I admit it's not as authoritative as I'd like but this is the best source I've found: > MCAS is a longitudinal stability enhancement. It is not for stall preve

I admit it's not as authoritative as I'd like but this is the best source I've found: > MCAS is a longitudinal stability enhancement. It is not for stall prevention or to make the MAX handle like the NG; it was introduced to counteract the non-linear lift of the LEAP-1B engine nacelles and give a steady increase in stick force as AoA increases. 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". MCAS was therefore introduced to give an automatic nose down stabilizer input during steep turns with elevated load factors (high AoA) and during flaps up flight at airspeeds approaching stall. http://www.b737.org.uk/mcas.htm http://www.b737.org.uk/mcas.htm However, on Boeing's own website they give the 'makes it fly just like the NG' explanation. On balance of probabilities I think that's unlikely to be the engineering justification. My reasoning being I don't believe that there is any formal requirement for an aircraft to exhibit the same handling behaviours to be counted on the same type rating. For example the 757 and the 767 shared a common type rating. The 757 was a pilots favourite precisely because it was sporty in comparison to the 767.