32-41-00
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A
747-400
MAINTENANCE MANUAL
SOURCE PRESS SW (CEILING AFT LEFT W/G W/WELL)
Brake Source Indication Schematic
Figure 9
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32-41-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
BRAKE PRESSURE TRANSMITTER
BRAKE PRESSURE TRANSMITTER
RIGHT BODY GEAR WHEEL WELL
Brake Pressure Indication Schematic
Figure 10
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MAINTENANCE MANUAL
(2)
The alternate brake system
(a)
Hydraulic systems 1 and/or 2 must be pressurized to operate the alternate brake system. When pressure is removed from hydraulic system 4, alternate-source-selector valve 1 opens to pass hydraulic system 1 pressure to the alternate-brake-metering valve. This pressure also operates the accumulator isolation valve to prevent the hydraulic brake accumulator from releasing fluid into the normal brake system when the brake-metering-valve assemblies operate.
(b)
When the brake pedals are pushed the brake metering valves open and pass hydraulic fluid to the alternate brake lines. Fluid then passes through the alternate antiskid valves, the alternate brake fuses and the antiskid shuttle valves (AMM 32-42-00/001) to the brakes. The brakes operate as they do with normal system pressure.
(c)
When the brake pedals are released the hydraulic fluid in the alternate brake lines is released through the alternate-brake-metering valves into hydraulic system 1 return lines.
(d)
When pressure is removed from hydraulic system 1, alternate-source-selector valve 1 closes and alternate-source-selector valve 2 opens. This permits hydraulic system 2 to pressurize the alternate brake system.
(3)
The hydraulic brake accumulator
(a)
When pressure is removed from hydraulic systems 1, 2, and 4 the brake system is operating on the hydraulic brake accumulator only. This causes the alternate-brake-pressure switch and the hydraulic-system-4-pressure switch to close. This sets a ground on the BRAKE SOURCE light and turns it on.
(b)
The accumulator isolation valve opens under the pressure of the hydraulic brake accumulator and pressurizes the normal brake system when the brake pedals are pushed. When the brake pedals are released, hydraulic fluid in the normal brake system is released to the hydraulic system 4 return lines. This decreases the pressure in the hydraulic brake accumulator, and the HYD BRAKE PRESS Gage on the captain's instrument panel shows a pressure decrease.
(c)
The direct-reading-pressure gage and the brake pressure transmitter are connected to the same pressure source so the direct-reading-pressure gage will show the same pressure as the HYD BRAKE PRESS Gage. The pressure gages will show pressure decrease each time the brake pedals are operated until the accumulator is empty of hydraulic fluid. The gages will then show hydraulic-brake-accumulator-precharge pressure. There will no longer be enough fluid in the brake system to operatate the brakes when the pedals are pushed.
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A
747-400 FAULT ISOLATION/MAINT MANUAL
HYDRAULIC BRAKE SYSTEM
COMPONENT SHT 102 FIG. QTY ACCESS/AREA REFERENCE AMM
ACCUMULATOR - HYDRAULIC BRAKE 6 1 RIGHT BODY GEAR WHEEL WELL 32-41-09
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