EFFECTIVITY BEJ ALL 78-34-00
Page 47
D633W101-BEJ May 05/2003
TRAS -FUNCTIONAL DESCRIPTION -ACTUATION
When both sleeves are less than 40 percent extended, the EEC energizes the thrust lever interlock actuator. When the polarity of the electrical power input is reversed, the actuator operates in the retract direction which continues until the retract limit switch is reached. If the limit switches malfunction, the load limit clutch slips to prevent damage to the actuator when it engages the mechanical stops.The interlock actuator retracts the rod end which turns the interlock crank assembly roller toward from the interlock stop on the autothrottle brake housing. The roller blocks the movement of the autothrottle brake assembly to command reverse thrust. There is no interlock actuator limitation when you command forward thrust.
Deactivation for Ground Maintenance
To deactivate the thrust reverser for maintenance, you open the thrust reverser control circuit breakers to keep electrical power from the isolation valve solenoid valves. On the isolation valve, you must also push the isolation shutoff valve plunger and install a pin to hold it in place. This keeps the shutoff valve closed which prevents hydraulic system pressure from going into the TRAS.
Manual Operation
To manually operate the thrust reverser sleeves you must deactivate the thrust reverser isolation valve for maintenance.
Open the thrust reverser control circuit breakers.
On the isolation valve, manually turn the crank to depress the plunger to move the bypass valve to the bypass position. The crank is then pinned to keep the valve in the bypass position. The bypass valve now connects the extend and retract pressure lines of the TRAS together. When the pin is removed, the bypass valve is spring-loaded to return to the closed position which pushes the plunger out. The bypass valve prevents a hydraulic lock in the TRAS when you manually extend the thrust reverser sleeve. The hydraulic fluid on the deploy side goes to the system return line.
On the isolation valve, push-in the plunger to keep the shutoff valve slide in the closed position and install a pin to keep the plunger pushed-in. When the pin is removed, the plunger is spring-loaded to push the plunger out; the shutoff valve slide will remain in the closed position.
Use the sync lock/manual drive unit to extend and retract the thrust reverser sleeve.
EFFECTIVITY BEJ ALL 78-34-00
Page 48
D633W101-BEJ May 05/2003
PW4000 SERIES ENGINES
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