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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
777 AIRCRAFT MAINTENANCE MANUAL
ELEVATOR CONTROL -COLUMN TORQUE TUBES
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ELEVATOR CONTROL -STICK SHAKER ACTUATOR
Purpose
Two stick shaker actuators cause the control columns to vibrate when the aircraft is near a stall condition. This warns the flight crew of a situation that can be dangerous.
Physical Description
The stick shaker actuator is an LRU and weighs approximately
1.6 lb (0.6 kg). It attaches with two bolts to the column torque tube.
A power source connects to the electrical connector on each stick shaker actuator.
Functional Description
When the airplane gets near a stall condition, the warning electronics system supplies power to the stick shaker actuators. This causes a 28v dc motor in the actuator to rotate a shaft.
On the motor shaft is an eccentric weight that makes the control column vibrate.
This supplies a warning to the pilots that the airplane is near a stall.
Training Information Point
The stick shaker actuators are identical and interchangeable.
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777 AIRCRAFT MAINTENANCE MANUAL
ELEVATOR CONTROL -STICK SHAKER ACTUATOR
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ELEVATOR CONTROL -COLUMN FORCE TRANSDUCER
Purpose
Two column force transducers measure the force that the pilot applies to the control column. The force transducers send analog electrical signals to the ACEs. The PFCs use these signals to know when a pilot applies a force to the control column.
Physical Description
The force transducer is a spring with two electrically isolated LVDTs inside. The ACEs supply 7v ac, 1800 Hz excitation power.
Each LVDT has a separate cable which connects to the ACE connector bracket. This bracket has two receptacles, one for each LVDT of the force transducer. The order in which each LVDT connects to the connector bracket determines the LVDT-to-ACE relationship.
The column force transducers are different from the wheel force transducer.
Location
There is a force transducer on each elevator torque tube. The force transducer attaches to the compliance spring at the aft end, and to the elevator feel unit connecting rod at the forward end. There is a column force transducer installed on the outboard end of each column torque tube.
Functional Description
When a pilot applies a force of 2.5 lb or more to the control column, the force transducers signal the PFC the columns are no longer in the neutral position.
When the force transducers find a force of less than 2.5 pounds, the PFC uses that signal to find that the column is at the neutral position.
Indications
The status message FLIGHT CONTROL SYS shows when one of the force transducers is defective.
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ELEVATOR CONTROL -COLUMN FORCE TRANSDUCER
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ELEVATOR CONTROL -COLUMN DAMPER
Purpose
Two control column dampers supply a resistance to the
movement of the vibrations and brings oscillation. control the column. column This to rest prevents with m column inimum
Physical Description
The column damper is an LRU and weighs about 1.6 lb (0.7 kg).
The column dampers are identical to the wheel and rudder pedal dampers. There are four of these identical dampers on the airplane.
The dampers are on each of the column torque tubes. Control rods connect from arms on the column torque tubes to splined cranks connecting to the dampers.
The column damper has an input shaft. The column damper uses a fluid to absorb vibrations that go to the shaft. A window on the column damper shows the position of the fluid level indicator.
The damper crank on the damper shaft, has a pair of rivets. These shear out in case of a jam of the column damper.
Location
The column dampers are just forward of each column torque tube.
Functional Description
As the control columns rotate the torque tubes, the connecting rods move the splined cranks on the column dampers. The dampers absorb the vibration in the control columns. The dampers add a small force to control column movement.
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