ASW 27 destroyed by lightning in trailer

wrote on 9/27/2019 2:47 PM:
Yes Eric it is, Im not sure but I think hes been hit a few times He is definetly our weather guru in AZ. Knows his ****, and we are teally happy when he shows up with a white hat on to the pilots meeting

If he shows up without a hat, does that mean it's too windy for a task?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Saturday, September 28, 2019 at 12:54:10 PM UTC-5, Eric Greenwell wrote:
cliffhilty wrote on 9/27/2019 2:47 PM:

Yes Eric it is, Im not sure but I think hes been hit a few times He is definetly our weather guru in AZ. Knows his ****, and we are teally happy when he shows up with a white hat on to the pilots meeting

If he shows up without a hat, does that mean it's too windy for a task?


A mere "zephyr" must have blown the hat off his head. :-)

Steve Leonard

Reminds me of a "Texas weather checker...".....rock on a chain, etc...etc....

On Saturday, September 28, 2019 at 9:19:03 AM UTC-7, wrote:
From the man who did inspection right after it happened. The fuselage was tilted in dolly. Horizontal stab pins were touching fin box. That is where lightening entered. There is no visible evidence of exit, anywhere. Suspected maybe went down the fin, jumped to trailer and forward out to ground through safety chain that was attached to tie down stake at front of trailer.. Inside of fin was shattered and frayed only partially down from entry point.No visible damage to fuselage. Aircraft was totalled because of these unknowns.

It's interesting that no exit points were identified, but they must exist somewhere, although they may be subtle and hard to find (that's why my job as a lightning forensics expert existed!) In any event, a path to the trailer from the fin must have been established somewhere.

The safety chains would provide a more than adequate ground and could easily have been the lightning path from the trailer chassis to earth. The Royal Navy used chains to protect the masts of sailing ships from lightning, back in the day when there was a British Empire!

My nickname of Mike the Strike was informally known to a few colleagues until it was used in a newspaper headline in the 1970s on a story involving my project to artificially trigger lightning. "Mike the Strike will make it thunder!" The name stuck since then!

Mike

On Saturday, September 28, 2019 at 3:19:14 PM UTC-6, Mike the Strike wrote:
On Saturday, September 28, 2019 at 9:19:03 AM UTC-7, wrote:
From the man who did inspection right after it happened. The fuselage was tilted in dolly. Horizontal stab pins were touching fin box. That is where lightening entered. There is no visible evidence of exit, anywhere. Suspected maybe went down the fin, jumped to trailer and forward out to ground through safety chain that was attached to tie down stake at front of trailer. Inside of fin was shattered and frayed only partially down from entry point.No visible damage to fuselage. Aircraft was totalled because of these unknowns.

It's interesting that no exit points were identified, but they must exist somewhere, although they may be subtle and hard to find (that's why my job as a lightning forensics expert existed!) In any event, a path to the trailer from the fin must have been established somewhere.

The safety chains would provide a more than adequate ground and could easily have been the lightning path from the trailer chassis to earth. The Royal Navy used chains to protect the masts of sailing ships from lightning, back in the day when there was a British Empire!

My nickname of Mike the Strike was informally known to a few colleagues until it was used in a newspaper headline in the 1970s on a story involving my project to artificially trigger lightning. "Mike the Strike will make it thunder!" The name stuck since then!

Mike

We had a 208u10 LPA (HF amplifier) struck by lightning (via LP antenna) at Mildenhall around 1980. Maintenance ordered parts as they found issues and troubleshot their repairs. By the time it was operational again, 100% of the subassemblies were replaced, excluding the chassis. Funny stuff lightning, especially when it travels through radio facilities. Hair raising at times.

Frank Whiteley

On Saturday, September 28, 2019 at 2:31:29 PM UTC-7, Frank Whiteley wrote:
On Saturday, September 28, 2019 at 3:19:14 PM UTC-6, Mike the Strike wrote:
On Saturday, September 28, 2019 at 9:19:03 AM UTC-7, wrote:
From the man who did inspection right after it happened. The fuselage was tilted in dolly. Horizontal stab pins were touching fin box. That is where lightening entered. There is no visible evidence of exit, anywhere. Suspected maybe went down the fin, jumped to trailer and forward out to ground through safety chain that was attached to tie down stake at front of trailer. Inside of fin was shattered and frayed only partially down from entry point.No visible damage to fuselage. Aircraft was totalled because of these unknowns.

It's interesting that no exit points were identified, but they must exist somewhere, although they may be subtle and hard to find (that's why my job as a lightning forensics expert existed!) In any event, a path to the trailer from the fin must have been established somewhere.

The safety chains would provide a more than adequate ground and could easily have been the lightning path from the trailer chassis to earth. The Royal Navy used chains to protect the masts of sailing ships from lightning, back in the day when there was a British Empire!

