Originally Posted by
alf5071h
DaveReidUK, #3647, Icarus2001, quentinc
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Indications in the EASA reference ‘Equivalent Safety Case’ suggest otherwise.
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.”
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However with serious trim malfunctions, the tail displacement together with adverse elevator load attempting to recover, might limit electric trim (latter diagrams). Add effects of elevator feel offset due to false stall warning, higher stick loads add to trim offset loads.
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Also remember that MCAS vs elect trim is 10 to 5 time ratio in favour of nose down.
I've seen this comment a few times, and I think there may be a misunderstanding about how MCAS and the electric trim switches interact.
While MCAS *can* operate for up to 10 seconds, it is inhibited by the activation of the wheel trim switches. When they are activated, MCAS stops until they are released, and waits 5 seconds. There isn't a ratio of time between one and the other. You can hold the trim switch for any length of time and MCAS will stay off until 5 seconds after it is released.
Nothing stops a pilot from trimming to neutral in one long press, then using the cutout switches, beyond the counterintuitive nature of that reaction.