The lightning spark barrier

Lightning protection of modern aerospace vehicles through the prevention of sparking in critical fuel vapor areas is discussed. In the past, it was particularly difficult to keep mechanical fasteners from sparking during a lightning event. Attempts to seal off the fasteners from the critical fuel vapor area by manual application of sealant material were ineffective due to gaps and voids produced by the application process. A technique was developed to control the application of dielectric sealant material to isolate the mechanical fastner sparking from the critical fuel vapor area. The technique consists of a specially designed dielectric cap that fits over the fastener, providing uniform and controlled application of dielectric filler material. An adequate thickness of filler material provides a barrier that prevents the sparks from entering the critical fuel vapor area. The lightning spark barrier is applicable to a wide variety of installations, including those with composite materials.