777 AIRCRAFT MAINTENANCE MANUAL
TRAS -FUNCTIONAL DESCRIPTION -ACTUATION
EFFECTIVITY BEJ ALL 78-34-00
Page 49
D633W101-BEJ May 05/2003
TRAS -FUNCTIONAL DESCRIPTION -REVERSE THRUST LEVER INTERLOCK
General
Each reverse thrust lever interlock actuator has two positions:
*
No interlock
*
Interlock.
When the interlock actuator is in the interlock position, you cannot move the reverse thrust lever beyond idle. When the interlock actuator is in the no interlock position, you can move the reverse thrust lever beyond idle to maximum reverse.
The left 28v dc bus supplies power to move the interlock actuator.
No Interlock
The electronic engine control (EEC) controls the interlock actuator through the thrust reverser interlock relay in the left power management panel. When the EEC supplies a ground to energize the relay, power goes to the actuator motor. This extends the interlock actuator to rotate the roller on the crank assembly away from the interlock stop. These conditions must be met for the EEC to energize the relay:
*
Both thrust reverser sleeves are more than 60 percent extended
*
The thrust resolver angle (TRA) is less than 30 degrees.
If the interlock actuator is extended and reverse thrust is not commanded, the REVERSER INTERLOCK status message shows.
Interlock
When the electronic engine control (EEC) removes the ground to the thrust reverser interlock relay, the interlock actuator retracts to rotate the roller on the crank assembly toward the interlock stop. These conditions must be met for the EEC to remove the ground:
*
Both thrust reverser sleeves are less than 40 percent extended
*
The thrust resolver angle (TRA) is more than 30 degrees.
If the interlock actuator does not retract, you can move the reverse thrust lever above the interlock position (idle). Also, the CMCS stores a fault but no EICAS message shows.
EFFECTIVITY BEJ ALL 78-34-00
Page 50
D633W101-BEJ May 05/2003
TRAS -FUNCTIONAL DESCRIPTION -THRUST LEVER INTERLOCK
EFFECTIVITY BEJ ALL 78-34-00
Page 51
D633W101-BEJ May 05/2003
TRAS -POWER EXTENSION/RETRACTION FOR MAINTENANCE
General
To do maintenance on the thrust reverser, you can extend or retract the thrust reverser sleeves without operating the engines. To do this, you supply electrical and hydraulic power. Then you use the electronic engine control (EEC) maintenance switch and the thrust reverser test enable switch.
Extension
WARNING: DO THE DEACTIVATION PROCEDURE FOR THE SPOILERS. THE SPOILERS CAN EXTEND QUICKLY AND CAUSE INJURY TO PERSONS AND DAMAGE TO EQUIPMENT.
WARNING: MAKE SURE ALL PERSONS AND EQUIPMENT ARE CLEAR OF THE AREA AFT OF THE APPLICABLE THRUST REVERSER. IF YOU DO NOT OBEY THIS INSTRUCTION, INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT CAN OCCUR WHEN THE THRUST REVERSER EXTENDS.
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