Originally Posted by
Peter H
I wondered this when Icelandair were doing flaps-1 ferries, and found this:
In
https://leehamnews.com/2019/09/27/bj...-wire-part-10/
MCAS is not active on the 737 MAX when flaps are deployed. This is because when flaps are out the slats are out as well and these
diminish the disturbance to the pitch moment curve from the larger and further forward-higher slung engine nacelles.
It would be interesting to know if Boeing ever actually tested this assumption. I always figured that the flaps cutout was an analog for height. For example, it would be a bit harder to blame the pilots if an inappropriate MCAS application pushed the nose into the ground at 50' (although they would find a way, I'm sure.) It is counterintuitive to this SLF why a mechanism that helps prevent the nose from being pulled too high is disabled at takeoff. Before this whole mess I would have assumed that there was lots of engineering and testing done to ensure that MCAS was truly not necessary when the flaps were out, but given what has come out about the design and testing process recently, I'm not so sure. Management would have been very, very upset if the MCAS scheme had to be "deep sixed".