Doubts over lightning's role in missing jetliner

PARIS (Reuters) - Two Lufthansa jets passed through turbulence before and after a missing Air France plane without incident on Monday, a source with access to data said, leaving experts scrambling to assess the weather's role in the disaster.

A frantic air-sea search was under way to locate the missing Airbus and its 228 passengers and crew more than 12 hours after it was presumed to have crashed into the Atlantic on a flight from Rio de Janeiro to Paris early on Monday.

Air France said the Airbus A330 plane had hit stormy weather and "strong turbulence" and a spokesman said it could have been hit by lightning.

If so, it would be the worst air disaster caused by lightning, according to the Aviation Safety Network, but most experts said such a strike was unlikely to down a modern jet.

In the worst previous recorded incident blamed on lightning, 113 people were killed in 1962 on a Boeing 707, also operated by Air France, the Dutch-based database organization said.

Brazil said Monday's aircraft last made radar contact at 0133 GMT after passing the Fernando de Noronha islands off its northern coast, about 250 miles south of the equator.

It was heading toward a notorious stormy patch that shifts around the equator known as the Intertropical Convergence Zone.

It had been preceded safely on the same track 30 minutes earlier by a Boeing 747-400 heading to Frankfurt for Lufthansa, according to a source with access to data transmitted from jetliners for the World Meteorological Organization.

Two hours later an MD-11 cargo plane also flown by Lufthansa passed just south of the same spot on the way to West Africa, the source told Reuters, asking not to be identified.

Neither aircraft reported any anomaly.

"You can't tie it down to lightning with the information we have; for me it's a red herring," said the source, who specializes in aviation weather. Lufthansa declined comment.

CIRCUIT FAILURE

An Air France captain operating on long-range routes, who agreed to speak to Reuters on condition of anonymity, said lightning alone was unlikely to have caused the presumed crash.

"I would not think it was possible that lightning could lead to a short-circuit and disrupt all of the plane's electrical systems. Test planes have resisted some 30 lightning strikes and nothing ever happened," the pilot said.

More likely, he said, is that the jet might have suffered an electrical system failure which would have turned off its radars and communications systems, turning it blind and making it more vulnerable to storms and strong lateral air currents.

Air France said the A330 plane sent an automatic message at 0214 GMT indicating an electrical circuit failure. There were no other official details on the possible cause of the crash.

Lightning strikes are fairly common but planes built out of metal like the A330 are designed to be able to shake them off.

The massive current passes along the metal fuselage and is allowed to arc toward earth without causing harm.

The idea is based on a principle known as a Faraday Cage, which protects passengers inside a mesh of conducting material.

(Additional reporting by Ben Berkowitz, Karen Jacobs, Nicola Lekse, John Bowker)