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Old 29th May 2011, 16:51
  #882 (permalink)  
J-Class
 
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If you think about what could have been done to prevent this accident, rather than about whether the crew were competent/incompetent or whatever, it seems as though if they had had available the information that we have from the FDR, ie alpha, airspeed and descent angle, they would have recognized the problem immediately and recovered. But that info was not provided evidently because the system designers considered this scenario impossible. But three identical pitots known to be able to be overwhelmed by ice are not triply redundant; they are a single point of failure. The airplane -- any airplane whose systems rely so heavily on airspeed -- needs a truly alternate airspeed source, a full-time angle of attack indicator, and a stall warning that does not go to sleep and then wake up at inopportune moments.
Garrison, I'm with you. Indeed, this view hasn't changed much since I made a similar point on p.24 of this thread (before the BEA report was published) where I said:

"Surely AoA (and perhaps a GPS speed indication for good measure) would be very helpful in instances where airspeed indicators have gone doolally and the aircraft computers are assaulting with pilots with a bunch of not necessarily consistent error messages and alarms?

All modern aircraft rely on system redundancy, but can any system be deemed truly redundant if it relies on the same components on each of its legs? (I'm imagining that more than one pitot tube iced up). Given the problems of producing 'true' redundancy in a single measurement system, why not admit that visible workarounds should always be available to the pilot?"
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