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Composite Aircraft and Lightning Strikes

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billhuntersemail(at)gmail
Guest

Posted: Thu Jun 30, 2016 4:35 pm Post subject: Composite Aircraft and Lightning Strikes

Hi All,



There is a discussion brewing on the Velocity Owners Builders Association

about composite aircraft and lightning strikes.



What sparked (sorry) this discussion was a question about static wicks and

if they could be useful on composite aircraft and now there is some good

bantering going on about lightning strikes and composite

aircraft...so...naturally I thought since there is some really sharp

electrical folks on this forum I would ask you all for your feedback on the

subject and I will certainly give you credit for your feedback and

suggestions (of course I could not try to pass this knowledge off as being

my own because that cat is already out of the bag and they would never

believe it came from me).



Anyhoo...here are some questions (if you think up others please feel free to

add):



-Would static wicks be beneficial to add to a composite aircraft?



-If adding static wicks to a composite airplane, where should they be added?



-Should control surfaces be bonded to the aircraft structure if static wicks

are used (and even if static wicks are not used)?



-Should all of the metal components of the aircraft be bonded together and

if so what technique should be employed to do so?



-Does anyone know of any lightning strike incidents to composite aircraft

and if so what damage to the aircraft structure/components have occurred?



-What causes lightning to be attracted to airplanes and/or why does

lightning hit airplanes (yes, I can understand why lightning hits

trees/buildings/other items that are connected to earth but an airplane is

not connected to earth...if it had just taken off I could see the static in

the wake leading to ground however an airplane in cruise flight is another

story)?



-Are composite aircraft more or less likely to be hit by lightning than

metal airplanes?



-Are there any techniques or design considerations that would mitigate the

chance of lightning strikes on the composite aircraft and/or the damage

being done should the aircraft be hit?



-On production composite aircraft, what if any equipment/design

considerations have been required by the FAA to be employed in reducing the

chances of and/or in mitigating the effect of a lightning strike?



-Some guys are discussing using Carbon Fiber or mesh being installed under

the surfaces of the airplane to transfer the energy of a lightning strike so

if a mesh of some sort is indeed used, will it help or hurt in reducing the

chances of and/or in mitigating the effect of a lightning strike (if the

mesh is not robust enough to conduct the extreme electrical current by a

lightning strike could it make the problem worse (as a lightning rod on a

house has a too small conductor then the lightning rod attracts the

lightning and then once the lightning does actually hit the rod the

conductor to ground melts and now the house structure becomes the conduit to

ground)?



Please dream up other thoughts in the area of lightning strikes and I will

certainly forward them on.



We appreciate your help in making the design of the Velocity aircraft more

safe during this time of year!!!



.



Cheers!!!



Bill  Hunter

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 30, 2016 7:44 pm Post subject: Composite Aircraft and Lightning Strikes

 	  Quote: 	
		  

 Anyhoo...here are some questions (if you think up others please feel free to

 add):



 -Would static wicks be beneficial to add to a composite aircraft? 	


    Depends. A 'static wick' is intended to REDUCE coronal

    resistance between CONDUCTIVE parts of the airframe and

    the surrounding atmosphere. Without static wicks, electro

    static potentials in the millions of volts can build up

    in various places on the airframe. The existance of

    high levels of static build up can manifest in (1) visible

    light (St. Elmo's Fire on prop tips, around window frames,

    sharp trailing edges), (2) radio noise that can totally

    cripple some systems and sometimes (3) excessive erosion.



    The purpose of a static wick is to ENCOURAGE dissipation of

    electro-static energies at LOW levels . . . levels too low

    to produce the deleterious effects cited.



    -If adding static wicks to a composite airplane, where should they be added?



    EXCELLENT question. Figuring out were to put them nn a metal

    airplane is not a simple task . . . an insulated airplne is 

    whole different ball game.



    I've seen airplanes perched on insulating jacks and excited

    with bunches of volts while a technician walks around the outside

    probing potential leak-off points on the airframe with a very

    long test probe. This is a good start on figuring out where

    potentially 



  	  Quote: 	
		  -Should control surfaces be bonded to the aircraft structure if static wicks

 are used (and even if static wicks are not used)?



