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Old 4th Apr 2019, 19:34
  #3153 (permalink)  
Just This Once...
Join Date: Apr 2005
Location: UK
Posts: 2,022
Originally Posted by GarageYears View Post

Aside from why the AP was successfully engaged, the three trim ND FCC commands (and one NU for good measure), DURING autopilot engagement are brief and likely STS driven - not MCAS. That comes after the AP is disconnected.

The first MCAS ND command occurs on deselection of the AP, and runs for 10 seconds as the system is expected to do. You can clearly see that in the FDR traces.
I'm not seeing it that way. With the AP engaged the 3x AND auto trim events kill the pitch attitude - from 8 deg positive decreasing all the way to zero by the time AP tripped-out. At that stage with the AP engaged, FD commanding a climb and with throttles parked forward with excess speed in hand the aircraft should have been going up like the proverbial. Indeed, the pitch attitude only becomes positive again when PF takes control and applies a generous amount of aft stick and ANU blips. Even then he does not achieve anything like the 8 deg positive achieved earlier.

Clearly I know what the aircraft 'should' be doing, but I'm just not finding it in the data provided.

If you see it differently please shout out as even after years of flight testing this has left me scratching my head.
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