Hi, all --
I came across this recently and think others may
find it interesting, especially as it relates to
composite aircraft.
It concerns the official investigation into a
lightning strike on a glider in the UK last year.
The narrative goes into extensive detail of
exactly what happens when the lightning arcs or
travels along any metal it can find, such as the
internal control system. For example, it's not
the maybe 200,000 amperes of electricity that's by
itself harmful (although sufficient electrical
resistance in, say, a torque tube assembly can
vaporize it), but any arcing in free air (foam
even?) within the structure creates ionized gases
that can reach 50,000 deg. F in a few
microseconds. That's also known as an explosion,
and it can and did blow the aircraft apart at the
bonded seams. Fortunately the occupants had
chutes and were able to hit the silk (canopy blew
off too), but maybe lost some hearing due to the
massive over-pressure.
Very fascinating. See:
www.open.gov.uk/aaib/dec99htm/bga3705.htm
Regards,
Fred Fillinger, A063
N3EU
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