Hardening lightning protection for avionics on composite aircraft

Electronic equipment on aircraft (avionics) are required to be immune to the indirect effects of lightning strikes to the airframe. The indirect effects of lightning strikes to airframes fabricated with carbon composite material are more severe in level and duration than those to metallic airframes. Thus, to use existing avionics deigned for aircraft with metallic airframes on aircraft with composite airframes, the lightning protection for these avionics may require additional protection (hardening). This paper outlines a three step process that allows quick evaluation of each signal line interfacing with the avionics equipment to determine if hardening is required. To facilitate the evaluation process, a graphical user interface (GUI) is introduced. Then, techniques for the hardening of the existing lightning protection with the least impact on the signal lines are outlined. Finally, an example design is provided.