Originally Posted by Graybeard
According to many prior posts here, the Stall Warning shuts off below 60 kt IAS. Why they have IAS input to SW is beyond me. The DC-10, for example, uses only AOA for SW.
Stall AOA is ~7deg when high&fast and ~16deg when low&slow.
Besides, AOA vanes are designed and calibrated for situations when air comes from generally front direction, not side or bottom. AOA was severe enough to cause Pitot readings off, variometer indications got flaky, etc.
Originally Posted by predictorM9
I completely agree. As long as the plane is in the air there is always 60 kts of relative wind, even if the angle of attack is so high that the pitot measure wrong speeds.
Nope. It's perfectly possible, as evidenced by previous accidents, to get airspeed below 60kts in a large plane (some poor guys happened to get negative airspeed before they crashed). But I agree that the real airspeed was above 60kts in this particular case.
Originally Posted by predictorM9
The fact that they certified the logic behind this is for me a huge mistake. As long as the AOA is not insane it doesn't matter. But if the aircraft is capable of 45 degrees AOA, they should do a logic that also works in this case
Certification does not bring much attention to situations so far away from flight envelope. Many airframe designs are considered totally unrecoverable even by heroic measurements when stalled so severely, yet they get certified.
Originally Posted by predictorM9
failure from the pilots to realize that the lack of stall warnings was wrong because they flickered
The stall warning was on for long enough to take proper action. It's debatable if the airplane could be recovered if they initiated proper action after stall warning continued for the whole minute.
You, and many posters here concentrate on what happened after the plane has severely stalled. But from a flight safety PoV things were already critically bad. Dealing with problems during "falling out of the sky" phase won't improve safety much (if at all).
What is really important is how it entered the stall and how there was no immediate proper attempt at unstalling it. Aural stall warning was active then, attitude indication was good, vario was good, even speed was good at least on PM's display and backup (ISIS) display.
So, if even, there is some human interface problem pertaining to that phase of flight ain't aural stall warning silencing itself when attitude gets so far away from flight envelope that pitot probes stop working.