Lightning

[Guest]

Sitting browsing the forum and the lightning and thunder are flashing and banging away overhead - made me think ...

If you're playing golf, they say you're in special danger 'cos you're in a wide open space, carrying a bag of steel rods!

What about sitting in a steel box that's floating on water? Often in a wide open space!

With trees along the side of the cut you're not the tallest thing around, but what about when you're in a place with no trees or buildings ... ??

Edited August 31, 2005 by Guest

[Jon]

Boating is actually quite safe because of the 'Faradays Cage', which was the same effect Richard Hammond demonstrated on Top Gear when he parked a VW Golf with him in it, and sent 10000 volts through the roof.

 

A very quick skim read of this article seems to indicate it might be relevent. Apologises if not.

 

Cheers

 

Jon

[dor]

As Jon says the Faraday's cage effect means you are completely safe inside your boat (your TV might not though and could literally explode).

 

This is because the steel structure of the boat will conduct any lightening strike through the steel and then to earth, the boat being well earthed sitting in the water. Aircraft routinely get hit by lightening with no ill effect.

 

Electricity is only a problem if you put yourself between two points at different potential. The voltage drop across the hull will be as good as zero.

 

However, standing on the stern holding a steel-shafted umbrella aloft is not to be recommended, especially if there are no nearby trees. If your hair starts to stand on end or your fingers begin to tingle, get inside quick!

Edited August 31, 2005 by dor

[maffi mushkila]

Aircraft routinely get hit by lightning with no ill effect.

 

Ha ha ha ha ha ha.

[dor]

Ha ha ha ha ha ha

 

Do you have a problem with that Maffi? For someone involved with aircraft maintenance I would have expected you to be better informed.

 

A quick google will give you, or anyone else interested, the details.

 

I would suggest for a start: http://www.lightningtech.com/d~ta/faq1.html

 

A sample quote:

 

How often are aircraft struck by lightning?

 

It is estimated that on average, each airplane in the U.S. commercial fleet is struck slightly more than once per year. In fact, aircraft often trigger lightning when flying through a heavily charged region of a cloud. In these instances, the lightning flash originates at the airplane and extends away in opposite directions. Although record keeping is poor, smaller business and private airplanes are thought to be struck less frequently because they usually do not adhere to rigid schedules.

[maffi mushkila]

Do you have a problem with that Maffi? For someone involved with aircraft maintenance I would have expected you to be better informed.

 

Having seen the pinprick entry hole and the 3ft exit hole in an aircraft yes I think I am better informed.

 

The crash in Toronto involved an Air France Airbus A340 airliner from Paris which slewed off the runway at Pearson International Airport in a storm, ended in a ravine and burst into flames. The 309 passengers and crew had managed to leave the aircraft with minor injuries before fire erupted.

When an aircraft gets hit by lightning, sometimes there's severe damage, says Martin Elliott, director of in-service engineering and technical support at Bombardier. It can be out of service for quite a long time. Consider that in 2004, 41 CRJs flown by Atlantic Southeast Airlines sustained significant lightning damage, putting them out of service anywhere from two to 10 days. Industry experts agree that at least three factors determine an aircraft's propensity to be hit: Altitude, temperature and geography.

Edited August 31, 2005 by maffi mushkila

[dor]

Well as far as the frequency is concerned, I'll leave it up to the experts in this field, as freely reported and available on the internet. If they say that an aircraft is hit on average once a year, i'll go with that. Yes some strikes are catastrophic, but many do no more than mark the paint.

 

Whilst not the world's most frequent flier, I've been in two aircraft that have been hit, one a light aircraft. It is unnerving, but as the statistics show, it generally does no more than superficial harm.

[Paul@CW]

This is because the steel structure of the boat will conduct any lightening strike through the steel and then to earth

29246[/snapback]

 

What happens if you are standing on or touching the steel?

 

Forgive my ignorance but I only know the following about electricity: Turn switch on, light go on... turn switch off, light stop working

[Breals]

Electricity finds it easier to travel through steel than through flesh, so you should be fine unless you are forming a bridge for it to travel across. In the open, electricity would find it easier to travel through flesh than through thin air, so without a protective steel cage, it could take a shortcut through you as it travels skywards!

Edited September 3, 2005 by Breals

[DHutch]

Should be fine.

- The steel is earthed really fairly well by bing sat in the cut.

- And even if wasnt, and the steel got to 2000v (relative to the ground), as your not touching the ground, it doent matter, you wont get shocked.

 

- You could swing on a highvoltage power line without geting a shock, just as long as you didnt then put your other hand on the (earthed) pilon!

 

 

Daniel

[Breals]

Which is why birds roost on power lines without getting fried!

[DHutch]

Which is why birds roost on power lines without getting fried!

indeed

[ChrisPy]

has anyone seen the documentary made for the South West Electricity Board where they use a helicopter to drop technicians onto live HV overhead lines to do maintenance?

[DHutch]

has anyone seen the documentary made for the South West Electricity Board where they use a helicopter to drop technicians onto live HV overhead lines to do maintenance?

No, sounds cool, got any more info in that?

 

Daniel

[Richard Bustens]

If faradays cage relies on the path to earth, how does an aircraft earth out?.

[Stephen Sugg]

No, sounds cool, got any more info in that?

 

I've flown in a helicopter piloted by one of those guys, superb pilot, he also did some of the stunt flying in one of the 007 films.

[Paul Evans]

In essence lightning is a huge spark, caused by the discharge of static electricity built up during the creation of a storm cloud. The little particles of water in the cloud jiggle around, rubbing themselves against the air and becoming charged. There are four types of lightning: the classic cloud-to-ground, intra-cloud (remaining within one cloud), inter-cloud (shooting between two clouds) and cloud-to-sky. An aircraft can be "hit" by any of these types as the lightning travels from its source to "earth" (which can be the ground, an oppositely charged part of the storm cloud, another, oppositely charged, cloud or even an oppositely charged part of the sky) but the aircraft's skin acts as a conductor between the two points. As long as there is nothing to stop the current flowing, the lightning should pass through the skin to earth.

[Maffi]

If Faraday's cage relies on the path to earth, how does an aircraft earth out?.

 

Three points:

 

1. The fuselage is only one part of the conducting path for the lightning.

 

2. If you have ever looked out of the window at the trailing edge of the wing and seen what amounts to small stick or wicks mounted on the trailing edge these 'static wicks' release static in to the air.

 

3. Aircraft tyres are made with a high carbon content that will allow any residual static charges built up in the airframe to discharge to earth on landing.