Originally Posted by
FlightDetent
I asked before: If the crew on MAX is holding the yoke thumb rocker for trim, and the MCAS comes for the second push after the cooling off period, will it override the pilot's elec command? And we do not know.
Boeing tells us while MCAS is active the thumb switch will kill it, and I trust them. The question above is about a priority rule in a different scenario, another mode. - and we do not know, only assume.
The connection here is that we see a blip of ELEC TRIM switch on the traces, but we really have no way of knowing what was the commanded input of the crew on the rockers. Or do we?
We have at our disposal three separate FDR outputs (2 Lion Air, 1 Ethiopian). In each and every one of these outputs, automatic trim inputs (STS, MCAS) and pilot trim inputs are shown on separate traces. On yet another trace,
stab position is shown. This is how we can tell that 1) the pilot trim was working, and 2) that this input stopped and countered MCAS every single time it was used. So yes, we actually do know.
As far as whether the pilot trim was taken directly from the rocker switch on the yoke or somewhere else, I don't know, but I submit that it does not matter. The only way for pilots to input trim through the electric stab motor is through the yoke rocker switch. I know some other aircraft have different setups for this, but not the 737.
Again, what is clear from these outputs is that at least 3 of the 5 pilots who actively controlled the aircraft during a MCAS malfunction were able to hold their own against these unwanted stab inputs. Two did not resulting in subsequent loss of control.
The issue as to why two of these pilots (particularly the Ethiopian Captain) lacked the basic flying skills the other three possessed should certainly be a key area of investigation.