Quote:
Originally Posted by ken0042
So here's a question- I've seen a couple of crashes caused by pitot tubes and failures. Why do modern airlines not have GPS as a backup? The $150 GPS I have for camping can give ground speed (I know air speed is more important; but it's better than nothing), direction, altitude, distance to landmarks, etc. You would think for a few thousand there could be a system installed as a backup that works completely differently than the pitot tubes.
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A bit of a loaded question.
In this specific case, I suppose they could have glanced at their ground speed, but that really wouldn't have helped. From a purely Human Factor perspective, those poor guys were faced with an onslaught of multiple failures in a span of a couple minutes, by the time they realized their airspeed was a factor they were in the ocean.
At that altitude they deal with Mach number which changes with temperature. Also your KIAS changes with air density. All a GPS gives you is your speed measured from point A to B, it really is apples to oranges comparing ground speed to air speed at that altitude.
To add to that, at that altitude they are nearing "coffin corner" which is basically the point where the aircraft's stall speed is coming close to the aircraft's maximum speed (or Critical Mach number) This is where automation helps tremendously because you are dealing with a narrow window. That could have compounded when they slowed to their Turbulence penetration speed, and then lost the autopilot.
So really at that point it would have been just as helpful to look at the current Playboy Centerfold as it was the groundspeed.
Still lots of speculation. I really hope we do hear some answers.