Those of a nervous
disposition when it comes to flying will not have enjoyed the news that
France's freshly inaugurated President was forced to return to Paris mid-flight
on Tuesday when his jet was struck by lightning. It was probably not the omen
Francois Hollande was seeking as he travelled to Berlin for his first meeting
with Angela Merkel.
But lightning strikes
are not something passengers need necessarily concern themselves with,
according to Professor Manu Haddad, who works at Cardiff University's recently
opened “Lightning Lab” — or, to use its more formal name, the School of
Engineering's Morgan Botti Laboratory. “On average, every commercial aircraft
is hit by lightning once a year,” says Mr. Haddad, whose lab specialises in
testing how to protect aircraft from lightning. “It is routine for an aircraft
to land as soon as possible after a strike, but this is a precautionary
measure. Lightning is extremely hot — up to 30,000°C. The typical damage is a
scorch mark where the point of contact was, usually a wing-tip. The plane's
electronics are well shielded these days.” Mr. Haddad says strikes normally
occur soon after take-off when the aircraft is still beneath the storm clouds
which are two-five km in altitude. “I don't know of a modern-era example where
a lightning strike alone has brought down a plane,” he says. “It's the same
principle as being protected in a car. A metal box such as a car or plane is
known as a Faraday cage, which protects them from the current. Planes are now
built to absorb 250,000 amps, whereas the average strike generates 32,000 amps.
It only gets really
serious when the radome [nose cone] is struck, the only part of the plane's
shell not made of metal as this is where the radar is located.
But nose cones have
special lightning conductors for just this reason.” And what of the passengers
inside? “They usually won't notice a thing, or they might just see a bright
flash.”
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