Details have emerged of the moments leading up to the disappearance of flight AF 447 with 228 people on-board, with error messages reportedly suggesting the plane was flying too slowly and that two key computers malfunctioned. Flight data messages provided by an Air France source show the precise chronology of events of flight AF 447 before it plummeted into the sea 400 miles off Brazil on Monday. These indicate that the pilot reported hitting tropical turbulence at 3am (BST), shortly before reaching Senegalese airspace. It said the plane had passed through tall, dense cumulonimbus thunderclouds. At this stage, according to a source close to the investigation cited by Le Monde, the Airbus A330-200's speed was "erroneous" - either too fast or too slow. Each plane has an optimal speed when passing through difficult weather conditions, which for unknown reasons, had not been reached by flight AF 447. Airbus is expected to issue recommendations today to all operators of the A330 model to maintain appropriate thrust levels to steady the plane's flight path in storms. At 3.10am, the messages show the pilot was presented with a series of major failures over a four-minute period before catastrophe struck, according to automatic data signals cited by the Sao Paulo newspaper, le Jornal da Tarde. At this time, the automatic pilot was disconnected – either by the pilot or by the plane's inbuilt security system, which flips to manual after detecting a serious error. It is unclear whether the pilot wanted to manually change course to avoid a dangerous cloud zone – an extremely difficult manoeuvre at such high altitude. At the same moment, another message indicates that the "fly-by-wire" electronic flight system which controls the wing and tail flaps shifted to "alternative law" – an emergency backup system engaged after multiple electricity failures. This system enables the plane to continue functioning on minimum energy but reduces flight stability. An alarm would have sounded to alert the cabin crew to this. Two minutes later, another message indicates that two essential computers providing vital information on altitude, speed and flight direction ceased functioning correctly. Two new messages at 3.13am report electricity breakdowns in the principal and auxiliary flight computers. At 3.14am, a final message reads "cabin in vertical speed", suggesting a sudden loss of cabin pressure, either the cause or the consequence of the plane breaking up in mid-air. Despite the precise details, sources close to the investigation contested the chronology and denied that the two computers providing altitude, speed and directional data malfunctioned. The suggestion that the pilot gradually lost control of the plane appears to counter reports that the plane exploded in mid-air. These were lent more weight today after a Spanish pilot in the vicinity at the time reported seeing an "intense white flash". "Suddenly we saw in the distance a strong and intense flash of white light, followed by a downward, vertical trajectory which broke up into six segments," the chief pilot of an Air Comet plane from Lima to Madrid told the Spanish newspaper, El Mundo. He has reported his observations to investigators. Some experts have supported the theory that the plane exploded, given the wide area where debris has been found. However, Brazil's defence minister, Nelson Jobim, said an explosion was "improbable" given the 13-mile trail of kerosine spotted on the sea. "If we have fuel slicks, it's because it didn't burn," he said. Paul-Louis Arslanian, the head of the French air accident bureau in charge of the investigation, also said there were other possible reasons for wide debris area, such as high winds and choppy seas. Yesterday he warned against hasty "speculation" and said that the search would take time. Four naval vessels and a tanker are in the area around 400 miles off Brazil's northeastern coast. Some 11 spotter planes are searching for more debris, after finding a seat and a 23-foot metal object thought to be part of the fuselage. A French mini-submarine will arrive in the zone next week.Air France pilots battled for 15 minutes to save doomed flight AF 447
Air France pilots battled for up to 15 minutes to save the doomed flight that went missing over the Atlantic this week, electronic messages emitted by the aircraft have revealed.
Friday, 5 June 2009
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