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The thrust reverser test enable switch permits the operation of the TRAS when the engine is not in operation. You use this switch for thrust reverser maintenance.
Extend
To extend the thrust reverser sleeves, you put the reverse thrust lever in the reverse thrust interlock position. This causes three control signals to go to the TRAS. These are the effects of the control signals:
*
The sync lock valve (SLV) opens and supplies hydraulic control pressure to release the sync lock/manual drive units.

*
The isolation valve opens and supplies hydraulic power through the directional control valve (DCV) to the hydraulic actuators.

*
The directional control solenoid valve opens and supplies hydraulic control pressure to the directional control valve (DCV). This moves the DCV to permit hydraulic power to go to the extend and retract sides of the hydraulic actuators.

Hydraulic power to the actuators releases the locking actuators and moves the sleeves to the aft (extended) position.
78-34-00

Page 5 D633W101-BEJ May 05/2003

 

TRAS -GENERAL DESCRIPTION

Retract

To retract the thrust reverser sleeves you put the reverse thrust levers in the forward thrust position. This causes two control signals to go to the TRAS. These are the effects of the control signals:
*
The directional control solenoid valve closes and removes the hydraulic control pressure to the directional control valve (DCV). This moves the DCV to permit hydraulic power to go to the retract side of the actuators.

*
The electronic engine control (EEC) begins a time delay before closing the isolation valve. The isolation valve stays open and supplies hydraulic power through the DCV to the actuators. The isolation valve closes when the time delay is complete.

*
The signal to open the sync lock valve (SLV) is removed. A time delay circuit in the electrical load management system (ELMS) keeps the sync lock solenoid valve energized. This keeps the SLV open and the sync lock unlocked. The sync locks remain unlocked until the time delay is complete.

Hydraulic power to the retract side of the actuators moves the thrust reverser sleeves to the forward (retracted) position.
Time delay circuits in the ELMS and the EEC cause the sync lock (SL) solenoid valve and isolation solenoid valve to stay open. When the time delays are complete, the valves close. The isolation solenoid valve closes the isolation valve which removes hydraulic power from the TRAS. The sync lock solenoid valve closes and causes the sync lock/manual drive units to lock the sync shafts
EFFECTIVITY BEJ ALL  78-34-00 
Page 6 
D633W101-BEJ  May 05/2003 

PW4000 SERIES ENGINES

 

777 AIRCRAFT MAINTENANCE MANUAL

 

TRAS -GENERAL DESCRIPTION

EFFECTIVITY BEJ ALL  78-34-00 
Page 7 
　
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