While we are on the subject of Lightning. I found this old email
and was greatly interested in the 2.53 million volt differential
between the canopy and metal airframe. I don't plan on penetrating
any big storms, but I experienced a severe case of Saint Elmos Fire
back in Monterey CA some 30 years ago in relatively light rain at
night. So it could happen without getting into trouble with the
big iron, so to speak.

Anyway, here it is in part.

>From an email back in Jun 1999, "Marvin Hamm" <mjhamm@home.com>
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.)

It is a one page article included on page 7 of the current June
newsletter (in pdf format).   It is very well worth reading on the
subject of static discharge through plastic canopies from buildup of
static electricity due to simply flying in the vicinity of thunderstorms
or buildups, or flying through "precipitation static sources" such as
dust or snow.

This was discovered in 1954 while investigating a series of fatal
Lockheed P-80 accidents---and resulted in the Air Force grounding the
plastic canopy with a 4 inch square copper wire grid.  ( Tests had
revealed a 2.53 million volt differential between the canopy and metal
airframe ! )

Gene says that he has installed thin copper tape in the canopy and
windshield frames and tied them to a ground on his Glasair.  In
addition, he reports that he has further tied all metal parts to the
engine and used heavy gauge wire back out to a static discharge wick on
the wing tip.  (total setup weighed nine ounces)

Thanks.


Gary Hall, FXE
http://www.uslan.com/hinge-kit.html