Le Bourget: French investigators unveiled a report on Thursday which said pilot error combined with defective sensors led to an Air France passenger plane crash in the Atlantic Ocean in 2009.
All 228 people aboard the Air France jet were declared dead.
According to the report, a pilot facing faulty data and deafening alarms in an oversea thunderstorm pitched his plane sharply up instead of down as it stalled, then lost control.
The fatal move was part of a chain of events outlined in the report that could have legal consequences for plane-maker Airbus and airline Air France — and could change the way pilots around the world are trained to handle planes manually.
"I don't have control of the plane at all," the pilot said, a minute before it crashed, according to a particularly gripping passage in the 224-page report.
Families of victims struggled to digest the report, the final of several studies into the crash by the French air accident investigation agency, the BEA. Some were disappointed that it didn't focus more on manufacturing problems and lay so much blame on the pilots.
The document is the result of three years of difficult digging into what caused Air France's deadliest-ever accident, and makes sweeping recommendations for better preparing pilots worldwide to fly high-tech planes when confronted with a high-altitude crisis.
The Airbus 330 passenger jet flying from Rio de Janeiro to Paris crashed on June 01, 2009. Over-reliance on automated signals and inadequate training were repeatedly fingered as contributing to the crash, along with mounting stress in the cockpit.
Ice was the initial culprit. Ice crystals blocked speed sensors on the underbelly of the plane known as pitot tubes, the "unleashing element" in the crash, said chief investigator Alain Bouillard.
Aircraft makers had known for years of problems with certain types of pitot tubes, and problematic tubes were ordered replaced in the wake of the Air France Flight 447 crash. Families of victims have long questioned why the aviation industry didn't act on pitot problems well before their loved ones died.
Thursday's report spelled out how the pitot problem led to other problems in the cockpit, where two co-pilots were guiding the plane through a storm while the captain was on a rest break.
The erroneous speed readings prompted the autopilot to disengage. Alarms started sounding in the cockpit.
The pilot at the controls couldn't tell if the plane was stalling or going too fast, the report said. One of the alarms was saying "Stall! Stall!" But the report says another alarm, ringing for 34 seconds straight, "saturated the aural environment within the cockpit" and confused the pilots.
Meanwhile, the plane's flight director system gave faulty, conflicting information.
The flight director shows the pilot what movements of the controls he needs to make to keep the plane on a set course and altitude — but the flight director relies on information from the pitots and other sensors. Investigators said the crew should have turned off the flight director at that point.
Instead, the pilot in control nosed the plane upward, thinking he was going too fast and the plane was in a dive, the report says. In fact, the plane was in an aerodynamic stall.
A basic manoeuvre for stall recovery, which pilots are taught at the outset of their flight training, is to push the yoke forward and apply full throttle to lower the nose of the plane and build up speed.
Bouillard said the decision to pull up so sharply instead of down was an "important element" of the cause of the crash.
In a tense exchange described in the report, the other pilot belatedly recommended pointing the plane downward, but the pilot at the controls didn't respond. The report does not say why.
Bouillard said only a well-experienced crew with a clear understanding of the situation could have stabilised the plane in those conditions.
"In this case, the crew was in a state of near-total loss of control," Bouillard said.
The pilots summoned the captain, but by the time he made it to the cockpit, it was too late.
BEA chief Jean-Paul Troadec was careful to stress both technical and human factors in the crash. He said the pilots should have turned off automatic signal systems and flown entirely manually as soon as they realised the pitots were blocked.
The report could have legal implications: A separate French judicial investigation is still underway, and Air France and Airbus have been handed preliminary manslaughter charges.
Airbus, the manufacturer of the A330 plane, said in a statement that it is working to improve the pitot tubes and making other efforts to avoid future such accidents.
Air France stressed the equipment troubles and insisted the pilots "acted in line with the information provided by the cockpit instruments and systems. .... The reading of the various data did not enable them to apply the appropriate action." It didn't address the training issue.
The final report included a study of the plane's black box flight recorders, uncovered in a costly and extraordinarily complex search in the ocean depths.
(With Agency inputs)
First Published: Friday, July 06, 2012, 09:19