AIR CONDITIONING -CABIN PRESSURE CONTROL SYSTEM -AIR SUPPLY CABIN PRESSURE CONTROLLER
EFFECTIVITY BEJ ALL 21-31-00
Page 5
D633W101-BEJ Jan 05/2002
AIR CONDITIONING -CABIN PRESSURE CONTROL SYSTEM -OUTFLOW VALVE -INTRODUCTION
Purpose
Forward and aft outflow valves control the flow rate of pressurized cabin air out of the airplane.
Location
The aft outflow valve is adjacent to the aft waste tank. Access is through the aft waste tank enclosure panel at the rear of the bulk cargo compartment.
The forward outflow valve is below the P110 left power management panel in the main equipment center.
Physical Description
Both forward and aft outflow valves are the same. The valve weighs approximately 30.25 lbs (13.72 kg). Each valve has these assemblies:
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Actuator assembly
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Frame assembly
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Gearbox assembly.
The actuator assembly has these line replaceable components:
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Outflow valve control unit
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Left outflow valve motor
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Right outflow valve motor
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Outflow valve gearbox assembly.
The frame assembly has these parts:
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Door (2)
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Nut plate (18)
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Push rod (2).
The valve control unit is a two channel controller. The unit has these parts:
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Airplane electrical connectors (3)
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RVDT electrical connector (1)
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Motor electrical connector (2).
The gearbox assembly has reduction gears, two internal RVDTs and an actuator crank.
Training Information Point
You can remove the forward outflow only from inside the airplane. You can remove the aft outflow valve from outside the airplane or from inside the airplane.
To prepare for pressurized flight with an outflow valve that does not operate, set the position of the valve to a specified position, then open the applicable circuit breakers.
To prepare the airplane for unpressurized flight with outflow valves that do not operate, lock the valves open.
EFFECTIVITY BEJ ALL 21-31-00
Page 6
D633W101-BEJ Sep 05/2002
AIR CONDITIONING -CABIN PRESSURE CONTROL SYSTEM -OUTFLOW VALVE -INTRODUCTION
EFFECTIVITY BEJ ALL 21-31-00
Page 7
D633W101-BEJ May 05/2002
AIR CONDITIONING -CABIN PRESSURE CONTROL SYSTEM -OUTFLOW VALVE -FUNCTIONAL DESCRIPTION
General
The outflow valve control unit (VCU) has two channels. The left channel controls the left outflow valve motor, and the right channel controls the right outflow valve motor. Each channel has a separate power supply.
The left channel has an interface with the left ASCPC and the right channel has an interface with the right ASCPC. The channels have interfaces with the ASCPC on an ARINC 429 bus. For manual mode operation, both channels have an interface with the bleed air/pressurization panel.
Outflow Valve Control Unit
The valve control unit has these functions:
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Controls motor speed and position
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Monitors valve position (RVDTs)
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Supplies BITE.
In the automatic mode, the motor control logic uses information from the related ASCPC to set motor speed and the position of the outflow valve. The valve can open or close completely in less than 10 seconds for the automatic mode. ASCPC information usually causes the VCU to change motor speed for smooth changes in cabin pressure.
In the manual mode, the motor control logic uses the signal from the outflow valve manual switches on the bleed air/ pressurization panel to open or close the outflow valve. The valve can open or close completely in approximately 27 seconds for the manual mode.
Two RVDTs that are part of the gearbox send valve position information back to the VCU and ASCPCs in automatic and manual modes.
Outflow Valve Motors
A brake solenoid in the motor stops movement when the motor does not have a command to turn. Sensors in the motor give rotor position information to the VCU. The VCU uses rotor position to monitor motor speed. Both motors mechanically connect to the gearbox.
Gearbox
The gearbox changes the motor inputs to door and RVDT positions.
BITE
The VCU continuously monitors for outflow valve faults. If the VCU finds a fault, the VCU supplies the fault data to the ASCPCs for indication and to keep in memory.
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