777 AIRCRAFT MAINTENANCE MANUAL
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SPOILER AND SPEEDBRAKE CONTROL -CABLE-CONTROLLED SPOILER PCU -FUNCTIONAL DESCRIPTION
General
The cable-controlled spoiler PCU operates in two different modes:
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Roll control
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Speedbrake control.
In roll control mode, the cable system supplies a mechanical input to the main control valve.
In speedbrake control mode, speedbrake lever movement causes the ACEs to energize the speedbrake solenoid. This bypasses the main control valve and sends a hardover command to the actuator.
The actuator LVDT supplies a position feedback signal to the ACEs.
Roll Control Mode
The PCU is in roll control mode when the ACE does not energize the speedbrake solenoid valve.
When there is no roll or speedbrake command, a spring forces the main control valve to the fully retracted position. Hydraulic fluid pressurizes the actuator to retract. The extension check valve stays closed. Its internal check valve permits the retract pressure to the actuator.
EFFECTIVITY
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When the pilot turns the control wheel, the spoiler PCU quadrant moves the main control valve. This sends hydraulic system pressure through the speedbrake mode valve to the actuator, and results in the actuator extension or retraction. When the command is to extend, the extension check valve opens and permits flow to return. When the command is to retract, the hydraulic pressure flow goes through the closed extension check valve. The angular output movement of the PCU about the trunnion supplies mechanical loop feedback to the main control valve.
Speedbrake Control Mode
The PCU is in speedbrake control mode when the ACE energizes the speedbrake solenoid.
When the pilot moves the speedbrake lever more than 54 degrees, the ACE energizes the speedbrake solenoid. This moves the solenoid valve. Hydraulic pressure then moves the speedbrake mode valve to the speedbrake position. Under these conditions, hydraulic pressure goes directly through the speedbrake mode valve to the actuator. The extension check valve opens and permits flow to return. This results in full actuator extension.
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SPOILER AND SPEEDBRAKE CONTROL -CABLE-CONTROLLED SPOILER PCU -FUNCTIONAL DESCRIPTION
When the pilot moves the speedbrake lever to less than 45 degrees, the ACE de-energizes the speedbrake solenoid. With no electrical input, internal springs force the speedbrake solenoid valve and the speedbrake mode valve to the closed position. This puts the PCU in the roll control mode of operation. If there is no roll command, the main control valve pressurizes the actuator to retract. Hydraulic pressure flows through the closed extension check valve.
Operation Without Hydraulic Pressure
Without hydraulic pressure to the PCU, the extension check valve closes and prevents extension of the PCU actuator.
If the spoiler panel is raised at the time of hydraulic power loss, the airload on the spoiler causes hydraulic fluid to flow through the speedbrake mode valve and the main control valve. This permits the actuator to retract.
The thermal relief valve cracks open at about 3700 psid and closes at approximately 3100 psid.
Manual Operation
You can open the extension check valve with the manual bypass. With the extension check valve open, you can raise the spoiler without hydraulic power. You can lower the spoiler panel with the extension check valve closed.
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SPOILER AND SPEEDBRAKE CONTROL -CABLE-CONTROLLED SPOILER PCU -FUNCTIONAL DESCRIPTION
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SPOILER AND SPEEDBRAKE CONTROL -INBOARD AND OUTBOARD SPOILER PCU -PHYSICAL DESCRIPTION
General
Except for spoilers 4 and 11, the inboard and outboard spoiler PCUs move their spoiler panel with electrical command signals from the ACEs. Each spoiler has one PCU.
Location -Inboard Spoiler PCUs
The inboard spoiler PCUs are on the inboard wing spoiler beams. Access to the PCUs is by hinged panels on the lower wings.
Trunnion pillow blocks connect the PCUs to the spoiler beam structure. Each PCU actuator rod connects to its spoiler panel clevis fitting.
An electrical connector attaches forward and left of the cap end of the PCU.
Two hydraulic tubes connect to ports at the cap end of the PCU.
Location -Outboard Spoiler PCUs
The outboard spoiler PCUs are on the outboard wing rear spars. Access to the PCUs is by hinged panels on the lower wings. 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 2(51)
