Originally Posted by
bimmerdriver
Big (and unanswered) questions in this report are why did the pilots allow the airspeed to get so high and why did they apparently reengage the stabilizer trim. There is no way they could have avoided the crash due to these decisions.
I'll bite.
Let's start with the speed. The report states:
05:39:42 Level Change mode was engaged. The selected altitude was 32000 ft. Shortly after the mode change, the selected airspeed was set to 238 kt.
05:39:55 The Autopilot disengaged,
05:40:00 Shortly after the autopilot disengaged, the FDR recorded an automatic aircraft nose down (AND) activated for 9.0 seconds and pitch trim moved from 4.60 to 2.1 units.
05:40:03 Ground Proximity Warning System (GPWS) “DON’T SINK” alerts occurred.
Now whether or not the pilots correctly engaged the autothrottle (etc), it seems reasonable to me that the pilots had mentally managed the speed, and then they moved on to other things. Yes, of course they should be monitoring the actual speed all along - but within 20 seconds of setting the speed (to a reasonable number), the plane is trying to drive into the ground and the GPWS is going off.
Given the situation, it may not excuse but it does help to explain why the throttles were never reduced ... they had "set" the speed, and they were kinda busy just trying to keep the plane from actively diving into the ground.
And about re-engaging the stabilizer trim:
05:41:46 the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try.
05:41:54 the First-Officer replied that it is not working.
05:43:04 the Captain asked the First Officer to pitch up together and said that pitch is not enough.
05:43:11 about 32 seconds before the end of the recording, at approximately 13,4002 ft, two momentary manual electric trim inputs are recorded in the ANU (aircraft nose up) direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units.
05:43:20 approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds. The aircraft began pitching nose down. Additional simultaneous aft column force was applied, but the nose down pitch continues, eventually reaching 40° nose down. The stabilizer position varied between 1.1 and 0.8 units for the remainder of the recording.
The first officer had already tried to manually adjust the trim and been unable to do so, and at 05:43:04 the captain says that the pitch is not enough. It's not stated in the report, but it seems obvious that the response to this interaction was that stabilizer trim cut-out was disengaged (aka, the trim was re-engaged). That does not seem in any way unreasonable to me .... and it helped a little. Then 9 seconds later the MCAS kicked in and killed them.
The more I read the report, the less fault I can find with the pilots.