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Author Topic: How many amps flow throught an aircraft?  (Read 5266 times)

Geezer

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How many amps flow throught an aircraft?
« on: 09/02/2010 20:26:49 »
Aircraft (that's aeromobiles to you Neil) get struck by lightning quite frequently. When this happens, how many amps are flowing through the aircraft, and why does the current not completely banjax the aircraft?

(Apologies in advance if this is a repeat question. If it is I suppose I'll have to reprimand myself and splice it on to the existing thread.)

yor_on

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How many amps flow throught an aircraft?
« Reply #1 on: 09/02/2010 20:55:18 »
Excuse me Mr Gezeer..
Flowing?

The areomobile might be flowing, even though I would be preferring it flying myself.
But, flowing 'amps', are we talking about the ocean here?
Introducing waves in our structure are we?
Really..

Ah, you didn't by any chance meant 'imps'?
Flowing Imps hmm, have a nice sound to it.
Are they dangerous Sir?

Quite enjoy areomobile btw.
Innovative concept Mr Gezeer..

Soul Surfer

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How many amps flow throught an aircraft?
« Reply #2 on: 09/02/2010 20:58:26 »
Look up faraday cage.  If something is confined within a conducting shell the electric current flows through the surface of the shell and not inside it is the way electricity works.  Equipment still has to be protected from some of the electromagnetic effects but these are much weaker.

Geezer

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How many amps flow throught an aircraft?
« Reply #3 on: 09/02/2010 21:03:44 »
Look up faraday cage.  If something is confined within a conducting shell the electric current flows through the surface of the shell and not inside it is the way electricity works.  Equipment still has to be protected from some of the electromagnetic effects but these are much weaker.

Yes, yes! But how many amps do you think? And why didn't the amps melt the aeromobile?

Geezer

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How many amps flow throught an aircraft?
« Reply #4 on: 09/02/2010 21:06:28 »
Excuse me Mr Gezeer..
Flowing?

The areomobile might be flowing, even though I would be preferring it flying myself.
But, flowing 'amps', are we talking about the ocean here?
Introducing waves in our structure are we?
Really..

Ah, you didn't by any chance meant 'imps'?
Flowing Imps hmm, have a nice sound to it.
Are they dangerous Sir?

Quite enjoy areomobile btw.
Innovative concept Mr Gezeer..

Much as I hate to quote Wiki, on this occasion it may be necessary. Just because Ampere was not Norwegian, it's no reason to ignore his contribution.

http://en.wikipedia.org/wiki/Andr%C3%A9-Marie_Amp%C3%A8re

yor_on

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How many amps flow throught an aircraft?
« Reply #5 on: 09/02/2010 21:25:43 »
French huh? Tested on frogs too?
Not that I mind but are you suggesting some sort of galvanism?

A Faraday cage allows a EM field to redistribute itself on the 'surface' of the hollow cage/cylinder. Meaning that the charge carriers inside the hull will rearrange the lightening using the currents created from the same, if I got it right?

"Once the charges have rearranged so as to cancel the applied field inside, the current stops. Faraday cages also shield the interior from external electromagnetic radiation if the conductor (hull in this case) is thick enough and any holes are significantly smaller than the radiation's wavelength."

Don't know if this explain anything though?
Gotta admit I liked the 'flowing Imps better' :)
And then I could have presented my own theory too..

Can I?
Pleassse.

I think it's good..

==
Btw: That explains why you will have a 'burn through'

If the 'break/hole' in the 'conductors/hulls' surface is larger than the radiations wavelength then you will have your hole in the hull.

======

" Edward J. Rupke, senior engineer at Lightning Technologies, Inc., (LTI) in Pittsfield, Mass., provides the following explanation: It is estimated that on average, each airplane in the U.S. commercial fleet is struck lightly by lightning more than once each 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 of their small size and because they often can avoid weather that is conducive to lightning strikes.

The last confirmed commercial plane crash in the U.S. directly attributed to lightning occurred in 1967, when lightning caused a catastrophic fuel tank explosion. Since then, much has been learned about how lightning can affect airplanes. As a result, protection techniques have improved. Today, airplanes receive a rigorous set of lightning certification tests to verify the safety of their designs. Although passengers and crew may see a flash and hear a loud noise if lightning strikes their plane, nothing serious should happen because of the careful lightning protection engineered into the aircraft and its sensitive components. Initially, the lightning will attach to an extremity such as the nose or wing tip. The airplane then flies through the lightning flash, which reattaches itself to the fuselage at other locations while the airplane is in the electric "circuit" between the cloud regions of opposite polarity. The current will travel through the conductive exterior skin and structures of the aircraft and exit off some other extremity, such as the tail.

