Hmm, this really is getting confusing. I thank you for your continued efforts to explain it. I am understanding the MCAS system better and better as a non-pilot. However, it seems there is different ways this system is described. For one, it's not clear that the MCAS is completely independant of the automatic stall prevention.If the primary purpose of MCAS were to "change the aerodynamics of the plane" (which I think is a misleading way of looking at it anyway) and force the nose down, it would function more like automatic stall prevention in a fly-by-wire system: if it detected that the plane was too close to a stall, it would simply override the pilot's input and use the yoke control system to force the nose down--i.e., it would force the yoke to a different position than the pilot wants to put it. But it doesn't do that.
I've seen it written many places that MCAS "commands nose down trim". That would suggest it is in effect commanding nose down by adjusting trim. Not providing force feedback to communicate to the pilot to provide nose down trim.
From: http://www.b737.org.uk/mcas.htmThis new location and size of the nacelle causes it to produce lift at high AoA; as the nacelle is ahead of the CofG this causes a pitch-up effect which could in turn further increase the AoA and send the aircraft closer towards the stall. MCAS was therefore introduced to give an automatic nose down stabilizer input during steep turns with elevated load factors (high AoA) and during flaps up flight at airspeeds approaching stall.
On the face of it this seems like a sensible, beneficial system. However following the accident to Lion Air MAX-8 PK-LQP on 29 October 2018, shortly after take-off, in which it appears that the Captains AoA sensor was faulty, it is believed that the MCAS used this erroneous AoA data to command nose down stabiliser which was not counteracted sucessfully by the crew until the aircraft impacted the water.