Originally Posted by
hans brinker
Because they can't certify the aircraft without MCAS. At high AOA the engines (being MUCH bigger and WAY further forward) provide too much aerodynamic lift ahead of the CG, pushing the nose up even further. MCAS adds AND trim in this scenario. Just compare the B737-100 with the B737-MAX and you see why they needed to add electronic band-aids to keep it legal.
The 737-100 was 93 feet long and the longest Max is 147 feet, quite a bit of stretching from original certification