Originally Posted by
MechEngr
There's no drastic pitch-up.
We don't know how pronounced the pitch-up tendency may be. We haven't seen data from testing of the bare airframe.
How does this get started and why is it repeated?
It got started because both Boeing and the FAA have indicated that the size/shape/positioning of the LEAP engines creates additional lift at some attitudes/corners of the envelope and that as a result of that, MCAS is required to provide linear stick force to discourage pilot input bringing the aircraft dangerously close to stall. There is a fair amount of skepticism about the assertion that a system with full authority over the horizontal stabilizer was truly developed and implement merely to control stick force.
Comparing the plan form to the NG and the differences are difficult to make out.Slight changes in configuration tend not to make drastic changes in performance. More than that, the Max has a thrust line closer to the CG than any other 737, so the pitch coupling should be less or about the same. The larger engine can produce more thrust, but unless the plane is a lot heavier than previous planes the only way to use that thrust is in uncomfortable sea level take-offs or in normal rate departures from high-hot-humid airports.
I don't think anyone has suggested (at least in many months) that thrust is the issue here. The issue, as far as we can tell, is increased lift due to the engine nacelles and their position.