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Concern over severe lightning strikes to helicopters in the North Sea resulted in a UK Civil Aviation Authority sponsored research programme. The programme investigated the polarity of lightning strikes in this region by remote sensing with a view to determining the likelihood of severe positive strikes. It also investigated correlations of individual incidents with meteorological conditions and .the lightning detected by remote survey on the day of the strike. The study shows that the strikes to helicopters occur only in winter, possibly triggered by the helicopter itself. The proportion of positive strikes, believed to be on average more energetic than negative strikes, is higher than the World-wide average, particularly in winter. The meteorological investigation found that temperature and updraft parameters allowed a predictive algorithm for helicopter strikes to be constructed.

In the EU FULMEN collaborative project a series of experiments based on AEA Technology’s Hawker Hunter airframe have studied coupling of E and dE/dt threats. Currents and fields were applied using either a low level lightning current simulator to the whole airframe, or by injecting the threats more locally. Coupling could be measured in two apertures at opposite ends of the airframe, in which cables were routed both parallel and perpendicular to the current paths. The different configurations for measurement and test allowed the various coupling methods to be separately elucidated. Likely levels of E-field and d2B/dt2 coupled transients which could couple to internal equipment are discussed in relation to the present consensus of external environments.

AEA Technology is carrying out an ongoing programme of lightning simulation testing work on carbon composite ‘T-joints’. These typically represent skin to spar bolted interfaces, and the tests help to determine whether aircraft fuel tanks incorporating such structures are liable to produce sparks during a lightning attachment. For testing, the T-joints are integrated into a complex test rig that is intended to provide representative current flow during the simulation tests. The intention is that the current distribution in the T-joint should be similar to the current distribution on the equivalent part of the aircraft structure during a lightning attachment. A combined experimental testing and computational modelling work programme has been carried out in order to investigate how representative the test-rig current distribution is to that on a real aircraft. In the first part of this study the test rig itself is modelled using the 3D code ELECTRA.