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Old 4th Apr 2019, 19:31
  #3150 (permalink)  
AfricanSkies
THUNDERTAILED
 
Join Date: Nov 1999
Location: L200
Posts: 320
Thoughts.

This aircraft had multiple pitot static malfunctions in the days prior to the accident as per the tech log quoted in the report. Altimeter and VSI erratic.

If they had had a bird strike on the vane, they would have noticed the thump and said something. I think we can rule a bird strike out. And frozen things. It was 17 degrees C on the ground.

Just after takeoff the crew got an almost immediate
Stick shaker
Airspeed disagree
Altitude disagree
F/D disagree
Which constitutes an unreliable airspeed non normal
(Together with an anti ice caution)
And did not apply the memory items for that , and seemed to be prepared to continue to FL320.
The trim problems started once the flaps were retracted , however the flaps seem to have been retracted despite the left stick shaker being continually active and the aircraft in an unreliable airpseed state which calls for a pitch and power setting with the flaps down (if I recall, 10deg NU, 85%N1) but the power wasn't reduced from 94% either.
The stabtrim cutout switches seem to have stopped the MCAS from moving the stab, but then the switches were re-engaged (2 ANU trims were recorded 2,5 min after the stab trim switches were set to cutout) and this then allowed the MCAS to pitch it down again.
As regards thrust and pitching moments I personally would prefer to take my chances with speedbrake, idle thrust and a bit of a dip than two engines at 94% when I'm pointing downhill.
And I don't think I'd be getting ATC involved until I had the beast back under some sort of control.
This seems to be more than an MCAS thing, it may be a pitotstatic adiru thing.
If one sensor gets extreme readings or if there's a sensor disagree, then no system should rely upon that sensor data.
Systems shouldn't rely on one sensor only.
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