LE BOURGET, France—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, sending the Air France jet and all 228 people aboard to their deaths in the Atlantic Ocean in 2009.
The fatal move was part of a chain of events outlined in a report by French investigators yesterday 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.
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 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 1, 2009.
Over-reliance on automated signals and inadequate training repeatedly were 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.
Yesterday’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 said 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 said.
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 stabilized 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 realized the pitots were blocked.
“You analyze, you see that there is a loss of speed reading, you wait calmly until the pitots thaw,” he remarked.
“The pitots come back and after 40 seconds, everything is forgotten.”
While it sounds puzzling in hindsight that the pilots didn’t respond to the stall warnings, it’s understandable that they were confused given the conditions in the cockpit, said John Goglia, an aviation safety expert and former U.S. National Transportation Safety Board member.
“It was like a giant pinball machine in there,” Goglia said. “You have lights and whistles going off all over the place.
“Which one do you believe? They have no reference to the sky because it’s night and stormy.
“At the very least, they didn’t know what to rely on,” he added.
He said other pilots in the same situation might have done the same thing as those on Flight 447.
“This accident is not the problem of this crew alone,” Goglia noted.