Perhaps you could explain how you are Fail Operational with 3 AP, but not with 2?
Because with 3 you still have comparison/monitoring left when one fails
Not quite a simple as that. Unless I am much mistaken, I have yet to find AP3 on an Airbus (A320 etc., and A340 as I recall...), but we are quite happy doing CAT3B No DH etc...
NoD