Lightning Effects on Hydraulic Transport Elements in Composite Aircraft

In this study, lightning effects on hydraulic transport elements in composite aircraft have been considered for the first time. Based on recent test results and analysis, several forms of possible structural damage and system component failures are presented. A unique approach in analysis has been taken to account that hydraulic transport elements, as a part of several aircraft systems, have a common interface with electrical wiring, and become complex electric networks. When an aircraft is exposed to a direct lightning strike, a metal skin on the wings and fuselage will conduct lightning currents in a way that only a small amount of induced electromagnetic energy will be present on hydraulic transport elements. So, in the past, hydraulic tubes, actuators, manifolds, and all other hydro-mechanical devices, as parts of various aircraft systems, have never been considered as lightning sensitive components. A new trend in the aerospace industry is the use of composite materials in the construction of aircraft wings and fuselages. This has brought about new technologies, with a reduction in weight being a major advantage. At the same time, lightning safety has become a new challenge, not only for aircraft system integrators but for component and subassembly designers as well. Due to the low conductivity of the composite structures, in the case of direct lightning strike, high currents will flow through the conductive structural elements. As a result of electromagnetic effects, a significant amount of energy will be present on all aircraft metallic assemblies, including electrical harnesses, cables and hydraulic transport elements. Considering that all hydro-mechanical components are connected with hydraulic tubes, they become part of conductive paths where induced currents and pulse voltages can cause serious damage. The intention of this article is to bring awareness to the Aerospace industry, and to outline safety boundaries concerning future projects with composite structures.