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AILERON AND FLAPERON CONTROL -AILERON PCU -FUNCTIONAL DESCRIPTION
The bypass solenoid valve blocks hydraulic pressure to the mode selector valve. However, pressure trapped between the bypass check valves and the thermal relief valve moves the mode selector valve to the bypass position. This pressure also keeps the extension check and relief valve open.
Under these conditions, the mode selector valve blocks control pressure from the EHSV to the actuator cylinder. It also allows free hydraulic flow between both sides of the piston on the failed PCU. The adjacent PCU controls the aileron movement and backdrives the failed PCU.
During rapid backdrive of the failed PCU, the compensator/relief valve supplies fluid to the actuator through the anti-cavitation check valves.
If there is a subsequent failure on the adjacent PCU, its ACE de-energizes its bypass solenoid valve. With both PCUs in the bypass mode, the airloads cause the aileron trailing edge to move up approximately 15 degrees from the faired (neutral) position.
Blocking/Damped Mode
The PCU is in the blocking/damped mode when the ACEs de-energize both the bypass and the blocking solenoid valves. This happens when the PCU has no power or the PCU has a failure at or above cruise speed.
In the blocking/damped mode, there is no hydraulic pressure on the mode selector valve. Its internal spring moves the valve to the blocking/damped position. The mode selector valve blocks control pressure from the EHSV to the actuator cylinder. It also connects both sides of the actuator through a restriction. Also, the extension check and relief valve closes.
Under these conditions, the actuator cannot extend but can retract very slowly.
During flight at or above cruise speed, when both PCUs of an aileron are in the blocking/damped mode, the closed extension check and relief valve prevents the aileron upward movement caused by aerodynamic lift.
On the ground, with no electrical or hydraulic power on the aileron PCUs, the PCUs are in the blocking/damped mode. The ailerons cannot move up but can move down. Turn the manual bypass to move the ailerons and the PCUs in the up direction.
Indications
The status message FLIGHT CONTROL SYS shows on the status display when one or more aileron actuator is failed or the actuator confidence test has failed.
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AILERON AND FLAPERON CONTROL -AILERON PCU -FUNCTIONAL DESCRIPTION
EFFECTIVITY BEJ ALL 27-11-00
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AILERON AND FLAPERON CONTROL -FLAPERON PCU -LOCATION
Purpose
The flaperon PCUs move the flaperons. Electrical command signals from the ACEs actuate the flaperon PCUs. Each flaperon has two PCUs.
Location
The two PCUs are on the rear spar of the inboard wing. Access to the PCUs is by a removable lower skin panel below each PCU.
The head end bearing assembly connects the PCU to the rear spar structural fitting. The actuator rod connects to the flaperon surface fitting.
One electrical connector connects to the PCU.
Hydraulic tubing connects to ports near the forward end of the PCU. The hydraulic tubing from these hoses have fuses and check valves to help prevent the loss of hydraulic fluid if there is damage to the PCUs or hydraulic tubing caused by the loss of a flaperon. The hydraulic fuses and check valves for the left and right hydraulic system are near the left flaperon. The fuse and check valve for the center hydraulic system are near the right flaperon.
Training Information Point
The head end bearing assembly stays in place when you remove and install the flaperon PCU.
Installation of the PCUs is with the control modules facing each other. One PCU is up-side-down in relation to its adjacent PCU.
During the adjustment of the flaperon surface, it is necessary to adjust the actuator null LVDT. Remove the LVDT access cover to adjust the LVDT.
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AILERON AND FLAPERON CONTROL -FLAPERON PCU -LOCATION
EFFECTIVITY BEJ ALL 27-11-00 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 飞行操纵 Flight Controls 1(37)
