hi gums;
Yes, the gang's all here, but only momentarily!
In wings level flight, AoA can be derived from the pitch and the inertial velocity vector regardless of the air data probes/cones. The Sluf and Viper HUD had a "zero sight line" cross, and usually the flight path marker ( FPM) was below it ( negative gees was something else, heh heh). That was your AoA in wings level flight.
Yes, I understand that, we've discussed that and I even had posted a schematic showing how AoA can be roughly approximated (while not precisely and not instantly due to lag but perhaps usefully if one is trained / skilled at such interpretation*) from the FPM / FPV and pitch angle, independent of the AoA sensors.
"Derived" in flight data work means usefully accurate and precise as well as timely and the FPM / FPV vs pitch method of "deriving AoA" in rapidly changing circumstances, is none of these.
While the FPM/FPV display is inertially-driven this still requires a working ADR (AF447s were intermittent and, in the time period available, essentially unusable) and a working AoA sensor (Perpignan, frozen sensor, erroneous stall speed display on the PFD).
The point I wished to make in regard to Lyman's statement that AoA can be derived is that it can't be in the sense that it could be used to display AoA when original sources as described, are not available.
*When the A320 first came online, we were trained that the FPV Flight Director should not be used as guidance during a go-around because of the lag in the FPV as the aircraft stops descent and begins the climb. The justification was, following a lagging display could lead to reduced climb performance. I believe that's now changed and the normal FDs are displayed automatically when the thrust levers are pushed to the TO/GA detent.