Indirect Lightning Prediction Codes

Codes have been written that allow designers to predict lightning indirect effects on aircraft wiring and structural elements. As a cost saving alternative to aircraft level testing, the codes will be used to calculate actual transient levels (ATL) on aircraft wiring with the purpose of verifying system lightning protection certification compliance by analysis. The code suite employs a CAD feature to enter the problem geometry. Additional user inputs include electrical characteristics of an airframe, excitation of the airframe with lightning attachments, and computation and display of the electrical response of any electrical member of the airframe versus time. The time series for an electrical response is calculated using inverse Laplace transforms of pole-zero terms fitted to the spectral response of the chosen element. In all cases tested to date, very few pole-zero terms are needed compared to the number of frequency samples required for the equivalent accuracy using standard Fourier techniques. Pole-zero terms are fitted using a specialized least-squares procedure.