Pilots blamed for Air France crash which killed 228 people
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The long-awaited report on one of the most mysterious air crashes in recent history has finally been released.
On the night of 1 June 2009, Air France flight 447 from Rio de Janeiro to Paris crashed into the Atlantic, killing all 228 people on board.
The report - a result of a three-year investigation - blames both human error and technical malfunction for the crash.
In makes 25 new safety recommendations, including better training for pilots and stricter plane certification rules.
Although the aircraft was experiencing turbulence from flying in a storm, there was no clear reason at the time for the Airbus A330 to fall out of the sky.
It took air investigators two years to find most of the plane - including the black box, containing the flight recorders.
Speaking on Radio 4's Today programme, M R Hall, a writer who has carried out extensive research into air disasters including the Air France crash said:
"As it approached the thunderstorm, the air temperature dropped, and the aircraft's Pitot tubes underneath the nose cone froze up.
These tubes are the aircraft's essential speed sensors - they measure the travelling speed from the air taken in.
"Once they froze up, the aircraft's computers thought that the aircraft was suddenly standing still at 36,000 ft and issued a stall warning," said Hall.
"A synthesised voice comes out of the cockpit saying 'stall, stall', and the autopilot disengaged at that point, handing control of the aircraft back to the two pilots.
"So up until that point, there was a simple equipment failure - a frozen tube," said Hall.
But then what followed was a sequence of human errors, it seems.
Hall explained that when an aircraft stalls at high altitude, there's a protocol whereby the pilots are meant to keep the nose of the plane five degrees up above the horizon and maintain 85 degrees of thrust.
"But they didn't do either of those things. There was a relatively inexperienced co-pilot at the controls, and he appears to have pulled back hard on the stick, and what he in fact did was fly the aircraft up beyond 38,000 ft, where the air gets very thin and the aircraft lost lift. The aircraft then suddenly started heading down towards the sea, belly first."
Leaked transcripts of the cockpit conversation reveal that the pilots were confused about whether they are ascending or descending.
The captain, on returning from a rest break, found his two co-pilots in a state of complete confusion in the cockpit. The recordings suggest that one of the pilots thought he was only a few hundred feet from the ground.
"Out of this comes an interesting technical aspect of this investigation," said Hall. "On the Airbus, the pilots only have little electronic gearsticks by their side, so they can't necessarily see what each other is doing.
"On a Boeing aircraft, there's a large central yoke so the both pilots are fully aware of what the other is doing."
Listen to the full interview with MR Hall on BBC iPlayer.
Since the crash, Air France has replaced its Pitot tubes with a newer model. The airline has insisted that the pilots were not to blame, saying the stall alarm had malfunctioned.
Announcing the report findings, chief investigator Alain Bouillard said that only a well-experienced crew with a clear understanding of the situation could have stabilised the plane in the conditions. "In this case, the crew was in a state of near-total loss of control," he said.
Family members of the passengers who died in the crash have shown sympathy towards the pilots, saying they were dealing with bad equipment in an exceptionally challenging situation, with dozens of warning signals going off.
A report from the Press Association says that one family member, Robert Soulas, who lost his daughter and son-in-law in the crash, noted that manufacturers had known for years about problems with the plane's speed sensors freezing over but did not order the faulty models to be systematically replaced until after the crash.
Both Air France and Airbus are being investigated in a separate judicial investigation for alleged manslaughter.
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