http://www.telegraph.co.uk/technology/9231855/Air-France-Flight-447-Damn-it-were-going-to-crash.html
Two hours in, Marc Dubois, the veteran captain, was heading for a routine break. His deputy, David Robert, a seasoned flier with 6,500 flying hours under his belt, was perfectly capable of coping with the tropical thunderstorm AF447 was flying towards. Pierre-Cédric Bonin was at the controls and, though the most junior pilot, he had clocked up a respectable 2,900 hours on commercial jets.
A few moments later the outside air temperature plummeted, the pitot tubes iced up and an alarm sounded briefly to warn that the autopilot had disengaged. From this moment, Bonin’s behaviour is strange. The flight recorder indicates that, without saying anything, he pulled back on the stick and, seemingly against all reason, kept the nose up, causing a synthesised voice to warn, “Stall! Stall!” in English as the airspeed began to drop dangerously. Robert took 20 or 30 seconds to figure out what was happening before ordering Bonin to descend. “It says we’re going up. It says we’re going up, so descend.” Seconds later Robert again called out, “Descend!” and for a few moments the plane recovered momentum and the stall warning ceased. But Robert was now anxious enough to call for the captain to return to the cockpit. Meanwhile, Bonin’s instinct was again to pull back on the control stick. He left it there despite the stall warning that blared out some 75 times. Instead of moving the stick forward to pick up speed, he continued to climb at almost the maximum rate. If he had simply set the control to neutral or re-engaged the autopilot, all would have been well.
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.
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.
Two hours in, Marc Dubois, the veteran captain, was heading for a routine break. His deputy, David Robert, a seasoned flier with 6,500 flying hours under his belt, was perfectly capable of coping with the tropical thunderstorm AF447 was flying towards. Pierre-Cédric Bonin was at the controls and, though the most junior pilot, he had clocked up a respectable 2,900 hours on commercial jets.
A few moments later the outside air temperature plummeted, the pitot tubes iced up and an alarm sounded briefly to warn that the autopilot had disengaged. From this moment, Bonin’s behaviour is strange. The flight recorder indicates that, without saying anything, he pulled back on the stick and, seemingly against all reason, kept the nose up, causing a synthesised voice to warn, “Stall! Stall!” in English as the airspeed began to drop dangerously. Robert took 20 or 30 seconds to figure out what was happening before ordering Bonin to descend. “It says we’re going up. It says we’re going up, so descend.” Seconds later Robert again called out, “Descend!” and for a few moments the plane recovered momentum and the stall warning ceased. But Robert was now anxious enough to call for the captain to return to the cockpit. Meanwhile, Bonin’s instinct was again to pull back on the control stick. He left it there despite the stall warning that blared out some 75 times. Instead of moving the stick forward to pick up speed, he continued to climb at almost the maximum rate. If he had simply set the control to neutral or re-engaged the autopilot, all would have been well.
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.
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.
Vastaukset 1
Vanhimmat
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
There the recording ends.