AF447: When hearing isn’t believing

Two short paragraphs of the Air France AF447 investigation report offer an curious insight into the brain’s response to aural alarm signals – and might go some way to explain not just the crew’s failure to recognise the A330′s stall but why terrain-warning systems sometimes seem to bark at pilots to ‘pull up’ in vain.

Stall warnings on the ill-fated Airbus sounded continuously for 54 seconds. But the inquiry report, sourcing seven different research papers, states that aural warnings demand the use of cognitive resources already engaged during periods of high workload.

“The ability to turn one’s attention to this [aural] information is very wasteful,” the analysis says, adding that the rarity – and even “aggressive nature” – of such warnings might lead to their being ignored.

Studies on visual-auditory conflict, it states, show a “natural tendency” to favour visual over auditory perception when information acquired by both senses appears to be contradictory.

“Piloting, calling heavily on visual activity, could lead pilots to a type of auditory insensitivity to the appearance of aural warnings that are rare and in contradiction with cockpit information,” the analysis adds. Visual-auditory conflict during heavy workload translates into “attention selectivity” which accepts visual information but disregards critical aural warnings.