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Aug 01/95 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 78-34-91 Page 403
THRUST REVERSER INDICATING SYSTEMS -DESCRIPTION AND OPERATION
1. General
A. Indicating systems are provided to monitor operation and condition of the thrust reverser on each engine. Indicator lights in the control cabin respond to sensors at the engines and pressure switches in the hydraulic system to alert the crew to abnormal system operation.
B. Two independent indicating systems are used. (See figures 1 and 2.) The position indicating system reacts to deflector door lock engagement to provide indication of thrust reverser position. The isolation valve indicating system provides visual warning any time system condition does not agree with valve position.
2. Thrust Reverser Position Indicating System
A. A thrust reverser position indicating system for each engine provides indication to the crew if both thrust reverser locks on either engine are not engaged and consequently, that the thrust reverser might not be in the full forward thrust position. The system for each engine consists of an amber light on the center panel in the control cabin, a proximity switch, and associated wiring. The proximity switch consists of a solid-state switch assembly (in the form of a printed circuit card, mounted in a switch module) and a proximity switch sensor (mounted on each thrust reverser lock assembly). (See figures 1 and 2.) The switch sensor is activated by the thrust reverser lock latch trigger providing a signal to the solid-state switch card.
B. The solid-state switch is actuated when the switch sensor trigger on the lock latch is brought near a sensitive surface on the switch sensor. The trigger alters the magnetic flux in the sensor to cause increased current flow in the switch circuit. The increased current flow actuates the switch to the open position and, if both latches are engaged, the amber light goes out. This is the position of the switch when the thrust reverser is forward and locked. When reverse thrust is selected, the trigger moves away from the sensor as the thrust reverser is unlocked causing the switch to close and the position indicating light to come on.
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Aug 15/72 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 78-36-01 Page 1
H27649
Thrust Reverser Indicating Systems Component Location 525
78-36-01 Figure 1 Aug 15/72
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
EFFECTIVITY
AIRPLANES WITHOUT NOSE GEAR AIR-GROUND SWITCH
508 Thrust Reverser Indicating System Circuits
Jun 20/90 Figure 2 (Sheet 1) 78-36-01
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
H27657
Thrust Reverser Indicating Systems Circuits 527
78-36-01 Figure 2 (Sheet 2) Jun 20/90
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
3. Thrust Reverser Isolation Valve Indicating System
A. An indicating system provides visual warning any time thrust reverser hydraulic system condition does not agree with isolation valve position. The system consists of an amber indicator light on the aft overhead panel, a pressure switch downstream of each isolation valve, and a solid-state switch card in the engine accessory unit module (Fig. 1 and 2).
B. The isolation valve indicator light will remain out during all normal operating conditions. The switch card responds to the isolation valve circuits and the hydraulic system pressure switches to turn on the indicator light any time an isolation valve is energized and hydraulic pressure is not sensed by the corresponding pressure switch. The indicator light will also be on anytime pressure is sensed downstream of a de-energized isolation valve. Refer to 78-34-01, Thrust Reverser Control System - Description and Operation, for a discussion of isolation valve control.
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Oct 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 78-36-01 Page 5
THRUST REVERSER INDICATING SYSTEMS -ADJUSTMENT/TEST
1. General
A. The test procedures included in this section provide a check of only the indicating systems and are intended to support special testing and trouble analysis of these systems. These procedures are not a substitute for a complete thrust reverser system checkout and should not be used in lieu of the system test per 78-32-01.
B. Separate procedures are presented for each of the independent indicating systems. Each procedure is complete for the system involved.
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