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MAINTENANCE MANUAL
REGULATEDPRESSURE ENGINE GEARBOX PRESSURE
CONTROLLER
SEE AAMBIENT HIGH PRESSURE
SHUTOFF VALVE
CONTROLLER PRV ACTUATOR+CLOSE 1
PRESSURE TUBE -C0MM0N 2
+0PEN 3 CASE
4
GROUND LATCHING S/OSOLENOID
SUPPLY ACTUATOR SERVO
(SHOW OPEN)
PRESSURE PRESSURE DOWNSTREAMREGULATED
ELECTRICALPRESSURE TUBE CONNECTOR
SCHEMATIC
UPSTREAM SUPPLY
A
PRESSURE TUBEENGINEGEARBOXPRESSURE
FWD
CONTROLLER
ELECTRICAL
CONNECTOR
A
Pressure Controller
Figure 9
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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B. The engine bleed air and the fan air flow at approximately 90 degree angles to each other in the precooler. The cooler fan air removes heat from the bleed air through the fins and cooling plates. Then the bleed air goes through the PRSOV and into the airplane pneumatic ducts.
8. Fan Air Modulating Valve (Fig. 11)
________________________
A. The fan air modulating valve is installed on the right side of the precooler. The valve is a nine inch diameter pneumatically-operated butterfly valve. It is spring loaded in the open position.
B. The precooler outlet servo pressure is used to operate the fan air modulating valve. When the valve receives the pneumatic signal from the fan air temperature sensor, it will move toward the closed position. The diaphragm, attached to the valve control lever, monitors the signal pressure. The movement of the control lever is transmitted to a servo poppet. The servo poppet controls the amount of closing force on the actuator piston.
C. There is a locking crank on the actuator to permit the valve to be operated manually. The valve can be deactivated in the 45° position with a positioning screw (AMM 36-12-04/201).
9. Fan Air Temperature Sensor (Fig. 12)
__________________________
BLEED AIR
AIR SUPPLY OUTLET
PRECOOLER FAN AIR
SEE A OUTLET
HIGH/INTERMEDIATE
PRESSURE INLET
FAN AIR
INLET
(ROTATED FOR CLARITY)
A
Air Supply Precooler
Figure 10
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747-400 MAINTENANCE MANUAL
FAN AIR MODULATINGVALVE
SEE A
PRECOOLER
LOCKING CRANK ELECTRICAL FILTER
CONNECTION BLOCK
ACTUATOR FWD
FROM FAN AIR TEMP SENSOR A
SHROUD AMBIENT COOLING PORT
CONTROL POPPET DISK
COOLING SHROUD
FAN AIR
MODULATING VALVE
B
OPEN
POSITION
SWITCHES
CLOSED
OPEN
AMBIENT
COOLING AIR
FAN
AIR
SCHEMATIC CAM
FEEDBACK
B
Fan Air Modulating Valve Figure 11
FAN AIR MODULATING VALVE
SEE B
PRESSURE REGULATING CONTROL
CLOSING PRESSURE FROM FAN AIR TEMP SENSOR
VALVE CONTROL LEVER
AMBIENT
PRE-COOLER
BLEED
AIR
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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747-400
MAINTENANCE MANUAL
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