Three-and-a-half-minute spiral – then Air France jet crashed into the sea

An error by a junior pilot may have sent an Air France airbus into a three and a half minute spiral into the South Atlantic which killed all 228 aboard in June 2009.

Although accident investigators refuse to apportion blame at this stage, chilling details of the last four minutes of Air France Flight 447, released yesterday, point to a mistaken decision by a pilot to lift the nose of the Airbus A330 when it went into the first of three stalls.

Preliminary findings from two black boxes, found three miles deep in the ocean last month, confirm that the failure of the aircraft's speed detectors, or pitot tubes, helped trigger the accident. An interim report released by the French air accident investigation bureau, also confirmed that the captain of the Rio-Paris flight was away from the cockpit when the airbus stalled for the first time.

His absence, first reported in The Independent earlier this month, was not in itself unusual but his two co-pilots are heard on the cockpit voice recorder making increasingly desperate appeals for him to return to the flight deck. By the time he did so, the plane had gone into an uncontrollable spin from 38,000 feet. It finally plunged into the ocean tail first, killing all 228 passengers and crew.

The details released yesterday suggest that the pitot tubes had frozen in stormy conditions, giving contradictory speed readings on the flight deck. The automatic pilot disconnected and the most junior of the three pilots on board took over the controls. As the aircraft stalled, he twice lifted the nose – a manoeuvre which aviation experts described yesterday as "inexplicable". The correct procedure, they said, was to "lower the nose" to take the aircraft out of its stall.

Other Air France pilots said it was routine practice for captains to take a nap in a staff cabin during a long transatlantic flight. Other aviation experts have suggested, however, that it was unusual for the captain, Marc Dubois, to leave the flight deck when severe storms lay directly ahead.

The report by the accident investigation bureau says that one of the black boxes recorded the voice of the pilot at the controls saying that the speed indications were "inconsistent". The automatic pilot switched off. The most junior of the three pilots aboard, took over the controls. The "stall alarm" rang twice. The pilot tried to climb. The aircraft stalled again, and again the pilot tried to climb.

The two junior pilots appealed several times for the captain to return. He finally did so but his last words were: "On n'a aucune indication qui soit valuable" – "No instruments are reacting correctly."