A minute after the autopilot disconnected, Bonin muttered something odd: “I’m in TOGA, huh?” TOGA stands for Take Off, Go Around. Bonin was apparently so disorientated that he believed he was operating at low altitude, in a similar situation to a pilot having to abort a landing approach before circling for a second attempt. Standard procedure on abandoning a landing is to set engines to full power and tilt the aircraft upwards at 15 degrees. But Flight AF447 was not a few hundred feet above a runway. Within a minute it had soared to 38,000 feet in air so thin that it could climb no more. As forward thrust was lost, downward momentum was gathering. Instead of the wings slicing neatly through the air, their increasing angle of attack meant they were in effect damming it. In the next 40 seconds AF447 fell 3,000 feet, losing more and more speed as the angle of attack increased to 40 degrees. The wings were now like bulldozer blades against the sky. Bonin failed to grasp this fact, and though angle of attack readings are sent to onboard computers, there are no displays in modern jets to convey this critical information to the crews. One of the provisional recommendations of the BEA inquiry has been to challenge this absence.
Bonin’s insistent efforts to climb soon deprived even the computers of the vital angle-of-attack information. An A330’s angle of attack is measured by a fin projecting from the fuselage. When forward speed fell to 60 knots there was insufficient airflow to make the mechanism work. The computers, which are programmed not to feed pilots misleading information, could no longer make sense of the data they were receiving and blanked out some of the instruments. Also, the stall warnings ceased. It was up to the pilots to do some old-fashioned flying.
With no knowledge of airspeed or angle of attack, the safest thing at high altitude is to descend gently to avoid a stall. This is what David urged Bonin to do, but something bewildering happened when Bonin put the nose down. As the aircraft picked up speed, the input data became valid again and the computers could now make sense of things. Once again they began to shout: “Stall, stall, stall.” Tragically, as Bonin did the right thing to pick up speed, the aircraft seemed to tell him he was making matters worse. If he had continued to descend the warnings would eventually have ceased. But, panicked by the renewed stall alerts, he chose to resume his fatal climb.
Yet if Bonin was now beyond his knowledge and experience, the key to understanding the crash is Robert’s failure to grasp the mistake being made by his colleague. It is here that Airbus’s cockpit design may be at fault.
Like all other aircraft in the modern Airbus range the A330 is controlled by side sticks beside pilots’ seats, which resemble those on computer game consoles. These side sticks are not connected to the aircraft control surfaces by levers and pulleys, as in older aircraft. Instead commands are fed to computers, which in turn send signals to the engines and hydraulics. This so-called fly-by-wire technology has huge advantages. Doing away with mechanical connections saves weight, and therefore fuel. There are fewer moving components to go wrong, the slender electronic wiring and computers all have multiple back‑ups, and the onboard processors take much of the workload off pilots. Better still, they are programmed to compensate for human error.
The side sticks are also wonderfully clever. Once a command is given, say a 10-degree left turn, the pilot can let the stick go and concentrate on other issues while the 10-degree turn is perfectly maintained. According to Stephen King of the British Airline Pilots’ Association, it’s an admired and popular design. “Most Airbus pilots I know love it because of the reliable automation that allows you to manage situations and not be so fatigued by the mechanics of flying.”
But the fact that the second pilot’s stick stays in neutral whatever the input to the other is not a good thing. As King concedes: “It’s not immediately apparent to one pilot what the other may be doing with the control stick, unless he makes a big effort to look across to the other side of the flight deck, which is not easy. In any case, the side stick is held back for only a few seconds, so you have to see the action being taken.”
Thus it was that even when Bonin had the A330’s nose pointed upward during the fatal stall, his colleagues failed to comprehend what was going on. It seems clear from the transcripts that Robert assumed the plane was flying level or even descending. Robert himself was panicking: “We still have the engines! What the hell is happening? I don’t understand what’s happening.” Ninety seconds after the emergency began the captain was back in the cockpit demanding: “What the hell are you doing?” To which both pilots responded: “We’ve lost control of the plane!”
Dubois took the seat behind his colleagues and for a while was as perplexed as they were. It was pitch black outside, warning lights were flashing and some of the screens were blank. The men in front partially blocked his view and evidently he did not take much notice of a horizon indicator, which must have shown the plane was still being held nose up. The Airbus was soon falling through the night at 11,000 feet per minute, twice as fast as its forward travel. Only 45 seconds before impact Bonin blurted out that he had been trying to climb throughout the emergency, giving his colleagues the first indication of what had been going wrong. There is one final, dramatic exchange:
02:13:40 (Robert) “Climb… climb… climb… climb…”
02:13:40 (Bonin) “But I’ve had the stick back the whole time!”
02:13:42 (Dubois) “No, no, no… Don’t climb… no, no.”
02:13:43 (Robert) “Descend… Give me the controls… Give me the controls!”
Robert takes control and finally lowers the nose, but at that moment a new hazard warning sounds, telling them the surface of the sea is fast approaching. Robert realises the ghastly truth – that he hasn’t enough height to dive to pick up speed. The flight is doomed.
02:14:23 (Robert) “Damn it, we’re going to crash… This can’t be happening!”
02:14:25 (Bonin) “But what’s going on?”
The captain, now acutely aware of the aircraft’s pitch, has the final word:
02:14:27 (Dubois) “Ten degrees of pitch…”
There the recording ends.
Mercifully, data recordings and impact damage on debris confirm the Airbus was still more or less level when it hit the sea. Some of the passengers might have dozed throughout the descent; others may have attributed it to violent buffeting. Those in window seats would have seen only darkness. There is reason to hope that there was not too much panic on board, but this is small consolation.
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ბოინგ 777 გაუჩინარდა
