FRENCH INVESTIGATORS have been unable to explain why Air France flight 447 crashed into the Atlantic last June, but have cast doubt on the reliability of the plane’s air-speed gauges.
In its latest interim report, France’s air crash investigation bureau confirmed yesterday that faulty speed sensors were one factor in a sequence of events that led to the crash, but that the failure to retrieve the aircraft’s “black boxes” meant a full explanation had not yet been found.
Air France flight 447 crashed into the Atlantic while en route to Paris from Rio de Janeiro on June 1st.
Some 228 passengers and crew – including three Irish women – lost their lives in the crash, making it the worst disaster in the airline’s 75-year history.
The report said study of the debris found at the site suggested that passengers had little warning of the crash, as life jackets were still in their wrappers and the aircraft had not lost cabin pressure. The inquiry believes the aircraft hit the sea belly-down and in one piece.
“At this stage, despite the extensive analyses carried out by the [bureau] on the basis of the available information, it is still not possible to understand the causes and the circumstances of the accident,” the latest report said.
However, it suggested that current industry tests of the speed sensors did not appear to replicate the conditions of actual flights, because not enough was known about the composition of cloud masses at high altitude.
Only small parts of the Airbus A330 were found. However, a string of automated messages just before the crash showed there were inconsistencies in data from the speed probes.
Investigators said it was difficult to know what impact the weather conditions could have had on these sensors.
The report identified turbulence, and said the accident area experienced rain and icy conditions, but also stated that there was no lightning in the area where the aircraft came down.
“The certification criteria [for probes] are not representative of the conditions that are really encountered at high altitude, for example with regard to temperatures,” it said.
“In addition, it appears that some elements, such as the size of the ice crystals within cloud masses, are little-known.”
The inquiry recommended that black boxes should be adapted to emit signals for longer, to make it easier to find flight recorders after crashes at sea. Moreover, passenger aircraft flying over the sea should be equipped with an additional beacon transmitting at a different frequency, in order to increase the chances of finding wreckage.
A new search for the black boxes from flight 447 is due to take place in February. The operation, which will focus on an area some 1,000km off Brazil’s northeast coast, will take up to three months and involve sonar and robot submarines.