Originally Posted by
ethicalconundrum
TAWS developed to counteract CFIT. I am a private pilot, and engineer(not aero). At the time of development, the TAWS systems out there would provide Warning, and with later advancements, advice on how to resolve the CFIT (warble, + "terrain, pull up, terrain, pull up"). However, there was no overtaking of the controls to manually take the pilot out of the loop, and force the column aft. As I think of the times, about 40-ish years ago, anything like this MCAS idea where the plane knows better than the pilot what control inputs to make, it was up to the pilots to operate the plane, and the TAWS to provide additional information on how best to operate the controls(pull up, avoid CFIT, everyone lives).
MCAS developed to resolve the design changes from excess lift in climbing caused by the engine location and thrust, as well as nacelle added lift. yes, it is a completely different set of circumstance than TAWS. Yes, it is 'needed' for certification to meet the control deflection force criteria.
What if -- something like the LEAP engine or similar had been developed for an earlier airframe, say the 727. Would Boeing have the philosophy to implement a control deflection system that overtook the pilots responsibility? Having grown up into aviation at that time, I can think that the 'old guard' pilots union would be up in arms, and defiant of anything like this. Given the results, and the later development of TAWS, why would Boeing not simply enhance the stall warming similar to "stall, push forward, stall, push forward", and leave the management of the controls to the pilot, where it belongs? Guessing the FAA/CASA would not allow that kind of change in control forces, but this seems to be a 'fix' to meet a regulation, and not a 'fix' to meet a clearly defined fault.
The fix may be worse than the fault(control force change).
Keep in m mind that the MCAS is not a stall prevention device; it is a stability augmentation device. The engine installation apparently led to a much reduced stick force gradient approaching the stall in some situations. All the MCAS was supposed to do was to artificially enhance the stick force. At 0.6 degrees per activation, that might have made sense. I cannot imagine ever needing 2.5 degrees of stabilizer movement to enhance any stick force gradient.
It's also worth noting that the elevator feel shift mechanism and the speed trim system have been doing this on the 737NG for quite some time. The MCAS appears to have been an extension of that philosophy, rather badly bungled.