Sunday, May 29, 2011

Findings of Air France Flight 447 Flight Recorder From The Airbus A330-203

The Air France flight from Rio de Jeneiro to Paris crashed into the Atlantic Ocean on June 1, 2009.  The flight recorder was recently found, and the results released by the Beueau d'Enquetes et d'Analyses, the French agency responsible for investigation of civil aviation accidents or incidents.  The report lays out in detail the last moments of Air France flight 447.

The flight traveled normally as it approached severe weather over the Atlantic.  The Airbus 330-203 is one of the most advanced fly by wire aircraft commercially available.  In fact, a pilot certified in the Airbus 330 is certified in the Airbus 320.  Fly by wire means that every interaction between the pilot and the aircraft is electronically, and digitally in the case of the 330.  Critics of the automated functionality of the Airbus 330 argue that the pilots become disengaged from the aircraft, and are poorly trained to handle in flight emergencies.  They reason that today's pilots don't have the actual flying experience necessary to fly the plane should the systems fail.  They might be right.

Flight AF 447 traveled normally for some time as it approached a system of heavy weather.  The captain was on break, away from the cockpit when the pilot disengaged the autopilot.  The pilots noted discrepancies in the air speed indicator, with readings from 265 knots to 60 knots.  The pilots then disengaged the autopilot and the following actions were recorded by the planes flight data recorder:
  • the airplane climbed to 38,000 ft from a cruising altitude of 35,000,
  • the stall warning was triggered and the airplane stalled,
  • the inputs made by the PF were mainly nose-up,
  • the decent lasted for 3 mins 30, during which the airplane remained stalled.  The angle of attack increased and remained above 35 degrees,
  • the horizontal stabilizer went from 3 degrees to 13 degrees and remained in that position through the end of the flight,
  • the engines were operating and always responded to crew commands.
The horizontal stabilizer is the 'wing' on the tail of the plane.  Based on these findings, authorities suspect the pilots tried ascending, perhaps because they believed their airspeed to be faster.  Likely, by climbing to 38,000 and increasing the angle of attack to 16 degrees, the aircraft stalled.

When an aircraft stalls it means it is no longer flying but falling.  An aircraft stalls because it does not maintain a certain threshold airspeed.  After the likely stall, the plane dropped at a vertical speed of -10,912 ft/min (terminal velocity for a skydiver falling to earth is roughly 10,000 feet/min.). The 38,000 foot decent lasted 3 minutes 30 seconds.  These findings and other details of the crash are contained the BEA report recently published.

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