|Image courtesy BEA|
The final report essentially re-states what has already been released till date.
The crash commenced with ice crystals blocking the pitot tubes, sending false information to the flight computers and causing the autopilot to shut down while the plane was at cruising altitude, and a reconfiguration of flight controls to alternate law.
A confluence of factors, including a barrage of alarms coupled with inadequate training of the flight crew, and false sensor readings, completely surprised the crew. As per the report "The crew likely never understood that it was faced with a ‘simple’ loss of all three sources of airspeed information.”
In a series of errors, the pilots relying on erroneous readings never recognised they were in a stall and kept nosing the Airbus A330 aircraft upward, rather than downward as was necessary. Chief investigator Alain Bouillard said "The crew was in a state of near-total loss of control". Ironically the flight captain, who was on a rest break, did not return to the cockpit until it was too late.
The BEA has passed the blame all around and its recommendations call for more training of pilots, an improved layout of cockpit instruments and warning systems to help crew better recognise and manage unusual flight situations, and thorough review of the flight director software..
Investigators recommended that the European Aviation Safety Agency (EASA) require the aircraft manufacturer Airbus S.A.S. to review the flight director’s design and to possibly modify the software so that it either disengages permanently in the event of a stall or displays “appropriate orders” when a stall warning is set off.
Read more details at the BEA's page for AF-447.
Read the final report here.
Read the final report summary here.