Originally Posted by
JulioLS
Can someone explain to me why anyone in their right mind would design a system whereby information from one sensor (in this case, the AoA sensor) corrupts the information coming from other independent systems (airspeed, altitude, and indeed even seemingly groundspeed)?
The equivalent in a car would be to allow the external temperature sensor to mess with the speedometer reading and the fuel gauge reading. Oh, and also allowing it to floor the throttle!!!
If airspeed and altitude readings remain unaffected, the pilot is surely going to have a much better view of what the plane is doing and what has gone wrong.
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).
What it may cause is the Air Data Computer informing other systems of this AoA disagree, and other systems acting on this. I.e., a flight augmentation system, which heavily depends on AoA for e.g. envelope protection, would most likely switch to a degraded mode and inform the pilots of this. Depending on the aircraft the auto pilot may disconnect as well. So while there are effects and a possible increased workload for the pilots, there is no reason think that a broken AoA sensor presents invalid airspeed and altitude as well.
Interestingly, as far as I know the failure of one or both AoA sensors is not often part of the simulator training curriculum (pilots, please correct me if I am wrong). At least not to the extent that unreliable airspeed is trained these days (in part because of the AF447 accident, which put more emphasis on this in the simulator).