Thanks Mike,

When I got my EE degree in 1972 they had not heard of such things, at
least where I went to school! I agree that it would take a lot of amps
to generate a magnetic field strong enough to cause the described damage
to the aileron pushrod.

All this talk of parachutes - I always wear my ram air rectangular
parachute when I fly my glider and I even went to the local jump club to
experience flying and landing one of the same size. It was so much fun
that I made seven jumps but it was too expensive for my tastes (at least
while renting the equipment and paying for the instructor's jumps). He
left the aircraft after I had a good chute.

On 3/18/2015 11:08 AM, Mike the Strike wrote:
Dan:

We know the lightning strike in the British accident was an extremely severe positive ground stroke for several reasons:

1) The EA technology lightning location system identified the likely stroke and estimated its peak current at 80 kA (it could have been higher)

2) The compression magnetic forces that deformed the push rod were extremely large and the effect could not be reproduced in the lab (and several tried!)

3) The quantity of metal melted indicates a very high charge transfer, likely in excess of 200 coulombs.

4) The damage incurred indicated a strike that exceeded the tests used for certification of aircraft and they are pretty conservative.

This was an unusually severe event that is unlikely to be experienced again any time soon. Most aircraft lightning involves fairly low current and low energy air discharges or leaders and it's pretty rare for an aircraft to be involved as part of the circuit in a ground flash, let alone a severe positive one.

If you stay half a mile horizontally away from any active storm cell and keep out of the precipitation shaft you are unlikely to be hit.

Mike (who plays with lightning a little bit)

On Wednesday, March 18, 2015 at 8:43:44 AM UTC-7, Dan Marotta wrote:
Excellent report. What does 'feeling very draughty' mean? Is that
a British idiom? Or does it simply mean he felt a draft?



Would someone please explain to me how only the aileron control
system, and not the adjacent air brake system, being damaged by the
lightening strike indicates that it was a positive discharge? Why
was only one system damaged? Why not both? Why one vs. the other?


I'm only half way through the report but have to leave to fly the
tug. I'll finish this evening.



So far, I think the apparent magnetic deformation of the aileron
control rod indicates a current level not attainable by a negative
strike, hence the assumption of a positive strike. I'm still
contemplating why only the aileron system was damaged. Perhaps
because it extended further into the wing (closer to the tip) and so
took the full current, bypassing the air brake.



Hmmmmmmmmmmmm...




On 3/18/2015 2:51 AM, Justin Craig
wrote:



At 16:55 17 March 2015, Dan Marotta wrote:


Yes, and I wear a chute when I fly my glider, but not when I'm giving
rides in a Grob, Blanik, 2-33, or Lark. Neither do I wear a parachute
when flying the tug and I've had four engine failures while flying tow
planes, in none of which would I have considered bailing out.

Does Poland really require parachutes in gliders? Are passengers with
no training required to wear a parachute?


*** I wonder about the outcome if


one of them should attempt to jump****


You could ask this chap? I suspect he was rather grateful to be wearing a
chute!

http://www.aaib.gov.uk/cms_resources...pdf_500699.pdf








--

Dan Marotta

--
Dan Marotta