Originally Posted by
Smythe
The LEAP engines are both larger and relocated slightly up and forward from the previous NG CFM56-7 engines to accommodate their larger fan diameter.
This new location and size of the nacelle cause the vortex flow off the nacelle body to produce lift at high AoA; as the nacelle is ahead of the CofG this lift causes a slight pitch-up effect (ie a reducing stick force) which could lead the pilot to further increase the back pressure on the yoke and send the aircraft closer towards the stall.
This non-linear/reducing stick force is not allowable under FAR §25.173 "Static longitudinal stability".
Do you realize that you have just contradicted your previous post, which claimed that MCAS was not added to manipulate stick feel? 25.173(c) is ALL ABOUT stick feel.
(c) The average gradient of the stable slope of the stick force versus speed curve may not be less than 1 pound for each 6 knots.