A cable transfers stabilizer movement to the cable drum on the three identical position module assemblies. Rotation of the cable drum causes rotation of an RVDT within the stabilizer position modules. The RVDTs send signals to the ACEs and the AIMS for stabilizer position.
Location
The stabilizer position modules are in the stabilizer compartment. They are near the ceiling on the aft side of a bulkhead above the stabilizer ballscrew assembly.
The stabilizer position indicators are on the aft end of the P10 control stand.
EFFECTIVITY
BEJ ALL
Physical Description
The stabilizer position module attaches to the position module assembly with three bolts. The module spline has a missing tooth and an alignment mark so removal and installation can be done without rigging.
Each stabilizer position module has an RVDT and two limit switches. The limit switches keep stabilizer movement to a limit.
See the horizontal stabilizer control section for more information about the position modules (SECTION 27-41).
The position indicators have a pointer that shows the stabilizer position. The indicator scale has 15 units. Each unit of pointer movement is equivalent to approximately one degree of stabilizer movement.
Also on the indicator is a green band that shows the safe takeoff range. These are the three green band displays that AIMS can select:
*
Upper and middle segments
*
Lower and middle segments
*
Middle segment only.
Failure Indication
Loss of signal or invalid signals causes the pointer and green band to go out of view.
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HORIZONTAL STABILIZER POSITION INDICATION -STABILIZER POSITION MODULE AND INDICATOR
Loss of power causes all of the display to go out of view.
EFFECTIVITY BEJ ALL 27-48-00
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HORIZONTAL STABILIZER POSITION INDICATION -STABILIZER POSITION MODULE AND INDICATOR
EFFECTIVITY BEJ ALL 27-48-00
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D633W101-BEJ Jan 05/2002
HORIZONTAL STABILIZER POSITION INDICATION -NOSE GEAR PRESSURE SWITCH
Purpose
The WEUs use a discrete signal from the nose gear pressure switch to make sure the stabilizer indicator green band calculation is correct.
Physical Description
The switch is a two position pressure sensing switch that sends an electrical discrete signal to the WEUs.
Location
The nose gear pressure switch is on the top of the nose gear strut.
Functional Description
The pressure switch receives pressure from the nose landing gear strut and sends a discrete to the WEUs. If the center of gravity of the airplane is forward, the pressure in the nose landing gear strut increases. This causes the pressure switch to close.
If the center of gravity of the airplane is aft, the pressure in the nose landing gear strut decreases. This causes the pressure switch to open.
The WEUs calculate the green band display for the stabilizer trim indicators to show the safe range of stabilizer trim for take-off. The WEUs use the discrete signal from the pressure switch to verify the green band calculation.
Indications
Disagreement between the green band calculation and the pressure switch discrete causes the STAB GREENBAND advisory message to show.
Training Information Point
To remove the pressure switch move the shutoff valve to the closed position and lock it with a rig pin. This isolates the switch from strut pressure.
EFFECTIVITY BEJ ALL 27-48-00
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HORIZONTAL STABILIZER POSITION INDICATION -NOSE GEAR PRESSURE SWITCH
EFFECTIVITY BEJ ALL 27-48-00
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D633W101-BEJ Jan 05/2002
HORIZONTAL STABILIZER POSITION INDICATION -FUNCTIONAL DESCRIPTION
General
The stabilizer position module RVDTs send analog signals to the ACEs. The ACEs change the signals to digital format and send them to the three PFCs. The PFCs calculate the stabilizer position signals and send them to the two AIMS which command the stabilizer position indicators to show the stabilizer position.
The flight management computing function (FMCF) of AIMS sends airplane data to the WEUs for green band computation. The WEUs also use the nose gear pressure switch signal to verify the green band calculation. The WEUs then send the green band signals to AIMS which commands the indicators to show the safe takeoff range.
Functional Description
The three stabilizer position module RVDTs send individual analog signals to the L1, C and R ACEs. The ACEs change the signals to digital and put them on the flight controls ARINC 629 busses where they are sent to the three PFCs.
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