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Lightning bonding

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TELEDYNMCS(at)aol.com
Guest

Posted: Tue Jun 10, 2008 3:46 am Post subject: Lightning bonding

In a message dated 6/10/2008 3:00:42 AM Eastern Daylight Time,  europa-list(at)matronics.com writes:

  	  Quote: 	
		  Before I head off to Asia, I plan to put aluminium mesh right along    

the aileron and flap close outs joining to the rear lift pin to allow wing    

tip to wing tip lightning travel 	


 

  

 Hi David,

  

 FWIW, my wife and I had lightning strike very near us while flying our  Ximango last summer on a 500K attempt. We were deep in a drought here and it  hadn't rained in 4 months. The lift was fantastic for this area during this  time, i.e, greater than 10 knots to going to 10,000'+ agl every day. I had  been flying long cross country flights every day for about 3  weeks, including several successful 500k attempts. There had not been even  a hint of weather overdevelopment during that time. We were about 300K  into the attempt and were approaching a nearby gliderport that was our last  turnpoint for the final home run leg to complete the 500K. There was a fairly  large storm about 20 miles away, but we were in clear air between puffy,  friendly cumulus clouds at about 9000'. We were gliding along engine off at  about 80 knots between thermals when a lightning bolt struck right out in  front of us out of clear blue sky. I'd always heard that this could happen, but  I'd never witnessed it first hand. We saw where it hit the ground and  where that was in relation to our turn point. According to the GPS and our  observation, the lightning was no more than 1/4th of a mile or  so in front of us. The flash and the resulting boom were almost  simultaneous. Needless to say it got our attention. I immediately aborted  the course in an abrupt 90 degree wingover and proceeded to put as much  distance between us and that storm as possible. The rest of the flight was  uneventful. Whether or not we triggered the strike is unknown.  It didn't hit us and there was no damage to the aircraft. I probably  hyper-extended my sphincter muscle, though.

  

 After we returned to my strip I began to wonder if the Ximango was  bonded. So, I started inspecting. Turns out that Aeromot did bond virtually  every metal surface in the aircraft together. They used fairly heavy  gauge braided jumpers made from tinned copper to tie everything  metal together to prevent arcing. I'm considering doing the same to my  Europa. 

  

 I certainly give thunderboomers a much wider berth these days.

  

 Regards,

  

 John  Lawton

Whitwell, TN (TN89)

N245E -  Flying



Vote for your city's best dining and nightlife. City's Best 2008.

  [quote][b]

fklein(at)orcasonline.com
Guest

Posted: Tue Jun 10, 2008 6:04 am Post subject: Lightning bonding

On Tuesday, Jun 10, 2008, at 04:43 US/Pacific, TELEDYNMCS(at)aol.com wrote:



 	  Quote: 	
		   They used fairly heavy gauge braided jumpers made from tinned 

 copper to tie everything metal together to prevent arcing.


	


Nice, thoughtful post John...thanks...If you locate a source for this 

braided jumper material, spread it around...I've known there was a 

reason I haven't closed my wings yet...Fred



-- 

This message has been scanned for viruses and

dangerous content by MailScanner, and is

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carl(at)flyers.freeserve.
Guest

Posted: Tue Jun 10, 2008 7:35 am Post subject: Lightning bonding

Not sure thats a terribly good idea.

  

 The lightning will take the path of least resistance and probably travel  through the aileron push rods and accross the fuselage (where the control rods  pass within an inch of the fuel tank !!!!)  If the current is high enough,  the alloy pushrods will melt like a piece of fusewire.

  

 If you dont believe me, read this. It is a sobering story - The  Dunstable glider lightning strike.

  

 Not sure if there is an easy solution.

  

  

 [quote]   ---

christoph.both(at)acadiau
Guest

Posted: Tue Jun 10, 2008 7:43 am Post subject: Lightning bonding

Time to take chutes up again like glider pilots do...

Best,

Christoph Both

#223 

Wolfville, Nova Scotia Canada

 



--

wdaniell(at)etb.net.co
Guest

Posted: Tue Jun 10, 2008 8:48 am Post subject: Lightning bonding

Displaying my ignorance yet again could somebody explain the principle involved?  

   

I am assuming that the lightning needs a conductive path to travel into, through and out the other side of the aircraft.  Is this correct?  Any gaps will acts as a giant spark plug gap and cause structural damage??   

