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TE FLAP SKEW
The Trailing Edge (TE) Flaps are protected against an unwanted asymmetrical or “crooked” skewed position which can negatively affect the aerodynamics of the aircraft. Detection is accomplished by the Flap & Slat Electronic Unit (FSEU) which, when detected, restricts further movement of the TE flaps.
An ASYMMETRY is present when a position misalignment is detected between similar TE flap panels on the opposite wing (top image)and a SKEW refers to a single TE flap panel where the inboard end misaligns with the outboard end (bottom image). In both cases, the FSEU commands the bypass valve to close, thereby stopping further movement of the TE flaps. The FSEU also sends this data to the SMYD computers for stall warning, and to the PSEU for the takeoff configuration warning which will be affected by the misalignment.
A skew condition is detected through 8 flap drive skew sensors and present when a skew revolver sensor misalignment exists of:
– 28 degrees between skew sensors 1 and 8
– 28 degrees between skew sensors 2 and 7
– 26 degrees between skew sensors 3 and 6
– 34 degrees between skew sensors 4 and 5.
The condition disappears when that misalignment becomes less than 13°. A TE flap skew condition is presented on the flight deck by a 15° split between the left and right needle on the flap position indicator. When a panel skew position sensor is further than the normal position sensor, the needle for the skewed flap indicates 15° toward the extend position, and if this position is less than the normal position sensor, the needle indicates 15° toward retract.
Power sources involved are:
– Left TE flap sensors and indicator needle 28 VAC XFR bus 2
– Right TE flap sensors and indicator needle28 VAC XFR bus 2
– Flap bypass valve (shut off valve) 28 VDC bus 2
(see electrical supplement)
Be aware that the skew detection is unavailable during Alternate flap operation!!