 -Should all of the metal components of the aircraft be bonded together and

 if so what technique should be employed to do so? 	


   Can't think of a single reason to do such things.

   I think Burt Rutan may have uttered such an opinion

   WAaaayyyy back when about control surfaces on the Ez

   series aircraft . . . But I'm at a lost to imagine, much

   less demonstrate how the action would benefit anything.



 

  	  Quote: 	
		  -Does anyone know of any lightning strike incidents to composite aircraft

 and if so what damage to the aircraft structure/components have occurred? 	


   One of our very own suffered just such an event



  http://tinyurl.com/hre2hkz



 

  	  Quote: 	
		  -What causes lightning to be attracted to airplanes and/or why does

 lightning hit airplanes (yes, I can understand why lightning hits

 trees/buildings/other items that are connected to earth but an airplane is

 not connected to earth...if it had just taken off I could see the static in

 the wake leading to ground however an airplane in cruise flight is another

 story)?



 -Are composite aircraft more or less likely to be hit by lightning than

 metal airplanes? 	


   Intuitively one might think so . . . but the airplane

   is only a triggering influence in what was going to

   be a strike whether the airplane was there or not.



   All images of airplanes being struck show the airplane

   in the middle of a strike that extends from one

   area of the storm (usually cloud) to another area

   or the ground.



 

  	  Quote: 	
		  -Are there any techniques or design considerations that would mitigate the

 chance of lightning strikes on the composite aircraft and/or the damage

 being done should the aircraft be hit? 	


   Yeah, it's called staying the (at)#$(at) away from

   areas for which no practical invincability can

   be demonstrated. This included lightning, ice,

   high winds, hail, etc.



 

  	  Quote: 	
		  -On production composite aircraft, what if any equipment/design

 considerations have been required by the FAA to be employed in reducing the

 chances of and/or in mitigating the effect of a lightning strike? 	


   It's exaclty the OPPOSITE. We cannot nor do we attempt

   to avoid being struck. We must ASSUME we WILL be struck

   and design for measured and predicted stresses.



  	  Quote: 	
		  -Some guys are discussing using Carbon Fiber or mesh being installed under

 the surfaces of the airplane to transfer the energy of a lightning strike so

 if a mesh of some sort is indeed used, will it help or hurt in reducing the

 chances of and/or in mitigating the effect of a lightning strike (if the

 mesh is not robust enough to conduct the extreme electrical current by a

 lightning strike could it make the problem worse (as a lightning rod on a

 house has a too small conductor then the lightning rod attracts the

 lightning and then once the lightning does actually hit the rod the

 conductor to ground melts and now the house structure becomes the conduit to

 ground)? 	


   Check with the Lancair and Glasair forums. These folks

   would come a close as anyone to knowing what was tried

   and either succeeded or failed to produce the desired

   mitigation of effects. There is a wealth of discussion

   on . . .



  http://tinyurl.com/zeay3x5



 

   . . . this is NOT a trivial task.   



  	  Quote: 	
		  Please dream up other thoughts in the area of lightning strikes and I will

 certainly forward them on.



 We appreciate your help in making the design of the Velocity aircraft more

 safe during this time of year!!! 	


   History is rife with examples of work done

   to make aircraft resistant to the effects of

   lightning strike. Lancair, Glassair and contemporaries

   wrestled with it. At Beech, we stayed with metal wings

   but the fuselage structures have large, flat conductive

   straps that run longitudinaly7 in the fuselage. These

   'fixes' are tested in direct effects of lightning laboratories

   to show that people, structure and systems within the airplane

   remain intact after events that are ASSUMED WILL HAPPEN.



   The simple answer to the question is: "Yes, you CAN do things

   to airplanes of any stripe to reduce risk due to lightning

   strike . . . but it's not a simple task. A task deeply intertwined

   with issues of structural integrity, weight, aerodynamics . . . and cost.

   

   In flight school, we were well advised to stay away from

   ice and convective activity. Risks to body and airframe go

   up exponentially . . . while costs for mitigation of those

   risks are breathtaking.



