Here is the basic summary:  The plane appears to have lost indications for speed in flight (although not in turbulence) while the Captain was taking a rest period.  The two inflight pilots systematically worked the problems but without much luck and resulting in a stall.  The captain did not take control.  The pilots appear to have “pulled up” instead of nosing over despite stall indications that were recorded.  The aircraft had gone into “alternate law” which does *not* prevent the aircraft from being flown into dangerous conditions.  The first read is that the pilots screwed up.

What gets ignored is that it also appears that the pitot tube(s) that were recording the speed of the aircraft did in fact freeze up which caused a loss of speed indication on the primary flight displays.  At their altitude, speed is a very fine envelope of conditions.  It’s possible to go too slow and too fast and the higher you go, the narrower the difference is between the two conditions.

The very puzzling thing is that 3 very, very experienced A330 pilots appear to have attempted to “pull up” (i.e. go nose up which would *slow* the plane) when things began to happen instead of pushing their nose down which would recover from a stall.  It’s always sporty recovering a stall in a large airliner but it *is* something one trains for. 

So, is it the pilots?  They may have perhaps contributed to their problem, yes.  But their actions make me wonder what information they were seeing on their backup instrumentation.  In other words, did they realize they were in a stall?  The A330 has no stick shaker and, instead, has a loud audible warning for a stall.  Presumably this could be heard on the cockpit voice record. 

The way this happened is just a bit too eery still.  With the altitude they had, there was nominally plenty of height to recover from problems.  Air France isn’t Colgan Air and they do train their pilots very, very well.  Their actions may suggest that they were reading their conditions very differently from what they actually were. 

The next step is to take this into a simulator and starting seeing and experiencing what happened and try to figure out the “why” of what happened.  This “ruling” is by no means definitive or informative necessarily.

Filed under: Airline News by ajax