Originally Posted by
QuagmireAirlines
How about this envelope protection cut-out: Turn off MCAS when airspeed is greater than 200 knots.
That is simple, and uses different sensor sources (pressure sensors on the nose) to disable MCAS which works off AoA vanes.
Ultimately the decision by Boeing to simply turn off MCAS when the dual AoA vanes disagree may be the best approach.
If it was me, I'd disable MCAS for those high (>200 knots should do it) airspeeds, and also compare the two AoA vanes to computed Inertial Alpha (pitch-gamma) as a sanity check to find the bad AoA vane when AoA disagrees happen.
I am not a pilot, but some of the suggestions on this thread seem like a contortionist trying too hard. It is perfectly possible to stall an aircraft at high speed and high altitude (ask the crew of AF447). Adding all sorts of flight envelope restrictions and inertial data to inhibit MCAS, does little to add safety, and creates the potential for new modes of failure. The proposed changes put forward by Boeing at least seem clear and coherent, even if not everyone agrees with them.