*
Down command
*
Actuation command.
Training Information Point
There is a rig pin hole in the forward quadrants and on the support structure.
Indications
The status message ALT PITCH TRIM LEV shows when one alternate pitch trim lever switch is defective.
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HORIZONTAL STABILIZER CONTROL -ALTERNATE PITCH TRIM LEVERS AND FORWARD QUADRANT ASSEMBLY
The status message FLIGHT CONTROL SYS shows when two or more alternate pitch trim lever switches are defective.
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HORIZONTAL STABILIZER CONTROL -ALTERNATE PITCH TRIM LEVERS AND FORWARD QUADRANT ASSEMBLY
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HORIZONTAL STABILIZER CONTROL -AFT STABILIZER QUADRANT ASSEMBLY
Purpose
The aft stabilizer quadrant assembly receives control movement from the two pairs of cables from the forward quadrant assembly. The aft stabilizer quadrant assembly transfers this movement to the input cranks on the STCMs.
Physical Description
The aft stabilizer quadrant assembly has an arm and a control quadrant on which the two alternate trim cable pairs attach. The arm quadrant is forward of the aft stabilizer quadrant assembly. The control quadrant is inside the quadrant assembly. Each quadrant connects to its own shaft by a spline which also connects to its output lever.
Control rods connect the output levers of the aft stabilizer quadrant assembly to the input cranks on the STCMs.
A travel limit drum assembly is at the aft of the quadrant assembly. The drum rotates on bearings on the aft quadrant assembly structure. A cable pair connects the drum assembly to the stabilizer structure.
Location
The aft stabilizer quadrant assembly is in the stabilizer compartment, near the ceiling just aft of the pressure bulkhead. The two STCMs are on either side of the quadrant assembly.
Functional Description
As the alternate pitch trim cable pairs move, in response to a movement of the alternate pitch trim levers, the arm and control quadrants rotate. Splined shafts transfer this rotation to the output levers. Control rods transfer the movement to the input cranks on the STCMs.
Training Information Point
There are rig pin holes in the arm quadrant, the travel limit hammer and aft stabilizer quadrant assembly structure.
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HORIZONTAL STABILIZER CONTROL -AFT STABILIZER QUADRANT ASSEMBLY
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HORIZONTAL STABILIZER CONTROL -AFT STABILIZER QUADRANT ASSY -TRAVEL LIMIT DRUM ASSEMBLY
Purpose
When the horizontal stabilizer is operated from the alternate pitch trim levers, the travel limit drum assembly stops the stabilizer at the up and down limits. These limits prevent contact between the stabilizer ballnut and the ballscrew stops.
Physical Description
The travel limit drum turns on bearings on the aft quadrant assembly structure. A cable pair connects the drum assembly to brackets attached on the front spar of the stabilizer. This cable also operates the left stabilizer position module. Stops on the drum assembly contact the travel limit hammer when the stabilizer reaches its travel limits. The travel limit hammer connects by splines to the control quadrant shaft of the aft stabilizer quadrant assembly.
Location
The travel limit drum assembly is at the aft side of the aft stabilizer quadrant assembly.
Functional Description
When you move the alternate pitch trim levers, the control quadrant shaft moves the travel limit hammer from its neutral position. The STCMs command causes the stabilizer to move. The pair of cables connected to the stabilizer front spar also moves. The cable movement causes the rotation of the travel limit drum assembly. As the stabilizer reaches its up or down limit, stops on the drum contact the hammer and move it back to its neutral position. This moves the control lever of the alternate pitch trim levers to the neutral position and stops the stabilizer command.
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