Pilots occasionally report temporary flickering of lights or short-lived interference with instruments. Most aircraft skins consist primarily of aluminum, which conducts electricity very well. By making sure that no gaps exist in this conductive path, the engineer can assure that most of the lightning current will remain on the exterior of the aircraft. Some modern aircraft are made of advanced composite materials, which by themselves are significantly less conductive than aluminum. In this case, the composites contain an embedded layer of conductive fibers or screens designed to carry lightning currents. Modern passenger jets have miles of wires and dozens of computers and other instruments that control everything from the engines to the passengers' headsets. These computers, like all computers, are sometimes susceptible to upset from power surges. So, in addition to safeguarding the aircraft's exterior, the lightning protection engineer must make sure that no damaging surges or transients can reach the sensitive equipment inside the aircraft. Lightning traveling on the exterior skin of an aircraft has the potential to induce transients into wires or equipment beneath the skin. These transients are called lightning indirect effects. Careful shielding, grounding and the application of surge suppression devices avert problems caused by indirect effects in cables and equipment when necessary. Every circuit and piece of equipment that is critical or essential to the safe flight and landing of an aircraft must be verified by the manufacturers to be protected against lightning in accordance with regulations set by the Federal Aviation Administration (FAA) or a similar authority in the country of the aircraft's origin.

The other main area of concern is the fuel system, where even a tiny spark could be disastrous. Engineers thus take extreme precautions to ensure that lightning currents cannot cause sparks in any portion of an aircraft's fuel system. The aircraft skin around the fuel tanks must be thick enough to withstand a burn through. All of the structural joints and fasteners must be tightly designed to prevent sparks, because lightning current passes from one section to another. Access doors, fuel filler caps and any vents must be designed and tested to withstand lightning. All the pipes and fuel lines that carry fuel to the engines, and the engines themselves, must be protected against lightning. In addition, new fuels that produce less explosive vapors are now widely used. The aircraft's radome—the nose cone that contains radar and other flight instruments—is another area to which lightning protection engineers pay special attention. In order to function, radar cannot be contained within a conductive enclosure. Instead, lightning diverter strips applied along the outer surface of the radome protect this area. These strips can consist of solid metal bars or a series of closely spaced buttons of conductive material affixed to a plastic strip that is bonded adhesively to the radome. In many ways, diverter strips function like a lightning rod on a building.

Private general aviation planes should avoid flying through or near thunderstorms. The severe turbulence found in storm cells alone should make the pilot of a small plane very wary. The FAA has a separate set of regulations governing the lightning protection of private aircraft that do not transport passengers. A basic level of protection is provided for the airframe, fuel system and engines. Traditionally, most small, commercially made aircraft have aluminum skins and do not contain computerized engine and flight controls, and they are thus inherently less susceptible to lightning; however, numerous reports of noncatastrophic damage to wing tips, propellers and navigation lights have been recorded. The growing class of kit-built composite aircraft also raises some concerns. Because the FAA considers owner-assembled, kit-built aircraft "experimental," they are not subject to lightning protection regulations. Many kit-built planes are made of fiberglass or graphite-reinforced composites. At LTI we routinely test protected fiberglass and composite panels with simulated lightning currents. The results of these tests show that lightning can damage inadequately protected composites. Pilots of unprotected fiberglass or composite aircraft should not fly anywhere near a lightning storm or in other types of clouds, because non-thunderstorm clouds may contain sufficient electric charge to produce lightning."
« Last Edit: 09/02/2010 22:07:53 by yor_on »

LeeE

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How many amps flow throught an aircraft?
« Reply #6 on: 09/02/2010 23:36:20 »
In the glider lightning strike I referred to in this post:

http://www.thenakedscientists.com/forum/index.php?topic=27283.msg289160#msg289160

the nearest recorded discharge was in excess of 80kA.  However, whilst attempting to reproduce the damage caused to the Right wing aileron centre control tube (which appeared to have been crushed along its length due to the intense induced magnetic field) currents of up to 312kA failed to create the same effects.

