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bus crank assemblies. This permits control of the left and right
brakes with the captain or the first officer pedals.
HYDRAULIC BRAKE SYSTEM - BRAKE PEDAL BUS MECHANISM
EFFECTIVITY
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HYDRAULIC BRAKE SYSTEM - BRAKE PEDAL BUS MECHANISM
HYDRAULIC BRAKE SYSTEM - BRAKE PEDAL BUS MECHANISM
EFFECTIVITY
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Purpose
The brake metering valve assemblies get input from the brake
pedals through control cables and a control quadrant that
operate a crank and control rod. Movement of the brake pedal
mechanism controls the brake metering valves that send out
metered brake pressure to the brakes.
location
There are two brake metering valve assemblies in the main
landing gear wheel well on the aft side of the ceiling.
Physical Description
The brake metering valve assemblies are interchangeable and
have these components:
* Normal metering valve
* Alternate metering valve
* Gear retract braking actuator.
The normal and alternate metering valve have identical
housings that are bolted together and share a common input
shaft.
The gear retract braking actuators are mounted integrally with
the alternate metering valve.
HYDRAULIC BRAKE SYSTEM - BRAKE METERING VALVE ASSEMBLY
EFFECTIVITY
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BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
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HYDRAULIC BRAKE SYSTEM - BRAKE METERING VALVE ASSEMBLY
HYDRAULIC BRAKE SYSTEM - BRAKE METERING VALVE ASSEMBLY
EFFECTIVITY
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32-41-00-005
General
On the brake metering valve assembly, the normal and
alternate brake metering valves are almost the same. They
attach together and use the same input shaft.
Only one valve at a time gets pressure, except during gear
retract braking. The alternate brake selector valve and
accumulator isolation valve control which metering valve gets
pressure.
The normal brake metering valve uses hydraulic system B or
accumulator pressure for the normal brake system.
The alternate brake metering valve uses hydraulic system A
pressure for the alternate brake system when hydraulic system
B does not supply pressure. It also uses pressure from the
landing gear retract line to stop the main gear wheel rotation
during retraction.
Normal and Alternate Brake Application
The brake pedal command goes to the metering valves through
cables and linkage. This moves the metering valve input shaft.
When the input shaft turns, it moves the metering valve spools
in both valves at the same time.
The metering valve spools are spring-loaded to the brakes OFF
position.
Metering valve spool movement sends pressure to the brakes
and to the feedback chamber. This pressure applies the brakes
and moves the metering valve spool to the brake pressure
maintained position. This also applies a feedback force back
through the brake control cables to the brake pedals.
Brake pedal release lets the springs return the metering valve
spools in both valves to the closed position. This sends brake
pressure to return and releases the brakes.
Gear Retract Wheel Braking
During landing gear retraction, landing gear retract pressure
from the landing gear selector valve pressurizes the gear
retract braking actuator.
The gear retract braking actuator moves a forked actuator lever
to operate the alternate brake metering valve spool. This
operation does not move the input shaft and does not move the
brake pedals.
The movement of the alternate metering valve spool sends
landing gear retract pressure to the brakes.
HYDRAULIC BRAKE SYSTEM - BRAKE METERING VALVE ASSEMBLY - FUNCTIONAL DESCRIPTION
EFFECTIVITY
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BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
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32-41-00-006
HYDRAULIC BRAKE SYSTEM - BRAKE METERING VALVE ASSEMBLY - FUNCTIONAL DESCRIPTION
　
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