Missing jet: We May Never Know What Happened.

The Air France jet carrying 228 people missing in the Atlantic had crossed a notorious storm patch near the equator where winds from the northern and southern hemispheres clash, meteorologists said Monday. Wreckage has been located but at this writing it is unconfirmed as from this flight. Brazilian authorities confirm there was a bomb threat made on this flight there is no evidence the plane was blownup.

The ocean is perhaps 12,000 deep where the debris field was found so recovery of the flight recorder which will continue to “bing” for 30 days will be very difficult.

The flight from Rio de Janeiro to Paris “was in what we call the intertropical convergence zone” when it sent out an automatic message reporting an electrical fault, Jean-Marie Carriere of the Meteo-France weather service said. Some commentators are confusing tis zone with the so-called horse latitudes that are notoriously becalmed areas 30-35 degrees north and south which is a high pressure zone.

Legend says the term horse latitudes originates from the days when Spanish sailing vessels transported horses to the West Indies. Ships would often become becalmed in mid-ocean in this latitude, thus severely prolonging the voyage; the resulting water shortages would make it necessary for crews to throw their cargo of horses overboard.

The intertropical convergence zone  is a low-pressure zone, also known as the monsoon trough, lies along the equator but shifts with the seasons, and sees the winds meeting head-on and then going upwards, often resulting in violent thunderstorms.

However, “airplanes were well used to crossing the zone” and their on-board radar systems enable them to avoid the most turbulent spots by either going through gaps in the bad weather or by climbing higher, he said.

Flight AF 447 hit fierce turbulence at about 0200 GMT Monday about four hours after it left Rio, and 14 minutes later sent an automatic error message reporting a fault in an electrical circuit, Air France said.

It was likely that the Airbus A330 was hit by lightning, it added.

Passenger jets are hit by lightning every 1,000 hours — on average twice a year. But technical experts say lightning alone could not have caused it to crash into the ocean.

Air France has said the A300-200 jet was probably hit by lightning as it passed through a violent storm on the flight from Rio de Janeiro to Paris on Monday.

But the airline’s chief executive Pierre-Henry Gourgeon said it suffered multiple technical failures before falling off radar screens.

“A succession of a dozen technical messages” sent by the jet showed that “several electrical systems had broken down” which caused a “totally unprecedented situation in the plane,” said Gourgeon.

“It is probable that it was shortly after these messages that the impact in the Atlantic came,” he added. The Airbus model has had computer and electronic problems in the past.

Nearly every commercial pilot has a tale of coming through a lightning storm. The French national office for aerospace study and research (ONERA) confirmed that on average a plane is hit by lightning every 1,000 hours.

“Lightning could cause a mechanical problem, it could pierce the aircraft, but usually it can continue to fly,” said Vincent Fave, an expert airline accident investigator told AFP.

Yves Deshayes, of the French national airline pilots union (SNPL) said a lightning strike could be damage a plane’s communications and navigation systems.

“But in a plane the systems are doubled, even tripled, so a lightning strike that threatens the security of a flight, and even the state of the aircraft, is extremely rare,” he said.

Deshayes suggested that a lightning strike could explain why there was no radio contact with the Air France plane, but nothing more.

“It is hard to imagine lightning hitting a plane and making it explode. It could cause a number of breakdowns, more or less serious, but to my knowledge there are no incidents of planes which were blown up by a lightning strike,” he said.

David Learmount of Flight International magazine said aircraft are designed to survive lightning strikes. But the disappearance of the Air France jet was a “chilling reminder that nothing is impossible, however unthinkable.”.

An expert on aircraft accidents, Francois Grangier, told AFP in a 2005 interview of his experience.

“In my career as a pilot I often experienced lightning as did all of my colleagues. It’s something which is often impressive, it makes a lot of noise in the aircraft and usually electrical power fails, but it’s just as if it happens at home: the fuses jump, you put them back and everything works.”

Usually, the electrical impact spreads across the surface of the aircraft “along the external skin, in aluminium alloy which is a very good conductor of electricity, and the fuselage and wings act as a Faraday cage.”

Under the Faraday phenomenon any external metallic frame prevents lightning from traversing the structure.

However, aluminium is giving way increasingly to composite materials based on carbon fibre and resin. Manufacturers are making increasing use of these materials because they offer weight, and therefore fuel, savings.

For example, Boeing’s new generation 787 Dreamliner depends on extensive use of such materials.

But composite materials are less effective in deflecting lightning and manufacturers have turned to another way of providing a shield.

They use the ‘metalisation’ of the aircraft: a kind of mesh is added, a superficial layer which acts as a Faraday cage and in this way the aircraft is protected.

In recent years, at least two air crashes are believed to have been caused by lightning.

On June 22, 2000 a bi-turboprop Yun 7 belonging to the Chinese carrier Wuhan Airlines was hit by lightning, according to the Chinese authorities, as it approached Wuhan airport. Forty-two people on the plane and seven on the ground perished when the plane crashed into a boat.

Lightning is also suspected in the crash of a Kenyan Airways Boeing 737-800 on its way from Abidjan in Ivory Coast to Douala, Cameroon on May 5, 2007. It went down in a violent storm and all 114 people on the plane were killed.