However, the stick force is simulated on the 737 using the stabilizer position and the stabilizer pitot system. A poster a few pages back said that the elevator feel computer is an analog hydraulic computer. If it were an electronic computer that runs software, the AoA could have been fed into it and the MCAS function could have been handled by it. Essentially, MCAS is tricking the elevator feel computer. Doing so requires the stabilizer trim to be changed.
That's why I say that MCAS and stall characteristics have nothing to do with each other. If the stick force gradient issue could have been solved by a software update to the EFC trim changes wouldn't have been necessary.
Stick force is NOT changed by moving control surfaces as MCAS does, plane movement is. Basically this is not about force, this is about MAX being more responsive to controls than NG at high AoA, near stall. Which fits purr-fectly into "easier to accidentally exceed critical AoA and enter into stall as less control movement is required for that"
Any other reading is a game of words.
You (and several posters here) really shouldn’t be commenting on aerodynamics if you have no formal understanding of it. Stabilizer AoA absolutely effects elevator load. In MCAS, the stabilizer essentially works in the opposite direction of the ANU elevator. The effect it creates is that it requires additional elevator deflection to maintain a given pitch. MCAS was intended to trim the stab down at the same time the elevator load was lightening. Thus the pilot would feel the elevator getting heavier. It’s not an artificial force, it’s due to increased load on the elevator. But it was not (from any document I’ve seen) intended to pitch the nose down.
If Boeing wanted to pitch the nose down they would have just put a stick pusher and used the elevator. The elevator can respond far quicker than the stab trim. My guess is that the increased MCAS speed was because in flight testing the pilots could pull back faster than MCAS could trim the stab.
Frankly speaking,this is not about aerodynamics. This is about control systems, control systems 101 or so. ANd by the way, I hope my PhD in physics allows to have a borader view of the problem, if we're talking about the formal understanding of things.
Stabilizer deflection (trim) changes lift generated by that stabilizer assuming wing AoA and airspeed are constant - would you argue with that? Thank you.
Any control stick forces are only secondary effects from there.
Yes, you can trade in the change of stabilizer lift for change of elevator deflection - and required stick force - to maintain the same pitch; that is normal "trim out of stick force" operation.
Or you can take that force at a face value and have a change of pitch at a given stick force - apparently, that is the way MCAS is using it. In this case, it is now up to the pilot to restore the pitch (into close-to-stall region for MCAS case) or accept a helping hand and enjoy safely reduced pitch/AoA at the same control input. Consider that as rudimentary envelope protection/stall avoidance action.
Are you still with me?
Why Boeing settled with a slower trim action instead of fast elevator action? Remember, timing is the same for either stick force or pitch change point of view. Extreme forces at high deflection come to mind. We're already in a situation, where higher mechanical leverage of the trim system is unable to overcome MCAS induced forces, overloading can be a problem here.
Second (slightly less realistic) explanation is that MCAS is slow to gradually compensate for entry into the hazardous region for same plane rotation speed - and it should be limited by the angular momentum of long body if nothing else. Again, you may interpret that as "plane requires more force to go to same pitch", or as "pitch response to fixed control force is cut back by the computer-generated movement", two sides of the same coin.
However, pilot input in an emergency - and MCAS is for abnormal situations! - should have relatively slow feedback, i.e. pulling controls starts with the same force; so my explanation of fixed control force which now produces reduced pitch is much more realistic.