Originally Posted by
MemberBerry
I was trying to understand why the Ethiopian pilots have retracted the flaps, which allowed MCAS to activate. Looking at their FDR traces it seems to have happened when they were getting close to 250 knots.
Also they had autopilot engaged. On LionAir accident flight MCAS problems appeared to start with flaps up, on ET it was with autopilot disengage.
By the time of the ET flight it was known that autopilot was a protection against MCAS, from one of the ASRS reports:
It was my leg, normal Ops Brief, plus I briefed our concerns with the MAX issues, bulletin, MCAS, stab trim cutout response etc. I mentioned I would engage autopilot sooner than usual (I generally hand fly to at least above 10,000 ft.) to remove the possible MCAS threat.
Unfortunately the autopilot didn't stay engaged - not sure why.
It also appears to have pitched, and trimmed, them down when apparently set to climb, this I do not understand. I cannot find any autopilot-engage preconditions other than "no stick force", but if the autopilot actually cares about AOA why on earth would it engage at 74deg - if that is true there is no way you are flying. On the other hand if it didn't care about AOA what on earth was it doing with the pitch when set to climb? One of several WTFs on this one.
Autopilot pitching down unexpectedly was also a feature of some of the MAX ASRS reports, including the one I quoted - issues may or may not be related.