There seem to be a handful of people spreading this talking point here. In every authoritative source, MCAS is described as anti-stall system.
(2) With the landing gear retracted at low speed, the stick force curve must have a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speed range, above and below the trim speed (except that the speed range need not include speeds less than 1.3 VSR1, nor speeds greater than the minimum speed of the applicable speed range prescribed in paragraph (b)(1), nor speeds that require a stick force of more than 50 pounds)[...]
The crucial phrase is "stick force curve", which is the characteristic MCAS was created to tweak.
As far as 'authoritative sources' go, I'll just mention the Gell-Mann amnesia effect.²
(me: non-active aircraft dispatcher)
¹—https://www.ecfr.gov/cgi-bin/text-idx?node=14:1.0.1.3.11#se1... ²—https://en.wikipedia.org/wiki/Gell-Mann_amnesia_effect?wprov...
How do you know this? Haven't seen that reported anywhere but in user comments here.
When speaking to the uninitiated, anti-stall system gets the point across.
When speaking reguspeak, and actual aerodynamics, MCAS is a compensatory system that is meant to allow the plane to be certified airworthy. It is the same class of system as a mechanical stick-pusher (though even less effective since all it does is changes the yoke pressure required to bring the plane to a stall).
It's not a meme sadly, which makes this all the more tragic in hindsight. Sibling poster has quoted the CFR.
Where did you get this information? My understanding is the airframe has the potential to nose up due to extra lift provided by engine placement (eg, lift not commanded by stick pull). MCAS is used to prevent this stall condition during high AoA.
One of the most important things to get right with a control system is to maintain some level of consistency throughout the entire range of the system you're actuating.
Get on your computer, and move your mouse around. Now go into the settings and muck with your mouse sensitivity/acceleration curves, and try to drop your cursor on a particular file.
Odds are, you'll have some degree of difficulty until your brain adjusts to the new settings.
Same thing is relevant with airplane yokes. The force required to deflect a control surface (and therefore the plane) in an airstream is a result of the forces imparted on the surface + plane while by the impinged airstream.
Now, a force response curve should be smooth and predictable. Some distance of deflection on the yoke at one position should yield approximately the same level of deflection from the yoke at another position. If there is a sudden change in the number of degrees of AoA you get per degree of deflection, this is a highly undesirable flight characteristic.
For a pilot's perspective, I recommend the D.P. Davies Interview Podcast from the Royal Aeronautics Society, specifically the Boeing episode where he describes his certification flights of the Boeing 727-300.
That plane had a similar interaction with high lift devices at high AoA, making the plane more eager to pitch into a stall when you got to a certain point AoA-wise. This was in direct violation of this CFR. As Davies puts it, "You can't certify a plane that wants to stall itself!"
The 727 was eventually certified though when they added a mechanical stick pusher which would shove the stick forward when the pilot was getting close to that flight regime to make sure they didn't stall.
MCAS, by all indications, serves a similar purpose, it detects current AoA and trims the plane to counter the extra lift so that the deflection of the elevator at the top of the AoA curve has to fight the nose-down trim, which to a pilot would feel like the plane takes the same amount of force to deflect for those last few degrees. Basically, to use the mouse analogy, it's bumping down the sensitivity of the yoke to compensate for the extra sensitivity created by the lift at high angles of attack.
All of this is fine and dandy at 17 or so degrees AoA. Not so much though in attempted level flight with a busted AoA sensor.
Much of the art behind control systems comes from translating technological activity into humanly processable control schemes. That CFR is a common sense guideline basically specifying that a transport plane must have a predictable response curve.
It reminds me of the way nuclear reactors work, which kinda made it click. There they make criticality dependent on neutrons donated by fission byproduct decay, allowing for control rod situations, and thereby criticality level changes to take place over minutes instead of seconds.
Plus, look at the name
Maneuvering Characteristics Augmentation System.
The important takeaway is it doesn't really do squat to make stalls not happen beyond making it increasingly impossible for the pilot to get enough oomph out of the control surfaces to get the plane in stall and stay there. I don't know if there is also a stick pusher for MAX aircraft to help recover from a stall.
If the MCAS was constantly variable, like a mechanical stick pusher, then what you're saying would make sense. IMO, as reported, it seems like an 'anti-stall device' that automatically adjusts the plane's pitch regardless of stick input. Depending on conditions, this presumably could be little to no stick input.
But AoA sensors freezing is apparently common enough where this system is frequently kicking in when the plane isn't in the situation it was designed for.