MadScientist
Surely alpha AoA is NOT suspect in Alt2 degraded mode. In fact AoA is (or should be) one of the easiest and most reliable of all transducers and can easily be kept independent.. that's why I find that a fully dynamically balanced vane was black-balled below 60 kts... It should never be black-balled... it should be extremely lightly spring loaded to a nominal 0 or 2,3 degrees +ve - for a low speed oscillating case, an RMS value could be used, and finally disregarded if mean and peak vales exceed a given ratio... for airspeed to be in any way involevd in its output IMHO is wrong.
There are also fairly easy ways to measure AoA less accurately as a fall-back value, electronically using hot-wire anemometry, as well as other methods