Original poster: boris petkovic <petkovic7@xxxxxxxxx>
Hi All,
This is bit off topic.Hopefully,Terry will let it go.
Many of You have probably heard of the recent Airbus
crash in Canada,near Toronto airport.
It was the accident with happy ending - miracle that
all the passangers made it out alive before the flame
escalation.
Some investigators speculate the cause of the crash
was the lightning since heavy thunderstorm was going
on in the area.
Lightning or not,I'd like to raise few points
regarding that matter.
First of all,how lightning initiated by aircraft can
be the cause of potentialy fatal accidents like
that?Having in mind that commercial aircrafts are
designed to be "lightningproof" and rigorous test
standards for commercial aircraft and aviation
equipment generally:
http://www.sae.org
Perhaps,situations in reality are way too complicated
to be imitated by voltage pulse generators tests-and
that can sometimes lead to different outcome of the
process?
Inspite of huge action integrals ,or specific
energies, (like 3MJ/ohm) and peak currents of 200 kA
in aircraft test standards,seems that danger is still
underestimated.How?
Lightning is a multicomponent transient,especially the
one ignited by a conducting object not attached to the
Earth.Bidirectional/bipolar leader phase development
could change triggered lightning pulses having other
(unexpected) consequences.
IIRC,URL to videoframes of a lightning strike to
Boeing during take off from an airport in Japan have
been posted before to TCML,clearly showing upward and
downward branched leader structures lounched by the
plane.
That plane survived the lightning event without damage
,as well as Apollo 12 spacecraft in 1969. did too.
But Boeing 747 struck in 1975 near JFK airport (NY)
and Lockheed jumbo jet near Dallas in 1985. did
not.Hundreds of passangers got killed.
Quite probably, most of the discharges relating
lightning and airborne vehicles go through the stage
of transient similar to that observed in inital stages
of so called altitude rocket-triggered lightning.
The latter has been well studied.It is one of popular
techniques to trigger lightning and is employed by
lightning researches in USA ,France,Japan (rocket and
wire techniques).
However,something remains mysterious about lightning
discharges to flying aircrafts.
According to eyewitnesses ,they have strange
properties of being very bright (almost blinding) and
they produce explosive booms sometimes accompanied by
sounds reminding of artllery salvos.
This is not characteristic for usual lightnings.
IOW,it appears such lightnings often involve large
charge transfers and very high action integrals.
Some airborne vehicles lightning accident reports can
be found in:
http://plaza.ufl.edu/rakov/ProgressinAerospaceSciencespaper.pdf
To keep this post tesla coil related,it would suffice
to mention suggestion of some researches to use large
TC to simulate arc attachment process to an
aircraft.Energy per pulse,even in the largest TC built
to date,is way too small and some other things are
inadequate if compared directly with lightning.
Nevertheless,if employed in connection with set of VP
generators capable of subsequent discharging under
control ,powerful TC may find important application in
HV testing of airborne vehicles.
The test facility for these purposes would have a
massive physical size (and great cost of cost).
On the other hand,constructing of the facility is
technically viable today I guess.
Findings relating mechanisms of lightning-aircraft
interaction may turn to be benefical to the lightning
protection science.
Comments,suggestions,critics are welcome;
Regards,
Boris