lightning stikes a ASK21

There is an article in this month of "Business & Commercial Aviation"
regarding lightning.

It says that in 1999, a ASK21 desintegrated large sections of the
fuselage, while flying in clear air, about 800 yards from a cloud.
Both pilots were ejected from the strike, but fortunately were wearing
parachutes.

The same article goes on to say fiberglass, especially carbon fiber is
conductive. So if you are on the ground and a thunderstorm is over the
airport, to seek shelter inside a building and NOT inside the glider
which has no protection.

Has nayone heard this before? Do you know someone who had a lightning
strike in a glider before?
I am just curious as I never heard of this before.

"jeplane" wrote in message
ups.com...
The same article goes on to say fiberglass, especially carbon fiber is
conductive. So if you are on the ground and a thunderstorm is over the
airport, to seek shelter inside a building and NOT inside the glider
which has no protection.

I have real problems with this statement. Caught in a storm, I would want the
most conductive shell possible around my vulnerable, conductive body. I would
think that an aluminum airframe, being highly conductive, would be perfect.

I thought that the problem with fiberglass was that it was not sufficiently
conductive, which can lead to instantaneous overheating and in-flight structural
destruction.

Vaughn

I witnessed this accident in which a London Gliding Club K21 was destroyed
in mid-air by what was later found to be an exceptionally powerful lightning
strike. Indeed, the strike was many times more powerful than the most
energetic that commercial aircraft designers typically allow for when
specifying composite components for their aircraft. The pupil, who was a
member of the public on a one day gliding course, parachuted out
successfully, while the instructor suffered minor injuries on landing from
the jump. He was back flying a few weeks later, none the worse for wear, and
continues to fly at the club.

The lightning entered one wing of the glider at roughly the point where the
aileron actuator connects to the aileron, and exited from approximately the
corresponding location on the other wing. The effect was to drive an immense
electrical current though the metal push-rods and other metal fittings in
the fuselage, some of which were vaporised, or else melted and severely
distorted. The effect of this current was to generate a massive amount of
heat which caused the explosive expansion of the air inside the wings. This
stripped the skin off a large part of the wings which, of course, are not
designed to withstand loads that are essentially trying to inflate the wing
from within and peel the skin away from the spar.

The UK Air Accident Investigation Branch took a considerable interest in
this event, not least because a senior investigator happens to be a member
of London Gliding Club and an extremely detailed analysis was published by
them later. This includes a fascinating account of the mechanism of
lightning strikes on aircraft. The UK AAIB report can be found he
http://www.aaib.dft.gov.uk/cms_resou...pdf_500699.pdf. The
accident also attracted the attention of various airlines and aircraft
manufacturers who were interested in the implications for composite
components of commercial airframes.

Contrary to jeplane's quote from Business & Commercial Aviation, the AAIB
report specifically says (in referring to GRP with foam or honeycomb filled
sections bonded together) that "These materials are electrically
non-conductive." Later on it says "In aircraft or gliders constructed from a
non-conducting material such as GRP, the lightning arc is likely to attach
to the extremities of any linked conducting components within that
structure". It was very clear from the AAIB examination of the glider that
it was the electrical conduction through the metal parts, and not through
the skin that caused the aircraft to disintegrate as a result of the events
I have described above.

David Starer

"jeplane" wrote in message
ups.com...
There is an article in this month of "Business & Commercial Aviation"
regarding lightning.

It says that in 1999, a ASK21 desintegrated large sections of the
fuselage, while flying in clear air, about 800 yards from a cloud.
Both pilots were ejected from the strike, but fortunately were wearing
parachutes.

The same article goes on to say fiberglass, especially carbon fiber is
conductive. So if you are on the ground and a thunderstorm is over the
airport, to seek shelter inside a building and NOT inside the glider
which has no protection.

Has nayone heard this before? Do you know someone who had a lightning
strike in a glider before?
I am just curious as I never heard of this before.

In article . com,
jeplane writes
There is an article in this month of "Business & Commercial Aviation"
regarding lightning.

It says that in 1999, a ASK21 desintegrated large sections of the
fuselage, while flying in clear air, about 800 yards from a cloud.
Both pilots were ejected from the strike, but fortunately were wearing
parachutes.

The same article goes on to say fiberglass, especially carbon fiber is
conductive. So if you are on the ground and a thunderstorm is over the
airport, to seek shelter inside a building and NOT inside the glider
which has no protection.

Has nayone heard this before? Do you know someone who had a lightning
strike in a glider before?
I am just curious as I never heard of this before.

I would have thought that if fibreglass was conductive it would protect
you from the Thunder God. But it isn't, at least not to the extent that
it could carry the heavy current a lightening strike produces without
getting hot enough to disintegrate.

