5 ms·

Supposedly they do de-ice themselves, but that obv didn't work properly here.

• bdonlan 15y ago
  According to the article, the pitots did, in fact, de-ice and return to normal functioning. However, apparently the alternate law needs to be manually reset, since the plane remained in direct input mode, and thus the pilots managed to stall the plane even though its instruments had all recovered.
  • omegant 15y ago
    Pitot tubes are always under strong heating during flight( so strong that the steel may blue). The problem with the 330 pitots brand in particular( there are several ) is that they cant evacuate water fast enought and sometimes they could become unserviceable ( as it happened to the af ) as they don't sense air preasure anymore.
• sliverstorm 15y ago
  Ah, I was not aware they already could. My next question is why not make themselves de-ice better? This maybe seems trollish or silly, but in all seriousness, if your sensors aren't good enough, first rule out improving the sensors before you try to compensate with the system.
  • bdonlan 15y ago
    According to the article's timeline, dual pitot failure occurred at about 02:10:06. Recovery of one pitot occurred at 02:10:36, and the other at around 02:11:03. That's about 30 seconds to recover one pitot, and 57 seconds to the recovery of the second. When you consider that this all boils down to melting off ice, that's not so bad, really. And if they hadn't royally screwed up their manual handling, it wouldn't have downed the plane - there is, in fact, a procedure for maintaining safe lift when airspeed indications are lost; somehow the copilots in command managed to screw it up, and continued to screw up even after the pitots recovered. The BBC tried replicating a pitot failure in a simulator, and when the sim pilots went by the proper procedure, there was no problem: http://www.youtube.com/watch?feature=player_detailpage&v=JqTPbPlyX5E#t=545s http://www.youtube.com/watch?feature=player_detailpage&v... So basically, this is human error, but exacerbated by a lack of training in cruise problems and poor feedback from the controls when the copilots gave conflicting commands.
    • crististm 15y ago
      The simulated test is always in a more relaxed environment. But anyway, if your instincts are good they you are OK. The problem is when your instincts tell you to do the opposite of what needs to be done. Probably the pilots need more training to break their instincts?
  • reledi 15y ago
    I agree. I know little about aviation, but wouldn't it be better if the sensors would automatically de-ice themselves rather than only being de-iced at the pilots' command?
    • jonah 15y ago
      I believe they're continually heated. At least every one I've seen is labeled "heated probe" or the like which probably wouldn't be necessary if they had to be manually de-iced. http://www.flightglobal.com/blogs/flightblogger/pitot-tubes_sm.jpg http://www.flightglobal.com/blogs/flightblogger/pitot-tubes_...
  • jrockway 15y ago
    There is other debris that can clog pitot tubes. Birgenair Flight 301 crashed because some wasps built a nest in a pitot tube during an extended layover: http://en.wikipedia.org/wiki/Birgenair_Flight_301 http://en.wikipedia.org/wiki/Birgenair_Flight_301 189 people died. (Also note the failure to react properly to the stall warnings. This comes up again and again.)
    • jarek 15y ago
      I wonder if in a couple of decades we'll look back at pitot tubes and wonder what the hell we were thinking using such a fragile solution. (Of course, in a couple of decades we'll probably have a much more accurate external method of finding out speed/airspeed.)
      • jrockway 15y ago
        It's hard to measure how fast you're going through the air without being able to sample the air. Pitot tubes are just the tubes that bring the air to the inside of the plane to be sampled; nothing more.
        • jarek 15y ago
          I mean, I know the physics behind pitot tubes, but I wonder if we'll come up with a better way of measuring this. Something like measuring deflections of a thousand tiny rods on the plane skin. Still vulnerable to icing and other mechanical damage, I suppose. Maybe we'll just have really accurate GPS and beam external local instantaneous wind-speed measurements to the plane.
          • sk5t 15y ago
            But, what would be taking those hyperlocal windspeed measurements--at the same altitude and within a mile or two? I can't think of any way at all to accomplish this short of a satellite with an incredible new method to measure many slices of moving air.
      • gnaffle 15y ago
  • antoinehersen 15y ago
    The fact that the heating element was not effective enough was a known fact. Since similar incident of lost of air speed had already happened. Pitot were being replaced with beefier heating elements. It was just not considered a high priority.
  • antoinehersen 15y ago
    The fact that the heating element was not effective enough was a known fact. Since similar incident of lost of air speed had already happened. Pitot were being replaced with beefier heating elements. It was just not considered a high priority.