Does Lightning Lab for aircraft have something to offer wind turbines?

With today’s newest commercial airliners now manufactured from carbon fibre, they are vulnerable to serious damage in a lightning strike, a worrying safety issue.

Metal aircraft are built to absorb such a strike without threatening their flight integrity but the carbon fibre variety are not – and statistics show that every airliner is hit by lightning once every year.

Cardiff University now hosts a Lightning Lab for Airbus, with scientists working on ways to make carbon fibre aircraft safe in such an event.

The blades of wind turbines are made form carbon fibre – which is of environmental concern in decommissioning – and with the towers themselves now to use the material in a cost-related move, the vulnerability of these structures to lightning strike is of concern. Most wind farms are, necessarily, located in places where they are the highest objects.

It may be that the research work going on at Cardiff will have an important application in the wind energy industry.

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4 Responses to Does Lightning Lab for aircraft have something to offer wind turbines?

  1. The quick answer is “no”.

    The slightly longer explanation is that aircraft with aluminium shells are relatively immune from lightning strikes as the fuselage acts as a Faraday cage. Carbon fibre is not as conductive (because of the resins) so may not conduct as well as an aluminium cage body, allowing electrical charge to penetrate the fuselage. Improving the conductivity of the fuselage removes the problem.

    It doesn’t matter if wind turbines are made of carbon fibre or steel (or aluminium). Because the structure is grounded, lightning will hit it and find its way to earth. If the path to earth is shortest through a vulnerable component then damage will occur. However, all turbines are protected by lightning conductors in their blades and in the towers that safely lead the charge to earth. Increased use of carbon fibre has no bearing on either the probability of lightning strikes or on the damage they can inflict (though it does increase the fire risk if the current is not safely earthed).

    Back to aircraft: the problem with carbon fibre in aircraft is not that it is carbon fibre but that it is not a conductive metal. Wooden aircraft would be just as vulnerable (which makes me wonder how many Mosquitoes were lost to lightning?).

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    • I suspect (I don’t know from my own experience) that the aluminium shell of the aircraft should, indeed, act as a Faraday cage, which should protect the internal electrical / electronic equipment. But the hazard would be if the current, in the metal skin at the point of a lightning strike, was high enough to melt the metal and leave the fuselage with a nasty hole, leading to depressurisation. (And if the current, being distributed around the shell, led to voltage differences across the shell sufficient to damage people or electronics.)

      In one of my previous existences, my department placed a (human) observer within a heavy-gauge copper Faraday cage, with suitable instruments, to measure the impact current on the cage when a simulated lightning strike hit it (by analogy with lightning strikes on the electricity grid). I recall that only one named individual was allowed to occupy the cage — probably for insurance reasons. (He survived.)

      Frivolously, I suspect that fewer Mosquitoes were lost to lightning than were Lancasters.

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      • In my earlier comment I used the term “relatively immune”. Lightning does damage aircraft but thankfully rarely catastrophically (I have been in a commercial aircraft coming into land at Edinburgh when we were struck and it was a sobering experience: we landed safely but they couldn’t get the flight back up again for hours because of damage to some of the control systems). Aircraft are designed to limit the damage lightning strikes cause
        http://www.niar.twsu.edu/agate/Documents/Lightning/WP3.1-031027-043.pdf

        Protection of wind turbines have taken a different approach than for aircraft that are comprised largely of composites: http://www.compositesworld.com/articles/lightning-strike-protection-for-composite-structures

        though the principle in all cases remains the same: use a conductive pathway to guide the electrical charge away from vulnerable components.

        I was watching a childrens’ fantasy film recently where the hero uses a Faraday cage while investigating Tesla coils but on at least one occasion I saw him touching the cage while the lightning was hitting it – which would have been a hair raising experience.

        Lancasters had an all metal fuselage – are you thinking of Wellingtons (which were metal framed but had wood and fabric coverings)? Or am I missing some more subtle remark?

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        • DDM: nothing more subtle intended! except that I am sure that I read, a long time ago (in Martin Middlebrook’s book) that several Lancasters were lost due to lightning during the last night of the raids on Hamburg, although Mosquitoes had already flown the route in the preceding hours specifically for weather-forecasting reasons. I may have read more into that description than was justified. In particular, I don’t know at all whether those Lancasters were affected by damage to skin metal, or to engines/propellors/fuel systems, or to what would now be called avionics (that latter possibility would probably not have brought down a Lancaster in 194x), or by injury to pilots, etc. (I take it that Lancasters, being non-pressurised, would not be vulnerable to small skin punctures in themselves.)

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