When lightning strikes

Discussion in 'Rules and Regulations / Flight Safety / Better Pil' started by autoreply, Jan 25, 2011.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Jan 25, 2011 #1

    autoreply

    autoreply

    autoreply

    Moderator

    Joined:
    Jul 8, 2009
    Messages:
    10,732
    Likes Received:
    2,552
    Location:
    Rotterdam, Netherlands
    Last edited by a moderator: Mar 20, 2019
  2. Jan 25, 2011 #2

    Lucrum

    Lucrum

    Lucrum

    Well-Known Member

    Joined:
    Jun 10, 2008
    Messages:
    956
    Likes Received:
    189
    Location:
    Canton, GA
    I've been hit before in flight.
     
  3. Jan 26, 2011 #3

    Monty

    Monty

    Monty

    Well-Known Member

    Joined:
    Jul 15, 2010
    Messages:
    1,294
    Likes Received:
    496
    Location:
    Fayetteville, AR / USA
    I remember when this happened. I was just learning to fly gliders. We got pictures of the remains of the glider in emails that circulated the gliding community at that time. The guy who was running the glider operation, and was the tow pilot where I was learning to fly, just happened to be one of the formost experts on lightning protection for aerospace vehicles in the US. It was nice to have an expert to explain things. For instance the way the control rod was malformed is caused by the rise and fall of magnetic fields caused by the lightening bolt. I've been in an airplane that was hit by lightening, but that was an airliner and scary enough...I've also had a canopy come open on tow in a glider....can't imagine the two things combined and the airplane disintegrating at the same time...must have been quite a ride.

    Both of them performed quite well given the circumstances I'd say......
     
  4. Jan 26, 2011 #4

    JamesAero

    JamesAero

    JamesAero

    Well-Known Member

    Joined:
    May 10, 2010
    Messages:
    46
    Likes Received:
    0
    Location:
    Salem, OR
    I was flying a Cessna 414 that was hit by lightning over the Cascades and while it scared the hell out of me for a split second it had no ill effects on the aircraft. That is one huge advantage of a metal airframe. Now that I'm building a composite homebuilt it is frequently in the back of my mind that I won't have that form of protection.
     
  5. Jan 26, 2011 #5

    Monty

    Monty

    Monty

    Well-Known Member

    Joined:
    Jul 15, 2010
    Messages:
    1,294
    Likes Received:
    496
    Location:
    Fayetteville, AR / USA
    The tow pilot...Joe..managed to convince me that plastic airplanes and static electricity do not mix well. If you remember the early pictures of the space shuttle punching through a cloud layer...you will note that they did not do that later in the program...Joe is the reason. As Joe related, the vehicle was not safe WRT lightning. Joe had lot's of neat stories. He had worked primarily with EMP and lightening protection during his career.

    For those with plastic airframes, you may find THIS interesting.
     
  6. Jan 26, 2011 #6

    WonderousMountain

    WonderousMountain

    WonderousMountain

    Well-Known Member

    Joined:
    Apr 10, 2010
    Messages:
    1,853
    Likes Received:
    193
    Location:
    Clatsop, Or
    Does that mean a plastic plane should have no conductive parts to avoid lightening failure modes?

    Building an all rubber plane will be difficult:tired:

    off topic,

    Wonderous Mountain
     
  7. Jan 26, 2011 #7

    autoreply

    autoreply

    autoreply

    Moderator

    Joined:
    Jul 8, 2009
    Messages:
    10,732
    Likes Received:
    2,552
    Location:
    Rotterdam, Netherlands
    LIGHTNING STRIKE PROTECTION from Aircraft Spruce

    I guess this is one of those things where neglect plays a big role. Pilots easily forget the dangers (microburst, turbulence, turning wind, lightning) and I've learned my lesson too. 3000 fpm ain't much fun if you can't stop the climb of the aircraft...
     
  8. Jan 26, 2011 #8

    Mac790

    Mac790

    Mac790

    Well-Known Member

    Joined:
    Jun 22, 2008
    Messages:
    1,529
    Likes Received:
    19
    Location:
    Poznan, Poland
    Ok, so what is an industrial approach to that problem, I'm talking about new Boeing DreamLiner, not to mention all those "plastic" UAV's. I didn't notice that "lighting protection grid" on them, here is better source for those grids than that posted by Jarno Expanded Metal - Expanded Metal Foil - Expanded Metal Mesh - Expanded Plastic - Dexmet Corporation . What's a point of making extremely smooth surface, and next apply that grid over it?

    Lighting strike protection for carbon bird http://www.dexmet.com/1_pdf/LSP%20for%20Carbon%20Fiber%20Aircraft.pdf

    Seb
     
  9. Jan 26, 2011 #9

    autoreply

    autoreply

    autoreply

    Moderator

    Joined:
    Jul 8, 2009
    Messages:
    10,732
    Likes Received:
    2,552
    Location:
    Rotterdam, Netherlands
    Not the slightest clue, but maybe they isolate the mesh with an (epoxy/vinylester) spray?

