure. A return spring transfers
Bellows Cover Assembly. The bellows cover
the piston in the purge valve to the purge position. In the
assembly is secured to the top of the governor housing
purge position, compressor discharge air flows through
and consists of two interconnected sections. These
the start fuel nozzle to clear the nozzle of residual fuel.
sections are the diaphragm and bellows housing and a
The residual fuel is directed to the combustor to be
lever housing. The diaphragm is located between the
burned.
pressure sensing portion of the bellows cover assembly
FUEL MANIFOLD ASSEMBLY. The fuel
and the lever housing which, through a mechanical
manifold assembly consists of a brazed assembly of six
connection, operates the differential pressure regulating
stainless-steel lines, each terminated with a 0.016-inch
valve in the governor housing. A diaphragm adjusting
orifice at the exit end. The main fuel transfer line is
screw is installed in the pressure sensing portion of the
connected between the main fuel solenoid valve outlet
bellows cover assembly.
and the distribution boss on the fuel manifold.
FUEL DISTRIBUTION SYSTEM. A single
The fuel manifold filter assembly contains a
low-pressure fuel line is necessary to supply the engine's
wire-cloth element. The filter is internally installed in
fuel system from an external source (5 to 40 psig with
the housing at the inlet end of the fuel manifold assembly
200 pounds per hour minimum flow). The turbine
and held in place by a retaining ring. The filter provides
engine's high-pressure fuel system has stainless-steel
a 10-micron, in-line filtration of the fuel before it enters
piping that connects the engine acceleration control
the combuster.
assembly with the fuel solenoid valves, compressor
pressure outlet port, purge valve, start fuel nozzle, and
ACCELERATION CONTROL ASSEMBLY.
fuel manifold assembly. An additional stainless-steel
The engine acceleration control assembly consists of
line supplies compressor discharge pressure to the load
three components secured together: (1) the governor,
control valve.
(2) the fuel control, and (3) the bellows cover assembly.
Governor. The governor includes a pressure relief
Lubricating Oil System
valve, a governor control spring, a flyweight assembly
mounted in a drivehead assembly, and a matched ball
The lubricating oil system provides lubrication to
bearing set, which supports the internally splined shaft
the high-speed input pinion, reduction and accessory
end of the drivehead assembly. The flyweight assembly
is located between the bearing and valve assembly and
lubrication system consists of the following parts:
the governor drivehead assembly. It is pivot-mounted
against the governor drivehead assembly and the
Oil pump
bearing plate of the bearing and valve assembly.
Oil filter and bypass relief valve
The threaded ports in the governor provide
attaching points for the fuel line to the main fuel solenoid
Oil pressure relief valve (main)
valve and the relief valve. The governor also includes a
Oil pressure switch
ported differential pressure regulating valve, which
maintains a differential pressure across the fuel metering
Oil temperature switch
valve ports proportional to compressor discharge
pressure and controls fuel flow to the APU.
Oil distribution ring assembly
