GIF of plane hit by lightning

GIF of plane hit by lightning:
http://bm6aak.myweb.hinet.net/file/456.gif
(Lightning hits planes everyday and is no big deal.)

On Mon, 31 May 2004 01:25:24 +0800, Dan Jacobson
wrote:

GIF of plane hit by lightning:
http://bm6aak.myweb.hinet.net/file/456.gif
(Lightning hits planes everyday and is no big deal.)

That's intense/disconcerting/cool and a million other adjectives all
rolled into one!

z

Dan Jacobson wrote:

GIF of plane hit by lightning:
http://bm6aak.myweb.hinet.net/file/456.gif
(Lightning hits planes everyday and is no big deal.)

What it clearly shows is that airplanes do not get "hit
by lightning". What actually happens is that a lightning
bolt already headed from ground to cloud sometimes
makes a small detour through a conductive object (airplane)
if it happens to be where the lightening bolt may have gone
anyway.

There are billions of volts cloud-to-ground before the strike.
Once the air in the lightning bolt path is ionized, the
current that flows is only a few thousand Amps.
A metallic aircraft, if it becomes part of the current path,
has a max voltage drop across it of only a few hundred volts.

The airplane is self-protected in the same way as installing
a #8awg copper wire from a "lightening rod" from the roof of
a barn, around the outside of the barn, to a ground rod.
During a strike, the potential from tip of the lightening
rod to the ground under the barn is constrained to a few
hundred volts... This keeps the destructive current path out
of the wood; it flows along the copper wire instead of in the
wood.

Dont try this with a plastic, composite or wood aircraft.
The current pulse instantly turns absorbed moisture into steam,
literally blowing the aircraft apart.

MikeM

"MikeM" wrote in message
...
Dan Jacobson wrote:

GIF of plane hit by lightning:
http://bm6aak.myweb.hinet.net/file/456.gif
(Lightning hits planes everyday and is no big deal.)

What it clearly shows is that airplanes do not get "hit
by lightning". What actually happens is that a lightning
bolt already headed from ground to cloud sometimes
makes a small detour through a conductive object (airplane)
if it happens to be where the lightening bolt may have gone
anyway.

There are billions of volts cloud-to-ground before the strike.
Once the air in the lightning bolt path is ionized, the
current that flows is only a few thousand Amps.
A metallic aircraft, if it becomes part of the current path,
has a max voltage drop across it of only a few hundred volts.

The airplane is self-protected in the same way as installing
a #8awg copper wire from a "lightening rod" from the roof of
a barn, around the outside of the barn, to a ground rod.
During a strike, the potential from tip of the lightening
rod to the ground under the barn is constrained to a few
hundred volts... This keeps the destructive current path out
of the wood; it flows along the copper wire instead of in the
wood.

Dont try this with a plastic, composite or wood aircraft.
The current pulse instantly turns absorbed moisture into steam,
literally blowing the aircraft apart.


Some occasional exceptions. One DC-10 I worked
had a real interesting bit of artwork after a strike. Along
the left side there was a splotch about three feet long as
if some artist had painted a jagged line with his paintbrush.
On closer exam, the splotch consisted of pitted and melted
aluminum.
Back when the Weather Radar (AVQ 10/30) used a parabolic
dish for a scanner, the scanner bearings could get welded solid.
The scanner probe consisted of an approx. 4 inch long 1/4 inch
diameter alloy rod for a probe. This rod was encapsulated into
a solid 3/4 inch Teflon cylinder. After a strike this Teflon could
look like a bit of Swiss cheese or a bad case of termites.

JK

In article ,
"Jim Knoyle" wrote:

"MikeM" wrote in message
...
Dan Jacobson wrote:

GIF of plane hit by lightning:
http://bm6aak.myweb.hinet.net/file/456.gif
(Lightning hits planes everyday and is no big deal.)

What it clearly shows is that airplanes do not get "hit
by lightning". What actually happens is that a lightning
bolt already headed from ground to cloud sometimes
makes a small detour through a conductive object (airplane)
if it happens to be where the lightening bolt may have gone
anyway.

There are billions of volts cloud-to-ground before the strike.
Once the air in the lightning bolt path is ionized, the
current that flows is only a few thousand Amps.
A metallic aircraft, if it becomes part of the current path,
has a max voltage drop across it of only a few hundred volts.

The airplane is self-protected in the same way as installing
a #8awg copper wire from a "lightening rod" from the roof of
a barn, around the outside of the barn, to a ground rod.
During a strike, the potential from tip of the lightening
rod to the ground under the barn is constrained to a few
hundred volts... This keeps the destructive current path out
of the wood; it flows along the copper wire instead of in the
wood.

Dont try this with a plastic, composite or wood aircraft.
The current pulse instantly turns absorbed moisture into steam,
literally blowing the aircraft apart.


