The interlock actuators can extend or retract in less than 1 second; make sure you are clear of the interlock actuators and the moving mechanism.
EFFECTIVITY BEJ ALL 78-34-00
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D633W101-BEJ May 05/2003
TRAS -REVERSE THRUST LEVER INTERLOCK ACTUATOR
EFFECTIVITY BEJ ALL 78-34-00
Page 41
D633W101-BEJ May 05/2003
PW4000 SERIES ENGINES
777 AIRCRAFT MAINTENANCE MANUAL
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78-34-00
Page 42 D633W101-BEJ May 05/2003
TRAS -FUNCTIONAL DESCRIPTION -CONTROL
General
When the engine fire switch is in, the thrust reverser actuation system (TRAS) uses electrical power from the left 28v dc bus to control the extension and retraction of the thrust reverser sleeves.
These components must get control signals before the thrust reversers can move:
*
Sync lock solenoid valve
*
Directional control solenoid valve
*
Isolation solenoid valve.
These components send the control signals:
*
Sync lock switch through the sync lock relay
*
Directional control valve (DCV) switch
*
Electronic engine control (EEC).
Extend
When you move the reverse thrust lever to the reverse idle position, the sync lock and directional control valve switches move to the extend position. The sync lock switch sends a control signal to the sync lock relay. When the sync lock relay energizes, power goes to the sync lock solenoid valve. The sync lock solenoid valve energizes so that hydraulic control pressure can release the sync lock/manual drive unit.
EFFECTIVITY
BEJ ALL
The directional control valve (DCV) switch energizes the directional control solenoid valve. This permits hydraulic control pressure to operate the DCV. The DCV moves to the extend position.
The electronic engine control (EEC) must have these inputs to energize the isolation solenoid valve:
*
TRA less than 31 degrees
*
Airplane on ground
*
Engine operating at idle.
The EEC gets TRA from the thrust lever angle (TLA) resolvers.
If the EEC finds the inputs to be in the proper configuration to extend the thrust reverser, the EEC energizes the isolation solenoid valve. This pressurizes the TRAS and extends the thrust reverser sleeves. The EEC uses data from the hydraulic pressure switch to make sure the isolation valve is in the correct position.
Retract
When you move the reverse thrust lever to the forward idle position, the isolation valve stays open. The electronic engine control (EEC) starts a 20 second time delay. The time delay keeps the isolation valve open to make sure retraction is complete. After the time delay, the EEC de-energizes the isolation valve solenoid.
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