Originally Posted by
Derfred
...He did say one strange thing though: if it is correct in translation, he asked the F/O "to trim up with him". This was after the second MCAS. He had only responded to the first MCAS with a relatively short "blip" (2.1 to 2.4 units). The response to the second MCAS (presumably with the F/O "helping") was around 11 seconds and took it from 0.4 to 2.3 units (if only they'd kept going another 11 seconds).
So why did he need the F/O's help to activate main electric trim? It's a thumb switch. Was the stick-shaker that annoying he couldn't activate the thumb switch? Could this mystery have anything to do with the two fatally short "blips" near the end of the flight?
Before the MCAS input the PF trims up twice with the thumb switch for appr. 3 s each. This results in appr 1 U uptrim stab movement, twice.
At 5:40:15 after the first MCAS ND he trims again up for appr. 3 s. The stab movement is barely visible now on the chart. Then, unusual:
At 05:40:27, the Captain advised the First-Officer to trim up with him.
Why? Is his switch not working correctly?
The trim up (together or) by the FO is the only long one in the entire FDR recording. It shows again a stab movement at appr 1 U / 3 s. It is followed by STAB TRIM CUTOUT.
Is it possible that the PF had a broken trimswitch?
