Originally Posted by
silverstrata
And if the high angle of attack persisted, the system would give another 2.5 degrees of forward trim.
Originally Posted by
MickG0105
Well, that's what I thought but that is not the case according to FCeng84:
Originally Posted by
FCeng84
MCAS will not command more than one increment of nose down trim without either having taken out the first one (via the same amount of nose up trim) or having sensed manual pilot electric pitch trim.
Hi Mick. I would suggest the difference in view is due to a difference in how you interpret the second last sentance, in the description of MCAS's operation. Here is the relevant text again:
The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.
It appears that FCeng84 is assuming the sentance describing how it is reset also applies to the second last sentance, as if it was written as one whole sentance like this:
The function is reset once .... or if ... and if the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command .."
In comparison, your interpreation see the two sentances as completely seperate, and as if the last sentance was before the second last sentance:
If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation. The function is reset once ...
Personaly, I think your view is quite valid, and is how I interpret the paragraph. If the AoA is high enough that MACS believes it should lower the nose, and it tries, but it does not succeed, would it really continue to do nothing, as the AoA would still be what it consders to be too high. But I think the way the statement is worded is quite ambiguous, and either interpretation has some merit. By the way, you seem pretty sharp to me..
Cheers