   Adding any feature intended to mitigate environmental

   risk brings some human factor's issues with it. More that

   one pilot with boots, prop-deice and a windshield heater

   patch was willing to 'press on just a little further' . . .

   with more than simply disappointing outcome. The same

   effect could beset a pilot flying an airplane with

   lightning mitigation enhancements . . . enhancements

   that did not benefit from a through checkout in the

   lightning lab by folks who have been there, done that.



   



 

   Bob . . .

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peter(at)sportingaero.com
Guest

Posted: Thu Jun 30, 2016 10:43 pm Post subject: Composite Aircraft and Lightning Strikes

Before getting really wound up about lightning protection first understand the risk and then figure the mitigation. Look at the accident statistics- how many light aircraft have been struck by lightning and not survived? The answer is very, very few - in the US and in Europe. For whatever reason. Thunderstorms kill many people but lightning does not. My conclusion is that airframe lightning protection is not worthwhile. Thunderstorm protection is difficult so I avoid them.

 Peter On 1 Jul 2016 04:50, "William Hunter" <billhuntersemail(at)gmail.com (billhuntersemail(at)gmail.com)> wrote: 	  Quote: 	
		  --> AeroElectric-List message posted by: "William Hunter" <billhuntersemail(at)gmail.com (billhuntersemail(at)gmail.com)>

 

 Hi All,

 

 There is a discussion brewing on the Velocity Owners Builders Association

 about composite aircraft and lightning strikes.

 

 What sparked (sorry) this discussion was a question about static wicks and

 if they could be useful on composite aircraft and now there is some good

 bantering going on about lightning strikes and composite

 aircraft...so...naturally I thought since there is some really sharp

 electrical folks on this forum I would ask you all for your feedback on the

 subject and I will certainly give you credit for your feedback and

 suggestions (of course I could not try to pass this knowledge off as being

 my own because that cat is already out of the bag and they would never

 believe it came from me).

 

 Anyhoo...here are some questions (if you think up others please feel free to

 add):

 

 -Would static wicks be beneficial to add to a composite aircraft?

 

 -If adding static wicks to a composite airplane, where should they be added?

 

 -Should control surfaces be bonded to the aircraft structure if static wicks

 are used (and even if static wicks are not used)?

 

 -Should all of the metal components of the aircraft be bonded together and

 if so what technique should be employed to do so?

 

 -Does anyone know of any lightning strike incidents to composite aircraft

 and if so what damage to the aircraft structure/components have occurred?

 

 -What causes lightning to be attracted to airplanes and/or why does

 lightning hit airplanes (yes, I can understand why lightning hits

 trees/buildings/other items that are connected to earth but an airplane is

 not connected to earth...if it had just taken off I could see the static in

 the wake leading to ground however an airplane in cruise flight is another

 story)?

 

 -Are composite aircraft more or less likely to be hit by lightning than

 metal airplanes?

 

 -Are there any techniques or design considerations that would mitigate the

 chance of lightning strikes on the composite aircraft and/or the damage

 being done should the aircraft be hit?

 

 -On production composite aircraft, what if any equipment/design

 considerations have been required by the FAA to be employed in reducing the

 chances of and/or in mitigating the effect of a lightning strike?

 

 -Some guys are discussing using Carbon Fiber or mesh being installed under

 the surfaces of the airplane to transfer the energy of a lightning strike so

 if a mesh of some sort is indeed used, will it help or hurt in reducing the

 chances of and/or in mitigating the effect of a lightning strike (if the

 mesh is not robust enough to conduct the extreme electrical current by a

 lightning strike could it make the problem worse (as a lightning rod on a

 house has a too small conductor then the lightning rod attracts the

 lightning and then once the lightning does actually hit the rod the

 conductor to ground melts and now the house structure becomes the conduit to

 ground)?

 

 Please dream up other thoughts in the area of lightning strikes and I will

 certainly forward them on.

 

 We appreciate your help in making the design of the Velocity aircraft more

 safe during this time of year!!!

 

 .

 

 Cheers!!!

