Originally Posted by
MechEngr
There's no drastic pitch-up. How does this get started and why is it repeated? 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'm not sure I'll fully agree with the above.
Small changes in configuration *can* lead to drastic change in flight qualities. Heavy tail buffet in a transport plane has been known to be due to windshield/windshield wipers perturbations, and had to be cured with VG's on top of the cockpit.
Some very little variations in airfoil, washout, dihedral, sweep or mechanical details can trip unwanted flow behaviour.
Boeing said the stability issue was due to the airflow over nacelles and adjacent wing portion rather than thrust line.
Not sure there is a way to foresee mach tuck etc. just by comparing 3-view drawings so I'd say there is more to the 737 stability issue than is officially published.