       

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of TELEDYNMCS(at)aol.com

 Sent: Tuesday, June 10, 2008 06:44

 To: europa-list(at)matronics.com

 Subject: Lightning bonding  

  

  

       

In a message dated 6/10/2008 3:00:42 AM Eastern Daylight Time, europa-list(at)matronics.com writes:  

   	  Quote: 	
		    

Before I head off to Asia, I plan to put aluminium mesh right along 

 [i]the aileron and flap close outs joining to the rear lift pin to allow wing 

 tip to wing tip lightning travel[/i]  	
  

    

   

    

Hi David,  

    

   

    

FWIW, my wife and I had lightning strike very near us while flying our Ximango last summer on a 500K attempt. We were deep in a drought here and it hadn't rained in 4 months. The lift was fantastic for this area during this time, i.e, greater than 10 knots to going to 10,000'+ agl every day. I had been flying long cross country flights every day for about 3 weeks, including several successful 500k attempts. There had not been even a hint of weather overdevelopment during that time. We were about 300K into the attempt and were approaching a nearby gliderport that was our last turnpoint for the final home run leg to complete the 500K. There was a fairly large storm about 20 miles away, but we were in clear air between puffy, friendly cumulus clouds at about 9000'. We were gliding along engine off at about 80 knots between thermals when a lightning bolt struck right out in front of us out of clear blue sky. I'd always heard that this could happen, but I'd never witnessed it first hand. We saw where it hit the ground and where that was in relation to our turn point. According to the GPS and our observation, the lightning was no more than 1/4th of a mile or so in front of us. The flash and the resulting boom were almost simultaneous. Needless to say it got our attention. I immediately aborted the course in an abrupt 90 degree wingover and proceeded to put as much distance between us and that storm as possible. The rest of the flight was uneventful. Whether or not we triggered the strike is unknown. It didn't hit us and there was no damage to the aircraft. I probably hyper-extended my sphincter muscle, though.  

    

   

    

After we returned to my strip I began to wonder if the Ximango was bonded. So, I started inspecting. Turns out that Aeromot did bond virtually every metal surface in the aircraft together. They used fairly heavy gauge braided jumpers made from tinned copper to tie everything metal together to prevent arcing. I'm considering doing the same to my Europa.   

    

   

    

I certainly give thunderboomers a much wider berth these days.  

    

   

    

Regards,  

    

   

    

John Lawton

 Whitwell, TN (TN89)

 N245E - Flying  

  



 

   

Checked by AVG.

 08-Jun-08 17:32  

     

  Checked by AVG.

 08-Jun-08 17:32

    [quote][b]

pete(at)lawless.info
Guest

Posted: Tue Jun 10, 2008 9:32 am Post subject: Lightning bonding

The problem is that the Europa is made of Tupperware so there is no metal skin for the electricity to flow through, hence it is possible for it to flow though the aileron push rods or the elevator push rod and possibly vapourise them in the process.  Some glass aeroplanes have a metal or carbon mesh built into the structure to conduct the lightning around the outside.  There was a glider over Dunstable a couple of years ago that had a wing literally blown apart by the effect of a lightning strike.  

   

Regards  

   

Pete  

   

--

wdaniell(at)etb.net.co
Guest

Posted: Tue Jun 10, 2008 11:23 am Post subject: Lightning bonding

Thanks that explaines it.  Hope they were wearing a parachute.  

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of Pete Lawless

 Sent: Tuesday, June 10, 2008 12:27

 To: europa-list(at)matronics.com

 Subject: RE: Lightning bonding  

The problem is that the Europa is made of Tupperware so there is no metal skin for the electricity to flow through, hence it is possible for it to flow though the aileron push rods or the elevator push rod and possibly vapourise them in the process.  Some glass aeroplanes have a metal or carbon mesh built into the structure to conduct the lightning around the outside.  There was a glider over Dunstable a couple of years ago that had a wing literally blown apart by the effect of a lightning strike.  

Regards  

Pete  

-----Original Message-----

  Checked by AVG.

 08-Jun-08 17:32

    [quote][b]

rampil

Joined: 04 May 2007
Posts: 870

Posted: Tue Jun 10, 2008 12:06 pm Post subject: Re: Lightning bonding

Lightning and composite a/c are just a bit more complicated than the

discussion so far suggests:



wing mesh is more useful for static dissipation rather than lightning 

protection. Static dissipation is important to assure your Nav/Comm

works in the clouds. The reason it does not work for lightning is that the

tiny conductors of a mesh will melt, or vaporize explosively if hundreds

to thousands of Amps pass through.  You can't put enough metal into

a composite a/c to safely conduct a direct lightning strike. Even metal a/c

burn through at the points of entry and exit where the current density is

highest.  The same applies to bonding straps to control surfaces - for

conduction of and reduction of microamps of static charge, not lightning protection.

_________________
Ira N224XS

pete(at)lawless.info
Guest

Posted: Tue Jun 10, 2008 1:51 pm Post subject: Lightning bonding

They were and both lived to tell the tale.  The lad in the back seat got burns to his neck.  

