Abstract: A method of protecting an air vehicle against lightning strikes includes inserting a fastener through a hole in conjoined structures, the fastener defining an axis along its length and having a threaded end and a sleeve, and installing a washer assembly over the threaded end and the sleeve, the washer assembly having a metallic washer and a polymer seal radially inward of the metallic washer. The seal includes a lower seal portion defining a counter-bore, and an upper seal portion extending axially from the lower seal portion. The method includes installing a counter-bored nut on the threaded end, and applying torque to the nut to compress the lower seal portion against a surface of the conjoined structures and around the sleeve at the counter-bore of the seal, and to compress the upper seal portion of the seal into a counter-bore of the nut and around the threaded end.

Abstract: A washer assembly including a metallic washer and a polymer seal. The metallic washer defines a cylindrical void and an axis therethrough. The polymer seal is attached to the metallic washer and is positioned radially inward thereof. The polymer seal includes a lower seal portion positioned at least partially within the cylindrical void and defining a counter-bore, and an upper seal portion extending axially from the lower seal portion. The lower seal portion is configured to engage, at the counter-bore, a fastener to form a seal to reduce escape of energized particles. The upper seal portion is configured to engage a counter-bore of a counter-bored nut to form a seal inside the counter-bored nut to reduce escape of energized particles.

Abstract: A method of protecting an air vehicle against lightning strikes includes inserting a fastener through a hole in conjoined structures, the fastener defining an axis along its length and having a threaded end and a sleeve, and installing a washer assembly over the threaded end and the sleeve, the washer assembly having a metallic washer and a polymer seal radially inward of the metallic washer. The seal includes a lower seal portion defining a counter-bore, and an upper seal portion extending axially from the lower seal portion. The method includes installing a counter-bored nut on the threaded end, and applying torque to the nut to compress the lower seal portion against a surface of the conjoined structures and around the sleeve at the counter-bore of the seal, and to compress the upper seal portion of the seal into a counter-bore of the nut and around the threaded end.

Abstract: A washer assembly including a metallic washer and a polymer seal. The metallic washer defines a cylindrical void and an axis therethrough. The polymer seal is attached to the metallic washer and is positioned radially inward thereof. The polymer seal includes a lower seal portion positioned at least partially within the cylindrical void and defining a counter-bore, and an upper seal portion extending axially from the lower seal portion. The lower seal portion is configured to engage, at the counter-bore, a fastener to form a seal to reduce escape of energized particles. The upper seal portion is configured to engage a counter-bore of a counter-bored nut to form a seal inside the counter-bored nut to reduce escape of energized particles.