777 AIRCRAFT MAINTENANCE MANUAL
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FLAP SKEW DETECTION -GENERAL DESCRIPTION
Purpose
The flap skew detection system monitors the position of the flaps. The FSEUs stop the primary and secondary mode flap operation if there is a skew, an asymmetry or a secondary mode disagree condition.
The flaps are in a skew condition if the inboard end of a flap does not align with its outboard end.
The flaps are in an asymmetry condition if the left flaps do not align with the right flaps.
There is a secondary mode disagree if the flaps do not move or move too slowly after a command to move in secondary mode.
There is no automatic shutdown of the alternate mode if there is a flap skew, asymmetry, or secondary mode disagree.
Interface
There are 16 flap skew sensors. Each FSEU has interfaces with one sensor at each flap drive mechanism.
If the flaps are in a skew, an asymmetry or a secondary mode disagree condition, the FSEUs stop the flap drive in primary and secondary modes. The FSEUs also send a signal to the AIMS to show the FLAPS DRIVE caution EICAS message. If this happens, the flap position display on EICAS changes to the secondary mode display and the flap position indication shows in amber.
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FLAP SKEW DETECTION -GENERAL DESCRIPTION
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FLAP SKEW DETECTION -FLAP SKEW SENSORS
Purpose
The flap skew sensors monitor the position of the flaps at each flap drive mechanism.
Location
The flap skew sensors attach to the flap drive arm and the flap drive mechanism support. Access to these sensors is by extending the flaps to 30. Access to the sensors on the inboard flap inboard drive mechanism is through the main gear wheel wells.
Physical Description
The flap skew sensors are linear variable differential transformers (LVDTs). Each sensor is a separate LRU.
The mounting bracket for each sensor has a shearout to prevent structural damage if the LVDT fails mechanically.
Training Information Point
The flap skew sensors do not need to be rigged after installation.
The electrical connectors for the outboard sensors on flap drive mechanisms 1, 2, 3, 6, 7, and 8 have a 45 degree bend. The connectors can be damaged if you install them on the wrong sensor.
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777 AIRCRAFT MAINTENANCE MANUAL
FLAP SKEW DETECTION -FLAP SKEW SENSORS
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FLAP SKEW DETECTION -FUNCTIONAL DESCRIPTION
General
There are 16 flap skew sensors. Each FSEU receives data from one of the skew sensors at each flap drive mechanism.
Both channels in the FSEUs use the flap skew data for failure detection. The FSEUs monitor for flap position failures and for sensor failures.
Flap Drive Shutdown
When both FSEUs find a failure, they stop the flap drive. There is a flap drive shutdown for any one of these conditions:
*
Skew sensors on symmetrical flap drive mechanisms do not agree (asymmetry or skew)
*
The left and right flap position sensors do not agree (asymmetry)
*
The flaps do not move within 10 seconds after a flap command in the secondary mode or the flaps move too slowly (secondary mode disagree).
If there is a flap skew, asymmetry, or secondary mode disagree, the FSEUs latch the shutdown of the primary and secondary modes. The FSEUs also send signals to AIMS to show the FLAPS DRIVE caution message. The flap positon display changes to the secondary mode display and the flap position indication shows in amber.
To reset the latch, cycle the alternate flaps arm switch or do the primary system test on the MAT.
Skew Sensor Failure
If one of the flap skew sensors fail, the FSEUs send a signal to the AIMS to show the FLAP/SLAT SKEW SNSRS status message.
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FLAP SKEW DETECTION -FUNCTIONAL DESCRIPTION
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SPOILER AND SPEEDBRAKE CONTROL -INTRODUCTION
General
The spoilers help the ailerons and flaperons control airplane roll about the longitudinal axis. They also supply speedbrake control to reduce lift and increase drag for descent and landing. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：777 AMM 飞机维护手册 飞行操纵 Flight Controls 2(45)
