Air France Flight 447--What COuld Have Happened

Air France Flight’s Doom Linked to 100 Mph Gusts, Lightning
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By John Lauerman


June 3 (Bloomberg) -- An Air France Airbus that crashed into the Atlantic Ocean may have flown into plane-shaking updrafts and lightning that helped knock the airliner from the sky, aviation experts said.

Wind measurements show the plane met tropical thunderstorms with updrafts of 100 mph (161 kilometers per hour), according to AccuWeather.com, a commercial forecaster in State College, Pennsylvania. Gusts that strong and lightning may have led to structural or electrical failures of the aircraft, the weather service said yesterday in a statement.

Airplanes are built to withstand roiling currents far stronger than maximum loads that arise in most storms, Hans Weber, president of Tecop International Inc., a San Diego-based consulting firm, said yesterday in an interview. The Air France plane may have hit something worse.

“These were young storms that were really developing as the plane flew into them,” Henry Margusity, a meteorologist for Accuweather.com, said in a telephone interview. “The updrafts were probably pretty tremendous and the plane probably got knocked around a lot. Whether it got hit by lightning remains to be seen.”

The Airbus A330-200 lost contact with controllers after hitting turbulence as it flew to Paris from Rio de Janeiro. The plane reported an electrical breakdown, then sent 10 automated distress signals and vanished. Nelson Jobim, Brazil’s defense minister, said yesterday that wreckage found off the country’s northeastern coast confirmed the aircraft crashed there.

Intertropical Convergence

Thunderstorms often contain punishing updrafts and downdrafts that pilots try to avoid, said John Hansman, an aviation expert at the Massachusetts Institute of Technology in Cambridge, Massachusetts. The Air France flight disappeared in an area called the “intertropical convergence zone,” a region close to the equator where tropical storms move from east to west, he said.

Like a mouse finding its way through a maze, pilots flying from South America to Europe look for holes among these storms, said Tecop’s Weber. Most intercontinental flights encounter at least some turbulence. Flights that can’t find a safe route may detour to Africa to refuel, often in Dakar, Senegal, Weber said.

While lightning strikes to airliners are common, a disabled electrical system would be very dangerous to an Airbus A330-200, which has “fly-by-wire” electronic controls connecting the cockpit to motors that move the plane’s steering surfaces and engine settings, Weber said.

Airbus said “it would be inappropriate for Airbus to enter into any form of speculation into the causes of the accident,” according to an e-mail statement from the French company. Air France said it isn’t ruling out lightning.

Adds to Mystery

The plane’s flight data recorders haven’t been recovered, so it’s almost impossible to determine a cause for the crash at this point, said Ray Valeika, a retired senior vice president of technical operations for Delta Air Lines Inc. The jet’s automated message indicating electrical failure, followed by disappearance, adds to the mystery, he said.

“It’s almost unheard of that you would have this total silence,” Valeika said. “Everything is a clue and nothing’s a clue right now.”

Airplanes depend on the properties of air to fly. Negative pressure above the wing and positive pressure below provide lift, literally pulling the airplane off the ground.

The same forces can lead to tragedy in turbulence, Hansman, director of MIT’s International Center for Air Transportation, said yesterday in an interview. Chaotic currents, slashing wildly through the atmosphere, can bat planes like toys, and challenge pilots’ skills, he said.

Seat Belts, Carts

“The normal hazard is that sometimes you’ll have people or things flying around inside the airplane,” Hansman said. “When the pilot sees he’s going to go through turbulence, he’ll tell the flight attendants to secure all carts and sit down with their seat belts on.”

Severe turbulence can whack planes with the strength of more than 1 g, or the equivalent of the earth’s gravitational pull, Weber said. That kind of force can send a plane up or down as much as 6,000 feet, and shoot an unbelted traveler into the airplane’s ceiling, he said.

In 1997, a passenger aboard United Airlines flight 826 died after the plane, a Boeing Co. 747, hit severe turbulence about 1,000 miles east of Tokyo. A 32-year-old woman died after her head struck the plane’s ceiling. The plane landed safely, with 110 other passengers injured.

Last year, Qantas Airways Ltd. pilots temporarily lost control of an Airbus A330 traveling from Singapore to Perth and abruptly lost altitude. Australian air safety investigators said in a preliminary report that a malfunction in a flight computer caused the nosedive.

Contributing Factors

A similar malfunction, combined with severe turbulence, might have been sufficient to send the Air France flight out of control, Weber said.

“Experience tells us in catastrophic accidents there tends to be more than one contributing factor,” Weber said in a telephone interview. “What if the computer acted up and the pilots, who would’ve been challenged to regain the aircraft in clear-weather conditions, may have been unable to regain control under turbulent conditions?”

There’s no way to know yet whether the Air France crash has similarities to the Qantas case, Stefan Schaffrath, an Airbus spokesman, said yesterday in a phone interview from the company headquarters in Toulouse, France.

To contact the reporter on this story: John Lauerman in Boston at jlauerman@bloomberg.net.

Last Updated: June 3, 2009 00:01 EDT