Originally Posted by
Concours77
Do you know the difference between speed, and velocity?
What in the world is your point? They hit the water at a speed of 152 knots - of which the horizontal component was 108 knots and the vertical component 107 knots (NOT ~240 knots as you earlier claimed). Horizontal or vertical doesn't make much difference - they'll both kill you with a sudden stop...
Originally Posted by
Concours77
I think the "cutoff" value was "60 knots", Incorporated so the StallWarn would not activate on the ground. It was determined, at least on thread, that a better trigger would be "weight on wheels", "WOW". Which makes more sense. Stall is not a function of airspeed. Stall is a result of exceeding a critical Angle of Attack. To WIt: 447's velocity through the air at impact was approximately 240 knots... Was she Stalled? ...... Boy Howdy
AOA was invalidated below 60 knots because it takes a minimum airspeed for the AOA vane to provide a meaningful measurement. This is a common engineering practice - below whatever speed is judged as a minimum for a reliable measurement, the output is labeled "NCD" or "No Computed Data". Similar limitations are on airspeed (typically 30 knots) and Mach (typically 0.10 Mach). Adding "On-Ground" to the AOA validity is a complication and has failure mode implications (and WOW isn't the most reliable indication in the world). As a designer, I doubt it would have ever occurred to me that an otherwise airworthy, flyable aircraft would ever get down to an indicated airspeed of 60 knots in-flight and that was a condition I needed to design for.
ure, in 20-20 hindsight perhaps that would have helped the PF to figure out he was doing something really stupid, but the bottom line was that he was not a competent pilot or he would not have kept pulling back from 30+ thousand feet until they hit the water. Had he sat on his hands instead of panicking and pulling full back, the aircraft would have been just fine.