   

--

davidjoyce(at)doctors.org
Guest

Posted: Tue Jun 10, 2008 2:14 pm Post subject: Lightning bonding

Fred & al, As I see it the problem with bonding aileron push rods is that 

they don't go to the end of the wings.Ideally I think you need a conductor 

that extends to the wing tips and also possibly one that is not inside the 

wing cavity. In the quoted glider incident (which happened in 1999 at 

Northall, just North of London, CAA occurrence no. 199902166) the heat 

generated by the lightning arcing through the wing surface to the control 

runs was thought to be enough to massively expand the contained air and blow 

the wing skins off. There is a caveat however to basing too much on that 

incident as investigation showed that the power of that particular lightning 

bolt was exceptional, in fact seven times higher than the power that 

certified aircraft are designed to withstand. Nevertheless I like the notion 

of a conductor that isn't connected to the bit I am holding, and feel there 

is a good chance of the aluminium mesh in the close out approach conducting 

lesser bolts straight through without giving me or my avionics a nasty 

shock!

        As an amusing postscript to the glider story the passenger in the 2 

seat glider was having a trial flight. As he hadn't had his money's worth 

the club offered him a free repeat, but he is said to have declined!

           Regards, David Joyce, G-XSDJ

---

wdaniell(at)etb.net.co
Guest

Posted: Tue Jun 10, 2008 2:28 pm Post subject: Lightning bonding

So they managed to jump?



--

TELEDYNMCS(at)aol.com
Guest

Posted: Wed Jun 11, 2008 4:10 am Post subject: lightning bonding

In a message dated 6/11/2008 3:03:20 AM Eastern Daylight Time,  europa-list(at)matronics.com writes:

  	  Quote: 	
		  Not    sure thats a terribly good idea. 	
  

 Hi Carl, et al,

  

 Apparently, the FAA and Aeromot think it is a good idea. The Ximango is a  certified aircraft, has aluminum fuel tanks and they, too, are bonded  to the rest of the metallic parts in the aircraft. In their parts manual,  Aeromot refers to these bonding straps installed as "lightning  bonding."

  

 As it has been explained to me by our resident composite Guru here at the  'Possum Werks, what happens in composite airplanes in a lightning strike to make  them explode is the super heating of residual moisture that is trapped within  the layers of epoxy and cloth at the time of manufacture. When the strike  passes through the composite, trapped moisture rapidly heats, expands and  the structure comes apart explosively.

  

 Having designed, installed and tested lightning protection systems on over  7000 cellular telephone sites, I've seen this phenomenon quite a  bit with fiberglass antenna masts on poorly grounded sites. When a cell antenna  takes a direct hit it explodes. The tower can take a direct hit and only slight  discoloration will result. The result of an exploded antenna mast is  similar to what you see after one of those exploding cigars goes off. If the  site is properly grounded and bonded, this almost never happens, though. 

  

 What you are trying to do with bonding metallic parts in a plastic  airplane is give the lightning a low resistance path to pass through and  exit the airplane so that it doesn't take a high resistance (i.e.,  through the composite) path to exit and destroy the airplane. Low resistance is  the key here. By providing a low resistance path for the  lightning to pass though you reduce or eliminate the instantaneous heating  that occurs in high resistance paths during a discharge. You also want to  prevent arcing that would occur at loose metallic fittings, such as rod  ends and any metallic parts that are bolted together. These are points of high  resistance and arcing (and welding) can result. What you are doing here is  making all the metallic parts equal in resistance, therefore equal in potential  when charged. Ohm's law at work. I've heard of more than one  occurrence of gliders that did not have bonded control systems being  struck in flight and having their control rods welded to the point where the  aircraft was no longer controllable and the occupant(s) were forced to bail  out. 

  

 These bolted connections are precisely where the bonding straps are  installed on the Ximango. The bonding straps that are installed, given  their size, are designed to take a lot more current than a simple static  discharge. They are essentially the same thing we install to bond  and protect towers, transmission equipment, batteries, fencing, coax,  antennae, etc., in cell sites from lightning. The reason braided cable is used  is surface area. The more surface area, the more current it can handle. Braided  cable has much, much more surface area than typical  Tefzel aircraft wire or a solid wire, thus more current handling  capacity.

  

 Is it a cure all? No. There is no such thing as perfect lightning  protection. Will it help save your bacon in a residual discharge situation?  Probably. Will it save your bacon in a direct hit? Probably not.

  

 Fred, as far as a source on the bonding straps, try Harger. www.harger.com. If it has anything to do with  lightning protection, Harger carries it.

  

 Hope it helps!

 

Regards,

  

 John  Lawton

Whitwell, TN (TN89)

N245E -  Flying



Vote for your city's best dining and nightlife. City's Best 2008.

  [quote][b]

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