The pilots of an Air France jet that crashed into the Atlantic Ocean two years ago apparently became distracted with faulty airspeed indicators and failed to properly deal with other vital systems, including adjusting engine thrust, according to people familiar with preliminary findings from the plane's recorders.
The final moments inside the cockpit of the twin-engine Airbus A330, these people said, indicates the pilots seemingly were confused by alarms they received from various automated flight-control systems as the plane bucked through some turbulence expected on the route from Rio de Janeiro to Paris but also faced unexpectedly heavy icing at 35,000 feet. Such icing is renowned for making airspeed-indicators and other external sensors unreliable.
Ultimately, the crew failed to follow standard procedures to maintain or increase thrust and keep the aircraft's nose level, while trouble-shooting and waiting for the airspeed sensors and related functions to return to normal, according to these people.
Slated to be disclosed by investigators on Friday, the sequence of events captured on the recorders is expected to highlight that the twin-engine jet slowed dangerously shortly after the autopilot disconnected. The pilots almost immediately faced the beginning of what became a series of automation failures or disconnects related to problems with the plane's airspeed sensors, these people said. The crew apparently had difficulty sorting out the warning messages, chimes and other cues, while monitoring essential displays showing engine power and aircraft trajectory.
The pilots were never trained to handle precisely such an emergency at high altitude, according to safety experts and a previous report by France's Bureau d'Enquetes et d'Analyses, which is heading up the investigation. All 228 people aboard died in the accident.
The senior captain, Marc Dubois, appears to have been out of the cockpit for a routine rest break when the fatal chain of events started, according to safety experts familiar with the details. But according to one person close to the probe, the cockpit-voice recorder suggests that once problems cropped up, he may have rushed back to the cockpit to join the other two pilots of Air France Flight 447.
Though Friday's announcement won't provide final conclusions or specific causes, investigators believe Air France never trained its pilots to cope with such automation problems in conjunction with a high-altitude aerodynamic stall, an emergency when the wings lose lift and the plane quickly becomes uncontrollable.
Spokesmen for Air France, a unit of
Air France-KLM, and Airbus, a unit of
European Aeronautic Defence & Space Co., have declined to comment on any details of the investigation. Airbus last week, however, issued a bulletin reassuring airlines that the preliminary readout of the recorders hasn't prompted any "immediate recommendation" regarding the safety of the global A330 fleet. French investigators, who gave the green light for that statement, also have said their preliminary findings don't highlight any major system failures or malfunctions that could have caused the fatal dive.
According to a report issued by French investigators in November 2009, Airbus identified 32 instances involving similar model jetliners between 2003 and 2009 in which external speed probes, known as pitot tubes, suffered ice buildup at high altitude and caused "erroneous air speed indications."
Most of the incidents involved probes similar to those on the A330 that crashed. Many were on Air France planes, according to the BEA report.
