If I may supplement what Retired F4 pointed out in re AoA indications in my response to Graybeard.
Graybeard
I don't know a lot about AOA vanes, which I why I asked for someone really knowledgeable to speak up
I don't think I am that much more knowlegable, but I am familiar with them on some aircraft.
The real measure of AOA is degrees, not knots, of course, although everybody has been shouting for a Stall Warning below 60 knots, not a specific AOA.
Not really. They've been arguing that clipping the stall warning in flight at 60 knots makes no sense. I agree.
IIRC, AoA is displayed in units, but that may be aircraft specific. For the Navy Trainers I am familiar with, T-45 stalls somewhere between 29 and 30 units, the T-34 at about 26 units AoA. See also Retired F4 comments above.
I don't have the numbers, but it appears that onset of stall of the A330 at that MAC and flap is less than 20 degrees.
OK
The report shows AF447 achieved AOA in excess of 40 degrees
Roger
How much AOA does it need to measure, 90 degrees, 120 degrees? What's the point?
To the point of stall, and beyond, as your barnyard theme suggests: let it weathervane in the airflow as it will.
You have to balance Stall Warnings in extremely rare events with far more common nuisance stall warnings, in order to maintain confidence in the system.
Yes about noise and distraction, but I see no reason to have a stall warning on the ground. There is an arbitrary decision to pick an airspeed. There is no reason to curtail it.
When you are flying, stall is about the most important thing to know about and unscrew first, since if you are in a stall, you aren't flying so much as falling.
Of all warnings, that ought to have primacy, don't you think?
Stall warning is not just another damn light or noise.
In fact, there was no doubt a point in the zoom climb to stall that airspeed was near zero, and the AOA vanes would fall with gravity, probably showing a negative AOA.
I don't agree with your assumption there. Airspeed near zero has little evidence to support it, and would have required IMO a much higher nose attitude than what FDR indicates.
I see no reason to clip AoA input based on any airspeed. That was my point. The WoW (squat?) switch would take care of the issue of spurious warnings, would it not?
AoA tied to stall warning would thus be tied to aircraft in flight/off the ground, which is where you both want and need stall warnings. It remains independent of the airspeed indicating system, as it should.
@bearfoil: I do not understand what you said regarding artificial horizon not being optioned by AF a couple of pages ago. There is one for each Pilot's Flying display, and a back up in the ISIS suite of instrumentation.
Can you elaborate?