When the pilot turns the control wheel, the control column cable drums turn and move the control cables. Stops mechanically keep the control wheel movement to a limit of 65 degrees right and left.
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AILERON AND FLAPERON CONTROL -CONTROL WHEEL

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AILERON AND FLAPERON CONTROL -WHEEL CABLE DRUM

Purpose

The wheel cable drums transmit the wheel cable motion to the force transducer and upper force limiter.
Physical Description

The wheel cable drums are cast assemblies. The right and left drums are not the same. Both drums have attachment points for the upper force limiter, which is part of the wheel jam breakout mechanism.
The left drum has an additional attachment point for the wheel force transducer. The left drum is bearing mounted on a sleeve which is spline mounted on the left shaft assembly. If there is a failure, the sleeve and left drum can connect through a lost motion device. The lost motion device permits connection after a control wheel rotation of 7.8 degrees in either direction.
The right drum is bearing mounted on the right shaft assembly. The right drum has a peg on the bottom side which is part of the lost motion device. If there is a failure, the lost motion device lets the right drum connect to the right shaft assembly after a control wheel rotation of 2.9 degrees in either direction.
Location

The wheel cable drums are on the shaft assemblies. They are between the flight deck floor and the nose gear well. Access to the drums is through the MEC, along the nose gear wheel well, or through the flight deck floor access panels.
Functional Description
When the pilots move the control wheels, the wheel cables turn the wheel drums.
Training Information Point
Each wheel cable drum has a rig pin hole.

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AILERON AND FLAPERON CONTROL -WHEEL CABLE DRUM

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777 AIRCRAFT MAINTENANCE MANUAL

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Page 20 D633W101-BEJ Jan 05/2002

AILERON AND FLAPERON CONTROL -WHEEL JAM BREAKOUT MECHANISM

Purpose

The wheel jam breakout mechanism supplies a load path for roll control. In normal operation, the mechanism permits either pilot to make roll control commands. If there is a jam of a control wheel, the breakout mechanism permits the pilot to operate the other control wheel. If the cable or connection breaks, the other control wheel still operates.
Physical Description

The wheel jam breakout mechanism has two identical force limiters and two lost motion devices.
Force Limiter

Each force limiter is a pogo. It contains an inner and outer rod and a spring. It takes a 50 lb (23 kg) force at the control wheel to breakout the force limiters.
The upper force limiter attaches directly to the two wheel cable drums. The lower force limiter attaches to the two cranks on the left and right shaft assemblies.
Lost Motion Devices

There is a lost motion device on the left and right cable drums.
If there is a failure, the left cable drum motion device connects the drum to the left shaft assembly after a control wheel rotation of 7.8 degrees.
EFFECTIVITY
BEJ ALL

The lost motion device on the right drum is a peg and notch type mechanism. The right wheel cable drum has a peg on the bottom surface which inserts in the slot of the right crank, directly below it. If there is a failure, the right lost motion device connects the right wheel cable drum to the right crank after a control wheel rotation of 2.9 degrees.
Location
The wheel jam breakout mechanism is between the flight deck floor and the nose gear wheel well. Access is through the MEC, then along the left side of the nose gear wheel well.
Functional Description -Normal Operation
In normal operation, the two force limiters supply the load path for roll control.
Movement of the left wheel cable drum goes through the upper force limiter to move the right cable drum and the right control wheel. The movement also goes through the force transducer to the left crank. The left crank moves the left shaft assembly. It also moves the right crank and the right shaft assembly through the lower force limiter.
Movement of the right wheel cable drum goes through the upper force limiter to move the left cable drum and the left control wheel. The rotation of the left cable drum moves both shaft assemblies in the same manner as above.
　
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