Questions after reading the report
The preliminary report leaves me with several questions:
Shortly after Takeoff the Captain who was pilot flying had stick shaker on his side only. Why not transfer control to the first officer at this point or at least a little while later? That is actually what the Captain of the Lion Air flight previous to Lion Air 610 flight did. If you see that there is stick shaker on your side but not on the other wouldn't it make sense to rely on the FCC B side in this case? Why engage the autopilot on the A side that has the stick shaker? The captain tried to engage Autopilot A two times unsuccessfully at 400 Ft and 630 Ft. That would be another indication to either continue manually or at least try the other side. Finally he succeeded in turning the autopilot A on at 1000 Ft (for 33 seconds). Possibly Autopilot B would have worked since it seems like there was no false sensor indications on that side an MCAS would not have activated (speculation).
Based on the report the situation for ET302 was basically exactly the same as for Lion Air 610. Stick shaker right after Takeoff and then as the flaps were retracted MCAS started trimming the nose down.
At 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. The climb was arrested and the aircraft descended slightly.
Knowing about the Lion Air Accident as the ET302 crew must have, were they expecting the nose down trim as they retracted the flaps? Based on their actions it seems like they did not even though the circumstances were the same. Would this not have been the point to carry out the runaway stab trim memory items?
At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.
Instead the crew trimmed the aircraft nose up from 2.1 units back to 2.4 units. Why not trim back to the original 4.6 units before MCAS engaged so that it isn't necessary to increase back pressure on the column? Some people on this forum suggest the electric trim switch will not work sufficiently against MCAS. The preliminary report on Lion Air 610 shows otherwise as they countered MCAS up to 30 times.
By now we know that MCAS activates again 5 seconds after the electronic trim switches have been used. They were used by the crew but apparently only to offset the MCAS trim input to a small degree and now MCAS starts trimming the nose down again:
At 05:40:20, approximately five seconds after the end of the ANU stabilizer motion, a second instance of automatic AND stabilizer trim occurred and the stabilizer moved down and reached 0.4 units.
This time the crew did trim against MCAS from 0.4 units back to 2.3 units therefore basically reversing the input from MCAS and showing that this is possible.
Now the First Officer suggested to set the stab trim cut out switches to cut out and MCAS was stopped.
Would it have been possible at this point to reduce the power and then trim the aircraft manually?
At the time the crew did try to trim the aircraft manually the aircraft was flying at the edge of it's envelope at 340 Knots according to the left side or outside of it already at 365 according to the right side. I am not surprised that at this point it was not possible to trim manually anymore.
At 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 direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units. At 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.
Since the crew said at 05:41:46 that electric trim did not work and now it was possible for them to trim electrically again it is likely that the stab trim switches were set back to their original position before being set to cut out. Aside from not reducing the power even when there was the overspeed warning, why did the crew not trim continuously as they did before in order really raise the nose? Also why did they then not set the stab trim switches back to cut out since it was to be expected that MCAS would engage again 5 seconds after release as it did before?
I am not judging the pilots or saying the same thing could not have happened to me. I am just asking myself these questions based on what I have read.