Description of an Aircraft Lightning And Simulated Nuclear Electromagnetic Pulse (NEMP) Threat Based on Experimental Data

Abstract
Most modern aircraft are designed to withstand a direct lightning strike. To accomplish this protection, the aircraft must have an external conductive path with a given skin thickness and a minimum amount of exposed areas and antennas that could allow energy coupling to the inside. Additionally, some modern military aircraft are also designed to operate in a nuclear electromagnetic pulse (NEMP) environment. This paper provides experimental lightning data and NEMP scalemodel data to characterize both phenomena. The lightning data were obtained by measuring the surface electromagnetic fields on a CV-580 research aircraft during an actual lightning strike. The aircraft was struck by lightning 48 times in central Florida between 1500- and 18 000-ft altitude during the summers of 1984 and 1985. One of these lightning events, for which an extensive set of data was available, has been analyzed. For this event, the maximum measured values were as follows: time rate of change of the surface magnetic flux density, 3750 T/s; total normal current density, 20 A/m2; peak current, 4.7 kA; and rate of rise of the current, 38 kA/ps. The NEMP data were obtained by measuring the surface electromagnetic fields during a simulated NEMP test in a 1:74 scale model of the same aircraft. During scale-model NEMP simulation, the maximum values measured were as follows: time rate of change of the surface magnetic flux density, 40 000 T/s; and total normal current density, 90 A/m2. The analyses of these results should provide new insights for combined lightning and NEMP protection.

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