Crew on doomed Rio-Paris flight did not follow textbook procedures
French air accident investigators are expected to provide further insights on Friday into the airliner crash that killed 228 people when an Airbus A330 plunged into the Atlantic two years ago.
The BEA crash investigation agency will present its latest findings on the disaster, after two months sifting through data from black box flight recorders recovered from the ocean floor in May.
Its report, to be presented at a 1230 GMT news conference attended by victims’ relatives, comes weeks after the second anniversary of one of an unexplained crash which led to a $50 million search operation to recover the black boxes.
The BEA will not attempt to give an official cause. Dozens of legal suits are pending on both sides of the Atlantic involving the airline, planemaker Airbus and their suppliers.
A final report is not due until later this year.
But sources close to the investigation say the BEA is for the first time ready to go further than just issuing rigidly factual summaries.
“This report will present the exact circumstances of the accident with an initial analysis and some new findings based on the data recovered from the flight recorders,” the BEA said.
An initial summary in May, shortly after the black boxes were hauled from the ocean floor, raised questions over the actions of the pilots, but it stopped short of blaming them.
Initial black box evidence suggested the junior pilot pulled the nose up as the aircraft became unstable, shortly after there were inconsistent speed readings and an audible stall warning.
Aviation experts say this contradicted procedures, which call for the nose to be lowered in response to an alert that the plane is in danger of losing lift and stalling.
“The main difficulty has been to understand why the pilots did what they did, starting from their earliest responses,” a source familiar with aspects of the investigation said.
Jean-Louis Barber, head of the Air France branch of the main French pilots’ union, told France Info radio the root cause of the accident was clearly a mechanical one, whatever the pilot response.
“What the first two reports from the BEA have shown is that, firstly, the event that triggered the accident was defective speed sensors, that it was a mechanical failure,” he said.
That triggered a chain of events that the pilots may have struggled to respond to, especially if the plane’s alarm system was apparently working against them and giving contradictory signals, he said.
The BEA has confirmed that cockpit speed readings went haywire shortly before the accident on June 1, 2009, something that may have been linked to icing up of the speed sensors on the outside of the aircraft.
In the worst previous accident linked to such sensors, in 1996, pilots of a Boeing 757 flown by Dominican airline Alas Nacionales were confused by poor speed data and lost control, according to records kept by the Flight Safety Foundation.
The jet struck the sea, killing all 189 people on board.