For a safety system it makes no sense to have a 'single point of failure' this is a
sine qua non of any safety related engineering. MCAS is obviously a safety system and (despite disparaging comments here) Boeing engineers will not have deliberately chosen to make it unreliable. So this begs a question.
First there are a LOT of 737's flying; from Wikipedia:
" As of 2006, there were an average of 1,250 Boeing 737s airborne at any given time, with two either departing or landing somewhere every five seconds"
A large number of those 737 (if not all) will have the same AoA feeding similar ADIRU and will get an Unreliable Airspeed alert plus stick shaker if AoA disagree. Out of 50 or so Max 8 they have already had two errors only months apart. If that was the rate in the whole fleet there would be continual unreliable airspeed reports and no engineer in their right mind would hang a safety system onto a single AoA if they were that unreliable. From that one can only assume that AoA is normally
very reliable to the extent that failures are very rare
on previous 737 models.
So the question is - why are the AoA systems on 737Max8 failing at a rate higher than acceptable? Is this just a sad coincidence that when a safety related system is designed to use the AoA output - two failures arise in 6 months -or- is there something different about the Max that is leading to AoA problems?
Even 'ramp rash' could be affected by the different position of the engines when push crews and catering used to NG have to work with the Max.
Any thoughts?