HORIZONTAL STABLIZER CONTROL -COMPONENT LOCATIONS -TAIL
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HORIZONTAL STABILIZER CONTROL -ANALOG AND DISCRETE INTERFACES
General
All the analog interfaces for the stabilizer pitch control within the PFCS go through the ACEs. Each ACE has interfaces with these components:
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Alternate pitch trim lever switches
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Control wheel pitch trim switches
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Stabilizer position indicators
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Auto shutdown relays
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Stabilizer trim control modules (STCM)
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Stabilizer position modules.
Alternate Pitch Trim Lever Switches
The alternate pitch trim lever switches on the alternate pitch trim forward quadrants send discrete signals to the AIMS. The signals represent pitch up or pitch down commands.
Control Wheel Pitch Trim Switch Modules
The pitch trim switches on each control wheel send pitch up, pitch down or off discrete signals to the ACEs.
Stabilizer Position Indicators
The two stabilizer position indicators receive analog signals from the AIMS that show stabilizer position.
Stabilizer Cutout Switches
Each stabilizer cutout switch controls a motor-operated shutoff valve in an STCM.
Auto Shutdown Relays
The ACEs can send discrete signals to the auto shutdown relays to close the motor-operated shutoff valves in the STCMs.
Stabilizer Trim Control Modules
Each of the two STCMs receive discrete signals from the ACEs and the auto shutdown relays. The discrete signals are for the:
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Control and arm trim solenoids
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Rate control solenoids
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Motor operated shutoff valves.
The pressure switches send discrete signals back to the ACEs.
Stabilizer Position Module
Three stabilizer position modules contain a position RVDT and limit switches.
The RVDTs send an analog signal to the ACEs that represents the stabilizer position.
The ACEs send discrete signals through the limit switches to the STCMs.
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HORIZONTAL STABILIZER CONTROL -ANALOG AND DISCRETE INTERFACES
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HORIZONTAL STABILIZER CONTROL -PITCH TRIM SWITCHES
Purpose
The pitch trim switches electrically command stabilizer movement.
Physical Description
Each switch has three positions: pitch up, pitch down, and off. It is spring loaded to the off position.
Location
Two pitch trim switch pairs are on the outboard side of each control column.
Functional Description
One switch of the pair sends an arm signal and the other sends a control signal to the ACEs.
The pilot moves both switches in the up position to command nose down trim. In the down position, the switches command nose up trim.
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HORIZONTAL STABILIZER CONTROL -PITCH TRIM SWITCHES
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777 AIRCRAFT MAINTENANCE MANUAL
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HORIZONTAL STABILIZER CONTROL -ALTERNATE PITCH TRIM LEVERS AND FORWARD QUADRANT ASSEMBLY
Purpose
The alternate pitch trim levers give the pilots mechanical control of pitch trim. The forward quadrant assembly transmits the movement from the levers to the control cables.
Physical Description
Two alternate pitch trim levers supply arm and control mechanical commands to the STCMs. The two levers are independent of each other. Springs move the levers back to the center position. Each lever connects by rod to its own forward quadrant.
Each quadrant has three alternate pitch trim lever switches. Cams on the quadrants operate the switches. A pair of cables connects each quadrant to the aft control module in the stabilizer compartment.
Location
The two alternate pitch trim levers are on the captain’s side of the P10 control stand. The forward quadrant assembly is just below the levers in the aisle stand.
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