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07-08-2011, 03:57 PM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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Isolated ground rods are actually pretty crappy low resistance grounds in a ton of situations....
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07-08-2011, 04:42 PM
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Join Date: Apr 2011
Location: SF East Bay
Posts: 852
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I was cruising down the Q routes between LA and FL one night in clear smooth air at 450 on top of a pretty good set of storms when we got nailed by lightning coming up from below. No obvious damage or issues as a result but we took the airplane to the manufacturer in KSAV for a lightning strike inspection. They found the entry and exit holes in the lower radome and top of the tail respectively. After repairing these small holes, checking all the filters etc we were on our way. I don't recall the interval or duration but for a period after that we did follow up filter checks at home for a while in accordance with the maintenance manual.
Fixing the obvious might not be your only damage. Look everything over very carefully and monitor your filters for a while.
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07-08-2011, 06:30 PM
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Join Date: Sep 2008
Location: Windsor, Ca
Posts: 129
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Entry or Exit Wound
Lightning usually starts on the ground and sends a streamer up into the atmosphere, so the melted metal on the VS most likely is an exit rather than an entry wound. There may be more damage where ever the plane came into close contact with the ground.
__________________
Mike Shook, RV-9A, Dynon HDX,
CPI-2 Ignition, Catto Prop, EAA 124
Last edited by mfshook62 : 01-25-2014 at 04:29 PM.
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07-08-2011, 08:57 PM
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Join Date: Jun 2006
Location: 8I3
Posts: 3,564
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http://wiki.answers.com/Q/Why_does_l..._a_jagged_path
As I recall there are more things that come into consideration with high voltage/low current discharges (ionization) which makes it not behave like a typical parallel circuit.
As a side note, aircraft plugs don't fire off of both electrodes no matter how closely matched they are.
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Please don't PM me! Email only!
Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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07-09-2011, 12:28 PM
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Join Date: Aug 2007
Location: Wichita Falls, TX
Posts: 2,182
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Wheel bearings can also suffer damage from a lightning strike. If a lightning bolt has just cruised thru 10,000 feet or more of the atmosphere, that couple inches of rubber tire does not make diddly squat of an insulator to stop it from going all the way down thru the landing gear.
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Neal Howard
Airplaneless once again...
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07-09-2011, 12:41 PM
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Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
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Now that I think about it..
Quote:
Originally Posted by mfshook62
....Lightning usually starts on the ground and sends a streamer up into the clouds, so the melted metal on the VS most likely is an exit rather than an entry wound. .
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I should have realized that lightning starts from the ground, since it's the negative pole, so the tiedowns (Roee) were the path of least resistance for starters, travelling upwards to the positive sky, exiting the highest of the three prop blades, in this case.
Best,
__________________
Pierre Smith
RV-10, 510 TT
RV6A (Sojourner) 180 HP, Catto 3 Bl (502Hrs), gone...and already missed
Air Tractor AT 502B PT 6-15 Sold
Air Tractor 402 PT-6-20 Sold
EAA Flight Advisor/CFI/Tech Counselor
Louisville, Ga
It's never skill or craftsmanship that completes airplanes, it's the will to do so,
Patrick Kenny, EAA 275132
Dues gladly paid!
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07-09-2011, 03:04 PM
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Join Date: Aug 2008
Location: Tehachapi,CA
Posts: 131
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Lightning can travel from ground to cloud or it can go the other way.
(negative lightning or positive lightning)
read the wikipedia page about lightning, you will see that it is more complex then a big spark from the sky.
bottom line is a large current flowed through the plane. even if you find the exit point you still don't know what it flowed through. lucky most of the time in a metal airplane the current flows in the skin, that is why an airliner can get hit and nothing happens on the inside.
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07-10-2011, 07:45 AM
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Join Date: Oct 2008
Location: Montreal
Posts: 12
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Interesting discussion.
I work as an aircraft maintenance engineer for a Canadian airline and I get to see aircraft that were hit by lightening almost every month. On Airliners, everything is bonded via bonding cables in order to dissipate static electricity and to give an easy alternate path to any static electricity that might otherwise travel through bearings.
Rarely do we ever find large damage. Usually an entry point is found with an exit point and in the worst cases, the electricity dances in and out along the fuselage giving us multiple entry and exit points. It is usually a matter of replacing a few rivets when damage is found but most strikes cause no harm at all due to the designs of the aircrafts.
?ric
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07-10-2011, 02:05 PM
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Join Date: Jun 2008
Location: Dallas, TX
Posts: 23
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Quote:
Originally Posted by John Clark
Some years ago we had a C-150 sustain a lightning strike on the rudder. The rudder was "welded" in position, stuck. Safe landing, but a tough thing to taxi.
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Quote:
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On Airliners, everything is bonded via bonding cables in order to dissipate static electricity and to give an easy alternate path to any static electricity that might otherwise travel through bearings.
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Aha! I always wondered about the true purpose of the bonding braids on control surfaces!
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07-10-2011, 04:32 PM
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Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
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We used bonding braids.
Years ago, when we dusted with sulphur, we had to bond our control surfaces to reduce static electricity generated by the ailerons, elevators and rudder, as the air flowed over them. There were reports of airplanes catching on fire as the sulphur fire followed the airplane in the field, all the way to the hopper
The hinges often didn't/don't provide a good current path because of paint, nylon bushings in Heim joints and so on.
Best,
__________________
Pierre Smith
RV-10, 510 TT
RV6A (Sojourner) 180 HP, Catto 3 Bl (502Hrs), gone...and already missed
Air Tractor AT 502B PT 6-15 Sold
Air Tractor 402 PT-6-20 Sold
EAA Flight Advisor/CFI/Tech Counselor
Louisville, Ga
It's never skill or craftsmanship that completes airplanes, it's the will to do so,
Patrick Kenny, EAA 275132
Dues gladly paid!
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