Originally Posted by
Flutter speed
As I mentioned in another post, the AoA data is used to calibrate the measured static pressure and therefore not fully independent as in your example. As such there is a direct link between AoA sensor data and airspeed / altitude. However, this calibration is small and a miscompare between the two AoA sensors is unlikely to invalidate airspeed (though as said, it may influence the displayed airspeed and trigger a disagree between IAS in extreme scenario's).
So, for a 737, what would be the largest difference between IAS, uncorrected for AoA, and CAS, within the range of AoA that could be reasonably expected in flight? The large airplanes I've flown didn't correct IAS for AoA, and without looking them up, I don't recall that the airspeed calibration charts having a correction larger than 5 ish knots. Seems if it came down to a choice between an IAS that differed from CAS about 5 kt at low airspeeds/high AoA and no usable airspeed indication at all if the AoA fails, I know what I'd prefer. Especially if my takeoff and landing charts were referenced to IAS, whcih makes CAS a relatively uninteresting number. (except in cruise, where IAS and CAS are usually fairly close anyway)