Originally Posted by
PEI_3721
Over focus on MCAS detracts from the many other systems which could be affected by AoA Disagree - stick shake, low speed awareness, airspeed differences, IAS / ALT Disagree, Feel Diff Press, no autopilot. It could be argued that these also require protection to improve resilience to the limitations of AoA input.
Beg to differ. On the 737, before the advent of MCAS, the AOA signal was a low risk one. All the other systems you mention, with the exception of the stick-shaker, are cross-monitored and have appropriate failure indicators and checklists. Pilots are trained to handle instrument failures and carry on flying. If IAS disagree, for example, does it matter if the problem is in the pitot or the AOA sensor?
Of course, once this signal is allowed to drive flight surfaces it is no longer low-risk. But as it was OK before, it is easy to understand (though not condone) how it could have slipped through.