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ELEVATOR CONTROL -GENERAL DESCRIPTION
The PFCs also supply column backdrive commands. The PFCs send these commands to the AFDCs, which supply column movement commands to the backdrive actuators. The backdrive actuators move the control columns the same amount as the pilot would move them manually for the same surface movement. This gives the flight crew visual feedback when the AFDS moves the flight control surfaces. The flight crew can override the autopilot with sufficient force on the control column to overcome the backdrive.
Protection Functions
Overspeed and stall protection functions in the PFCs supply flight envelope protection in both manual and autopilot operation. The overspeed protection supplies a pitch-up elevator command. The stall protection supplies a pitch-down elevator command.
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ELEVATOR CONTROL -GENERAL DESCRIPTION
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ELEVATOR CONTROL -COMPONENT LOCATIONS
General
Pitch control components are in these areas:
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The flight deck
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Below the flight deck floor
*
The tail.
Flight Deck Components
The control columns are in the flight deck.
Components Below the Flight Deck
These forward controls are below the flight deck floor and above the nose gear wheel well:
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Column torque tubes
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Column balance weights
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Column dampers
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Stick shaker actuators
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Column force transducers
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Elevator feel units
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Column backdrive actuators
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Column breakout mechanism.
Access to these components is through the forward equipment center door.
Tail Components
The elevators and their PCUs are on the rear spar of the horizontal stabilizer. Two PCUs connect to each elevator. Access to the PCUs is by panels under the stabilizer.
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ELEVATOR CONTROL -COMPONENT LOCATIONS
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ELEVATOR CONTROL -ANALOG AND DISCRETE INTERFACES
General
All pitch control analog interfaces within the PFCS go through the ACEs. Each ACE has interfaces with these components:
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Column position transducers
*
Column force transducers
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Elevator feel actuators
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Elevator PCUs.
Column Position Transducers
There are six position transducers, three for each control column. The transducers send control column position and movement data to the ACEs.
Column Force Transducers
Two column force transducers measure the forces applied to the control column. The transducers send this data to the ACEs.
Elevator Feel Actuators
An elevator feel actuator is in each of the elevator feel units. They supply a feel force to the columns through the feel units. The ACEs command the elevator feel actuators. The elevator feel actuators also send position feedback signals to the ACEs.
Elevator PCUs
Each of the four elevator PCUs receive analog and discrete electrical signals from the ACEs. The discrete signals are for the bypass, blocking, and pressure reducer solenoids. The analog signal is for the electrohydraulic servo valve (EHSV).
Each of the four elevator PCUs sends these analog feedback signals to the ACEs:
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EHSV position LVDT
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Actuator position LVDT
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Actuator null LVDT
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Differential pressure LVDT.
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ELEVATOR CONTROL -ANALOG AND DISCRETE INTERFACES
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ELEVATOR CONTROL -FORWARD CONTROLS
General
These are the forward controls of the pitch control system:
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Control columns
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Column torque tubes
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Column force transducers
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Compliance springs
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Column dampers
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Column balance weights
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