Having seen the signs of many lightning strikes on commercial aircraft,
I can say the damage it does is dependant on the path it takes through
the aircraft.
In the vast majority of cases it goes in somewhere in the upper half of
the nose section and goes out at the wingtips or the tail.
If the aircraft is set up right, it will only produce tiny burn spots in
the nose skin or melt a fraction of a rivethead and nothing out of the
rear as there is metallic bonding leads to control surfaces and static
dischargers bonded to the structure with conductive paste and rivets.
An added nuisance can be the tripping of contactors and generators and
occasionally a change in residual magnetism around the stby compass.
I have seen flight crew come out of the cockpit, white in their faces of
terror after being hit by series of lightning expecting to see the tail
half fallen off, only to find the above mentioned minor damage on
subsequent inspection.
Failing to do it right can burn out secondary and tertiary structure and
composite around the trailing edges.
The path it should take is through the metallic fuselage and this is
where we have a problem, Beechcraft approached it thus on their first
civilian composite aircraft by placing a very fine metallic mesh in the
surface of the skins. (Skins made of conductive carbonfiber that
otherwise would take the full current right through all the structure,
hence the extra preoccupation.)
Recent know-how of lightning shows that an object such as a tower will
try to build up a static charge in a storm and if it is not well
grounded, (I think it was to be less than 15 ohms) the charge will build
up and up until the lightning strikes.
That shows theres truth to the old wivestale that says you should
throw yourself to the ground, if you feel your hair raising during a storm.
Static charges are supposed to dissipate through the needle points of
the static dischargers as already said, I had the case of a Fokker 27
that would lose all communications every time it flew through cloud at
less than 0C when flying freight at night in central Germany. Needless
to say the controllers were getting rather peed off after a few nights,
so we pulled it out of service.
The problem was found to be in broken bonding leads to an elevator.
The point is, that the only time there was sufficiently static to start
arcing in the bearings was when flying through ice crystals.
As it is difficult to quantify such things, I would consider embedding
metallic foil or using conductive paint in certain areas, if I was to
skirt a lot of storms. It should get rid of any build-up, leaving only
the strikes that happens anyway- I wont do that though!
Alex, kit 529:
> Wings to be closed, rudder and ribs to fit, engine and instruments to
> buy and fit...paint and upholstery........and then all the little
> things on the wishlist!
> (Glider quality finish, magnetic fuel level indication, lots of clever
> and light glass in the panel, an emergency pop out ram air generator
> and a rubber band aileron trim..I will probably have to wait a few
> years for the Stirling engine to be available so the 912S and VP prop
> is going to drive it in the beginning )
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