AFDS -BACKDRIVE ACTUATOR INSTALLATION -3
General
The left control wheel backdrive actuator and the left rudder pedal backdrive actuator are below the flight deck floor.
Access is through the left side of the main equipment center.
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AFDS -BACKDRIVE ACTUATOR INSTALLATION -3
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AFDS -BACKDRIVE ACTUATOR INSTALLATION -4
General
The right control wheel backdrive actuator and the right rudder pedal backdrive actuator are below the flight deck floor.
Access is through the right side of the main equipment center.
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AFDS -BACKDRIVE ACTUATOR INSTALLATION -4
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AFDS -BACKDRIVE ACTUATOR -FUNCTIONAL DESCRIPTION
General
Each backdrive actuator contains:
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Two tachometers
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A DC motor
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An engage clutch
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An override slip clutch.
Tachometers
The two tachometers supply motor rate feedback to the AFDC processors. Tachometer A feedback goes to processor A. Tachometer B feedback goes to processor B.
DC Motor
The AFDC supplies a variable dc current to the motor. The current to the motor limits the motor torque.
Engage Clutch
The AFDC supplies 28v dc to operate the engage clutch. The clutch connects the output crank to the motor and gear train. With the clutch not engaged, the output crank is free to move with the flight controls.
Override Slip Clutch
The override slip clutch lets the pilot override the backdrive actuator if it jams.
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Actuator Authority
The AFDC controls the motor current to each backdrive actuator. This limits the force that a backdrive actuator applies to the control columns, control wheels, and rudder pedals. This force is sufficient for the actuator to overcome the feel and friction forces in the control system. The force is limited so that the pilot can override the backdrive, feel, and centering forces. The autopilot disengages if the pilot overrides the backdrive, feel, and centering forces.
The AFDS engages one control column and one control wheel backdrive actuator in cruise. The override forces necessary to make the autopilot disengage are approximately:
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50 pounds for the control column
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27 pounds for the control wheel.
The override forces that show are the sum of the backdrive force and the feel and centering forces from the flight controls system.
The AFDS engages all six backdrive actuators in autoland. The backdrive forces for this condition are approximately two times the force for a single actuator. The override forces are approximately:
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81 pounds for the control column
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49 pounds for the control wheel
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186 pounds for the rudder pedals.
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AFDS -BACKDRIVE ACTUATOR -FUNCTIONAL DESCRIPTION
If one control column actuator fails during autoland, the force limit of the remaining column actuator is two times as high. This makes sure there is enough force to prevent accidental column movement by the pilot during autoland.
If a control wheel or rudder pedal actuator fails during autoland, the force limit of the remaining actuator does not increase.
The force to cause the override slip clutch to slip is always more than the backdrive actuator motor torque.
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AFDS -OPERATION -OVERVIEW
General
The autopilot flight director system (AFDS) operates on the ground and in flight.
The AFDS calculates commands for these flight sequences:
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Takeoff
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Climb
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Cruise
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Descent
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Approach
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Autoland
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Rollout
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Go-around.
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777 AIRCRAFT MAINTENANCE MANUAL 中國航空網(wǎng) m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：777 AMM 飛機維護手冊 自動飛行 Autoflight(12)
