REFLECTOR: Re: Lightning strike

["Simon Aegerter [KPIE]" <100256.3710@compuserve.com>]

> I had a bolt of lightning hit my plane while it was on the ramp.  Do
> glass airplanes have a greater chance of being hit by lightning or is
> this just bad luck?  

Let's take a look at the physics of lightning:

what decides where the bolt strikes? Electric field, that's what. The electric
field is essentially voltage divided by distance of the charges. However, it is
not really that simple: on the surface of a charged conductor the field
strength is inversly proportional to the radius of curvature of that surface.
If that conductor is a point like spike, the field can get so strong that the
insulation of air (or epoxy) breaks down and a small volume of ionized air
ensues. If it stays that way, it is called St. Elmo's fire. It may develop into
a "leader", rapidly (with lighntning speed, actually <g>) growing towards the
opposite charge (in the clouds) and initiate a strike.

The copper strip antennas in the wings and winglets have pretty sharp corners
and even if they are not grounded, an induced charge will develop and that
could be enough to create a "leader". I don't know if spam cans have similarily
sharp spikes.

I have been shown a winglet that was struck on the ramp. Makes me shudder to
think that this happened inflight. The sight convinced me to spend the money
for a Strike Finder.

my $ -.02

Best
Simon