Originally Posted by
A Squared
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)
Just ran some numbers, in very general terms, depending on sensor position and factors like Mach number, in extreme cases... expect up to 5kts difference. Probably enough to trigger an IAS and ALT disagree on a modern airliner. For a plane flying at moderate speed the difference will be more towards 2kts.