PPRuNe Forums - View Single Post - MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
Old 6th Sep 2019, 07:59
  #2208 (permalink)  
FlightDetent

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Join Date: Apr 2003
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Originally Posted by Notanatp View Post
(i.e., rejecting a many invalid conditions as possible while minimizing the rejection of valid conditions) could be subject to some discussion and judgment. But AoA of 20 degrees seems like a no-brainer. At most, it might have required that the FCC "remember" a period of AoA history so it could determine, at the point where the algorithm became active (A/P disengaged, flaps retracted) that the AoA had never been in a valid range.

The bigger issue seems to be that the programmers never questioned the absence of any input validation requirement at all. I fully expect someone to quibble with my assertion that >20 degrees is clearly invalid, but what about 75 degrees?
It is a valid proposal, but supercaution is advised. The AF447 doomed crew was not helped by the stall warning silencing nor by FDs re-appearing in nose up position. All due to validity boundaries being exceeded, while the data were actually true in the deep stall.
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