John & Ira , With the greatest of respect for your professional
electrical & aeroengineering backgrounds, I think there are two rather
different issues here:
For certified commercial aircraft lightning protection standards seek
to enclose all passengers and key aircraft components in a Faraday cage
conducting system that will cope with the fairly frequent strikes
affecting commercial operations without any significant damage. To bring
composite aircraft to that standard clearly involves incorporating some
conducting material in the entire surface of the plane and this is a
nonstarter (or at least a non retrospective mod option) for a plane like
ours.
The other issue is the possibility of minimising any damage to a plane
like ours in the event of a lightning strike, ( absolutely going along
with the assertion that it is much preferable to avoid it). There are
three good accounts of fibreglass small aircraft strikes that I have
come across and in every case lightning went from wingtip to wing tip
causing significant damage. These cases are the UK glider, previously
mentioned (www.aaib.gov.uk/cms_resources/dft_avsafety_pdf_500699.pdf
[10] ) , another glider referred to in that AAIB report of the first
glider and the Europa strike suffered by Paul McAlister
(www.sarangan.org/europa_forum/2004-08/msg00094.html [11] ). In each
case the pilot thought he was well clear of threatening clouds it seems.
The gliders had the strike track along the aileron control rods whereas
with the Europa it tracked along the wing tip lights wiring killing a
number of the avionics in passing. I would strongly recommend folk
reading all these reports. Having personally done so I cannot avoid the
conclusions that :
1. Getting struck by lightning is a real possibility for any sensible,
cautious pilot let alone someone contemplating flying through the ITCZ
where rapidly developing massive Cu Nims are endemic
2. Lightning can and will pass from wingtip to wing tip along the most
available conducting track
3. More debateable perhaps but my third conclusion was that there is
much to be said for offering a track that steers clear of vital
structures, and in the light of this I had (in 2006) planned laying
expanded aluminium mesh in the wing close outs connected to aluminium
foil over the wing tip and to the rear lift pins/connecting rod.
Nowadays I would no doubt use Aluminium Microgrid obtainable at modest
cost from Aircraft Spruce. I would not for a moment want to suggest that
this would give commercial plane standard immunity to damage, but that
it would improve the chances of avoiding either the wing exploding or
the loss of avionics or other key electrical systems. I had toyed with
the idea of static diffusers but without a system of conducting static
---From other parts of the aircraft I was not convinced this was workable (
and I guess that this non conductance of static is what saves us from
sparking when we touch ground - we are only discharging the immediate
area of contact.
Regards, David Joyce, G-XSDJ
On 2014-11-14 08:42, John Wighton wrote:
>
> Ira,
>
> You echo may own opinion on this subject. Fortunately my Europa does not seem
to generate a lot of static (of a kind that can be detected at least). There
is not a lot that could be done if it did collect static whilst airbourne.
>
> I had concerns about static build up and discharge on the ground, particularly
whilst fuelling. I adopt the standard procedure of grounding everything to the
same potential by touch, relying on terra firma to act as a ground. So far
there has never been the hint of a discharge even after a vigorous polishing
session.
>
> Being involved in aircraft certification myself l am aware of the often heavy
and costly solutions on larger aircraft. I am a structures signatory on the
A350,
this has a high level of composites content and poses new issues and solutions
on many fronts, including bonding and lightning protection.
>
> --------
> John Wighton
> Europa XS trigear G-IPOD
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=433644#433644 [1]
>
Links:
------
[1] http://forums.matronics.com/viewtopic.php?p=433644#433644
[2] http://www.aeroelectric.com
[3] http://www.buildersbooks.com
[4] http://www.homebuilthelp.com
[5] http://www.mypilotstore.com
[6] http://www.mrrace.com
[7] http://www.matronics.com/contribution
[8] http://www.matronics.com/Navigator?Europa-List
[9] http://forums.matronics.com
[10] http://www.aaib.gov.uk/cms_resources/dft_avsafety_pdf_500699.pdf
[11] http://www.sarangan.org/europa_forum/2004-08/msg00094.html
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