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Standby Hydraulic System Component Location 500
29-21-0 Figure 1 Nov 15/67
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
525 Standby Hydraulic System Schematic
Jul 15/70 Figure 2 29-21-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
3. Standby System Electric Motor-Driven Hydraulic Pump
A. One electric motor-driven hydraulic pump supplies fluid under pressure to the hydraulically-operated systems supplied by the standby system. Pump operation is controlled by either the RUDDER standby control switch, or the ALTERNATE FLAPS control switch (Ref to Chapter 27, Rudder Hydraulic Control System, and Leading Edge Flaps and Slats System).
B. The pump assembly consists of a 3-phase 115 volt ac motor and a variable delivery, positive displacement hydraulic pump. The hydraulic pump consists of the units shown in Fig. 3. Pump pressure is regulated at 2975 to 3100 psi and maximum output is 3 gpm. Pump pressure, return and supply ports are connected to flexible hoses. The pump assembly is installed on the keel beam between the wheel wells. 28 volt dc relays control motor power. Pressure compensation inside the pump varies the ratio between the volume of fluid that is delivered to the system and the volume that is recirculated within the pump. Some fluid is discharged out the return port.
C. The pump control (compensator) consists of a compensator cylinder, a compensator stem with a plate carrying piston sleeves, and a compensator spring unit. A small difference in the stem diameter provides an annular area on which the pressure of discharged fluid produces a force. This force is opposed by the control spring. When the discharge pressure exceeds 3000 psi, the hydraulic force on the stem overcomes the control spring and pushes the compensator stem with piston sleeves away from the driving shaft. The sleeves keep the discharge holes uncovered during nearly the whole discharge stroke, and no fluid is delivered to the pressure line. A small quantity of fluid discharged through the piston bypass holes to the return line, provides fluid circulation for cooling and lubrication of the pump during idling periods.
4. Standby System Modular Unit
A. The modular unit (Fig. 4) is provided to manifold hydraulic fluid to various easily replaceable cartridge type component. The modular unit consists of a 6-port housing providing attachment provisions for the cartridge type hydraulic pump pressure filter, rudder shutoff valve, leading edge flap standby shutoff valve, pressure switch, check valve, standby system pressure relief valve, and male fittings for attaching system tubing connectors. The modular unit housing has drilled passages to provide fluid flow through the unit. The modular unit is installed on the aft bulkhead of the wheel well area.
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29-21-0 Page 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Aug 15/80
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506 Standby System Electric Motor-Driven Pump
Feb 15/68 Figure 3 29-21-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Standby System Modular Unit 525
29-21-0 Figure 4 Feb 15/78
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5. Standby System Hydraulic Filters
A. Pressure Filter
(1) A cartridge type pressure filter in the pressure line from the electric motor-driven hydraulic pump filters the hydraulic fluid before it enters the hydraulic systems (Fig. 2). The pressure filter is installed in the standby system modular unit and consists of a filter bowl and a noncleanable element (Fig. 5).
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