Lightning Currents on Fastening Assemblies of an Aircraft Fuel Tank, Part II: FDTD Modeling Merged With a Circuit Model Supplemented by a Statistical Model

This paper presents a fastening assemblies FDTD model based on a lumped element circuit integrated into thin wire formalism. It can be used to quantify current dispersion or extreme current in aircraft fuel tank fasteners and to optimize the lightning protection in hotspot zones. An original method allows the characterization of the fastener lumped resistances. This method dealing with dc measurement and an optimization process is validated provided that 1) the measurements number is greater than the lumped elements number and 2) each node of the circuit is used at least once. Due to the large uncertainties from one fastener to the other one in the same family, the circuit model is supplement with a statistical model using the results about the fastener resistances state after a lightning shot presented in part I. Stochastic distribution values are applied to each lumped resistance of the fastener circuit model. Making a hybridization between a circuit solver and the finite difference time domain (FDTD) method, the circuit model is added in the same three-dimensional FDTD generic fuel tank modeling as presented in part I. Comparing the current distributions of the simple model of the part I and the circuit model, the uncertainties introduced by each model are presented.