F86468
Hydraulic Reservoir Pressurization Relief Valve Installation 510
29-09-351 Figure 401 Feb 20/89
Page 402
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
HYDRAULIC SYSTEM A - DESCRIPTION AND OPERATION
1. General
A. Hydraulic system A (Fig. 1) supplies fluid under pressure of 3000 psi to the ground spoilers, inboard flight spoilers, ailerons, leading edge flaps and slats, landing gear, nose wheel steering, elevators, trailing edge flaps, rudder, main wheel inboard brakes and thrust reverser.
B. Hydraulic system A includes the equipment necessary to store, pressurize, deliver, control, monitor, and filter the hydraulic fluid to operate the systems supplied by system A (Fig. 2). Hydraulic fluid for system A is stored in a pressurized reservoir. The reservoir is pressurized by engine bleed air routed through a filter and a pressure regulator to ensure a positive supply of hydraulic fluid to the pumps. Two supply shutoff valves controlled by separate engine fire switches are installed downstream of the reservoir to stop the flow of hydraulic fluid to the engine area in case of an engine failure or fire. Two variable displacement engine-driven pumps supply fluid to the various systems upon demand. Each pump is equipped with an electrically controlled depressurizing valve to depressurize the pump if pump output is not required. A filter in the pressure line from each pump filters the fluid before it enters the various subsystems. A pressure switch in the pressure line from each pump is connected to a pump low pressure warning light on the pilots' overhead panel to provide an indication of low hydraulic pressure. A pressure relief valve protects the system against damage by abnormally high pressures. A pump case drain filter in each pump return line is provided to detect incipient pump failures and to filter return fluid before it enters the reservoir. A hydraulic fluid heat exchanger in the pump return line is provided to cool the hydraulic fluid. A system return filter located ahead of the reservoir, filters return fluid from the subsystem supplied by system A.
C. For ground operation system A can be pressurized to provide normal pressure without engine operation by attaching an external hydraulic source to the hydraulic ground power modular unit located just forward of the right wheel well. System A can also be pressurized without engine operation by attaching electrical power, opening the ground interconnect valve and operating system B pumps.
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Feb 15/78 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 29-11-0 Page 1
F86503 F86581 F86520 F86744 F86757
Hydraulic System A Component Location 500
29-11-0 Figure 1 (Sheet 1) Nov 15/66
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
543 Hydraulic System A Component Location
Feb 15/73 Figure 1 (Sheet 2) 29-11-00
Page 3
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Hydraulic System A Component Location 540
29-11-0 Figure 1 (Sheet 3) May 01/74
Page 4
540 Hydraulic System A Schematic
May 01/74 Figure 2 (Sheet 1) 29-11-0
Page 5
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Hydraulic System A Schematic 500
29-11-0 Figure 2 (Sheet 2) Jun 15/66
Page 6
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
2. System A Hydraulic Reservoirs
A. Hydraulic fluid for system A is supplied by a main reservoir. The reservoir provides a total capacity of 4.1 U.S. gallons. The reservoir is installed in the upper central area of the wheel well (Fig. 1). Attached to the main reservoir is a gage and a fluid quantity transmitter which is connected electrically to a gage on the first officer's panel. The gages indicate total available fluid quantity in the reservoir (Ref 29-33-0). The gages show empty when 0.55 gallons remain in the reservoir. The reservoir is pressurized by engines No. 1 and 2 bleed air. Engine bleed air is routed through check valves, a filter, and a pressure regulator to pressurize the reservoirs to approximately 45 psi, thus ensuring a positive supply of hydraulic fluid to the engine-driven pumps.
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