Originally Posted by
pchapman
Not sure about jumping into this 3300+ post thread but here goes:
I'm concerned about the crew's actions both for the manual trim attempt, and with the electrical trim attempts just before they lose control. And I can't help but distrust the inexperienced First Officer more.
To summarize:
- they had the MCAS pitch control problems
- got the Cut-out switches to stop MCAS from trimming down any more
- they're flying OK, got some altitude banked, although still in crisis mode, still having to hold back pressure, deal with the one stick shaker, overspeed clackers after some point, and what not
- there's a discussion about the manual trim not working. We don't know the exact words used.
- Interpretation: Might have to do with high forces on the manual trim wheel, but it is also unclear whether the First Officer really doing what was expected. Was he just hitting the thumb trim switch, or trying to roll the trim wheel (without much experiences of the forces that might be involved) or did he actually have the fold-out handle open and still find he was unable to turn it?
- either way, they keep flying OK for another minute or so
- then there are the 2 very short electrical up trim attempts (as others have also commented on). I agree that the graphs show a small up trim effect. Hard to see on the graph but really does look like a little bit of nose up trim change. Barring any totally unexpected electrical issue, this is only possible with electric trim turned back on!
- very soon after, MCAS kicks in, trimming a bunch nose low, and the pilots lose control and nose over.
The preliminary report gives no indication that the pilots discussed turning electric trim back on. Nothing about, "Despite the AD saying to leave it off, you turn electric trim back on, I'll trim out these awful control forces, you turn it back off before this thing tries to pitch down again."
Did the Captain try turning it back on? Or was the First Officer fiddling around on his own? Trim gets turned back on with no consultation and but only 2 ineffective short trim activations are made. Were jackscrew forces so high that electric trim wasn't working well? Who knows, I'll leave that to the experts. But the electric trim attempts were two short blips, not like trying mashing that button down a full 5 seconds to see if they got some effect out of it.
That really messed them up, ineffective trim attempts without killing the electric trim system again afterwards.
So, before you bad mouth the FO,
AFAIK he was the one suggesting using the stab cut out switches, inhibiting the third MCAS input. We don't know who switched the trim back on, or who made the insufficient inputs close to the crash, so if I were you I would give it a rest.