AF-447 Stall Recognition:
Were the Air France 447 Airbus 300-200 flight crew members trained in stall recognition by:
A) Angle of Attack (AoA) based stall warning alarm system or
B) Loss in altitude, as displayed on the altimeter, due to loss of lift?
C) Both A and B
D) Neither A nor B?
1. A stall of relative wind flow over the Airbus 330 wing occurred at Stall AoA, setting off the flight crew cockpit stall alarm system. The stall warning signaled that the AoA had increased above the Relative Wind Flow Stall AoA, and by aerodynamics, the wing was no longer producing enough lift for flight, and so the altimeter was unwinding rapidly, telling the flight crew that the aircraft was descending. But did the flight crew see the loss of altitude as a symptom of trouble, or the exacting cause of the trouble and their cue to enact stall recovery procedures? If they understood the loss of altitude as their cue that they were in a stall, why did they not immediately begin stall recovery procedures, such as lowering their nose attitude? I do not think that the other multiple alarms and warnings confounded the flight crew. I think that they did not see the unwinding altimeter as the stall recognition cue. If they did, they would have lowered the nose at 37,000 feet and resumed level flight. What was the confusion therefore, that confounded the AF 447 flight crew?
2. Is not the altimeter a very good and reliable indicator of a stall? Along with the AoA Stall Warning system, didn’t the flight crew have this very reliable and verifiable stall indicator, all the indication that they needed to solve their problem? Without a doubt, a rapidly decreasing altimeter is a very good stall indication, especially when the crew has nose up control inputs. Acting on that information alone, the crew would have been able to carry out published stall recovery procedures of lowing the nose to lower the AoA.
3. I would argue that, as the Air France Airbus descended from above 37,000 feet to the surface of the sea, loosing its altitude due to loss in lift, the flight crew never recognized that the loss of altitude was their stall recognition cue. As a result, the crew never attempted standard operating procedure stall recovery by lowering the nose. Was the reason that the flight crew never realized that they were in a stall, due to the fact that they did not understand that the decreasing altitude as displayed on their altimeter, was the stall indication? Why was that the case for AF447? Is that still the case today at many commercial airlines around the globe?
4. From their stall recognition and stall recovery training at Air France Airbus training program, were the flight crew trained to recognize and recover from stall based only on the installed AoA-based stall warning system? Did AB and AF not require the altimeter as the next instrument to be checked for decreasing altitude, in the stall recognition and recovery procedure? How many other commercial pilots are their out flying the line, that do not understand stall recognition and stall recovery procedures?
5. Once a stall is recognized by observing the decreasing altitude on the altimeter, wouldn’t the next procedure in stall recovery be the same procedure of decreasing the nose attitude, just as in the case for stall recovery for AoA based stall warning? In the altimeter case, doesn’t the altimeter substitute for the AoA-based stall system for the stall recognition? Since the AF 447 flight crew never attempted stall recovery procedures, is it correct to conclude, that they never recognized that they were in a stall at all?
6. Should Air France, all airlines flying Airbus, and Airbus Training, and perhaps all commercial airlines, shift stall recognition and stall recovery procedures from focusing solely on AoA-based stall warning for recognition and reaction, and rewrite procedures and redirect training to include scanning the altimeter for loss of altitude, as part of the procedures for stall recognition and stall recovery? Is this a new idea that should be considered by all airlines and training facilities?
Perhaps you could pass this procedural good idea on to your airline’s training department and your pilot association’s training committee? By understanding aerodynamics, you can enjoy safe flying. Remember that $afety Pay$.
International Captain Paul Miller
Safety Forecast 