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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
TROUBLE PROBABLE CAUSE ISOLATION PROCEDURE REMEDY
Pressure below normal (2800 psi) (Cont) Hydraulic fluid low NOTE: When system B reservoir low level warning light is on, approx. 2.0 gallons have been drained from system A reservoir Hydraulic leak (Cont) System B pressure relief valve System A fluid quantity indicator and/or transmitter System B low level warning system switch NOTE: Warning light comes on when system B reservoir is 50% of normal capacity. (1.3 gallons) to 1.6 ±0.2 gallon indication (3.6 gallon indicates full) before system B low level warning light will come on due to leak in system B If system B pressure indication is still below normal after following above procedures, relief valve is opening at too low pressure Service hydraulic reservoir system. See Chapter 12, Hydraulic Servicing. If system A quantity indicator still reads low, indicator and/or transmitter is defective. If indicator is replaced and still reads low, transmitter is defective. If indicator is replaced and reads full, removed indicator is defective If system B low level warning light is on and system A reservoir is full, system B reservoir must be full and low level warning switch is defective If system A reservoir is full, low level warning switch has been replaced and warning light is still on check for short circuit Remove and replace system B pressure relief valve Test quantity transmitter and indicator. Replace as required. See 29-33-0, Fluid Quantity Indicating Systems Replace low level warning switchCheck system B low level warning system electrical circuit
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
HYDRAULIC SYSTEM B - MAINTENANCE PRACTICES
1. General
A. The following procedure provides instructions for pressurizing (par. 2) and depressurizing (par. 3) hydraulic system B.
2. Pressurize Hydraulic System B
A. General
(1)
To pressurize hydraulic system B, two methods may be used. System B electric motor-driven pumps or a hydraulic test stand. Pressurizing hydraulic system B will supply hydraulic power to the elevator, rudder, ailerons, outboard spoilers, and outboard brakes.
WARNING: CHECK THAT PERSONNEL AND OBSTRUCTIONS ARE CLEAR OF ALL FLIGHT CONTROL SURFACES BEFORE TURNING HYDRAULIC POWER ON. ISOLATE OR TAG SYSTEMS NOT BEING TESTED TO PREVENT INJURY TO PERSONNEL OR DAMAGE TO AIRPLANE.
(2)
On hot days or when fuel temperature is known to be above 90°F, monitor the system B overheat indicator on the forward overhead panel while running the system B pumps for ground maintenance and checkout procedures. Switch pumps off when overheat is indicated.
(3)
Deleted.
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B. Pressurize Hydraulic System B (Electric Motor-Driven Pump)
CAUTION: DO NOT OPERATE SYSTEM B PUMPS MORE THAN 2 MINUTES UNLESS THE NO. 2 FUEL TANK CONTAINS AT LEAST 1675 POUNDS (760 KILOGRAMS) GALLONS OF FUEL. IF PUMPS ARE OPERATED 2 MINUTES WITHOUT FUEL IN TANK, ALLOW RESERVOIR TO RETURN TO AMBIENT TEMPERATURE BEFORE RESUMING TEST.
(1)
Provide electrical power (Ref 24-22-0 MP).
(a) Place battery switch to ON.
(2)
On the forward overhead panel, switch HYDRAULIC SYSTEM B - ELEC PUMP 1 and/or ELEC PUMP 2 to ON.
(3)
Pressurize hydraulic system for a sufficient time to complete al1 necessary checks.
NOTE: When using system B pumps as a power source for pressurizing the hydraulic system with interconnect valve closed and flight control switches ON, turn on both No. 1 and 2 electric pumps to maintain a pressure indication between 2800 and 3100 psi. With flight control switches OFF, pressure indication should be between 2900 and 3100 psi.
(4)
When operation is complete, check that switch is in ON position.
NOTE: The engine-driven pump should be left in the ON position after maintenance has been performed. This will help to prolong the life of the depressurization solenoid which becomes energized when the pump switch is placed in the OFF position.
C. Pressurize Hydraulic System B (Hydraulic Test Stand)
(1)
Equipment and Materials
(a) Hydraulic test stand - 0 to 3000 psi, with BMS 3-11 hydraulic fluid
(2)
Pressurize System
(a)
Open air conditioning duct access panel on right side of airplane.
(b)
Connect hydraulic test stand to hydraulic ground power modular unit.
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