ACRONYMS AND SYMBOLS

Lightning strike incidents to commercial and military aircraft and helicopters have produced damage unlike what is usually inflicted by laboratory tests conducted in accordance with the aircraft lightning environment defined in present aircraft lightning environment standards including SAE ARP5412 and EUROCAE ED 81 and US Military Standard 464A (and predecessor standards dating back to 1970). These standards define a first stroke current of 200 kA peak amplitude and overall time duration of 500 µs followed by intermediate and continuing currents whose amplitudes do not exceed 4 kA. There is no recognition of the possibility of lightning stroke currents of higher amplitude than 200 KA or, more likely, of lower than 200 kA amplitude, but of longer time duration than 500 µs. The physical damage effects that have prompted this review appear to have resulted from lightning stroke currents that have long durations and moderate to severe amplitudes, but not the fast rates of rise (di/dt) usually associated with lightning stroke currents especially those that lower negative charge to earth. A proposal is made to add to the present aircraft lightning standards a current component that represents a long duration stroke current of moderate amplitude. It is suggested that this proposal be taken up by the committees responsible for updating aircraft lightning standards: SAE AE2 and EUROCAE WG31. This proposal might be extended to incorporate a higher amplitude version of this current component to account also for some effects that can only be attributable to strokes of very high action integrals, but such an extension is not discussed in this paper