Originally Posted by
oggers
The advice to control pitch using electric trim has been in the NNC for 19 years now. It is number 2 memory item. Furthermore, the amplifying remarks promulgated with the AD were a de facto amendment to the FCOM that the operators were required to action within 3 days.
Oggers,
re-read parallely the abnormal procedure AND the interim accident report.
You'll conclude that the pilots have followed the procedure until flipping the cutout switches.
1 Control column. . . . . . . . . . . . . . . . . Hold firmly
2 Autopilot (if engaged) . . . . . . . . . . . . .Disengage
Do not re-engage the autopilot.
Control airplane pitch attitude manually with control column and main electric trim as needed.
3 If the runaway stops:
- - - - - -
4 If the runaway continues: STAB TRIM CUTOUT
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer trim wheel . . . . . . . . . . Grasp and hold
- - - - - - - - - - - - - - - - - - - - - - -
5 Stabilizer . . . . . . . . . . . . . . . . . . . Trim manually
6 Anticipate trim requirements.
7 Checklist Complete Except Deferred Items
And, in the accident interim report, you can read:
05:39:56: auto-pilot disconnects
05:40:00: MCAS kicks in and trims down for a duration of 9 seconds
05:40:13: the pilot trims up for 3 seconds
05:40:21: MCAS trims down for a reduced duration of 7 seconds (interrupted by the pilot trimming up)
05:40:28: the pilot trims up for 10 seconds
05:40:38: end of pilot trim up action. Somewhere between 05:40:38 and 05:40:43 the cutout switches are actioned.
05:40:43: the next MCAS activation doesn't move the STAB.
So:
- As per item number 2 in the check list, the pilots did control the airplane with control column and main electric trim after noticing the uncommanded trim behaviour.
Then, as the runaway continued, they actioned the cutout switches (item number 4)
- The whole sequence took place in 43 seconds.
If one has plenty of time to consider the situation and choose the best course of action, he could read the point 4 in the check list as
4 If the runaway continues: STAB TRIM CUTOUT
main electric trim. . . . . . . . . . . . . . . trim until needed control column force is light
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer trim wheel . . . . . . . . . . Grasp and hold
Unfortunately, if one is shaken and startled, it is the written list that will be executed.