Originally Posted by
FCeng84
When AOA reduces to below the MCAS sctivation threshold MCAS runs the stabilizer airplane nose up the same amount so that it is back where it started.
Does it?! Can I ask where you got that information from please. I can't recall having seen anything saying that MCAS provides nose up trim commands under any circumstances.
Originally Posted by
FCeng84
The only way to get MCAS to insert more than one increment of airplane nose down trim is for all of the following to occur:
1. High AOA is detected leading to one MCAS increment of stabilizer.
2. Manual pilot electric trim command is detected thus causing a reset of MCAS
3. Pilot does not fully command stabilizer to its trimmed position
4. High AOA is once again detected leading to another MCAS increment of stabilizer
Are you sure about that? The Boeing Multi Operator Message
SUBJECT: Information - Multi-Model Stall Warning and Pitch Augmentation Operation of 10 November stated:
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.
My reading of that is that MCAS will command more than one increment of nose down trim '
If the original elevated AOA condition persists.' That is, if after having commanded one increment of nose down trim the sensed Angle of Attack still exceeds the Angle of Attack threshold, MCAS will command another increment of nose down trim. That should be entirely independent of any manual trim interventions.