Originally Posted by
Gilles Hudicourt
Correct me if I’m wrong, but in the case of the Lion Air accident, from what I understood, an AOA probe fault caused the MCAS to put a forward trim on the horizontal stabilisor, causing a fault that essentially looked like a runaway trim, a situation that a pilot could have recovered from by treating it like a runwaway trim.
If the above statement is correct, my question is this : did the MCAS also activate the stick shaker or any other kind of stall warning?
Because recovering from a down trimming runaway trim (pulling back on a very heavy control wheel) while at the same time having a stick shaker and some other indication telling you you are about to stall (which normally would require lowering the nose).....
The stick shaker was indeed activated on the Lion Air flight due to the incorrect AoA sensor readings, but the stick shaker has nothing to do with MCAS, its triggering mechanism is independent from MCAS.
In fact the stick shaker has also been active for almost the entirety of the previous flight, 90 minutes, for the same reason: incorrect AoA sensor readings.
And the pilots from the previous Lion Air flight seemed to fail to mention that the logs, for some unfathomable reason. Also not sure how they could stand having a stick shaker active for 90 minutes and not return to the departure airport. They might have pulled its circuit breaker to silence it.
The previous Lion Air crew also failed to mention in the logs they had to disable the automatic trim, after fighting with it for 5 minutes, to make the plane flyable.
Having done so would have helped the next Lion Air crew to diagnose the issue faster and apply the workaround before the plane become uncontrollable and crashed.