Originally Posted by
SouthernCross
Are you positive that the MCAS uses a single pitot probe? I’m no aircraft designer, but at the pricetag of a 737 I’d expect 2 or even better 3 redundant voting inputs.
My understanding is that while there are multiple AoA sensors (not pitot tubes), the MCAS system will initiate a stall avoidance maneuver (by trimming the nose down) if any of the sensors indicate an excessive AoA. I assume the logic behind this is that one of the scenarios where the plane could be flown into a stall condition is when there is an AoA sensor disagreement, in which case the plane will need to be flown manually with conflicting, and hence confusing, data. However, the logic doesn't allow for the case where the plane is flying perfectly well, at a normal AoA, but one AoA sensor has failed in a mode giving an excessive reading.