Originally Posted by
Lost in Saigon
It is pretty basic. An aircraft has to fly like an aircraft. If you pull the nose up, and then release back pressure, the nose must return to somewhere near the original attitude and speed. If you disable MCAS, the B737 MAX will not meet the FAA stability requirements of Sec. 25.173 (Static longitudinal stability)
I suspect that without MCAS there would need to be a major aerodynamic redesign to meet the stability requirements.
The autopilot does not need MCAS. I don’t know which part of 25.173 MCAS was there for but I thought it was the stick force gradient. There is an exception to the trim speed requirement if exceptional attention is not required of the pilot. The lack of concern of FAA/Boeing to identify an envelope of concern if you actually had a malfunction involving turning off MCAS makes me think you could certify the MAX without MCAS if waivers are allowed for Part 25.