Engine bleed air flows through the precooler coils. Fan air flows over the precooler coils. This decreases the temperature of the engine bleed air.
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777 AIRCRAFT MAINTENANCE MANUAL
ENGINE AIR SUPPLY SYSTEM -PRECOOLER
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ENGINE AIR SUPPLY SYSTEM -FAN AIR MODULATING VALVE
Purpose
The fan air modulating valve (FAMV) controls the quantity of fan air that goes to the precooler.
Location
The FAMV is on the inside of the right thrust reverser half. The valve attaches to the FAMV inlet ducting and the transition ducting.
Physical Description
The FAMV is spring-loaded to the open position. It is pneumatically controlled and operated. The FAMV has these parts:
*
Manual override and position indicator assembly
*
Control pressure line connection
*
Valve body
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Valve disc
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Actuator
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Electrical lead and connector
*
RVDT.
Training Information Point
The FAMV has a flow direction arrow to help install it correctly.
The manual override and position indicator assembly locks the FAMV in the open or closed position. The valve must be locked in the closed position for removal or installation.
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ENGINE AIR SUPPLY SYSTEM -FAN AIR MODULATING VALVE
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ENGINE AIR SUPPLY SYSTEM -FAMV -TRAINING INFORMATION POINTS
General
The manual override and valve position indicator assembly lets you manually lock the valve closed or open and gives actual valve position.
Location
The assembly attaches to the valve body opposite from the actuator.
Physical Description
The assembly has these parts:
*
Valve shaft
*
Position indicator
*
Lock plunger
*
Locking cam.
Functional Description
The position indicator and locking cam attach to the valve shaft. As the valve shaft turns so does the indicator and locking cam.
The locking cam has two slots. One is for the valve locked OPEN position and one is for the valve locked CLOSED position.
The lock plunger has two positions: in and out. The in position lets control pressure go to the valve actuator and permits free movement of the valve. The out position blocks control pressure, vents pressure from the valve actuator, and stops movement of the lock cam and valve. The plunger is spring-loaded out. The plunger is also threaded so you can push it in and turn it until it stays in (position for usual valve operation).
Operation
When the valve is in the open position, you turn the lock plunger counterclockwise (CCW) until it moves out to lock the valve open. To lock the valve closed, you first turn the lock plunger CCW until it moves out. Then push the plunger in and turn the valve shaft towards CLOSED position. The lock cam holds the plunger down as you turn the valve shaft to the closed position. The plunger moves out and stops movement of the cam and valve shaft when the valve is in the closed position.
You unlock the valve from the locked OPEN or CLOSED positions when you push the lock plunger in and turn it clockwise. The plunger must be torqued to make sure control pressure does not leak when you unlock the valve for usual operation.
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ENGINE AIR SUPPLY SYSTEM -FAMV -TRAINING INFORMATION POINTS
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ENGINE AIR SUPPLY SYSTEM -HIGH PRESSURE AND FAN AIR CONTROLLER
Purpose
The high pressure and fan air controller (HPFAC) regulates the control pressure that goes to the FAMV actuator and the HPSOV actuator.
Location
The HPFAC is on the lower right side of the engine fan case at the 5:00 position.
Physical Description
The HPFAC is an electropneumatic controller. The controller has these parts:
*
Two electrical connectors (FAMV and HPSOV)
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Two control pressure line connectors (FAMV and HPSOV)
*
One supply pressure line connector and filter
*
Two torque motors (TM) (FAMV & HPSOV)
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Two reference pressure regulators (FAMV & HPSOV)
*
Electrical heater.
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