Originally Posted by
Lake1952
I think it is a mistake to say that the tendency to pitch up with added thrust due to nacelle created lift is "inherently unstable." In hindsight, Boeing and its customers would have been better served by skipping MCAS, requiring some training in the pitch up tendency even if, God forbid, the flight characteristics required a new type rating. And it probably would not have actually required a new type rating anyway!
No, you cannot simply waive certification requirements on stability by saying you will provide some more training. And how have you arrived at the conclusion that training would do a better job than a small system that provides the required control forces at high angles of attack? This is a system that helps return the aircraft to its normal flight envelope when it already is at a high angle of attack. Typically this is a situation where something else has already gone wrong, and that almost always implies a high workload, where it is vastly preferable to have the airplane return to fully controlled flight by itself rather than relying on a task-saturated pilot to remember some bit of training highly specific to this type of aircraft.
Obviously, these kinds of assistive devices require a proper hazard assessment to be performed, including adequate assumptions about human behaviour, especially in a high-workload environment, which is exactly where this system is most likely to be active, and an analysis of worst-case consequences of single failures. Arguably that could have been done better in the case of MCAS.
On the whole, I'm sure you will find that fly-by-wire airliners generally have a far better safety record than conventionally controlled ones. That is not to say that it is only due to the computer-controlled flight controls, but also because FBW types are newer and incorporate other advances in safe design and systems reliability. But it is also clear that computer-assisted flight controls do not generally make flying less safe, QF72 notwithstanding. Case in point: The A320neo has had no accidents and perhaps one incident (tailstrike), despite being on the market somewhat longer and having almost twice as many airframes in service as the 737MAX.
Bernd