Crew response to A340 incident interests AF447 inquiry

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French investigators are examining whether the crew reaction to an upset involving a transatlantic Air France Airbus A340 has parallels with the loss of flight AF447.

Air France said the aircraft "encountered unexpected and severe turbulence" about 1h 30min into the Caracas-Paris Charles de Gaulle service, as the A340 passed north of the West Indies.

The aircraft had been cruising at 35,000ft - the same altitude as AF447 - when it encountered a sharp increase in wind speed, taking the jet beyond its maximum operating Mach of M0.86 to reach M0.88.

A source close to the inquiry said there was a "temporary" overspeed warning and the autopilot was disconnected, "very likely" by one of the pilots. Nose-up inputs then followed.

The aircraft's pitch attitude increased to 11° and it climbed at about 5,000-6,000ft/min (25-30m/s) - a response bearing similarities to the sudden pitch-up and rapid climb of AF447 before the A330's fatal stall.

As with AF447, the aircraft reached 38,000ft (11,590m), while its speed reduced to M0.66, compared with a "green dot" speed - for best lift-to-drag ratio - of M0.78.

The source pointed out there was no malfunction of the pitot system but investigators are interested in the crew's response.

Air France said: "They are two different types of event. No technical fault with the speed probes was faced."

The carrier said the incident involved a "rare but not unique" event involving windshear and a "significant change of altitude" but added that the crew corrected the flight path and continued safely to Paris.

BEA said it had been notified by the carrier about the incident but cautioned against drawing any immediate links to AF447, not least because although the A340 and A330 are "very similar", they are "not the same".