비행기가 벼락을 맞으면? Why lightning strikes don’t harm the planes we fly in: VIDEO

Why lightning strikes don’t harm the planes we fly in

An Icelandic airport worker recently captured the dramatic sight of a plane being hit by lightning. How do they survive such spectacular strikes?

파리로 가던 아이슬란드 비행기가 벼락을 맞았다

비행기는 손상되지 않았고 운항을 계속했다.

그 이유는 무엇일까?

'패러데이 새장 효과' 로 낙뢰에도 안전

악천후 공역을 비행할 때 항공기가 낙뢰를 맞는 경우도 가끔씩 있다. 

그러나 벼락 때문에 항공기가 추락하거나 승객이 타격을 입었다는 얘기를 들은 적은 아마 없을 것이다. 항공기에는 낙뢰의 여파가 기내에 영향을 미치지 않도록 한 방전 시스템이 잘 갖춰져 있기 때문이다

과학적으로 검증된 이른바 ‘패러데이의 새장 효과’라는 원리를 적용한 이 시스템으로 항공기 내에 탑승한 사람은 안전한 것이다. ‘패러데이의 새장 효과’란 새장에 전류가 흐르더라도 새장 속의 새가 안전하다든지 천둥이 칠 때 자동차 안으로 피신하면 안전한(다만 자동차 문이 열려 있을 경우는 문제가 달라지지만) 원리와 비슷하다.

항공기에 낙뢰가 칠 경우 항공기의 표면이 벗겨지는 등 그 흔적은 남지만 항공기 내부까지는 충격이 미치지 않으므로 안심하셔도 된다. [참조: 대한항공 운항승무부 고형주 차장]

* '패러데이 새장 효과'

번개에 맞으면 아래 사진과 같이 전자들이 이동한 경로가 몸에 흉터로 남는다.

이 경로를 리히텐베르크 무늬(Lichtenberg's figure)라 부르며 위 사진의 흉터는

고에너지의 전자가 이동하면서 발생한 열에 의해 생체조직이 손상되어 생긴 것이다

손에 도체를 들고 벼락을 맞으면 감전되어 죽는다.

하지만 도체로 폐곡면을 만들어 그 안에 들어가 있으면

패러데이 새장효과에 의해 감전되지 않는다.

도체로 된 구조물 안에 있으면 테슬라 코일로부터 발생되는 고압 전류로부터 안전하다.

전기장은 도체 내부로 침투할 수 없기 때문이다.

즉 전류는 도체 내부에서 흐를 수 없다.

즉 비행기가 자체가 새장인 것이다.

황기철  콘페이퍼 에디터

ki chul, hwang conpaper editor 

By Chris Baraniuk

4 October 2016

Halldor Gudmundsson had just seen a huge lightning strike near his office, northwest of Keflavik International Airport in Iceland. He flipped open the camera app on his phone and started recording, hoping to catch another fork of electricity rip through the sky. But suddenly a plane, taking off from the airport, flew into view – and was immediately struck by a flash of lightning.

It was an extraordinary sight, but the aircraft soared on regardless, through heavy rain. “It was very fun to see, but also a bit scary,” says Gudmundsson, whose footage provided this extraordinary photograph.

The Wow Air flight from Iceland’s capital Reykjavik to Paris on 3 October arrived safely and the airline confirmed to the BBC that the plane was not damaged in any way. As a Wow Air spokeswoman pointed out, it’s not uncommon for aircraft to be struck by lightning. How, then, do they survive a sudden shock amounting to approximately 1 billion joules of energy – equivalent to a quarter-of-a-tonne of TNT.

The “skin” around the cabin and interior compartments of an airplane is designed to conduct electricity but keep it away from the crew, passengers and electronics inside, explains Chris Hammond, a retired pilot and member of the British Airline Pilots Association (Balpa).

“There’s a metal mesh that goes into the skin of the airplane,” he says, “a sort of gauze that goes the whole way through – and that’s how the electricity is conducted.”

In addition, the electronics and connections to the fuel tank, for example, are heavily shielded to protect them from external electrical bursts. All of this is rigorously tested before an aircraft goes into service – a process that involves simulating lightning strikes to the skin and internal components.

Gudmundsson’s photograph, notes Hammond, is an illustration of everything working exactly as it should. The bolt appears to enter the plane at the nose and then exit via the tail and part of the wing. Like a flying Faraday Cage, everything on board is protected.

A lightning strike is still likely to be noticed by people on board, though. Passengers on two flights that were hit over west London in April reported hearing loud bangs, for example.

Years ago, aircraft were not as well insulated from strikes. Hammond remembers piloting an early airliner while waiting to land in San Francisco. After a particularly bad flash, he recalls, “all the screens went blank”. Thankfully, the aircraft was equipped with analogue instruments at the time. While the computers gradually came back online, the plane was able to land safely.

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http://www.bbc.com/future/story/20161004-why-lightning-strikes-dont-harm-the-planes-we-fly-in

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