Sensor icing caught out crew in French A320 crash

Pilots of an Airbus A320 of XL Airways, registration D-AXLA, which crashed into the Mediterranean Sea were caught out by unexpected angle-of-attack sensor icing while conducting a poorly-organised low-speed flight test under pressure at low altitude.

French investigators have determined that the aircraft's angle-of-attack sensors were not protected during a water-rinsing carried out at maintenance company EAS Industries three days before the accident.

At least two of the three sensors ingested water which subsequently froze while the aircraft was at cruise altitude during a pre-handover flight on 27 November 2008, as the A320 came off lease from XL Airways to Air New Zealand.

The failure by the crew to realise that the sensors were not functioning correctly resulted in the pilots' inadvertently allowing the aircraft to stall while attempting a low-speed flight test.

After the aircraft departed Perpignan, with the two XL pilots flying and an Air New Zealand pilot riding in the cockpit, it climbed to cruising altitude at which point the water trapped in the angle-of-attack sensors froze.

With the workload mounting in the cockpit, because the aircraft was on approach to Perpignan, the low-speed test commenced. But the blockage of the angle-of-attack sensors resulted in an underestimation of the limit speeds for the A320's angle-of-attack protection.

Although the stall warning sounded, and the captain increased thrust and pitched the aircraft nose-down, the configuration of the aircraft - notably a progressive pitch-up deflection of the horizontal stabiliser as the A320 decelerated - and the failure to understand the jet's behaviour, resulted in the situation deteriorating and the crew's losing control of the stall recovery. All seven occupants were killed when the A320 struck the water, just 62s after the stall alarm.

Here are a selection of photos from the aircraft`s previous airlines