Charge Control Strategy for Aircraft-Triggered Lightning Strike Risk Reduction

Abstract

We propose a charge control strategy to reduce the risk of an aircraft-triggered lightning strike that exploits the asymmetry between the positive and negative ends of the bidirectional leader development, which is the first phase of an aircraft-initiated lightning event. Because positive leaders are initiated and can propagate in lower fields than negative leaders, in general, a positive leader would occur first. During propagation of the positive leader, initiation of the negative leader is favored through the removal of positive charge from the aircraft. Based on this well-accepted bidirectional leader theory, we propose hindering the initiation of the positive leader by charging the aircraft to a negative level, selected to ensure that a negative leader will not form. Although not observed so far, a negative leader could be initiated first if the field enhancement at the negative end were much greater than at the positive end. In this situation, the biasing of the aircraft should be to positive levels. More generally, we propose that the optimum level of aircraft charging is that which makes both leaders equally unlikely. We present a theoretical study of the effectiveness of the strategy for an ellipsoidal fuselage as well as the geometry of a Falcon aircraft. The practical implementation, including the necessary sensors and actuators, is also discussed.