 

 BillÂ  Hunter

 

 

 

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glastar(at)gmx.net
Guest

Posted: Thu Jun 30, 2016 11:17 pm Post subject: Composite Aircraft and Lightning Strikes

There is a very narrative report from a glider in the UK, which was hit 

by lightning and disintegrated, in the same report a helicopter with 

carbon fiber blades is described as well.



http://www.pas.rochester.edu/~cline/ASK%20lightning%20strike/ASK%20accident%20report.htm



For my feeling stay away from possible lightning 



Cheers Werner

On 01.07.2016 01:37, William Hunter wrote:

 	  Quote: 	
		   



 Hi All,



 There is a discussion brewing on the Velocity Owners Builders Association

 about composite aircraft and lightning strikes.



 ........



 -Does anyone know of any lightning strike incidents to composite aircraft

 and if so what damage to the aircraft structure/components have occurred?



 -

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peter(at)sportingaero.com
Guest

Posted: Fri Jul 01, 2016 3:17 am Post subject: Composite Aircraft and Lightning Strikes

Read the AAIB report, aircraft was in good VMC. The energy of the strike meant that no protection would have made any difference. The control rods melted - nothing much could be done about that... On 1 Jul 2016 8:30 a.m., "Werner Schneider" <glastar(at)gmx.net (glastar(at)gmx.net)> wrote: 	  Quote: 	
		  --> AeroElectric-List message posted by: Werner Schneider <glastar(at)gmx.net (glastar(at)gmx.net)>

 

 There is a very narrative report from a glider in the UK, which was hit by lightning and disintegrated, in the same report a helicopter with carbon fiber blades is described as well.

 

 http://www.pas.rochester.edu/~cline/ASK%20lightning%20strike/ASK%20accident%20report.htm

 

 For my feeling stay away from possible lightning 

 

 Cheers Werner

 

 

 On 01.07.2016 01:37, William Hunter wrote:

  	  Quote: 	
		   --> AeroElectric-List message posted by: "William Hunter" <billhuntersemail(at)gmail.com (billhuntersemail(at)gmail.com)>

 

 Hi All,

 

 There is a discussion brewing on the Velocity Owners Builders Association

 about composite aircraft and lightning strikes.

 

 .......

 

 -Does anyone know of any lightning strike incidents to composite aircraft

 and if so what damage to the aircraft structure/components have occurred?

 

 -

 	
 

 

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 errer" target="_blank">http://wiki.matronics.com

 ===========

 b Site -

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 rel="noreferrer" target="_blank">http://www.matronics.com/contribution

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lyleapgmc

Joined: 19 Feb 2014
Posts: 57

Posted: Fri Jul 01, 2016 5:22 am Post subject: Composite Aircraft and Lightning Strikes

On 6/30/2016 9:04 PM, Robert L.       Nuckolls, III wrote:

     

      	  Quote: 	
		  the problem worse (as a lightning rod on       a

       

         

          	  Quote: 	
		  -Are there any           techniques or           design considerations that would mitigate the

           chance of lightning strikes on the composite aircraft and/or           the           damage

           being done should the aircraft be hit? 	
         

           Yeah, it's called staying the (at)#$(at) away from

           areas for which no practical invincability can

           be demonstrated. This included lightning, ice,

           high winds, hail, etc.

         

         

          	  Quote: 	
		    	
       

       

           

       

           

         

              

             Bob . . .     	
     

     ROTFLMAO

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jul 01, 2016 6:07 am Post subject: Composite Aircraft and Lightning Strikes

At 01:35 AM 7/1/2016, you wrote:



  	  Quote: 	
		  Before getting really wound up about lightning protection first understand the risk and then figure the mitigation. Look at the accident statistics- how many light aircraft have been struck by lightning and not survived? The answer is very, very few - in the US and in Europe. For whatever reason. Thunderstorms kill many people but lightning does not. My conclusion is that airframe lightning protection is not worthwhile. Thunderstorm protection is difficult so I avoid them. 	


   Excellent point . . . Similarly, few engines

   stop cold because of mechanical or electrical

   failure. The majority of 'engine trouble' on

   airplanes is fuel exhaustion. The moral of the

   story is that the pilot is the weakest link in

   the chain of risk for operating an airplane.



   Static wicks (also a topic of this thread)

   are another matter. They go to a more mundane

   issue . . . radio noise and miscellaneous damage

   to systems.



   The windshields in many high performance airplanes

   are vulnerable to the high voltage discharge

   often observed around the edges of a window

   frame. When that window is fitted with embedded

   heater wires, replacement can be VERY expensive.

