How is lightning strike protection provided for composite aircraft structures?

CFRP is less conductive than aluminum, requiring lightning protection systems: Expanded metal foil (ECF) or wire mesh bonded to exterior surface provides conductive path; Diverter strips and grounding connections ensure current flows safely to structure; Fastener and fuel system protection prevents sparking and internal arcing; Zone-based protection (Zone 1A direct attachment areas require most protection); and Structural protection against thermal damage and mechanical effects. Protection weight penalty is 0.3-0.5 lb/sq ft. Testing per SAE ARP5416 validates protection to 200kA peak currents. Paint requirements allow conductivity while meeting aesthetic needs. Repairs must maintain protection continuity.