A REALISTIC APPROACH TO AIRCRAFT LIGHTNING PROTECTION G . L . Weinstock McDonnell

Lightning protection for fighter aircraft is presently based on the requirements of MIL-B-5087 and refined by the recently issued MIL-STD-1757. These documents specify current and energy levels sufficient to cover greater than 99 percent of the cloud-to-ground strikes. These levels are applied to aircraft according to lightning strike zones established by attach point ftnalysis and tes*. .the application of these specifications to aircraft is made without consideration of mission, probability of strike occurrence, or penalties associated with protective designs. Data from recent in-flight test programs, a tabulation of aircraft strike rate per aircraft type, and an examination of strike damage records, all show that the requirements may be too stringent and that a revision to the method of applying lightning specifications to aircraft may be justified. In conventional and V/STOL high-technology fighter aircraft, weight has a direct effect upon performance, combat effectiveness, losses, and life-cycle cost. Unnecessarily stringent lightning protection requirements can add weight out of proportion to the lightning risk. A systematic method of tailoring requirements to risk or damage probability is desirable to provide a more balanced protective design. This paper presents a probabilistic approach to the design of aircraft lightning protection which may be a useful method of avoiding conventional worst case design