Stall warning vs AIRCRAFT STALLED!
The purpose of the Stall Warning is to warn of an approaching stall condition and in this accident it is clear that the fact the aircraft WAS STALLED wasn't identified, at least explicitly.
It has been noted that at one point the Stall Warning was sounding continuously for some 54 seconds, with apparently no attention - not one of the crew ever uttered the word "stall", at least in any of the released CVR content. It remains to be seen in the future whether the full CVR transcript will indicate otherwise (assuming it makes the light of day at some point downstream).
However my question (or perhaps statement) is why is there no "YOU ARE STALLED - DO SOMETHING ABOUT IT!" warning? Something that cannot be ignored.
Certainly, overspeed, for example, is upsetting and may lead to bits of the airplane falling off, so being concerned about that is reasonable, but in the order of things being stalled certainly trumps an overspeed condition.
Unless I am having a seriously bad day, all the necessary conditions for the computing system of the aircraft to be aware that things were seriously pear-shaped were still available - and I think it takes just two:
- AoA seriously negative
- Altitude (or vertical speed) winding off the scale
Can there ever be a legitimate combination of such an AoA and vertical speed that is NOT a stalled aircraft? If not then how about flashing a warning on the center glass reading: "AIRCRAFT STALLED! AIRCRAFT STALLED! REDUCE AoA!"?
There are far better qualified folk on this board to define better conditions (factoring more parameters I'd bet) for such a warning, but what is wrong with doing this?
Given the horizontal speed can be suspect whether or not this need be factored into such a critical warning I will leave as an exercise for the reader, but it seems to me this incident and the Buffalo crash seem to warrant a stage 2 warning beyond approach to stall, that instantly and unequivocally let's the crew know what is happening and has the key resolution (AoA reduction) as the key tag-line?
Make the cockpit displays FLASH the message in RED TEXT on a white background every 5 seconds, whatever, but make it clear and unambiguous.