Lightning Induced Voltages on Differently Protected and Routed Wires in a Carbon Fibre Wing Box

This paper presents the results of lightning tests performed on a carbon fibre (CFC)-wing box of about 6m length. The intention of the tests was to measure and compare lightning induced voltages on various electrical wires typically routed and protected by different shielding techniques like braided wire bundle screens or solid metallic raceways. All measurements were performed by passing a 5kA double exponential current pulse through the wing structure. The pulse had a waveform very similar to component A of the EUROCAE/SAE waveform standard. The close similarity to the component A standard test waveform makes it easy to extrapolate the test results to other test pulse levels of the same wave shape. The common mode voltages were measured and evaluated with respect to their amplitudes and wave shapes.

It was found that most wire screens are quite effective in reducing magnetic and electric field induced voltages. But, to be effective also in reduction of IR induced voltages, the screens must have a very low transfer impedance which requires a large cross sectional area making effective screens very heavy.