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777 AIRCRAFT MAINTENANCE MANUAL
ELEVATOR CONTROL -COLUMN DAMPER
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ELEVATOR CONTROL -ELEVATOR FEEL UNIT
Purpose
Two elevator feel units supply feel forces to the control columns. They also supply a centering function that returns the control column to neutral.
Physical Description
The two elevator feel units are similar but not interchangeable.
Each elevator feel unit has a single cam and roller unit. The cam attaches by a spline to the shaft of the feel unit. The input crank, connected to the column torque tube, turns the shaft and the cam. The follower assembly has a roller which rides on the cam. A centering arm, which pivots on the elevator feel unit structure, supports the follower assembly and attaches to the feel springs. Two feel springs, between the centering arm and the spring arm, keep the roller on the cam. The two feel springs provide the feel force and the centering function. The output crank also attaches to the shaft of the feel unit. The output crank connects to the aft torque tube with a control rod.
An elevator feel actuator and three column position transducers are on each elevator feel unit.
The elevator feel actuator connects to the variable feel mechanism. This mechanism consists of levers and a linkage which connect to the spring arm. A spring connects to the mechanism to take up any play in the mechanism. A bias spring, near the feel actuator, forces the feel actuator to fully retract when it does not operate.
Location
The two elevator feel units are under the flight deck. Access is by the forward equipment door or from the MEC.
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ELEVATOR CONTROL -ELEVATOR FEEL UNIT
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ELEVATOR CONTROL -ELEVATOR FEEL ACTUATOR
Purpose
The feel actuators change the geometry of the elevator feel units to change the feel force at the control columns.
Physical Description
The two actuators are identical and interchangeable LRUs.
The feel actuator has a 28v dc reversible electric motor. The actuator extends 2.5 inches (63.5) maximum. Each actuator weighs about 4.27 lb (1.6 kg).
The actuator attaches to the elevator feel unit structure. The actuator rod end attaches to the input lever of the variable feel mechanism.
Location
The elevator feel actuators are on the aft side of the elevator feel units.
Functional Description
When the elevator feel actuator extends, it changes the configuration of the feel mechanism in the feel unit. When the column moves, this causes an increase in the extension of the feel springs. This increases the feel force at the columns.
The rod end of the actuator moves in response to the commands from the ACEs. The L2 ACE sends commands to the left feel actuator and the C ACE sends commands to the right feel actuator. An RVDT in the feel actuator supplies a position feedback signal to the PFCs through the ACE.
Indications
The status message FLIGHT CONTROL SYS shows when one, or more, elevator feel actuator is defective.
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ELEVATOR CONTROL -ELEVATOR FEEL ACTUATOR
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ELEVATOR CONTROL -ELEVATOR FEEL -FUNCTIONAL DESCRIPTION
General
The elevator feel unit supplies a feel force to the control columns. The elevator feel actuator changes the feel force. The feel at the control column increases with the amount of column movement and the speed of the airplane.
Feel and Centering
When the pilot moves the control column, the cam in the elevator feel unit rotates. This causes the cam follower to move and the centering arm to extend the feel springs. At low airspeed, the feel force at the control column is from 6.4 lb (2.9 kg) at breakout to a maximum of 43.3 lb (19.6 kg) at column maximum travel.
When the pilot releases the control column, the feel springs force the cam follower back to the cam detent. This returns the elevator control system to the neutral position.
Variable Feel
As the speed of the airplane increases, the feel actuator extends gradually. This causes the levers of the variable feel mechanism to move the mechanism pivot point. The feel springs extend further with the mechanism in this position. When the pilot moves the column, the increased spring extension causes an increase of the column feel force. 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(5)
