For what i understand of lighning and it's effect on composite aircraft it
works like this:
Lightning will take the shortest route between the negative and the
positively charged area if the voltage is large enough to ionise the air
in the gap. A metal airplane will occasionally shorten that gap as will a
metal pushrod in a composite with the result of a lightning strike. The
current will flow and heat will be produced on the outside of the conductor
causing an explosionlike expansion of air. In case of a metal plane, it
will be nasty, but survivable. In case of a pushrod, it will blow
everything around the pushrod to smithereens. In my meteorology book the
advice about thunderstorms is to avoid them by at least 10 nm, and at
higher altitudes by 20 nm or more! because of windshear, turbulence, icing,
hail, reduced visibility, lightning and interference to radio and radio
nav. Thinking about the 10 to 20 nm distance, i guess that this order of
thunderstorm dangers is the realistic one.
Jos Okhuijsen
Paul Atkinson <paul@theatkinsons.demon.co.uk> kirjoitti Mon, 15 Dec 2003
> <paul@theatkinsons.demon.co.uk>
>
> I am very hazy about the science of all this, so don't quote me, but
> metal aircraft rely on good bonding to ensure that lightning has
> somewhere to go without affecting the contents (i.e. passengers, radios
> etc). As Carl suggested, I assume that the presence of metal in a
> composite aircraft can have disastrous effects because there is nowhere
> for the energy to go once it has entered.
>
> My "Handbook of Aviation Meteorology" suggests that lightning strikes can
> occur anywhere if the conditions are right, even in clear air, though
> much more likely in CBs. It also suggests that a good way of attracting a
> strike is to trail a long aerial or cable out the back :-).
>
> The only strike I have had, happened flying through an innocent looking
> cu (it was no more than 2000' in extent). Our passage through it set it
> off, and all the others nearby.
> Existing thunderstorms are not too difficult to avoid but we have no way
> of telling when the conditions might be right in other circumstances.
>
> So I have a fairly fatalistic approach to this, in that if my Europa is
> struck by lightening it probably won't do me much good, but on the other
> hand the chances of that happening are relatively slim, particularly
> flying VFR most of the time. On the other hand I am more concerned about
> the turbulence that CBs produce. Even a quite small CB can produce enough
> turbulence to make flying a light aircraft very difficult, not just in
> the cloud; windshear near the ground can seriously damage your health.
>
> Paul Atkinson
>
> ps I heard a story once about a metal glider that broke an altitude gain
> record in Argentina. The pilot thermalled into the base of a CB. When he
> regained conciousness the tail of his aircraft was at an odd angle but it
> was still flyable. The barograph, which had been running, showed that he
> had broken a record by a considerable margin. I suspect that he would
> have enjoyed the experience far less if he had had his oxygen mask on.
>
>> From: n3eu@comcast.net
>> Subject: Re: Europa-List: Lightning Strikes to Composite Aircraft
>>
>>
>>> Hi All,
>>> According to the AAIB at the last PFA Rally at Kemble, aircraft do not
>>> attract lightening, so it will only strike if the aircraft flies
>>> through the
>>> path of lightening when it is already travelling. This is my
>>> understanding
>>> of what was said. I therefore try to give CBs a wide birth.
>>> Regards,
>>> William
>>
>> Perhaps the AAIB guy didn't come across so clearly, or the "dog ate his
>> homework."
>> The below research document is long and technical, but the very first
>> sentence
>> will do: "Not until the 1980's was it convincingly demonstrated that the
>> vast majority of lightning strikes to aircraft are initiated by the
>> aircraft,
>> as opposed to the aircraft's intercepting a discharge in progress."
>>
>> http://plaza.ufl.edu/rakov/ProgressinAerospaceSciencespaper.pdf
>>
>> Regards,
>> Fred F.
>>
>>
>
>
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