David Joyce wrote:
> ...
> Paul's experience strongly suggests that the fitting of a
> ground wire from wing tip to wing tip gives a significant
> degree of protection.
> I had been thinking of retro-fitting nav lights when/if UK
> Permit privileges are extended, but this makes me feel that
> it would be worth getting on with it soonest.
I think we need to be careful with words like "significant." I have
relevant tech documents by the experts, plus reports of other
incidents to composite aircraft with lighting systems, and it seems
lightning enters/exits/or doesn't as it wishes.
It is true that the tips of the 4 aircraft extremities are involved in
almost all incidents for known reasons. What I cannot find is
anything suggesting that adding wire out to the tips (into the
relevant "Zone 1A" as they call it) will makes things safer. If
lightning sees nowhere to travel from a tip in the pre-events
preceding the actual electrical discharge, it may just do nothing.
Seems to me that if the answer were as simple as heavy gauge wire
sufficient for many kiloamperes -- from the 4 extremities and easily
calculated to be a safe arcing distance from other metal -- were a
solution, it would be an attractive one. But the only approved
solution after all the research and testing done is metal mesh in the
skins.
The other thing about a ground and hot wire doing such double duty is
that it's connected to many other wires. In my case, this includes
the sender in the fuel tank. Paul has sent me add'l "forensic"
tidbits concerning his strike, and it seems these pathways may have
whacked an avionics box and the battery contactor.
In the famous UK glider incident, it involved a metal aileron control
tube extending out to within Zone 1A. On an unlighted Europa, the
metal extends only out to about 60% of semispan, electrically miles
away from this zone.
I also have a doc which suggests one incident, and Paul's, was only a
little "streamer," not the full bolt. Likely also the one I
encountered years ago. Hence, minimal physical damage.
Reg,
Fred F.
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