*
Locking crank/position indicator
*
Shutoff solenoid
*
Torque motor
*
Valve disc
*
Valve body
*
Plug and filter (internal)
*
Locking plug.
The valve is electrically controlled and pneumatically operated. This valve is not spring-loaded open or closed. The valve is fail safe off, if no power goes to the torque motor.
EFFECTIVITY
BEJ ALL
Functional Description
Control air pressure pushes on the open side of the pneumatic actuator to move the valve to open. Supply air pressure pushes on the close side of the pneumatic actuator to move the valve towards close. A change in the amount of the control air pressure makes the valve control trim air pressure downstream of the valve. The CTC uses the torque motor to set the amount of control air that goes to the pneumatic actuator.
The torque motor operates like a spring-loaded-closed modulating valve. With no current to the torque motor, it is spring-loaded to stop control air and vents control pressure from the open side of the pneumatic actuator. This lets supply pressure move the actuator to close the trim air PRSOV (fail safe off). The amount of current that goes to the torque motor is directly related to the value to which the trim air PRSOV controls trim air pressure to. When the CTC increases current to the torque motor, control pressure to the pneumatic actuator increases, the valve disc opens more and downstream pressure increases.
The ASCPC uses the solenoid to give backup shutoff control for the trim air PRSOV. With no voltage to the solenoid, it is spring-loaded to let control pressure go from the torque motor to the open side of the pneumatic actuator. With 28v dc to the solenoid, it stops control air and vents control pressure from the open side of the pneumatic actuator.
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AIR CONDITIONING -TRIM AIR PRESS REGULATION AND SHUTOFF CTRL -TRIM AIR PRSOV
See the page on the functional description of the trim air pressure regulation and shutoff control section for more information on trim air pressure control.
Training Information Point
You can use the locking plug and locking crank/position indicator to lock the trim air PRSOV closed. When you remove the locking plug from its stowed position, control pressure is vented.
EFFECTIVITY BEJ ALL 21-62-00
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D633W101-BEJ Sep 05/2002
AIR CONDITIONING -TRIM AIR PRESS REGULATION AND SHUTOFF CTRL -TRIM AIR PRSOV
EFFECTIVITY BEJ ALL 21-62-00
Page 7
D633W101-BEJ Jan 05/2002
AIR CONDITIONING -TRIM AIR PRESS REGULATION AND SHUTOFF CTRL -TRIM AIR PRESSURE SENSOR
Purpose
The trim air pressure sensor monitors air pressure at the outlet of the trim air pressure regulating and shutoff valve.
Physical Description
The sensor is an electronic device. It connects to the air duct through a small pressure line.
Location
The sensor mounts on the keel beam adjacent to the trim air pressure regulating and shutoff valve.
EFFECTIVITY BEJ ALL 21-62-00
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D633W101-BEJ Jan 05/2002
AIR CONDITIONING -TRIM AIR PRESS REGULATION AND SHUTOFF CTRL -TRIM AIR PRESSURE SENSOR
EFFECTIVITY BEJ ALL 21-62-00
Page 9
D633W101-BEJ Jan 05/2002
777 AIRCRAFT MAINTENANCE MANUAL
THIS PAGE IS INTENTIONALLY LEFT BLANK
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Page 10 D633W101-BEJ Jan 05/2002
AIR CONDITIONING -TRIM AIR PRESS REGULATION AND SHUTOFF CTRL -FUNCTIONAL DESCRIPTION
CTC Control
The left cabin temperature controller (CTC) gives usual control of the trim air pressure regulating and shutoff valve (PRSOV). The left CTC uses information about airplane conditions to calculate the position of the trim air PRSOV. These components and systems give information to the left CTC:
*
AIR COND RESET switch, resets latched conditions in the CTCs
*
L TRIM AIR switch, in or out position
*
Remote cabin pressure sensor, backup source for cabin pressure
*
AGS, airplane on the ground condition used during the ASCPC preflt test
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AIMS, ground test conditions and indications
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WES, stall condition
*
Left trim air pressure sensor, trim air supply duct pressure
*
ASCPCs, primary source for cabin pressure and alternative close control for the trim air PRSOV.
The left trim air PRSOV opens only if all of these conditions occur:
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