Air France 447 downed as crew ignored alarms

Paul Marks, senior technology correspondent

Sometimes, one simple statement about a complex tragedy can throw all the issues at hand into sharp relief. And in the case of an Airbus A330-200 which crashed into the Atlantic Ocean on 1 June 2009, killing 228 people, this line pretty much sums it up:

"The crew never understood they were in a stall situation and therefore never undertook any recovery manoeuvres."

How a trained crew flying in level cruise flight in an advanced airliner failed to spot they were suffering the most basic of aerodynamic failures is baffling - but the?BEA, the French aviation investigator whose final report that telling line comes from, hopes?the recommendations it issued today?will stop it happening again.?Air France flight 447 left Rio de Janeiro for Paris in the evening of 31 May 2009. While cruising at 35,000 feet an hour-and-a-half later it hit stormy conditions that iced up the pitot tubes used to calculate airspeed. Without an airspeed measurement, fly-by-wire computers cannot cope - and they ceded control (with an audible alarm) to the two pilots. Bizarrely, the pilot flying the plane decided to climb rapidly to the plane's ceiling of 38,000 feet - whereupon it stalled, it's angle of attack into the airflow being too high to sustain lift from the wings.?Despite a stall warning sounding continually, it was ignored and the pilot kept the plane's nose pointing upward - while the plane was in fact plummeting toward the ocean. All the crew needed to do was push the nose down to regain lift - but they didn't. "In the first minute after the autopilot disconnection, the failure of the attempt to understand the situation and the disruption of crew cooperation had a multiplying effect, inducing total loss of cognitive control of the situation," the BEA says. ?

"The combination of the [Airbus] warning system ergonomics, and the conditions under which [Air France] pilots are trained and exposed to stalls during their professional and recurrent training, did not result in reasonably reliable expected behaviour patterns," the BEA adds with massive understatement. ??

In addition, the safety watchdog says, pilots need to be aware of the loss of automatic protection from stall they get when the autopilot hands control back to them. They don't, in fact, get any angle of attack protection when in manual flight mode - so the BEA has called on the European Aviation Safety Agency to ensure pilot training programmes make crystal clear the levels of protection available to pilots in different flight modes.?

The BEA also recommends ensuring pilots have a solid knowledge of the physics of flight at high altitude. And in simulators, better reproduction of "abnormal situations" is being mandated, with the effects of "surprise events" included in training when the atmosphere in a cockpit is "emotionally highly charged", as it was in the confusing moments of AF447's fall.

At the heart of this tragedy is the fact that the stall alarms were ignored. The BEA says the industry assumption is that pilots will at the very least assign a "minimum degree of legitimacy" to such alarms. "A review of pilot training did not provide convincing evidence that the associated skills had been correctly developed and maintained," it says.

Source: http://feeds.newscientist.com/c/749/f/10897/s/210d063d/l/0L0Snewscientist0N0Cblogs0Conepercent0C20A120C0A70Caf4470Efinal0Ereport0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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