Saturday, April 28, 2012

Air France Flight 447: 'Damn it, we’re going to crash’

The Telegraph 28 April by Nick Ross

With the report into the tragedy of Air France 447 due next month, Airbus’s 'brilliant’ aircraft design may have contributed to one of the world’s worst aviation disasters and the deaths of all 228 onboard.

In the early hours of June 1 2009, Air France Flight 447 from Rio de Janeiro to Paris went missing, along with 216 passengers and 12 crew. The Airbus A330-200 disappeared mid-ocean, beyond radar coverage and in darkness. It took a shocked and bewildered Air France six hours to concede its loss and for several agonising days there was no trace.
The official report by French accident investigators is due in a month and seems likely to echo provisional verdicts suggesting human error. There is no doubt that at least one of AF447’s pilots made a fatal and sustained mistake, and the airline must bear responsibility for the actions of its crew.

But there is another, worrying implication that the errors committed by the pilot doing the flying were not corrected by his more experienced colleagues because they did not know he was behaving in a manner bound to induce a stall. And the reason for that fatal lack of awareness lies partly in the design of the control stick – the “side stick” – used in all Airbus cockpits.
 
The plane’s pitot (pronounced pea-toe) tubes – small, forward-facing ducts that use airflow to measure airspeed had apparently frozen over, blanking airspeed indicators and causing the autopilot to disengage. From then on the crew failed to maintain sufficient speed, resulting in a stall which, over almost four minutes, sent 228 people plummeting to their deaths.

But why? Normally an A330 can fly itself, overriding unsafe commands. Even if systems fail there is standard procedure to fall back on: if you set engine thrust to 85 per cent and pitch the nose five degrees above the horizontal, the aircraft will more or less fly level. How was it that three pilots trained by a safe and prestigious airline could so disastrously lose control? Either there was something wrong with the plane, or with the crew. Airbus and Air France, both with much to lose, were soon pointing accusing fingers at each other.

In July last year the French air crash investigation organisation, the Bureau d’Enquêtes et d’Analyses (BEA), published its third interim report. For Air France the conclusion was crushing: the crew had ignored repeated stall alerts and kept trying to climb, instead of levelling off or descending to pick up speed. The A330 had become so slow that it simply ceased to fly. Its reputation on the line, Air France came as close as it dared to repudiating the finding. The pilots, said the airline, had “showed unfailing professional attitude, remaining committed to their task to the very end”.

But the airline’s case seemed thin. All indications suggested the aircraft had functioned just as it was designed. The black box recordings showed that the plane was responsive to the point of impact. The case against the pilots looked even worse when a transcript of the voice recorder was leaked. It confirmed that one of the pilots had pulled the stick back and kept it there for almost the entirety of the emergency. With its nose pointed too far upwards, it was little wonder that the Airbus had eventually lost momentum and stalled. But this analysis begs the question: even if one pilot got things badly wrong, why did his two colleagues fail to spot the problem? The transcript of increasingly panicky conversations in the cockpit suggests they did, but too late.

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