High Voltage Test for a Research of Reducing the Number of Aircraft Lightning Strike

Most of lightning strikes to aircrafts are thought to be triggered by the aircraft itself. When an aircraft flies near thunderclouds, leaders are formed from a local concentration of electric field on the surface of the aircraft, and one of the leaders connects to a leader that comes from thunderclouds, and then the high lightning current flows through the aircraft. The Japan Aerospace Exploration Agency (JAXA) and SUBARU focus on this leader initiation and are seeking the way to reduce the frequency of aircraft lightning. High voltage impulse discharge tests were conducted for a simple shape and an aircraft shape. Both are made from aluminium. Those were suspended in the air under a relatively wide electrode (⌀1200mm) with a 600-800mm gap to the ground. In general, if the discharge gap is too short, leaders won’t be appeared, so that the setting of the size was considered enough to observe the leaders that propagates from the specimens. Also, uniform electric fields with Rogowski shaped electrode was used to prevent that the leaders from the electrode appear quicker than that of the specimen. Even though the results obtained in the laboratory can’t be applied directly to the natural lightning to an aircraft in flight, this experiment was worth enough to realize the basic patterns of discharge phenomena of a floating object. Two still cameras and a high-speed video camera was used to observe those discharges, and the detail sequence of how the leader was formed and growing and turned into a flashover was observed. The up-and-down method was used to estimate 50% flashover voltage, and there was a significant difference depending on the combination of the body shape, attitude, the electrical charge to the body and electrodes’ polarity. The results show that the body shape, the body attitude, and the electrical charge to the body were playing the important role for a breakdown