The K21 which was destroyed near the London Gliding Club's Dunstable
site had some control rods which took so much current they more or less
exploded, much like a fuse wire when it takes about 50 times it's rated
load. This explosion blew the skin off the wings.

I once read a book about a glider which fell apart in a Cu-nim in
Germany, the pilot was killed because his parachute carried him up to
even higher levels. But I don't know if this was due to lightening, or
over-stressing the airframe. I believe this happened in about 1928.
I wish I could remember the name of the book and its author, it was what
got me into gliding in the first place.
--
Mike Lindsay

we know that GRP (glass fibre) has a low conductivity, is carbon fibre as low?
My understanding was the glues and surrounds of the fibres are the problem, the varios fibres themselves act as a lightglobe type resistor, rapidly heating, then the resins go booooomph.

Any experts?

bagger

I live in the lightning capital of the world, Central Florida. I am
not aware of any incidents here but I think we all pretty much give
the old CuNims a wide margin. I have seen bolts strike out and away
from thunderstorm cells by at least several miles. I believe up to 10
miles would not be too rare. If a nasty one was very near at all, I
would get down.
Craig

On Apr 14, 5:26 pm, Mike Lindsay wrote:
In article . com,
jeplane writes

There is an article in this month of "Business & Commercial Aviation"
regarding lightning.

It says that in 1999, a ASK21 desintegrated large sections of the
fuselage, while flying in clear air, about 800 yards from a cloud.
Both pilots were ejected from the strike, but fortunately were wearing
parachutes.

The same article goes on to say fiberglass, especially carbon fiber is
conductive. So if you are on the ground and a thunderstorm is over the
airport, to seek shelter inside a building and NOT inside the glider
which has no protection.

Has nayone heard this before? Do you know someone who had a lightning
strike in a glider before?
I am just curious as I never heard of this before.

I would have thought that if fibreglass was conductive it would protect
you from the Thunder God. But it isn't, at least not to the extent that
it could carry the heavy current a lightening strike produces without
getting hot enough to disintegrate.

The K21 which was destroyed near the London Gliding Club's Dunstable
site had some control rods which took so much current they more or less
exploded, much like a fuse wire when it takes about 50 times it's rated
load. This explosion blew the skin off the wings.

I once read a book about a glider which fell apart in a Cu-nim in
Germany, the pilot was killed because his parachute carried him up to
even higher levels. But I don't know if this was due to lightening, or
over-stressing the airframe. I believe this happened in about 1928.
I wish I could remember the name of the book and its author, it was what
got me into gliding in the first place.
--
Mike Lindsay

I too live in Central Florida, where overdevelopment and heavy T-
storms are common during the summer months. The power pilots will tell
you to avoid a convective cloud by 10 miles for every 10,000 ft of
cloud tops. I use a simpler formula, if I can't see the sun because a
cloud is blotting it out I go inside and play X-box.

N

The Beech Starship (composite business turbo prop - RIP) had a copper
mesh layer between the layers of fiber glass precisely for lightning
protection. I'm reasonably certain that other like (and larger) aircraft
do too.

Tony V.

"Tony Verhulst" wrote in message
. ..

The Beech Starship (composite business turbo prop - RIP) had a copper mesh
layer between the layers of fiber glass precisely for lightning
protection. I'm reasonably certain that other like (and larger) aircraft
do too.

Tony V.

That's true. Years ago I saw video of "test" lightning strikes (nowhere near
as strong as the real thing) on unprotected GRP composite material and
composite with mesh, done by either Glasair or Lancair. The difference in
size and impact of the damaged area was dramatic. Without the mesh the hole
in the wing was very big. Without the mesh is was just big. If being zapped,
I'd rather be in an aluminum skinned plane.

I understand that carbon fiber explodes when struck even without metal
control rods to heat up and expand the air within the wing. The carbon does
a fine job of heating and turning moisture into steam

bumper

Wasn't there a two-place glider in England destroyed in the air by a
lightening strike? I recall control rods in the wing fused and the
fibreglass "exploded" Both aboard succssfully bailed out -- the
passenger was on his first ride but had been briefed. Good thing, eh?

"Tony Verhulst" wrote in message
...


The Beech Starship (composite business turbo prop - RIP) had a copper mesh
layer between the layers of fiber glass precisely for lightning
protection. I'm reasonably certain that other like (and larger) aircraft
do too.

Tony V.



That's true. Years ago I saw video of "test" lightning strikes (nowhere near
as strong as the real thing) on unprotected GRP composite material and
composite with mesh, done by either Glasair or Lancair. The difference in
size and impact of the damaged area was dramatic. Without the mesh the hole
in the wing was very big. Without the mesh is was just big. If being zapped,
I'd rather be in an aluminum skinned plane.

I understand that carbon fiber explodes when struck even without metal
control rods to heat up and expand the air within the wing. The carbon does
a fine job of heating and turning moisture into steam

bumper





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