My nickname of Mike the Strike was informally known to a few colleagues until it was used in a newspaper headline in the 1970s on a story involving my project to artificially trigger lightning. "Mike the Strike will make it thunder!" The name stuck since then!

Mike

We had a 208u10 LPA (HF amplifier) struck by lightning (via LP antenna) at Mildenhall around 1980. Maintenance ordered parts as they found issues and troubleshot their repairs. By the time it was operational again, 100% of the subassemblies were replaced, excluding the chassis. Funny stuff lightning, especially when it travels through radio facilities. Hair raising at times.

Frank Whiteley

Lightning-induced voltages are many KV, so all normal electrical insulators will arc. Lightning rods aren't used to conduct the current of a strike, but to dissipate the high electric field created before the strike, which prevents the strike from occurring (this is why you don't see large gauge wire going to the rod). An old friend did an investigation of how to prevent lightning from striking a building where nuclear weapons were being assembled in Mississippi. He talked to well drillers who had the best lightning rods in the state. They all reported that their rigs had never been struck. Perhaps the pilots in FL should put up lightning rods...

Tom


Tom

2G wrote on 9/28/2019 3:30 PM:
Lightning rods aren't used to conduct the current of a strike, but to dissipate the high electric field created before the strike, which prevents the strike from occurring (this is why you don't see large gauge wire going to the rod).

I've read and heard several times that lightning rod systems can and do conduct a
lightning strike to ground. For example:

"A lightning rod is very simple -- it's a pointed metal rod attached to the roof
of a building. The rod might be an inch (2 cm) in diameter. It connects to a huge
piece of copper or aluminum wire that's also an inch or so in diameter. The wire
is connected to a conductive grid buried in the ground nearby."

https://science.howstuffworks.com/na...lightning7.htm

I'm sure some of them also work as you described, and that the system design
depends on the what's being protected and where it's situated.

On Saturday, September 28, 2019 at 7:48:57 PM UTC-4, Eric Greenwell wrote:
2G wrote on 9/28/2019 3:30 PM:
Lightning rods aren't used to conduct the current of a strike, but to dissipate the high electric field created before the strike, which prevents the strike from occurring (this is why you don't see large gauge wire going to the rod).

I've read and heard several times that lightning rod systems can and do conduct a
lightning strike to ground. For example:

"A lightning rod is very simple -- it's a pointed metal rod attached to the roof
of a building. The rod might be an inch (2 cm) in diameter. It connects to a huge
piece of copper or aluminum wire that's also an inch or so in diameter. The wire
is connected to a conductive grid buried in the ground nearby."

https://science.howstuffworks.com/na...lightning7.htm

I'm sure some of them also work as you described, and that the system design
depends on the what's being protected and where it's situated.

Trying to control lightning is like herding cats. You get it right every now and then...

After fifty years, they mostly gave up driving ground rods for light poles. They realized they are one big waste of time and money. They serve no purpose as to there original intent. Some thought it was to protect from lightning, some to protect humans.

We are installing new lightning protection on a 14 story building. Cost the owner about 100K. Who knows if it makes a difference or not. But, we all feel better knowing it's UL listed and approved! Hopefully, lighting will find those two 37 strand aluminum downlead wires to its liking...

On 9/27/19 6:14 AM, Mike the Strike wrote:


Where the lightning exited the trailer to ground is also not known from the available photos. Many lightning-damaged vehicles I have examined have one or more flat tires, destroyed by lightning current. Tires are not very good insulators - they are black because they are full of carbon and may also have steel wire inserts. Flashover to ground from the axle or wheels is commonly seen in videos of vehicle lightning strikes. Just remember, lightning has traveled around 5 miles through air, which is a pretty darned good electrical insulator - a few inches from trailer to ground is nothing!

The support arms from the trailer dolly to the wing lift pins look like
a possibility for the exit point.

Does anyone know, are all the control rods on the 27 are earthed
together? Does the 27 have a metal subframe like some S-H gliders?

How conductive is carbon fibre? Could a carbon skin carry the current of
a strike without damage (except and entrance and exit points?)

Thanks

Ian

Could a carbon skin carry the current of
a strike without damage (except and entrance and exit points?)

If the entrance was up in the tail, and the exit down low, then from the pictures:

CF appears to be able to carry current because the fluffy stuff is localized to the entrance and the current went somewhere.

But that's a LOT of energy, so for my butt, it seems prudent to assume there was some other, so far unseen, structure damage along the path.

It would be interesting to look over the ground, trailer and then glider in more detail to hopefully find the exit. This might give some clues as to the current path thru the glider.

Also, I wonder if any of the control circuits feel different due to welding at moving joints.