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by inferiorhuman 2365 days ago
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.

If the graphs are to be believed neither the electric commands nor hand crank were able to move the stabilizer. Again, how is that a pilot training issue?

1 comments

I don't know what graph you're looking at. The reports I saw was that the EA pilots did not follow the procedure:

1. trim to normal with the electric trim switches

2. cut off the stabilizer trim

What the EA pilots did was:

1. cut off the stabilizer trim

2. try to use the hand cranks to trim to normal

I don't know what graph you're looking at.

Graphs of the FDR data from the (preliminary) accident reports. The Ethiopian authorities even annotated theirs with things like "automatic trim command with no change in pitch trim". You can see quite plainly the stabilizer was not moving as intended.

2. try to use the hand cranks to trim to normal

Per Boeing's documentation this should've worked. Unfortunately Boeing's documentation is mostly wishful thinking. Boeing's also suggested that a pilot try unloading the stabilizer with a roller coaster type maneuver. Unfortunately Boeing removed detailed instructions on this maneuver decades ago and the FAA's already demonstrated that with the altitude that the Ethiopian crew had, unloading the stabilizer would've just flown the plane into the ground.

There's a reason Boeing's largely backed off of the whole pilot error nonsense: the 737 MAX crashed due to shitty design not pilot error.