FAN AIR FAN AIR TEMPERATURETEMPERATURE SENSORSENSOR
(INSULATION REMOVED SEE A FOR CLARITY)
POPPET AND SWITCH PRESS BITE TEST PORTNOZZLE TO FAN AIR MODULATING VALVE CLOSING PRESSURE TUBE SIGNAL PRESSURE A FWDTUBE COOLING AIR STRUT ACCESS
SWITCH PRESS BITE LEVER SPRINGS COMPENSATING DIAPHRAM SENSOR CONTROL POPPET FILTER REGULATOR POPPET BALL
TEMP PROBE SENSOR TEMP BITETEMP INCREASING
FROM PRECOOLER BLEED AIR TO PRESSURE REGULATING INLET AND SHUTOFF VALVE
SCHEMATIC
A
Figure 12 Fan Air Temperature Sensor
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A
747-400
MAINTENANCE MANUAL
A. The fan air temperature sensor is installed on the pneumatic duct in the left side of the strut. The sensor body has a lever and a crank that are operated by a bimetallic-temperature probe. The temperature probe extends into the pneumatic duct. The sensor also has an insulation blanket.
(1) The fan air temperature sensor controls the servo pressure that controls the fan air modulating valve. The bimetallic-temperature probe in the pneumatic duct connects the compensating springs to the control lever. The temperature changes in the duct cause the temperature probe to change the force on the control lever. The movement of the control lever causes the poppet to open or close. This will change the pressure signal that is sent to the fan air modulating valve.
10. Pressure Regulating and Shutoff Valve (PRSOV) (Fig. 13)
_____________________________________________
A. The PRSOV is installed in the strut. The valve is made of the following components:
-a six-inch butterfly valve
-an actuator assembly
-
a pressure control assembly
-
a reverse flow prevention system
-an overtemperature control system
-two pressure switches that send signals to the ASCTU
-an open and a closed position switch that sends signals to the ASCTU
-a control system latching solenoid
-an electrically operated reverse flow solenoid.
(1) The PRSOV also has a manual override that permits you to put the valve in the open, closed, or locked closed position. The position switches inside the valve are operated by an arm on the valve manual override. The switches send signals to the ASCTU.
B. PRSOV Operation (Fig. 14)
(1)
When the OFF/AUTO solenoid is in the OFF position, the servo pressure is sent to ambient. With no servo pressure, the valve will move to the spring loaded closed position.
(2)
When the OFF/AUTO solenoid is in the AUTO position, the valve can be opened by pneumatic air. The valve opens when the air pressure is more than the spring force. This causes the pneumatic actuator to open the valve. The operation of the valve requires a minimum pressure of 10 psi. The valve servo pressure is controlled by these three functions: pressure control, temperature control, and reverse flow check control.
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A
747-400
MAINTENANCE MANUAL
PRESSURE REGULATINGAND SHUTOFF VALVE (PRSOV) SEE A PRSOV SEE B
LOCKING PIN (STOWED POSITION) STRUT
FWD
A ACCESS
SHUTOFF
TEMPERATURE SOLENOID
SENSOR
MAIN FILTER
POSITION
SWITCHES
TEMPERATURE SENSOR PROBE DISK HEX FOR MANUAL OPERATION (VALVE SHAFT EXTENSION)
B
Figure 13 Pressure Regulating and Shutoff Valve
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