Geezer

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How many amps flow throught an aircraft?
« Reply #7 on: 10/02/2010 04:53:01 »
Pretty amazing Lee - Thanks. It sounds as if the rate of change of current was quite large! I'm a bit mystified as to why the tube would compress. If anything, I would have guessed the force produced by the current(s) would have had the opposite effect and tended to expand the tube. However, at those potentials, and with that amount of charge, I'm sure things get a bit unpredictable.

I hope the aircraft manufacturers are paying a lot of attention to this as they make more use of composites.

LeeE

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How many amps flow throught an aircraft?
« Reply #8 on: 10/02/2010 17:45:30 »
I hope the aircraft manufacturers are paying a lot of attention to this as they make more use of composites.

Indeed.  Re the damage to the Right wing aileron centre control tube, I have to wonder, in view of the failure to reproduce the damage, whether it might not have been caused by the same overpressure that blew the wing panels off instead of magnetic collapse.  They're the experts though.

Geezer

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How many amps flow throught an aircraft?
« Reply #9 on: 10/02/2010 19:43:51 »
Here's a cheery comment.

"As a result of their greater power, as well as lack of warning, positive lightning strikes are considerably more dangerous. At the present time, aircraft are not designed to withstand such strikes, since their existence was unknown at the time standards were set, and the dangers unappreciated until the destruction of a glider in 1999.[41]"

Above from: http://en.wikipedia.org/wiki/Lightning

(It's the same glider that you referenced.)

syhprum

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How many amps flow throught an aircraft?
« Reply #10 on: 10/02/2010 20:52:59 »
Geezer

The compression of a conductor carrying a large current is a well known effect that was utilised in the 1950,s in the ZETA experiments that attempted to produce nuclear fusion.
This research caused quite a stir at the time as some Neutrons were detected but soon proved to be failure.
« Last Edit: 10/02/2010 20:55:45 by syhprum »

Geezer

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How many amps flow throught an aircraft?
« Reply #11 on: 10/02/2010 21:24:01 »
Geezer

The compression of a conductor carrying a large current is a well known effect that was utilised in the 1950,s in the ZETA experiments that attempted to produce nuclear fusion.
This research caused quite a stir at the time as some Neutrons were detected but soon proved to be failure.

Thanks Syhprum. I never knew that. It must be a function of the way the forces resolve.

I vaguely remember ZETA. As I recall, it was supposed to produce unlimited energy from seawater. I will now go and look it up, and likely discover I'm full of seawater.

EDIT: I googled ZETA. Don't see anything and it does not show up on Wiki. Yaaaay! I think you should start another thread and see how many people can answer the question "What was ZETA?" Wiki won't help them
« Last Edit: 10/02/2010 21:46:56 by Geezer »

Geezer

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How many amps flow throught an aircraft?
« Reply #12 on: 20/02/2010 05:08:42 »

syhprum

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How many amps flow throught an aircraft?
« Reply #13 on: 20/02/2010 12:47:09 »
I wonder when in 2100 or 2200 when the first nuclear fusion power plant is tested it will be classed another British invention like TV and Jet engines etc.

Graeme Cooper

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How many amps flow throught an aircraft?
« Reply #14 on: 20/02/2010 22:39:06 »
Hi, I was just doing a Google search and I see you have been talking about the glider accident, Well My Name is Graeme Cooper and I am the passenger that was in the glider that was destroyed by lightning . You may be interested to see my "Scrap book" of the days events. Click on this link:- newbielink:http://sites.google.com/site/thebig40reachfortheskiesagain/ [nonactive]
The attachment on that page is my Scrapbook with photos of the wreckage etc. there are also radio and TV interviews/reconstructions that you watch / listen to on that page.
I went up again in a glider last year with the same pilot, you can read all about it.
Regards
Graeme Cooper

LeeE

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How many amps flow throught an aircraft?
« Reply #15 on: 21/02/2010 12:59:29 »
Heh! - you really only needed to post once about it

Graeme Cooper

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How many amps flow throught an aircraft?
« Reply #16 on: 21/02/2010 16:52:38 »
Yes sorry lee, I have already been asked to remove some of the other posts but this post and two others were in response to the original threads. I will try to remove the post that I started from the general section.
regards Graeme

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How many amps flow throught an aircraft?
« Reply #16 on: 21/02/2010 16:52:38 »