FUEL
SCHEDULING
VALVE
(PNEUMATIC
GOVERNOR)
AIR-PRESSURE-RATIO
SOLENOID VALVE
FILTER
MECHANICAL
ADJUSTMENT
GOVERNOR
COVER
AUXILARY FUEL SHUT
OFF SOLENOID VALVE
EXTERNAL VIEW
FUEL SCHEDULING
BALL VALVE
VALVE DIAPHRAGM
REMOVABLE SEAT
DRAIN
DIAPHRAGM
FILTER
RETAINER
PIN
ALTERNATE FUEL INLET
CRACK
HIGH PRESSURE RELIEF VALVE
PRESS
ADJUST
FUEL
INLET
PUMP
MECHANICAL
LIP
GOVERNOR
SEAL
DIAPHRAGM
HIGH SPEED
ADJUST
ADJUSTMENT
INPUT
COVER
SHAFT
LOW
FLYWEIGHT
SPEED
BUSHINGS
CONTROL-
ADJUST
FLYWEIGHT
FILTER
AIR PORT
CAGE
AIR-PRESSURE-RATIO
MECHANICAL GOVERNOR
SOLENOID VALVE
ASf12017
BYPASS VALVE
CUTAWAY VIEW
Figure 12-17.--Fuel control assembly.
actuating solenoid valve, and a hydraulic piston servo
constant shaft output speed under varying conditions
assembly. One other component of the bleed-air
of engine load, inlet temperature, and discharge
system is the load control thermostat located in the
temperature. Selection of the output air switch
turbine exhaust duct.
energizes the normally closed solenoid valve (fig.
12-18) that opens to bleed air to the servo valve. The
The main component for surge control is the
hydraulic servo valve positions the butterfly through a
pneumatic shutoff valve (air scheduling valve), which
crank, piston rod, and piston actuator. Modulation of
incorporates a poppet valve, a spring-loaded piston,
and a solenoid valve. Other components of the surge
the butterfly position is performed by the bleed action
control system are a pressure-differential probe and a
of the load control thermostat that bleeds air from the
cutout switch, which is remotely mounted in the
variable pressure regulator; modification of the load
enclosure.
control thermostat action to accommodate variations
in inlet air temperature is provided by action of the
The bleed-air components function to provide
valve thermostat on the pressure regulator.
modulation of bleed airflow while maintaining
12-20
