AF447 inquiry recommends ‘startle training’ and stall-warning review

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Adjustments to stall-warning criteria and introduction of surprise effects into pilot training feature among 25 new recommendations contained in the final report into the loss of Air France flight AF447.

The French investigation agency BEA concludes that a loss of airspeed information and disconnection of the autopilot, initiated by pitot icing on the Airbus A330, took the pilots by surprise.

While the loss of airspeed was a relatively simple situation, the BEA says that the pilots' failure to understand and the subsequent "de-structuring" of crew co-operation "fed on each other until the total loss of cognitive control".

This breakdown of understanding combined with heavy-handed inputs to the sidestick to destabilise the A330's flightpath, eventually leading to a fatal stall which - despite the onset of buffet and a persistent stall warning - went unrecognised.

In its report the BEA says: "The combination of the ergonomics of the warning design, the conditions in which airline pilots are trained and exposed to stalls during their professional training, and the process of recurrent training, does not generate the expected behaviour in any acceptable reliable way."

The BEA has recommended that crews be trained to have a solid understanding of the mechanics of flight, and that training be tailored to include specific aircraft characteristics as well as limitations resulting from a reconfiguration of flight-control laws.

It also says that "startle effects" should be introduced to the training regime to ensure pilots can react efficiently to situations with a "highly-charged emotional factor".

"All of the effort invested in anticipation and predetermination of procedural responses does not exclude the possibility of situations with a 'fundamental surprise' for which the current system does not generate the indispensable capacity to react," says the BEA.

Simulators should be capable of reproducing abnormal situations with a greater degree of fidelity, it adds.

While human factors issues feature strongly in the final report, the BEA has also addressed a number of technological matters. Air France has suggested that the intermittent stall warning - caused by a silencing of the alarm under certain low-airspeed conditions - contributed to the crew's confusion over the aircraft's predicament.

The BEA says that the European Aviation Safety Agency (EASA) should determine the conditions in which, on approach to stall, the presence of dedicated visual indications and aural warnings should be mandatory - as well as review the airspeed conditions under which the stall warning functions.

It is also recommending that EASA requires a review of flight-director logic to present "appropriate orders" when a stall warning triggers.

Given that inspections of Air France did not indicate any major deviations from regulatory requirements, the BEA adds, the "fragile nature" of crew resource management and the "weakness" of AF447's pilots in manual handling went undiscovered. It has recommended that the French civil aviation regulator DGAC reviews its oversight "so as to improve its cohesion and effectiveness".