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SLAT SKEW DETECTION -OUTBOARD SLAT SKEW MECHANISM AND CABLE

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777 AIRCRAFT MAINTENANCE MANUAL

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SLAT SKEW DETECTION -FUNCTIONAL DESCRIPTION

General

There are 12 slat skew sensors. Each FSEU receives data from one of the skew sensors at each slat skew sensor location.
Both channels in the FSEUs use the slat skew data for:
*
The inboard slat skew monitor

*
The outboard slat skew monitor

*
Failure detection.

Inboard Slat Skew Monitor

The inboard slat skew monitor receives data from the inboard and outboard skew sensors for slats 7 and 8. This monitor also receives data from the slat position sensors to predict the condition of the skew sensors.
The inboard slats are in a skew condition if:

*
The condition of the inboard and outboard skew sensors for slat 7 (or 8) disagree with each other, or

*
The condition of the inboard and outboard skew sensors for slat 7 (or 8) both disagree with the predicted condition.

Outboard Slat Skew Monitor
The outboard slat skew monitor receives data from the skew sensors in slats 2 and 13. Normally, these sensors are in the target-near condition. The outboard slats are in a skew condition (or a slat is lost) if these sensors are in the target-far condition.
Slats Drive Shutdown
The failure detection function in the FSEUs receives input from these sensors:
*
The slat skew sensors

*
The slat position sensors

*
The flap lever position sensors.

When both FSEUs find a failure, they stop and shutdown the slats drive. There is a slats drive shutdown when any of these conditions occurs:
*
The inboard or outboard slat skew monitors find a failure (slat skew or lost slat)

*
The left slat position sensors do not agree with the right slat position sensors (slat asymmetry)

*
The slats do not move within five seconds after a slat command in the secondary mode (disagree).

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SLAT SKEW DETECTION -FUNCTIONAL DESCRIPTION

If there is a slat skew, asymmetry, or secondary mode disagree condition, the FSEUs latch the shutdown of the primary and secondary modes. The FSEUs also send signals to AIMS to show the SLATS DRIVE caution message. The slat position display changes to the secondary mode display and the slat position indication shows in amber.
A slats drive shutdown still permits the flaps to operate in primary or secondary mode. The flaps then move to their commanded position independently of the slat position. If the slats are not at the gapped position when the slats drive shutdown occurs, the flaps cannot move more than the 20-unit position. If the slats are at the gapped position when the slats drive shutdown occurs, the flaps can move more than the 20-unit position.
To reset the latch, cycle the alternate flaps arm switch or do the primary system test on the MAT.
Skew Sensor Failure

If one or more of the slat skew sensors fails, the FSEUs send a signal to the AIMS to show the FLAP/SLAT SKEW SNSRS status message.
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details. 

SLAT SKEW DETECTION -FUNCTIONAL DESCRIPTION

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