Was there a problem with stalling on 737 jets before the 737 Max, if not then why is MCAS needed on the 737 Max 8.If it was a problem why did Boeing wait so long.
Was there a problem with stalling on 737 jets before the 737 Max,
The flight characteristics, including high angle of attack operations, of the previous models of the 737 did not warrant the kind of action the MCAS system provides.
why is MCAS needed on the 737 Max 8
The Max 8 engines are physically bigger—69.4 inches fan diameter versus 61.0—heavier, mounted farther forward and higher than previously. This changed the thrust line and flight characteristics. MCAS is used to restore "normal" 737 flight characteristics.
See http://www.b737.org.uk/737maxdiffs.htm for details.
Previous 737 models had acceptable stall characteristics.
The Max introduced new and larger engines. There was not enough room for them between the wing and the ground, so they were moved forwards further in front of the wing to make room for them to sit high enough and clear the ground. This affected the handling of the Max at high pitch angles.
But the intention was to introduce the Max without the need for significant pilot re-training and type re-certification, so the change in handling was unacceptable. MCAS - the Manoeuvring Augmentation Control System - was introduced to manage the aircraft handling at high pitch angles and avoid the need for pilot re-training.