    Mold=>gelcoat=>glass/kevlar=>mesh=>glass/kevlar=>carbon=>foam=>carbon

    Then, the gelcoat and outer layer still vaporizes, but your structure remains in tact. Afaik, this is what's used in small aircraft.
     
  10. Jan 27, 2011 #10

    Othman

    Othman

    Othman

    Well-Known Member

    Joined:
    Aug 23, 2004
    Messages:
    355
    Likes Received:
    4
    Location:
    Ottawa, ON, Canada
    This is a very good topic. Thanks for starting it Autoreply.

    The aluminum or copper mesh material is quite thin (.002" and up), less than a ply of glass. It is layed up in situ with the glass plies in the laminate (co-cured). The mesh is located at the outer most surface of the laminate just under a surfacing ply (a lightweight glass fabric). If the laminate is carbon fibre with an embedded aluminum mesh, then an isolation ply of glass should be used between the two materials to prevent galvanic corrosion.

    You can still achieve a smooth surface in the end. The main problem is when you have compound curves. In that case there are other lighting strike protection options such as flame spray coating or aluminized fabrics.

    See the following resources for more in depth information.

    Aircraft Lightning Protection Handbook
    This was later made into the DOT/FAA/CT-89/22, LIGHTNING PROTECTION HANDBOOK. I have a copy of the PDF but it is too large to post.

    A similar handbook was produced under the AGATE program focussed on General Aviation applications.
    http://www.niar.wichita.edu/agate/Documents/Lightning/WP3.1-031027-043.pdf
     
  11. Jan 27, 2011 #11

    Monty

    Monty

    Monty

    Well-Known Member

    Joined:
    Jul 15, 2010
    Messages:
    1,294
    Likes Received:
    496
    Location:
    Fayetteville, AR / USA
    No, it means that you should not fly in your plastic plane near convective sigmets.....If you do make sure you have metal mesh in the top layer of the laminate...and hope you don't intersect a main channel or worse yet, a positive stroke.
     
  12. Feb 4, 2011 #12

    Orwasi

    Orwasi

    Orwasi

    Member

    Joined:
    Dec 18, 2009
    Messages:
    17
    Likes Received:
    0
    Location:
    Sydney, Australia
    Excuse my ignorance, but what happens to that thin mesh during a lightning strike? Is it damaged in some way, like a fuse exposed to excessive current and/or voltage? If it is damaged, replacing it (to maintain the protection for the airplane) sounds like an expensive exercise.
     
  13. Feb 11, 2011 #13

    teknosmurf

    teknosmurf

    teknosmurf

    Well-Known Member

    Joined:
    Aug 17, 2010
    Messages:
    133
    Likes Received:
    1
    Location:
    Queen Creek, AZ
    I doubt much would happen to the mesh assuming there is a relatively effective discharge path (static rods, etc), and there is little/no path of least resistance (exposed mesh somewhere, etc). I would expect the mesh to pretty much spread the electrons over the a much larger surface area, thereby reducing the amount of power going throuh any specific location.

    As I understand it, aircraft rarely take a direct hit from an actual lighting bolt. While the following description is very similar to the way a lightning bolt is created, it has some important differences. Usually what is described as a lighting strike is just a build up of electons as the plane moves through the air/clouds (much like dragging your feet on the carpet). Because "plastic airplanes" are made of insulated material, the charge builds up to a sufficient level before discharging into the surrounding atmosphere (like touching the doorknob). By wrapping the plane in the mesh, and putting static rods on the back of your wings, you are effectively putting a metal glove on your hand with a wire to the ground, and allowing the charge a path to disipate before it ever becomes a "lightning bolt". Think of it as replacing the air between your finger and the doorknob with a piece of metal. As you drag your feet the electrons are discharged through the metal directly to the doorknob so there is never a spark (or lightning bolt) to begin with.
     
  14. Feb 11, 2011 #14

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    12,039
    Likes Received:
    3,469
    Location:
    Memphis, TN
    The strike is not what does the damage it is the exit of the power. The planes I am familiar with are SAABs and CRJs. All the structures are suppose to be bonded so the potential is the same everywhere. When lightning hits, you want it to not find a place to exit until it gets to the dischargers/ static wicks. If it finds a place that is not bonded, that is when the damage happens. The composite parts have a foil or a fine mash between the structural and visual parts of the composite part. When installed it ends up being bonded(grounded) the adjacent areas. The biggest damage I have seen has been a composite fairing behind the wing on a CRJ burn all its resin out so it was just a giant cloth flapping in the breeze, seen a wing tip do that too, and on the metal side, CRJ melted a hole I could put my arm into. Most normal strikes you can see it skip down the fuselage, blowing out rivets every 5 feet or so. A local Cirrus got struck and it cost him a lot of money before Cirrus was happy with the repair; they dont have the mesh.
     

Share This Page

Group Builder
arrow_white