LABORATORY STUDY OF THE BI-LEADER PROCESS FROM AN ELECTRICALLY FLOATING CONDUCTOR - PART 1 - GENERAL RESULTS

In-flight experiments have shown that in most cases the aircraft strik ing process is initiated by the bidirectional propagation of two leade rs of opposite polarities. A laboratory experiment has been designed t o analyse in detail the development of such a 'bi-leader' fi-om an ele ctrically floating conductor suspended in a 10.5m plane-to-plane gap, submitted to an impulse voltage. The shape of the floating object, the electrode configuration and the voltage waveshape have been optimised to allow the observation of the simultaneous development of both disc harges before their junction with the planes. Current and electric fie ld probes have been installed at both ends of the floating object, and synchronised with time-resolved optical diagnostics. The authors give a detailed description of the observed phenomena and compare the char acteristics of the positive and negative discharges with those already studied in classical rod-to-plane gaps.