Lightning Currents on Fastening Assemblies of an Aircraft Fuel Tank—Part III: Validation of the Current Assessment Method With Measurement

This article proposes a new fastener model and validate the stochastic process for the lightning current assessment in the aircraft assemblies proposed in the previous parts. In particular, the stochastic method concerns the finite-difference time domain (FDTD) fastener modeling for which the variability of the contact resistance has to be taken into account. The principle is to merge an electromagnetic fastener model with an uncertainty model. The new fastener model proposed in this article is a wire with a lumped resistor on a low conductive plate. This model is an improvement of the model of Part I, where the fastener is only represented by a wire with a lumped resistor. The proposed model in this article is able to ensure a good shielding effectiveness without current distribution disruptions provided that the conductivity of the plate is weak in contrast to the lumped resistor. Moreover, it has the benefits to be able to represent any fastener without location constraint in the FDTD grid. A log-normal distribution has been previously established as uncertainty model that represents the variability of the resistive parameter. The fastener model is included in the FDTD modeling of a realistic fuel tank with each lumped resistor taking a probabilistic value according to the log-normal law. To take into account, the variability of resistors, several simulations with different sets of resistance values are performed. The aim is to surround current measurements with simulated currents at various locations of the fuel tank for a lightning injection performed directly on a fuel tank fastener. This article demonstrates that a specific attention must be given to the modeling of fasteners close to the lightning injection point for the current assessment. Moreover, the results highlight the relevance of the use of an uncertainty model and its reliability for the lightning current assessment.