Some occasional exceptions. One DC-10 I worked
had a real interesting bit of artwork after a strike. Along
the left side there was a splotch about three feet long as
if some artist had painted a jagged line with his paintbrush.
On closer exam, the splotch consisted of pitted and melted
aluminum.
Back when the Weather Radar (AVQ 10/30) used a parabolic
dish for a scanner, the scanner bearings could get welded solid.
The scanner probe consisted of an approx. 4 inch long 1/4 inch
diameter alloy rod for a probe. This rod was encapsulated into
a solid 3/4 inch Teflon cylinder. After a strike this Teflon could
look like a bit of Swiss cheese or a bad case of termites.

JK

OK, but all of these verify what I think I know about lightning - it is
a very high frequency phenomena and will tend to only flow through the
skin of the conductor. So while it may mark or weld exterior
attachments, interior "stuff" - instrumentation; people; etc. will be
quite safe.

(And as for the wooden or plastic aircraft, wouldn't the qualities of an
aircraft to attract lightning in the air be mostly to be a better
conductor than non-ionized air? And mostly for cloud to cloud strikes?
So I'm unclear on how good an electrical conductor this stuff would be.
And how about titanium - like in "Blackbird"?)

HR.

"Rowbotth" wrote in message
...

OK, but all of these verify what I think I know about lightning - it is
a very high frequency phenomena and will tend to only flow through the
skin of the conductor. So while it may mark or weld exterior
attachments, interior "stuff" - instrumentation; people; etc. will be
quite safe.

(And as for the wooden or plastic aircraft, wouldn't the qualities of an
aircraft to attract lightning in the air be mostly to be a better
conductor than non-ionized air? And mostly for cloud to cloud strikes?
So I'm unclear on how good an electrical conductor this stuff would be.
And how about titanium - like in "Blackbird"?)


Tend to agree with you as for the safety of the passengers but an
occasional lightning strike helped keep us avionics types employed,
not to mention the A&P and his sheetmetal skills. He also may get
to degauss a windshield frame or some area that can put a very
noticeable error into the standby magnetic compass. If a localized
degaussing won't handle the problem, moving the whole aircraft into
a special degaussing area should. Then we'd get to re-swing the
compass(s).
My knowledge may be a bit dated. Welded radar scanners and
zapped radar receiver crystals may be something that is not a
problem with newer designs that use much less radiated power.
I've replaced a bunch of HF radio lightning arrestors after a strike
rendered those systems inop but I wouldn't be surprised to learn
that SatCom has replaced HF radio. I don't know.
Anybody noticed any of those long trailing antennae from the tips
of the wings of newer overwater 747s? With other AC usually
using the vert stab leading edge, it's harder to spot. Guess I'll just
tune up some of our old company freqs on my scanner.
Bottom line: They have two or three (or more) of all the important
bits on the aircraft.

JK ( Just tuned in 5,574 Mhz HF and heard the old familiar SelCal )

Now the thing to be worried about is St. Elmo's Fire... I have read some
strange things on this phenomenon, including a seasoned aircarrier pilot
seeing a floating ball of blue light which passed right through him.... Go
check it out your self..
http://www.physics.northwestern.edu/...lightning.html
"Jim Knoyle" wrote in message
...

"Rowbotth" wrote in message
...

OK, but all of these verify what I think I know about lightning - it is
a very high frequency phenomena and will tend to only flow through the
skin of the conductor. So while it may mark or weld exterior
attachments, interior "stuff" - instrumentation; people; etc. will be
quite safe.

(And as for the wooden or plastic aircraft, wouldn't the qualities of an
aircraft to attract lightning in the air be mostly to be a better
conductor than non-ionized air? And mostly for cloud to cloud strikes?
So I'm unclear on how good an electrical conductor this stuff would be.
And how about titanium - like in "Blackbird"?)


Tend to agree with you as for the safety of the passengers but an
occasional lightning strike helped keep us avionics types employed,
not to mention the A&P and his sheetmetal skills. He also may get
to degauss a windshield frame or some area that can put a very
noticeable error into the standby magnetic compass. If a localized
degaussing won't handle the problem, moving the whole aircraft into
a special degaussing area should. Then we'd get to re-swing the
compass(s).
My knowledge may be a bit dated. Welded radar scanners and
zapped radar receiver crystals may be something that is not a
problem with newer designs that use much less radiated power.
I've replaced a bunch of HF radio lightning arrestors after a strike
rendered those systems inop but I wouldn't be surprised to learn
that SatCom has replaced HF radio. I don't know.
Anybody noticed any of those long trailing antennae from the tips
of the wings of newer overwater 747s? With other AC usually
using the vert stab leading edge, it's harder to spot. Guess I'll just
tune up some of our old company freqs on my scanner.
Bottom line: They have two or three (or more) of all the important
bits on the aircraft.

JK ( Just tuned in 5,574 Mhz HF and heard the old familiar SelCal )