C31349
510 78-34-01 Jun 20/93 Page 8B
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
G53230
515 Thrust Reverser Isolation Valve
Nov 01/73 Figure 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 78-34-01 Page 9
7. Operation
A. The thrust reverser control system is controlled entirely by use of the reverse thrust lever. Hydraulic pressure is supplied by the A hydraulic system.
B. Reverse thrust operation is initiated by positioning the reverse thrust levers in the control cabin. The operation of each thrust reverser is independent of the other. The forward thrust lever must be returned to idle before the reverse thrust lever can be moved sufficiently to initiate reverse thrust actuation. This prevents accidental actuation of the reverser during forward thrust operation. Initial movement of the reverse thrust lever aft to an interlock position provides sufficient thrust control shaft rotation for the thrust reverser control cam to reposition the control valve, causing pressurized hydraulic fluid to be routed through the deploy port to the thrust reverser actuators (Fig. 5). Pressurized hydraulic fluid is supplied to the unlock port of the lock actuator and the deploy port of the thrust reverser actuator simultaneously. Since less pressure is required to move the lock actuator piston than is required to move the thrust reverser actuator piston, the lock actuator piston retracts to the unlock position first. Operation of the lock actuator to the unlocked position also moves the thrust reverser position indicating system switch actuating bar from near the switch sensor causing the thrust reverser position indicating switch to close to illuminate the REVERSER UNLOCKED light in the control cabin. The thrust reverser follow-up cam prohibits movement of the reverse thrust lever beyond interlock until the thrust reverser deflector doors approach the full reverse thrust position. When sufficient pressure builds up at the deploy port on the thrust reverser actuator, the actuator piston retracts causing the guide carriage to move forward. Movement of the guide carriage forward causes the feedback control lever to rotate. This pulls the push-pull cable aft causing the telescopic section at the reverser to extend and the telescopic section at the engine controls thrust shaft to retract, rotating the follow-up cam. When push-pull cable travel is completed (deflector door near end of travel) the follow-up cam has rotated sufficiently to allow thrust shaft movement for application of maximum reverse thrust.
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78-34-01 Page 10 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 15/80
C. To return the thrust reverser to the forward thrust position, the reverse thrust lever is moved forward. As the reverse thrust lever nears the off position, the thrust reverser control cam, rotating with the throttle shaft, repositions the control valve. The thrust reverser follow-up cam prohibits movement of the forward thrust lever beyond interlock until the deflector doors have almost reached the forward thrust position. Pressurized hydraulic fluid is supplied to the lock port on the lock actuator, and the stow port on the thrust reverser actuator (Fig. 5). The lock actuator piston extends and positions the lock latch to the closed position. The thrust reverser actuator then extends, moving the guide carriage aft to close the deflector doors. The push-pull cable, which is slaved to the guide carriage retracts at the thrust reverser telescopic section through the feedback control lever, and extends at the control shaft end. This rotates the follow-up cam to free the control shaft to allow maximum cruise thrust application after the deflector doors have nearly retracted to the cruise position. When the thrust reverser reaches the forward thrust position, the thrust reverser position indicating switch actuating bar is close to the switch sensor causing the position indicating switch to open and the REVERSER UNLOCKED light to go out.
D. The interlock provision limits power setting if the thrust reverser is not in the correct position for the selected thrust condition. If the thrust reverser inadvertently moves to reverse thrust position during forward thrust operation, the push-pull control drives the follow-up cam at the control shaft, forcing the throttle control shaft to a reduced thrust setting. If the thrust reverser inadvertently actuates to cruise while in reverse thrust, the same sequence of actions occurs to reduce the thrust setting, except that all control movements are in the opposite directions.
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