K42021 H80062
521 Landing Gear Position Indicating and Warning Schematic
Aug 15/77 Figure 7 32-61-0
Page 11
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Landing Gear Position Indicating and Warning Functional Schematic Diagrams 521
32-61-0 Figure 8 Aug 15/77
Page 12
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
LANDING GEAR POSITION INDICATING AND WARNING SYSTEM - TROUBLE SHOOTING
1. General
A. The trouble shooting charts in the following pages are designed as an aid for locating causes of troubles that may appear in the landing gear position indicating and warning system. The charts are arranged so that by starting at the top and proceeding downward the trouble may be isolated and corrected. These charts do not cover every possible trouble, however they may be used as a guide for isolating troubles not covered. No attempt has been made to give detailed instructions for measuring voltages or continuity. These may vary for different airplane configurations. Therefore, the applicable wiring diagrams must necessarily be used in conjunction with the trouble shooting charts. Prior to trouble shooting, the engine pressure ratio function of the engine indicating system must be functioning properly (Ref Chapter 77).
B. The proximity sensors used in this system fail to the normal nonenergized condition. Therefore if a sensor is shorted or open, the related switch is in its normal nonenergized condition. This condition may be simulated by disconnecting the sensor at the disconnect nearest the sensor or by jumpering the sensor at this point. The position switch circuits may be actuated by placing a strip of ferrous material against the face of the sensor or by replacing the sensor with a 1000-ohm resistor. Sensors may be checked for malfunction by measuring dc resistance between sensor leads. The resistance between the blue and yellow leads should be 350 +35 ohms. The resistance between the red and yellow leads should be 30 +6 ohms.
C. In the following charts, the airplane will be in one of the following conditions unless specified otherwise:
(1)
Airplane on ground; electrical power on; all circuit breakers closed; gear down and locked; lockpins installed; hydraulic system depressurized; throttles advanced; landing gear lever in OFF position.
WARNING: CHECK THAT GROUND LOCK ASSEMBLIES ARE INSTALLED IN ALL LANDING GEAR TO PREVENT INADVERTENT OPERATION OF GEAR. INJURY TO PERSONNEL AND/OR EQUIPMENT COULD RESULT IF GEAR RETRACTS.
(2)
Airplane on jacks; electrical power on; all circuit breakers closed; gear up and locked; hydraulic system depressurized; throttles advanced; landing gear lever in OFF position.
NOTE: It may be necessary to pressurize the hydraulic system momentarily to obtain flap position called for (Ref 29-11-0 MP and 29-12-0 MP).
D. Landing gear position indicating and warning system trouble symptoms are best identified by performing a test of the system (Ref Landing Gear Position Indicating and Warning System -A/T). If the system does not react as specified, proceed to the following charts.
2. Trouble Shooting Charts
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