Old 28th Dec 2018, 05:33
  #33 (permalink)  
Capt Quentin McHale
Join Date: Oct 2013
Location: McHales Island
Age: 64
Posts: 139

The AoA sensor vane is aerodynamically shaped and can swing through 360deg without a problem (on the ground) and you often see the vanes on a parked aircraft drooping vertically or with a good breeze blowing, 180deg in reverse and anywhere in between. This is NOT a problem and is merely the nature of the beast. The SMYD computers ignore this because the aircraft is in "ground mode" signalled through squat switches, no engines running, park brake on, airspeed <30kts etc, etc, etc.

When the aircraft is starting to accelerate down the runway, the airflow around the nose of the aircraft will reposition the vanes to the required position. I don't know the exact requirements/signals for the SMYD's to start paying attention to AoA vane position/angle (transmitted by internal resolvers/synchro's) but it could be when (don't quote me) BOTH engines are started and >80% N1, park brake off, all cabin doors closed, airspeed >30kts etc, etc, etc. Hope this helps.

Rgds McHale.
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