This handbook addresses the direct effects of lightning strikes. Its intent is to provide guidance and educate engineering personnel responsible for lightning protection of primary aircraft structure. The recommendations included in this document are specific to the design of small personal aircraft and may not be as applicable to large composite aircraft designs. It is intended to assist engineers with limited experience in the design of aircraft lightning strike protection. Information is included on the natural lightning environment, the interaction between aircraft and lightning, and the mechanism of the lightning strike effects on the aircraft.