As part of the technology research engaged in the EU Clean Sky 1 project, we present in this paper an electrical structure network (ESN) designed to prevent the impact on an electronic equipment of unwanted voltage drops appearing when nonmetal composite materials are used for grounding. An iterative process has been followed to reach an optimal tradeoff solution meeting all the aircraft requirements: structural, safety, low weight, electrical, etc. Guidelines on the design of a low-impedance metal ESN, to minimize the inductive behavior of the power distribution network, are outlined in this paper. To this end, we employ the UGRFDTD simulation tool, combining finite-difference time domain to analyze the general EM problem, and a multiconductor transmission-line network to handle internal coupling between cables running along coinciding routes. The capability of this tool to create time-domain snapshots of surface currents is shown to provide a useful way to optimize the ESN, thanks to the insight gained on the physics of the problem. Index Terms-Carbon-fiber-reinforced plastic (CFRP), electrical structure network, electromagnetic compatibility (EMC), finite-difference time domain (FDTD), green regional aircraft (GRA). I. INTRODUCTION T HE design of an aircraft (A/C) must comply with the aerodynamic, structural, safety, fuel efficiency, cost, and electromagnetic (EM) requirements, among many others, this requiring the parallel work of several departments. Clean Sky 1 is one of the largest European R&D projects focused on the design of the A/C of the future: low-CO 2 and highly cost-efficient air-transport system. Its objective is to speed up the technological breakthrough developments and to shorten the time-to-market for new solutions that introduce green technology into aviation. Within the framework of Clean Sky 1, this paper deals with the design of low-weight configurations Manuscript