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747-400
MAINTENANCE MANUAL
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29-11-00
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747-400 MAINTENANCE MANUAL
TO VENT
QX SG RESERVOIR RESERVOIR PRESSURIZATION MODULE TX
DEMAND PUMP
PIPE STAND
MODULE CASE DRAIN
AUX AUX CASE FILTER 4 ONLY SYSTEM 1 AND
NACELLE FIREWALL
PS PRESSURE MODULE
EDP
PS
RETURN MODULE
PX HEAT TO SYSTEM EXCHANGER
RESERVOIR
FILL
FROM SYSTEM
RESTRICTOR ONE-WAY SELECTOR VALVE
PRESSURE SUPPLY GROUND LEGEND PS PRESSURE SWITCH
SERVICE
ACP ELECTRIC PUMP PX PRESSURE TRANSMITTERRETURN DISCONNECT
ADP AIR-DRIVEN PUMP QX QUANTITY TRANSMITTER
AIR
EDP ENGINE-DRIVEN PUMP SG SIGHT GLASS
DIFFERENTIAL PRESSURE
M ELECTRIC MOTOR TX TEMPERATURE TRANSMITTER
INDICATOR
Main Hydraulic Supply System Schematic Figure 2
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL
3. Demand Pump
___________
A. Each hydraulic system has a demand pump that will be used if there is an EDP malfunction. The demand pump will also be used if the pressure output of the EDP decreases below 1,400 psi.
B. The ADP and turbine drive are installed on the aft side of the strut torque box for systems No. 1 and No. 4. The ADP is of the same type as the EDP. The turbine drive uses pneumatic pressure and supplies power to the ADP. The ADP will operate at a constant speed of 3,200 rpm and supply a pressure output of 2,900 psi (AMM 29-11-08/001).
C. The ACMP is installed on the aft side of the strut torque box for systems No. 2 and No. 3. The ACMP is of the same type as the EDP. An electric ac motor supplies power for the pump.
D. The auxiliary AC motor-driven pumps are installed on the aft side of the ADP for systems No. 1 and 4. These auxiliary pumps are different from the ACMPs. The ac motor and the hydraulic pump are installed as one unit. The AUX ACMP on System 4 is only used for the brake system when the airplane is on the ground. The AUX ACMP on System 1 is used for body gear steering during ground operations. The output of an auxiliary pump is 5.7 gpm at 2,700 psi (AMM 29-21-00/001).
4. Reservoir
_________
A. The hydraulic reservoir for each main system is installed aft of the demand pump in the nacelle strut. The reservoir supplies hydraulic fluid for the EDP and demand pumps. The design and operation of the reservoirs are the same and are different only in capacity. The reservoirs for systems No. 1 and No. 4 have a capacity of 10.6 gallons (40.1 liters). Systems No. 2 and No. 3 have a capacity of 6.95 gallons (26.3 liters). Each reservoir has:
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a hydraulic fluid quantity transmitter
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a sight glass
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a manual drain valve
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a negative-G trap
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a fluid sampling valve
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an air pressure relief valve.
B.
Hydraulic return fluid will go into the reservoir, through a diffuser and into the negative-G trap. During a negative-G condition the trap will make sure that there is a positive fluid supply to the pumps. If the negative-G valve becomes locked in the negative-G (closed) position, air will be released by the fluid and become caught in the lower part of the reservoir. Pump cavitation will occur if sufficient fluid is moved to cause the EDP supply port to be open to the air. The pneumatic system supplies regulated air pressure of 45 psi to the reservoir. This air pressure will make sure that the pumps have a positive supply of fluid. The air pressure relief valve will release air at 62 psi.
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