Originally Posted by
zzuf
Really interesting, can the aircraft be stalled with the MCAS operating?
I think MCAS was a rudimentary attempt to prevent a stall developing.
When at high angles of attack, the 2.5 degrees of forward stab trim would apply control column pressure, and thus urge the pilot to lower the nose (presumably with the stick shaker also operating). And if the high angle of attack persisted, the system would give another 2.5 degrees of forward trim. So far, so good.
However....
2.5 degrees of trim is quite a lot. And if you get the second dose, 5.0 degrees is a helleva lot. And the system can apparently run to full nose down trim, which is simply insane.
Ok, you are now in a 15 or 20 degree nose down dive, to recover from the stall. So how do you pull out of the dive, with full stab trim forward? I recon that is impossible. (I see no evidence in the explanations given, that the MCAS system will automatically rewind - although that might be a sensible option.)
As the description says...
MCAS is implemented on the 737 MAX to enhance pitch characteristics ... at elevated (high) angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during ... flaps up flight at airspeeds approaching the stall ... If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command.
To ‘enhance pitch characteristics’ is lawyer-speak for “get the flippin nose down”. And if the nose is not lowered, you get another dose of nose-down trim - until you are pointing vertically at the ground. I really think that nobody thought this system through....
(And yet Bergerie1 still cannot understand that a device that operates to lower the nose when approaching the stall, is an anti-stall device...! Takes all sorts, I suppose.)
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