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The main purpose of the experiments described here is the analysis of the mechanisms of radome protection with lightning diverters of various types and sizes. A high voltage arrangement and associated diagnostics have been implemented to perform a quantitative study of the inception and propagation mechanisms of the corona and leader discharges that precede the final breakdown. It is shown that ambient humidity plays a significant role on the discharge process and that the nature of the discharge initiated from the strip is very different depending on the strip type. Segmented strips are more likely to allow energetic discharges to propagate from an internal antenna leading to radome puncture.

In the framework of an EC (European Community) project EM-HAZ (Electromagnetic Hazard), an Automatic Lightning System Detection And Recording (ALISDAR) has been developed. Electrical and magnetic field measurements are the best way to characterize the lightning strike to aircraft. A finite difference time domain (FDTD) method is used to estimate the lightning current from E and H field measurements. The severity and the location of the lightning strike could be used to optimize the maintenance operations. The best location in terms of cost for the ALISDAR sensors is a dummy window. The validation of the ALISDAR system is planned through two laboratory experiments.

The definition of lightning attachment zone in the standard regulatory documents have been inferred from empirical approach. In the framework of the European FULMEN program, the actual physical processes involved in a lightning strike to aircraft or helicopter are studied to improve the determination of the initial lightning attachment. In flight experiments performed in the 80’s have shown that there are two main processes which lead to a lightning strike to aircraft. The first process occurs when an aircraft flies into a region of the thunderstorm where the electric field is intense. The result is the triggering from the aircraft of preliminary discharges which lead to lightning development. The second process is the interception by the aircraft of a natural lightning channel developing in the vicinity of the aircraft. The experiment, performed at the test center of CEAT in November 1997, has been designed to simulate the initial phases of both processes.

Indirect effects of lightning refer to upset of or damage to electrical equipments and systems. Evaluation of aircraft susceptibility to indirect effects of lightning is usually performed through experimental tests. A current homothetic to the real threat but with a lower amplitude is injected through the aircraft structure. Analysis of aircraft transfer functions is carried out by measuring induced current and voltage and extrapolating the results to the standardized threat. The extrapolation process may influence the results especially if non linear effects appear during the test. An analysis of non linear effects has been carried out in the framework of the European FULMEN program and is part of the global definition of aircraft interaction with lightning at the equipment level (internal threat). The different sources of non linearity are identified : arcing and sparking, non linear protection devices, non linearity of material and influence of the extrapolation method.