PPRuNe Forums - View Single Post - MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
Old 6th Sep 2019, 07:35
  #2207 (permalink)  
hans brinker
Join Date: Nov 2010
Location: Denver
Age: 52
Posts: 39
Originally Posted by Notanatp View Post
l feel you are nit picking here. First, the DFDR data from the two accidents suggests that the normal, stationary reading for the vanes is somewhere around zero. I'm sure someone else on the thread can comment knowledgeably, but its looks to me like a stationary reading of more than 20 degrees is a pretty strong sign of a problem. Beyond that, the AoA signal surely becomes valid at some point during the take off roll, so the FCC could mark it as invalid if it's outside a reasonable range before rotation.
I think you are replying to someone who is more knowledgeable, but I will add the same thing:

AOA sensors (of the type used on the B737) have an outside vane, and an inside counterweight. Unless the aircraft is moving fast enough (and I would guess around 60-80kts) the information from the AOA is ABSOLUTELY useless. I see them pointed in every random direction during the preflight ( not on the 737, but A320 has similar).

Not an engineer, but during strong crosswinds there will be substantial difference in airflow between the sides, so it might be better to wait until the aircraft is airborne and better aligned with the airflow.
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