Originally Posted by
positiverate20
I agree with you on the sensor problem, but entirely disagree with the perception that a failure of the system would have minimal risk to the aircraft.
In the scenario given, hundreds of feet above ground, stick shaker, the captain is in a pretty tough situation and is trouble shooting- does stab memory item, switches stab cut-out. Alarms off, and thanks to yoke and increased thrust returns to some form of climb. At this stage, despite your argument that the pilot should be able to return trim to normal, he has just followed the procedures that Boeing themselves have instructed. Checklist complete, some stability back and now focus on safely trying to get back to ground.
Trimming the plane for neutral stick force is part of safely trying to get back to the ground. This is a fundamental airplane flying concept since the 172 presolo days. Literally lesson one. At what point does this get lost? Are you seriously proposing that someone cease trimming since the emergency checklist does not say to trim? What about the fact that the emergency checklist doesn't say to use the ailerons to turn back toward the airport, what do you do then? Say well we're stuffed now, we're out of options, we have to take whatever is straight ahead?
Now, throughout this next phase, with the stab having X° nose down, it may not present itself as a problem due to the additional engine power, because, at increased thrust, as you've explained, the Max set-up has a tendency toward a higher AoA, which is why MCAS is required in the first place!
NO! As multiple people including FCEng have explained multiple times, this is not why MCAS is required!
So, in a sense, the characteristics of the MAX set-up will be masking the trim. MCAS is required for certification to counteract the increasing rotation around the CG caused by the both the thrust moment and aerodynamic behaviour of the engine cowling of the Max engine. So, in this precise stage of the hypothetical flight the PIC may not actually notice the plane being out of trim, and if he does, will surely not realise just how much out of trim he actually is.
I'm not following. If there's a neutral stick force given all the current pitch moments (including the thrust couple) then it is, by definition, in trim. If thrust is reduced then it well get out of trim toward nose down (stick force to hold steady pitch will become a pull)
Any other time in normal MAX operation the autotrim or the MCAS trim would be operating anyway. MCAS, as you've said, is a certification requirement for MAX aircraft because of it's specific aerodynamic characteristics. What I'm portraying in this scenario is that if the pilot functioned perfectly during the emergency at 190, but in doing so cut-off the trim at X° nose down. That trim hasn't changed and the checklists didnt require the crew to make any manual trim wheel changes.
You're joking, right? This has to be a joke.