*
Install the fill port dipstick in the PDOS pump.
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PW4000 SERIES ENGINES
777 AIRCRAFT MAINTENANCE MANUAL
PDOS -PUMP/POWER PACK
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PDOS -PUMP/POWER PACK -FUNCTIONAL DESCRIPTION
The PDOS pump/power pack has a hydraulic reservoir, a pump, a filter, and five solenoid valves. The pump takes fluid (engine oil) from the reservoir and sends it through the filter and solenoid valves to the fan cowl and T/R opening actuators.
Power
The PDOS pump/power pack gets power from the 115v ac ground handling bus. The actuation and control switches get power from the 28v dc ground handling bus.
Fan Cowl and Thrust Reverser Opening
When you push one of the actuation and control switch buttons, power goes to the necessary solenoid valve(s) and the pump motor. The solenoid valves let pressure go to one of the cowl opening actuators. The cowl opening actuator then opens a fan cowl or a T/R half.
Fan Cowl and Thrust Reverser Closing
The PDOS uses gravity to close the fan cowls and T/Rs. The electric motor does not operate when you close the fan cowls and T/Rs. The DOWN button on the actuation and control switch operates the solenoids. The solenoids release hydraulic pressure, and gravity closes the fan cowl and T/R halves. When the fan cowls and the T/R halves close, the oil goes back to the reservoir.
This table shows which solenoid(s) energize to open the cowl listed:
OPEN V1 V2 V3 V4 V5
L Fan Cowl X
R Fan Cowl X
L T/R X X
R T/R X X
This table shows which solenoid(s) energize to close the cowl listed:
CLOSE V1 V2 V3 V4 V5
R T/R X X X
L T/R X X X
R Fan Cowl X X
L Fan Cowl X X
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PDOS -PUMP/POWER PACK -FUNCTIONAL DESCRIPTION
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PDOS -OPERATION -FAN COWL
When you work on engine components under the fan cowl, you open the fan cowl only. If engine components under the thrust reverser (T/R) need repair, you open the fan cowl first, and then you open the T/R. You must have electric power before you use the PDOS.
Open the Fan Cowl
Here is a summary of how you open the fan cowl:
*
Make sure the area around the engine is clear
*
Open the four fan cowl latches
