777 AIRCRAFT MAINTENANCE MANUAL
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MAIN HYDRAULIC SYSTEMS -FUNCTIONAL DESCRIPTION -AIR DRIVEN PUMP
General
The pneumatic system supplies the pressurized air to operate the air driven pumps.
The ADP selectors are on the hydraulic/RAT panel.
The ADP selectors send pump control signals to the overhead panel ARINC 629 system (OPAS). The OPAS sends these control signals through the systems ARINC 629 buses to the HYDIM cards. The HYDIM cards use these signals to operate the pumps in the demand mode. HYDIM CR controls ADP C1 in the demand mode. HYDIM CL controls ADP C2 in the demand mode. The control circuits on each card are equivalent.
The HYDIM cards do not control the ADPs in the continuous run (ON) mode. The ADP selectors send electrical signals directly to the LSCU to operate the pump in the continuous run mode.
An LSCU for each ADP gets the input signals to open the MSOV to permit the ADP to operate.
Demand Mode
With the two ADP selectors in AUTO, the HYDIM cards start one or both of the ADPs when the center hydraulic system must supply a large hydraulic flow rate.
The HYDIM cards get the ADP selector input signal from the ARINC 629 systems buses. The HYDIM cards must also get a hardwire electrical signal from the AUTO position of the ADP selector.
The HYDIM cards prevent or stop demand mode ADP operation during main engine start on the ground.
One ADP operates during any of these conditions:
*
Landing gear extension
*
Flap/slat operation
*
Low pressure (less than 2400 psi) in the center system or in both center system ACMPs
*
Touchdown (airspeed more than 80 kts and altitude less than 30 feet)
*
Air mode, flaps and slats not up, and one ADP selected OFF or does not operate (in case of autoslat demand)
*
Failure of the ADU heaters on both ADPs and groundspeed is more than 80 knots (turns on ADP C1).
When an ADP turns on for low pressure, the pump turns off 15 seconds after the pressure goes above 2700 psi.
The ADP turns on during the touchdown conditions to supply pressure to operate the auto speedbrakes. The pump turns off 5 seconds after the speedbrake lever moves to the stowed position.
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MAIN HYDRAULIC SYSTEMS -FUNCTIONAL DESCRIPTION -AIR DRIVEN PUMP
The HYDIM cards CL and CR make a selection of one of the two ADPs during single pump operation. They use the other ADP the next time they turn on a single pump. This equalizes the pump wear.
Both ADPs operate for these conditions:
*
Autoslat operation
*
Landing gear retraction
*
Takeoff roll (ground mode, airspeed is more than 80 kts, and the flaps are in the takeoff position).
Both ADPs turn on during the takeoff roll to make sure that at least one of them operates if there is an engine loss. This makes sure that there is sufficient hydraulic flow to operate the rudder for the thrust asymmetry compensation function. The ADPs turn off 10 seconds after the airplane takes off.
Reserve Mode
If one of the two ADPs does not operate and there is an autoslat signal, the HYDIM cards will operate the remaining ADP in the reserve mode. This permits the ADP to operate at a higher speed to make sure sufficient hydraulic flow goes to the leading edge slats. The reserve mode turns off after 8 seconds. The reserve mode operates when the selector is in AUTO or ON.
Continuous Operation
An ADP selector in the ON position sends a signal directly to the related LSCU. The LSCU then opens the MSOV to operate the ADP continuously.
Training Information Point
The ADP C1 selector must be in the OFF or AUTO position for ADP C2 to run continuously. If both ADP selectors are in the ON positions, only ADP C1 will operate.
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MAIN HYDRAULIC SYSTEMS -FUNCTIONAL DESCRIPTION -AIR DRIVEN PUMP
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777 AIRCRAFT MAINTENANCE MANUAL
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MAIN HYDRAULIC SYSTEMS -FUNCTIONAL DESCRIPTION -ALTERNATING CURRENT MOTOR PUMP
General
The control switches and selectors on the hydraulic control panel send pump control signals to the overhead panel ARINC 629 system (OPAS). The OPAS sends these control signals through the left and right systems ARINC 629 buses to the ELMS. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：777 AMM 飞机维护手册 液压 Hydraulic Power(16)
