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Gary Hall wrote:
>....
> There is a very timely and fascinating account "Of Lightning Bolts,
> Sandstorms and Snow" by Gene Spaulding (of the Dallas EAA Chapter 168)
> at:
> http://www.vline.net/eaa168/jun99/jun99.pdf (NOTE: not online, if
> anyone knows of where this document can be found now, it would be
> appreciated.)
You can find the newsletter in html format (not the PDF file) at:
http://web.archive.org/web/20001012085036/www.vline.net/eaa168/jun99/jun9907.htm
Since it takes awhile to get to this page, I've taken the liberty of
putting the text below.
(Note the first part of the URL -- web.archive.org --) You can use this
site to find old web sites that have disappeared, just as I did for this
article. Not something you do everyday, but just the ticket when going
after a site that has demised or deleted the information you are after.
It doesn't have everything, but it is very surprising how much it does
have.
Regards,
Charles R. Patton
N360JM
*****************
OF LIGHTNING BOLTS, SANDSTORMS AND
SNOW
Gene Spaulding N18GS
This is written especially for all the plastic airplane drivers and also
for those with large plastic canopies on metal airframes a la RVs.
First, a little history. In the ancient 50's the Air Force had a new jet
fighter called "the P-80 Shooting Star'. In two years time, squadrons
training in West Texas, New Mexico and Arizona had an unusually high
accident rate with many fatalities. The usual safety investigations had
failed to turn up any positive reasons for the crashes. In early 1954 a
P-80 was found gear up and intact in the sand at the White Sands Missile
Range, the plane was basically undamaged, but the young Air Force
Captain was dead. The fuel tanks were empty and the electrical system
and radios were burned out. The cause was remaining a mystery until a
detailed autopsy on the pilot found a small hole about the size of a pin
from the top of his skull to underneath the jaw. A re-look at the P-80
revealed some dark area in the top of the canopy and the pilot's Gentex
helmet had a small hole through the helmet that corresponded with the
hole in the pilot's skull. The final accident report listed the cause of
the accident as: "electrically incapacitated pilot loosing control of
the aircraft causing premature arrival at the ground" (You have very
little control when you are dead).
The company I worked for at the time received a contract to instrument a
new P-80 from Lockheed along with a companion two-place T-33. The plan
was to fly them around in the Southwest and take some voltage
measurements. One afternoon early in the program the P-80 landed after
skirting around a thunderbumper hanging north of the field at
Albuquerque. The approach also took the pilot thru a nice dust devil
cloud off the end of the runway. After rollout and taxi back to the ramp
prior to the pilot opening the canopy we measured the voltage on the
canopy compared to the metal airframe and it measured 2.53 million
volts! A charge had built up on the canopy from the electrical field
surrounding the thunderbumper and also the dust cloud. We discharged the
canopy with a lead pencil before the pilot got out and the arc set the
wood pencil on fire. At this point our intrepid civilian test pilot
decided that selling insurance was now his chosen profession and we
began the search for a new pilot. Before the next series of flights we
installed a four-inch square of copper screen in the top of the canopy
with tape and ran a wire from the screen to the metal canopy frame. By
this time the Air Force was in full panic mode and grounded all the
P-80s and T-33s until a copper wire grid was installed with a ground
wire to the canopy frame. The specification for the standard Gentex hard
hat was changed to require each production helmet be subjected to
5-million volt 'Hi-Pot test prior to acceptance. That winter further
flights in some snowstorms produced the same high voltages on the
canopy. At this point it was agreed that the culprit was precipitation
static caused by dust or snow in the flight path. To this day all
military aircraft with plastic canopies have a wire grid tied to the
frame and grounded. Flight helmets still get 'hi-potted'.
Now I know we homebuilt airplane drivers don't go flying our pride
and joy around in thunder, dust, or snow storms but I installed some
thin copper tape in the canopy and windshield frames and tied these to a
ground plane on my Glasair. In addition, all metal parts (yes, there are
some in a Glasair) were bonded together to the engine which was tied
with a large gauge wire back out to a static discharge wick on the wing
tip. The whole set-up weighed nine ounces installed. In my many trips
back and forth to California I have flown thru a few dust storms and
even one snow storm in far West Texas and I never worried and I didn't
have on a Gentex helmet either.
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