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Loss of Control: Human Factors in Air France Flight 447

Investigating the crash of Air France Flight 447 [1], from Rio de Janeiro to Paris, into the Atlantic Ocean on 01 June 2009, the French Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA = Bureau d’Enquêtes et d’Analyses pour la Sécurité de l’Aviation Civile) released an interim report on 29 Jul 11. This report pertains to the emerging safety issues found in the wake of the crash, which resulted in tragic loss of all 216 passengers and 12 aircrew [2].

Some of the facts brought out in the third interim report are [2] :-

  • “The Captain’s departure occurred without clear operational instructions.
  • There was no explicit task-sharing between the two copilots.
  • The AP (autopilot) disconnected while the airplane was flying at upper limit of a slightly turbulent cloud layer.
  • There was an inconsistency between the measured speeds, likely as a result of the obstruction of the Pitot probes in an ice crystal environment.
  • At the time of the autopilot disconnection, the Captain was resting.
  • Even though they identified and announced the loss of the speed indications, neither of the two copilots called the procedure “Unreliable IAS”.
  • The copilots had received no high altitude training for the “Unreliable IAS” procedure and manual aircraft handling.
  • No standard callouts regarding the differences in pitch attitude and vertical speed were made.
  • There is no CRM training for a crew made up of two copilots in a situation with a relief Captain.
  • The approach to stall was characterised by the triggering of the warning, then the appearance of buffet.
  • A short time after the triggering of the stall warning, the PF applied TO/GA thrust and made a nose-up input.
  • In less than one minute after the disconnection of the autopilot, the airplane was outside its flight envelope following the manual inputs that were mainly nose-up.
  • Until the airplane was outside its flight envelope, the airplane’s longitudinal movements were consistent with the position of the flight control surfaces.
  • Neither of the pilots made any reference to the stall warning.
  • Neither of the pilots formally identified the stall situation.
  • The Captain came back into the cockpit about 1 min 30 after the autopilot disconnection.
  • By design, when the speed measurements were lower than 60 kts, the 3 angle of attack values became invalid.
  • Each time the stall warning was triggered, the angle of attack exceeded its theoretical trigger value.
  • The stall warning was triggered continuously for 54 seconds.
  • The airplane’s angle of attack was not directly displayed to the pilots.
  • Throughout the flight, the movements of the elevator and the THS were consistent with the pilot’s inputs.
  • The engines were working and always responded to the crew’s inputs.
  • No announcement was made to the passengers.”

Although the investigations are still continuing, an earlier interim BEA report had already suggested that the crash occurred due to aerodynamic stall at high altitude. The pitot tubes were found have provided inconsistent readings minutes prior to the accident [3]. Going further, the third interim report suggested certain training related issues viz., that the co-pilots were not “trained to fly the aircraft at high altitude in manual mode with unreliable airspeed indication” [2]. BEA has recommended mandatory training on flying with the autopilot disabled, as well as recovery from high-altitude stall [2].

C. B. “Sully” Sullenberger, the celebrated US Airways pilot, famous for his successful ditching of an Airbus 330 in Hudson river [4], observed that, “”The Air France 447 crash was a seminal accident. We need to look at it from a systems approach, a human/technology system that has to work together. This involves aircraft design and certification, training and human factors. If you look at the human factors alone, then you’re missing half or two-thirds of the total system failure” [5].

Limiting to the Human Factors, the vital facts emerging from the third interim report are:-

Another issue to consider is CRM, especially operations with two co-pilots or with relief captain, in the absence of the Captain in the cockpit. 

Reference
1. Accident Description: Air France Flight 447
2. BEA: Safety Investigation…flight AF447
3. BEA: Interim Report No. 2
4. C.B. “Sulley” Sullenberger
5. High Altitude Upset Recovery 

Acknowledgement  Photo courtesy Wikimedia Commons

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