   I thing the price tag on a GP180 window was around

   $20K in 1980 dollars.



   There have been many experiments with aircraft

   finishes and shapes conducted to understand how

   static electricity can be better managed on

   high performance aircraft.



   Not all static wicks are the same. Walk around

   the ramp and check out the variations you'll find.

   I recall John Cooper, head cheese of our EMC lab

   building a fixture to survey static wick performance.

   Various samples being tested might vary as much as

   3:1 with respect to their 'conductivity'.



   Once you identify a 'good' wick design, then finding

   the 'right' place to install them was another

   grand experiment. And this was on all metal

   aircraft.  Airplanes of glass and plastic are

   another matter. Imagine how you might modify

   a glass rod (used to demonstrate static electricity

   phenomenon in physics class) to dampen if not

   eliminate it's ability to stand up the hairs

   on your cat.



   Further, your successful technique cannot materially

   change structural characteristics, it must be

   durable, and it cannot add too much cost.



   If anyone discovers some literature

   describing successful application of static wicks

   to plastic/glass/carbon aircraft . . . I'd REALLY

   like to read it.



   



 

 

   Bob . . .

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billhuntersemail(at)gmail
Guest

Posted: Fri Jul 01, 2016 9:24 am Post subject: Composite Aircraft and Lightning Strikes

Hi All,  

THANK YOU FOR YOUR HELP!!! Very good information and I will be passing the information on to the VOBA Forum.  

Bill Hunter 

 +1 408-464-1902 On Jul 1, 2016 7:14 AM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote: 	  Quote: 	
		    At 01:35 AM 7/1/2016, you wrote:



  	  Quote: 	
		  Before getting really wound up about lightning protection first understand the risk and then figure the mitigation. Look at the accident statistics- how many light aircraft have been struck by lightning and not survived? The answer is very, very few - in the US and in Europe. For whatever reason. Thunderstorms kill many people but lightning does not. My conclusion is that airframe lightning protection is not worthwhile. Thunderstorm protection is difficult so I avoid them. 	


 Â  Excellent point . . . Similarly, few engines

 Â  stop cold because of mechanical or electrical

 Â  failure. The majority of 'engine trouble' on

 Â  airplanes is fuel exhaustion. The moral of the

 Â  story is that the pilot is the weakest link in

 Â  the chain of risk for operating an airplane.



 Â  Static wicks (also a topic of this thread)

 Â  are another matter. They go to a more mundane

 Â  issue . . . radio noise and miscellaneous damage

 Â  to systems.



 Â  The windshields in many high performance airplanes

 Â  are vulnerable to the high voltage discharge

 Â  often observed around the edges of a window

 Â  frame. When that window is fitted with embedded

 Â  heater wires, replacement can be VERY expensive.

 Â  I thing the price tag on a GP180 window was around

 Â  $20K in 1980 dollars.



 Â  There have been many experiments with aircraft

 Â  finishes and shapes conducted to understand how

 Â  static electricity can be better managed on

 Â  high performance aircraft.



 Â  Not all static wicks are the same. Walk around

 Â  the ramp and check out the variations you'll find.

 Â  I recall John Cooper, head cheese of our EMC lab

 Â  building a fixture to survey static wick performance.

 Â  Various samples being tested might vary as much as

 Â  3:1 with respect to their 'conductivity'.



 Â  Once you identify a 'good' wick design, then finding

 Â  the 'right' place to install them was another

 Â  grand experiment. And this was on all metal

 Â  aircraft.Â  Airplanes of glass and plastic are

 Â  another matter. Imagine how you might modify

 Â  a glass rod (used to demonstrate static electricity

 Â  phenomenon in physics class) to dampen if not

 Â  eliminate it's ability to stand up the hairs

 Â  on your cat.



 Â  Further, your successful technique cannot materially

 Â  change structural characteristics, it must be

 Â  durable, and it cannot add too much cost.



 Â  If anyone discovers some literature

 Â  describing successful application of static wicks

 Â  to plastic/glass/carbon aircraft . . . I'd REALLY

 Â  like to read it.



 Â  



 

 

 Â  Bob . . .

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