777 AMM 飞机维护手册 起落架 Landing Gear(40)

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Location
The autobrake valve module is on the keel beam in the right main landing gear wheel well.
Functional Description
When the autobrake function does not operate, the solenoid valve is not energized. This stops hydraulic pressure downstream of the solenoid valve. During autobrake operation, the BSCU energizes the solenoid valve. This causes the solenoid valve to send right hydraulic system pressure to the shutoff valve.
This pressure causes the shutoff valve to open and permits the system pressure to go to the control valve.
The solenoid valve pressure switch sends a signal to the BSCU when the pressure downstream of the shutoff valve is more than 750 psi. The BSCU uses this signal to find solenoid valve faults.
The control valve is a two-stage servo-operated valve. The BSCU controls this valve to let the necessary hydraulic pressure to go to the brakes.
The control valve pressure transducer sends autobrake pressure output signals to the BSCU for feedback.
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ANTISKID/AUTOBRAKE SYSTEM -AUTOBRAKE VALVE MODULE

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ANTISKID/AUTOBRAKE SYSTEM -AUTOBRAKE SHUTTLE VALVE

Purpose
Two autobrake shuttle valves select the highest of autobrake or normal brake metered pressures and send it to the brakes.
Location
The autobrake shuttle valves are on the forward wall in the left and right main landing gear wheel wells. They are inboard of the brake metering valves.
Physical Description
The valves are un-biased shuttle valves with detents and are interchangeable.
EFFECTIVITY BEJ ALL  32-42-00 
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ANTISKID/AUTOBRAKE SYSTEM -AUTOBRAKE SHUTTLE VALVE

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ANTISKID/AUTOBRAKE SYSTEM -BRAKE METERED PRESSURE TRANSDUCERS

Purpose
Four brake metered pressure transducers send normal and alternate metered pressure information to the BSCU for anti-skid and autobrake control.
Location
The two normal brake metered pressure transducers are on the left and right autobrake shuttle valves in the main landing gear wheel wells.
The two alternate brake metered pressure transducers are on the landing gear beams inboard of the left and right alternate antiskid modules.
Functional Description
The BSCU uses inputs from the normal brake metered pressure transducers for autobrake disarm logic and for the taxi brake release function.
All four transducers supply the BSCU with metered pressure data to send to the AIMS. The data shows on the landing gear brakes/steering maintenance page.
The BSCU also sends the pressure data to the flight data recorder.
EFFECTIVITY BEJ ALL  32-42-00 
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ANTISKID/AUTOBRAKE SYSTEM -BRAKE METERED PRESSURE TRANSDUCERS

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ANTISKID/AUTOBRAKE SYSTEM -FUNCTIONAL DESCRIPTION -INTRODUCTION

General
The BSCU uses antiskid transducer signals to control the normal and alternate antiskid valve modules.
These modules receive metered pressure from the brake metering valves or the autobrake valve module and send it to the brakes through the antiskid shuttle valves.
When the BSCU gets input of a skid condition, it commands the antiskid valves to release pressure from the related brake to hydraulic system return.
When the BSCU gets input from the autobrake selector, it controls pressure to the brakes with the autobrake valve module when the airplane lands or on rejected takeoffs.
Normal Antiskid Operation
The normal brake metering valves send metered right hydraulic system or accumulator pressure through the autobrake shuttle valves to the normal antiskid modules. The normal antiskid modules use BSCU input and this metered pressure to control pressure to each brake.
The left normal antiskid module uses an antiskid surge accumulator to absorb high pressure release surges. The right normal antiskid module uses the right hydraulic system reservoir.
Alternate Antiskid Operation
The alternate brake metering valves send metered center hydraulic system pressure to the alternate antiskid modules. The alternate antiskid modules use BSCU input and this metered pressure to control pressure to each fwd-mid group of brakes and each aft brake.
Autobrake Operation
When all conditions for autobrake operation occur, the BSCU uses the autobrake valve module to control brake pressure to the normal brake system.
　
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