Lightning bolts a risk for modern jets

June 2, 2009 by Celine Le Prioux
Passenger jets are hit by lightning every 1,000 hours -- on average twice a year -- and experts say the risk from the bolts of electricity is growing.

Passenger jets are hit by lightning every 1,000 hours -- on average twice a year -- and experts say the risk from the bolts of electricity is growing.

But technical experts, astounded like everyone else by the disappearance of an Air France jet in the Atlantic with the feared loss of 228 lives, say 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 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 ," said Gourgeon.

"It is probable that it was shortly after these messages that the impact in the Atlantic came," he added.

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

"Lightning could cause a mechanical problem, it could pierce the , 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.

(c) 2009 AFP

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1 / 5 (1) Jun 02, 2009
no modern plane in 60 years has gone down cause of lightning. if lightning was the culprit, i would be very very surprised. more likely one of the wonderful violent protesting groups may have made a statement, and lightning is the only thing the state can come up with to cover it with that till real facts are found out.

lets just say that there is about 15,000 feet of water between where the plane is and any passing ships.
not rated yet Jun 02, 2009
Airfrance plane was not hit by lightning but it was hit by a bluejet or a sprite
not rated yet Jun 02, 2009
I just have to think that fly-by-wire aircraft, which most Airbus aircraft are, must be more susceptible to lightning damage compromising the primary flight controls than a conventional hydraulic-boosted aircraft. Of course, fly-by-wire is the way of the future, and for a lot of good reasons (it is now showing up in the controls of high-end autos). Hope that they recover the flight data recorders and can find out what happened as anyone who flies has in interest in the findings.
not rated yet Jun 02, 2009
Until the CVR black box is recovered we will not know the true cause. I doubt it was lightning.
The design of the Airbus has the computer over-ride a pilots control actions. Like ABS in a car when you slam on the breaks.
However the downside is that if the computer receives a faulty sensor reading then it can take erroneous corrective action. Recently this happened to a Quantas aircraft of the same type causing a radical nose down and loss of altitude. Any pull up by the pilot being over-ruled by the computer. The computer received an erroneous sensor reading and thought it was doing the right thing - even though it was obviously wrong to the pilot.
Personally I would put more faith in a pilot than a software programmer. Hence I avoid airbus and prefer boeing. I think the computer should be a tool and the captain should be able to over-ride.
In this tragedy the fact that no Mayday happened is an early clue. Loss of cabin pressure indicates a breach in the hull. Electronics failure indicates a loss of power. Area of wreckage can be a clue. Small area means it crashed intact. Large area means it broke up at high altitude.
Modern on-board weather radar identifies major storms which pilots go around. No aircraft can survive flying through a bad thunderstorm without getting ripped apart. These thunder clouds show up as big red on the radar screen.
not rated yet Jun 02, 2009
There has been some spurious news regarding the FDR/CVR. These units contain underwater accoustic beacons. Hence they should actually be easier to find underwater than on land by triangulating the sonar ping emitted by the box(es). The only problem will be getting ships with unmanned subs to the location and extracting the recorder from wreckage.
1 / 5 (1) Jun 03, 2009
No, No, Yes. It wasn't a sprite or a bluejet. I saw the whole thing in a vision. The ghost of Ronald Reagan riding in an open spaceship whacked it out of the air with his particle board beam.
1 / 5 (1) Jun 03, 2009
Al Queda - "the toilet" - surely had a hand in this - Dick Cheney is all over this on FAUX news!
not rated yet Jun 03, 2009
Read today that they are triangulating the black box signal.
[Bloomberg, http://www.bloomb...20601082&sid=a2L_VtqSdA_A&refer=canada]
The boxes emit signals that can be captured over one kilometer for 30 days following any accident. He said the signals were faint, and investigators are using %u201Ctriangulation,%u201D a surveying technique in which a region is divided into a series of triangles, to try and locate them.
He said the black boxes are at a minimum depth of 1,000 meters. They %u201Caren%u2019t essential%u201D to the investigation, he said.

I am perplexed how they can say it might not be recoverable when they have already located it. All that remains is for a remote unmanned sub to go pull it. At around 1-3km depth it is well within operational range. I would say it is extremely likely to be pulled. Worst case the sub would have to attach cables and they raise the entire wreckage using a large barge or naval sub recovery vessel.
Naval sonar are extremely sensitive. So triangulating a recovery beacon will be trivial. The more readings the more accurate the triangulation (it is actually a polygon if you take more than 3 bearings).

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