Read Online Understanding Air France 447 by Bill Palmer - Free Book Online
Authors: Bill Palmer
Tags: Air France 447 Accident, A330
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from -3° to +7°, and that the maximum angle of attack was 13 degrees. (The normal value for both is around 2.5°.) Stall warnings were momentary and no loss of control had occurred.
After the accident, six additional events, not filed as air safety reports, were found by analyzing recorded flight parameters from the fleet and maintenance reports.
Meanwhile in 2007, prompted by the earlier incidents caused by water ingestion on A320 aircraft, an exercise incorporating the “flight with unreliable airspeed” procedure conducted in an after-takeoff scenario was added to Air France’s 2008-2009 training program. The exercise was considered to be representative of the main difficulties in conducting the procedure in all flight phases. However, when conducted in a low-altitude environment, the procedure calls for pitch attitudes between five and fifteen degrees. When conducted above the minimum safe altitude, the procedure calls for maintaining level flight for troubleshooting. There were no simulator exercises added to reflect the high altitude environment events that were encountered in 2009.
In September and October 2008, Air France asked Airbus for information about the cause of these events and the solutions. They also asked if the Thales BA probe could resolve these problems. Airbus replied that the cause of the problem was probably probe obstruction by a rapid accumulation of ice crystals, and that the Thales BA probe was unlikely to improve the performance in an ice crystal environment.
From October 2008 onward, Air France alerted Thales about the increasing problem of icing at high altitude. Thales started an internal procedure to perform a technical analysis of these incidents.
During the autumn of 2008, Air France considered that flight safety was not immediately affected by this type of incident.
Four Air Safety Reports (ASRs) relating to these incidents were published during this period in several issues of the Sûrvol flight safety bulletin, which was circulated to Air France pilots. On November 6, 2008, information about the airspeed anomalies that had occurred in cruise and that affected the A330/A340 fleet was circulated as an operational memo titled Info OSV within Air France to the pilots working in the sector. The document indicated that six events of this type were reported by crews. First Officer Bonin was about to check out on the A330 when this bulletin came out. He received his type rating in December 2008.
The Info OSV document stated that the incidents are characterized by losses of airspeed indication, numerous ECAM messages, and in some cases, configuration alarms. The events occurred at high altitude in turbulence, in zones in which icing was forecast or observed, for aircraft flying at a Mach of 0.80 to 0.82, with autopilot and autothrust engaged. The chronology of the anomalies was described. It stated that, “during this phase, which lasted for approximately a few minutes, the crews did not report any feeling of over-speed (vibration, acceleration) or the approach to stall (pitch attitude, angle of attack, reference to the horizon) despite the activation of the stall warning.”
It stated in bold red letters “be vigilant in flight conditions of high altitude, icing, and turbulence.”
Four general recommendations were included in the document. (Approximate translations)
Read the complementary technical information carefully.
Do not be taken by surprise.
Identify and confirm the situation.
Recovery in case of manual control of the aircraft. Proceed by making small corrections.
The presence of this information and the dissemination of these bulletins indicates that Air France pilots, especially A330 & A340 pilots, should have been aware of these incidents. The conditions that AF447 encountered were exactly the conditions that the bulletins and Air Safety Reports referred to.
Unfortunately, the “Flight with Unreliable Airspeed” procedure and the conditions for its application
After the accident, six additional events, not filed as air safety reports, were found by analyzing recorded flight parameters from the fleet and maintenance reports.
Meanwhile in 2007, prompted by the earlier incidents caused by water ingestion on A320 aircraft, an exercise incorporating the “flight with unreliable airspeed” procedure conducted in an after-takeoff scenario was added to Air France’s 2008-2009 training program. The exercise was considered to be representative of the main difficulties in conducting the procedure in all flight phases. However, when conducted in a low-altitude environment, the procedure calls for pitch attitudes between five and fifteen degrees. When conducted above the minimum safe altitude, the procedure calls for maintaining level flight for troubleshooting. There were no simulator exercises added to reflect the high altitude environment events that were encountered in 2009.
In September and October 2008, Air France asked Airbus for information about the cause of these events and the solutions. They also asked if the Thales BA probe could resolve these problems. Airbus replied that the cause of the problem was probably probe obstruction by a rapid accumulation of ice crystals, and that the Thales BA probe was unlikely to improve the performance in an ice crystal environment.
From October 2008 onward, Air France alerted Thales about the increasing problem of icing at high altitude. Thales started an internal procedure to perform a technical analysis of these incidents.
During the autumn of 2008, Air France considered that flight safety was not immediately affected by this type of incident.
Four Air Safety Reports (ASRs) relating to these incidents were published during this period in several issues of the Sûrvol flight safety bulletin, which was circulated to Air France pilots. On November 6, 2008, information about the airspeed anomalies that had occurred in cruise and that affected the A330/A340 fleet was circulated as an operational memo titled Info OSV within Air France to the pilots working in the sector. The document indicated that six events of this type were reported by crews. First Officer Bonin was about to check out on the A330 when this bulletin came out. He received his type rating in December 2008.
The Info OSV document stated that the incidents are characterized by losses of airspeed indication, numerous ECAM messages, and in some cases, configuration alarms. The events occurred at high altitude in turbulence, in zones in which icing was forecast or observed, for aircraft flying at a Mach of 0.80 to 0.82, with autopilot and autothrust engaged. The chronology of the anomalies was described. It stated that, “during this phase, which lasted for approximately a few minutes, the crews did not report any feeling of over-speed (vibration, acceleration) or the approach to stall (pitch attitude, angle of attack, reference to the horizon) despite the activation of the stall warning.”
It stated in bold red letters “be vigilant in flight conditions of high altitude, icing, and turbulence.”
Four general recommendations were included in the document. (Approximate translations)
Read the complementary technical information carefully.
Do not be taken by surprise.
Identify and confirm the situation.
Recovery in case of manual control of the aircraft. Proceed by making small corrections.
The presence of this information and the dissemination of these bulletins indicates that Air France pilots, especially A330 & A340 pilots, should have been aware of these incidents. The conditions that AF447 encountered were exactly the conditions that the bulletins and Air Safety Reports referred to.
Unfortunately, the “Flight with Unreliable Airspeed” procedure and the conditions for its application
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