78-11-02
ALL ú ú N01 Page 404 ú Oct 18/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
THRUST REVERSER SYSTEM - DESCRIPTION AND OPERATION
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1. General
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A. The fan section is equipped with a hydraulically actuated, cascade type thrust reverser. There is no turbine thrust reverser. The thrust reversers are for ground use only and are only used to decrease the speed of the airplane during landings or refused takeoffs.
B. The thrust reverser is of an annular cascade design, hydraulically actuated and electrically controlled. It is operated by motion of the conventional "piggyback" reverse thrust lever which commands the thrust reverser to extend and retract which controls engine power while the thrust reverser is extended. A feedback Linear Variable Differential Transformer (LVDT)/interlock actuator for the thrust reverser position prevents application of engine power more than idle unless the thrust reverser is in the commanded position. Thrust reverser positions (stowed, unstowed and deployed) are shown on the pilot's instrument panel.
C. The thrust reverser system includes:
(1)
The fan bypass air flow deflector devices which include the translating sleeve, the cascade vane segments and the blocker doors.
(2)
The engine control system which includes a reverse thrust lever connected by autothrottle clutch pack linkage and thrust lever angle transducers to the Electronic Engine Control (EEC). For more data, refer to Engine Control System (AMM 76-11-00/001).
(3)
The electrical control system which includes the fire switch, the AIR/GND relay, reverser control switches in the reverse thrust lever and microswitch pack all of which must be closed to operate the isolation valve solenoid, the directional control valve solenoid and sync locks. For more data, refer to Thrust Reverser Control System (AMM 78-34-00/001).
(4)
The hydraulic system which includes the isolation valve which isolates the thrust reverser system from the airplane's hydraulic system, the directional control valve and flow control tees.
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78-31-00
ALL ú ú N02 Page 1 ú Jun 18/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
(5)
The thrust reverser actuation system includes locking and non-locking hydraulic ballscrew actuators, flexible rotary drive shafts between the locking and non-locking hydraulic actuators and sync locks.
(6)
The thrust reverser position/feedback interlock system includes the feedback LVDT on each locking hydraulic actuator which supplies thrust reverser position to the EEC, and the feedback interlock actuator commanded by the EEC and installed below the autothrottle clutch pack.
(7)
The thrust reverser position indicating system uses proximity sensors on each thrust reverser half to sense stow, unstow, and deploy conditions. This system uses the upper cathode ray tube for the Engine Indicating and Crew Alerting System (EICAS) to show the thrust reverser indication. When one of the locking actuator becomes unlocked, the EICAS shows an amber REV symbol above the display of the target EPR. The amber REV symbol changes color to green when the two thrust reversers are more than 90 percent deployed. The ENG REV DISAGREE indication is supplied to annunciate a malfunction in the thrust reverser control system.
D.
The major components of the thrust reverser assembly are installed to the torque box of the thrust reverser. The torque box holds the dynamic loads created by thrust reverser operation.
E.
The thrust reverser is attached to the nacelle strut immediately to the rear of the engine fan case. The thrust reverser has two halves which make the fan air exhaust duct. The thrust reverser includes a translating sleeve, blocker doors, cascade vanes, track sliders, tension latches, latch band, louvered exhaust door, locking and non-locking actuators, rotary flex shafts, sync locks and different hydraulic tubes and fittings (Fig. 1 and 2).
F.
Thrust reversers are opened and closed by the cowl opening actuators. The opening acutators are pressurized by a (ground support) hand pump which is connected to a quick release manifold near the bottom of the thrust reverser.
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