The cockpit transcripts from the Air France jet that crashed into the Atlantic while on a flight to France in 2009 has given a clue to the important piece of equipment that couldn't handle the situation: the human brain.
Last week, the French agency in charge of investigating the crash released its report, indicating "pilot error" as the cause. That prompted the Globe & Mail, and many others to write fairly arrogant reviews of the pilots, who were -- it should be pointed out -- first to the scene of the crash.
Nor is it clear how all three pilots became confused and in disagreement about whether they were pointed up or down, and managed to ignore loud and repeated "Stall" warnings. The warning, an artificial voice calling "Stall, Stall," is accompanied by a loud chime and a red warning light on the instrument panel. Yet for more than three minutes, the pilots failed to push the nose down, regain flying speed, and recover. (In aerodynamics, a stall is when airflow over the wings slows to the point where lift is lost. Recovery requires an immediate lowering of the nose.) Air France will face massive - perhaps record-setting - civil damages if, as now seems likely, it can be proven that the pilots failed to regain control of an undamaged aircraft, with all its flight controls and engines functioning. Those damages will be even higher if the long minutes of fall were evident to the doomed passengers.
Sure, that's pretty easy to say. The pilots obviously knew what needed to be done. Stupidity wasn't the problem.
The problem is they didn't know which way was up. Close your eyes, have someone spin you around, and then drop you off in the middle of a busy intersection. You know you need to get to the sidewalk. Try to figure out how to get there.
There's only so much data the human brain can handle. Keep in mind it's night, the cockpit is dark, there are no references outside to tell you where you are, lights are flashing, alarms are going off and a simple airspeed indicator isn't working (declining airspeed can tell you you're going up, increasing airspeed means you're probably going down), the noise from passing air is changing and telling you something, but what? Your body -- which lies to you at times like this -- is telling you one thing, some working instruments might be telling you another. Which one do you believe?
Oh, and you've got one minute to get all this sorted out.
Today, France's BEA released the cockpit transcripts (French version here, an English translation hasn't been released).
David Learmount, who writes about aviation, has evaluated them:
The PNF then says: "We are losing...Wing anti-ice." He switched the anti-ice on, and two seconds later exclaimed - twice: "Pay attention to your speed", to which the PF replied: "Okay okay okay I will descend again," but in the next 15s or so the two pilots exchanged words indicating confusion about whether they were still climbing or had achieved descent.
But the aircraft was still, indeed, climbing, and the PF, despite temporarily relaxing the stick-back input, had resumed it.
Some 25s elapsed between the PNF warning the PF to "watch his speed" before the aircraft starts to descend. But when it does, the aircraft's attitude is still between 6deg and 13deg nose-up, and at that vertical speed reversal point the "stall, stall" warning returns, this time with the "cricket" sound as well, and five seconds later the crew moves the throttle levers from the Climb detent into TOGA (take-off/go-around) position to obtain full power.
No words are spoken by either of them for about 10s, the descent rate is increasing, and then the PNF says: "Above all avoid applying lateral [roll] control", to which the PF replies: "I'm in TOGA, eh?" and 18s later the PNF says: "We have the power, so what's going on?"
Nobody has mentioned the aircraft attitude so far. In fact no-one ever mentions it in a substantive way. The attitude is actually about 18deg nose up, which is the reason the engine power is not producing the results the crew expect to see. Vertical speed (descent) is still increasing dramatically, and the speed the pilots see is varying between 130kt and 160kt.
The PF says: "I don't have control of the aeroplane here. I have absolutely no control of the aeroplane." His stick input is on the nose-up and full-left stops. The attitude is nearly 15deg nose up and the roll angle is varying between 16deg right and 40deg right.
Pulling the nose of the airplane up degraded airspeed (remember, they don't have a working airspeed indicator), causing the plane to drop even faster.
Unfortunately, the plane was doing everything the pilots were telling it to do.
I saw a show on Nova about this flight that seemed to suggest that the iced-up airspeed sensors were the root cause of the crash. Are we to understand now that even without information about airspeed, the pilots should have been able to regain control?
I saw that, too.
Because the airspeed indication (via the Pitot tube) went hinkey, the autopilot disenaged, basically it said, "you're on your own, fellas."
It's possible there were other pitot instruments that were OK, but I hadn't heard that.
I suppose in theory if you don't have airspeed, you could still rely on a vertical speed indicator to tell you whether you're going up or down, and the altimeter; but I'm not sure.
I think one of the factors here -- and I won't know this until there's an English translation available -- is spacial disorientation. Somewhat like the Kennedy crash in which the guy is in a descending spiral and he thinks he's flying straight and level.
When you think of your body and all of its senses as a "flight instrument," and when you throw in all the other flight instruments screaming at you, I tend to believe at some point the brain just shuts down OR -- more likely -- becomes incapable of accepting any more data.
Perhaps that's why once the pilots believed they were in a dive, they continued to believe that even if there was other data to be considered.
I tend to think this accident isn't about stupid pilots making dumb decisions, it's about the human factors of flight.