Originally Posted by
ernst_mulder
A (possibly stupid) question from SLF,
What I am wondering about is why, after a struggle with MCAS, the plane ends up in a nosedown dive. Wouldn't the pilots in principle be able to keep fighting the unwanted trim commands indefinitely? Also earlier in this thread I read that it is possible to fly an airplane even with a full downward trimmed HS. Could another mechanical problem be the cause, i.e. elevator(s) breaking off after too much stress trying to compensate for the full downward trimmed HS?
The pilots of Lion Air kept trimming up, but the manual trim bursts were shorter, which was apparently enough for the trim to completely run away. Perhaps busy with something else? Without cvr transcription we (the public) don't know, but the investigators and Boeing probably do.
Originally Posted by
MPN11
IMHO that makes a lot of sense, on several levels. Certainly the ‘persistence’ of MCAS demanding nose down would require a LOT of persistent winding of manual trim if MCAS was not disabled. That incessant input (5 seconds?) is hardly helpful if it takes more than 5 secs to wind it off ... while struggling with everything else ... and then have to do it all again!
Same as above, look at the lion air FDR data. It's a horrible situation to be in.
Originally Posted by
Dave Therhino
Yes, the pilot could keep counteracting the MCAS input with equal and opposite trim, and get into a trim cycle where, while the ride is wild, control is never lost until the electric trim is shut off or by flap selection for landing.
The Lion Air crew briefly extended the flaps and got the situation under control, but then they retracted them agin :-(