An objective analysis of the the FR24 supplied ADSB data raises many questions.
The first MCAS event (and perhaps the only one), seems to have occurred just after the aircraft left the ground.
The data shows a spike in the V/S at the approximate time the aircraft would have been leaving the ground coincident with a drop in altitude, at the 05:38:47z datapoint.
Remember the aircraft has an IVSI where accelerometers amplify V/S readings at the beginning of a climb or descent.
This spike make have been caused by an instinctive "yug" on the control column following a sensed drop in altitude.
Reports state that ATC knew the aircraft was in trouble even just after this point due to its undulating flight path at low altitude.
The pilot reports of a "flight control problem" occurred one minute after takeoff, around the time that the aircraft was first beginning to pitch down from about 300' AAL.
So what has happened here?
The MCAS will not operate with flaps extended. Yet it appears it was operating when it should not have been.
In conversation with 737 pilots it was stated to me that the A/C can do Flaps 1 takeoffs. At a high altitude airport a low flap/low drag takeoff setting is preferable for an engine out condition.
We know the FO was VERY inexperienced. Perhaps still being trained or on his first line sector.
The question is; Was the flap raised instead of the gear after rotate, thus activating the MCAS?
It would explain much, but not everything.
The MCAS stops operating when the high AOA condition is corrected, is opposed by the electric trim (but only while the trim switches are operating), or if the STAB switches are turned off.
However it
does not automatically return to a lower stab incidence. It must be trimmed back to a proper value commensurate with the speed and configuration of the aircraft. If the Stab switches have been turned off as per the procedure, then the STAB must be manually trimmed back to a proper position.
ETH302 accelerated continuously till it crashed; indicating perhaps that the crew weren't minding the shop as they attempted to deal with the trim issue. It went way past VMO.
IF the STAB had not been sufficiently trimmed back from the nose down position, the increasing speed would have given the same impression of a runaway stab even if the switches had been cutout; an increasing nose down trim change, even though the stab trim was inactive.
The increasing force with the increasing speed would have made it eventually impossible for them to counter, perhaps indicated by the recovery at the 05:40:18 datapoint but no recovery at the final dive.
I stress I don't know what happened; however this makes some sense. Happy to be corrected. Kremin
