*
A thermal relief valve
*
A compensator/relief valve
*
An inlet check valve
*
An inlet filter.
Hydraulic Actuator
The actuator piston has an LVDT that sends actuator position feedback signals to the ACE. The actuator piston also has a null LVDT to adjust the null position of the actuator piston LVDT during adjustment of the control surface.
EHSV
The EHSV controls the hydraulic power to the extend and retract sides of the actuator. The EHSV has an LVDT that sends EHSV position feedback signals to the ACE.
Bypass Solenoid Valve
The bypass solenoid valve controls the pilot pressure from the hydraulic system to the mode selector valve and the extension check and relief valve.
Blocking Solenoid Valve
The blocking solenoid valve controls the pilot pressure from the actuator to the mode selector valve and the extension check and relief valve.
Mode Selector Valve
Pilot pressure from the bypass or blocking solenoid valves commands the mode selector valve in one of three positions:
*
Normal
*
Bypass
*
Blocking/Damped.
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AILERON AND FLAPERON CONTROL -AILERON PCU -PHYSICAL DESCRIPTION
Extension Check and Relief Valve with Manual Bypass
The extension check and relief valve opens when the PCU is in normal mode. It also opens in bypass mode by the pilot pressure trapped between the bypass check valves and the thermal relief valve.
The extension check and relief valve has a manual bypass. The manual bypass permits the actuator to extend manually for maintenance.
Bypass Check Valves
The two bypass check valves permit pressure from either side of the actuator to reach the blocking solenoid valve.
Anti-cavitation Check Valves
The two anti-cavitation check valves permit return fluid from the compensator/relief valve to flow to the actuator. This prevents cavitation of the actuator during rapid backdrive of the PCU.
Thermal Relief Valve
The thermal relief valve protects the actuator from thermal expansion of the hydraulic fluid.
Compensator/Relief Valve
The compensator/relief valve holds a small quantity of fluid above hydraulic system return pressure. This fluid is available to the actuator to prevent cavitation.
Inlet Check Valve
The inlet check valve keeps the hydraulic fluid in the actuator when the hydraulic system power is lost.
Inlet Filter
The inlet filter protects the actuator from solids in the hydraulic fluid.
Training Information Point
Only the bearings in the actuator rod end and the reaction link, where they attach to the aileron, require lubrication.
All the other bearings at the kick link and the reaction link are teflon coated bearings. They do not require lubrication.
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AILERON AND FLAPERON CONTROL -AILERON PCU -PHYSICAL DESCRIPTION
EFFECTIVITY BEJ ALL 27-11-00
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777 AIRCRAFT MAINTENANCE MANUAL
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27-11-00
Page 40 D633W101-BEJ Jan 05/2002
AILERON AND FLAPERON CONTROL -AILERON PCU -FUNCTIONAL DESCRIPTION
General
The aileron PCU operates in three different modes:
*
Normal
*
Bypass
*
Blocking/Damped.
In the normal mode, the ACE energizes both the bypass and blocking solenoids with flight below cruise speed. Above cruise speed, the ACE de-energizes the blocking solenoid.
In the bypass mode, the ACE de-energizes the bypass solenoid.
In the blocking/damped mode, the ACE de-energizes both the bypass and the blocking solenoids.
PCU Operational Matrix
The table below shows the various conditions of the PCU valves in the three modes of operation.
SOLENOID CONDITIONS PCU MODES OF OPERATION
NORMAL BYPASS BLOCKING/ DAMPED
BYPASS SOLENOID E *[1] D *[2] D *[2]
BLOCKING SOLENOID *[1]E/D *[2] E *[1] D *[2]
*[1] E = ENERGIZED *[2] D = DE-ENERGIZED
EFFECTIVITY BEJ ALL Normal Mode
During operation below cruise speed, the PCU is in normal mode when the ACE energizes both the bypass and the blocking solenoid valves.
Hydraulic system pressure moves the mode selector valve to the normal position and opens the extension check and relief valve. Under these conditions, an electrical command to the EHSV results in the actuator extension or retraction.
Aileron Lockout
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