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I asked my old boss, Andy Marshall about lightning strikes in composite planes. Here is his reply.
I also suggested that perhaps it would be a great subject to discuss in the next edition of his book "Composite Basics".
I am still curious as to whether by being conductive, the carbon and metal planes are more prone to strikes but suffer less damage than glass planes. A conductor such as metal will bleed the charge out better than a non-conductive material will (such as fiberglass and resin).
In boats, the theory is that if you throw chains overboard from the shrouds, you can carry the electrical discharge overboard but you are likely to get hit more often. And the charge may still do considerable damage with the grounds. Of course on a sailboat, you are the tallest thing around, regardless. And there have been times when I felt the lightning hitting close to me without ever getting hit myself (quite a jolt, too!). This charge was carried from the metal keel up through the reinforcing wires to a track on the deck that I was sitting on. I don't know what the results would have been if the boat would have been metal or carbon.
Maybe Andy will have some more insights to that by the time he does his next edition.
Dan
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Dan Newland
Application engineer
Orcon Corporation
1570 Atlantic Street
Union City, California 94587
phone: (510) 476-2150
cell: (510) 290-6885
fax: (510) 489-6702
----- Forwarded by Dan Newland/Union City/ORCON on 06/10/03 11:00 AM -----
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| MARSHALLCONSULT@aol.com
06/10/03 10:38 AM
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To: Dan.Newland@orcon.com
cc:
Subject: Re: |
DEAR DAN:
IT LOOKS AS IF PAUL WILL GO TO OSHKOSH AGAIN, BUT WILL MAKE IT PART OF A
LONGER TRIP STARTING OUT WELL BEFORE OSH.
LIGHTNING STRIKES HAVE ALWAYS BEEN A PROBLEM FOR ALL AIRCRAFT, BUT ONLY SEEM
TO BE SERIOUS WHEN THEY IGNITE A PARTIALLY FILLED FUEL TANK. THE GENERAL
THREAT HAS CAUSED A LOT OF WORK TO BE DONE ON PROTECTING GLASS AND CARBON
AIRPLANES, MOSTLY BY PUTTING A GRID OF COPPER WIRES IN THE SKIN ALL OVER THE AIRPLANE,
AND THEN CONNECTING THEM ALL TOGETHER SO THAT THE LIGHTNING THINKS IT IS
LOOKING AT A METAL AIRPLANE. YOU ARE RIGHT IN THINKING THAT THE PROBLEM IS
REGARDED SERIOUSLY, BUT NOT MUCH CONCLUSIVE DATA EXISTS. ALSO, YOU ARE CORRECT IN
THAT A CARBON FIBER STRUCTURE IS MUCH MORE SUSCEPTIBLE TO LIGHTNING DAMAGE THAN A
GLASS ONE. LIGHTNING STRIKES ON AN ALL CARBON STRUCTURE SEEM TO RESULT IN AN
EXPLOSION AT THE POINT OF PENETRATION, ENOUGH TO COMPLETELY DESTROY SMALL
STRUCTURES LIKE A FLAP OR AILERON. AT ANY RATE, EVERYBODY FEELS THAT YOU SHOULD
NOT VENTURE INTO LIGHTNING TERRITORY IN A CARBON FIBER AIRPLANE. IN SPITE OF THE
LACK OF DATA ON THE CATASTROPHIC EFFECTS ON GLASS PLANES, MOST PILOTS OF
THOSE PLANES ALSO AVOID EXPOSURE TO THE PROBLEM AS MUCH AS POSSIBLE. OF COURSE
PART OF THE PROBLEM IS THAT LIGHTNING HAS ALMOST NO EFFECT ON METAL AIRPLANES,
EXCEPT FOR MAKING SMALL HOLES AT THE POINT OF ENTRY AND EXIT. AS LONG AS NO FUEL
IS IN THE PATH OF THE STRIKE, DAMAGE IS USUALLY VERY MINOR. IN ONE THREE YEAR
PERIOD WHEN UAL FOLLOWED THE PROBLEM, THEY HAD AN AVERAGE OF ONE STRIKE ON
EACH AIRCRAFT EACH YEAR. NONE OF THESE STRIKES RESULTED IN ANY OPERATIONAL
PROBLEM, OTHER THAN SCARING HELL OUT OF EVERYBODY ON BOARD AT THE TIME.
YES, I WILL PROBABLY DO ANOTHER EDITION OF MY BOOK, BUT NOT FOR ABOUT ANOTHER
YEAR. IT PROBABLY WILL IGNORE THE SUBJECT AGAIN, AS I HAVE NO SPECIFIC
INFORMATION TO CONVENIENTLY QUOTE. PERHAPS I SHOULD FIND SOMETHING, HOWEVER, AS I AM
SURE THE PROBLEM IS NOT GOING AWAY ANYTIME SOON.
AT THE MOMENT I HAVE NO PLANS FOR LUNCH IN UNION CITY, BUT THAT COULD CHANGE
. WE WILL BE GONG UP TO TAHOE IN A WEEK OR TWO, SO THE MOST LIKELY TIME FOR
ANOTHER LUNCH IS NEXT SEPTEMBER.
REGARDS TO BOTH YOU AND CONNIE.
ANDY
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