SAE International Aircraft Structure Paint Thickness and Lightning Swept Stroke Damages 2013-01-2135

During its flight an aircraft can be struck by lightning and the induced high current will require a highly conductive airframe skin structure in order for it to propagate through with minimum damage. However an aircraft skin is generally coated with paint and the airframer does not always have control on the paint thickness. Paint thickness generates heightened concerns for lightning strike on aircraft, mainly because most of coatings dedicated to that purpose are non-conductive. Using insulating material or non-conductive coating with certain thickness may contribute to or increase damage inflicted by the swept stroke lightning energy, even on metallic structures Due to its high relative permittivity, a non-conductive paint or coating on a fuselage skin surface will contribute to slow down the lightning current propagation through structure. With this comes the risk of increasing heat that will favor structural damage and possible melt through. The correlation between paint thickness, lightning dwell time, and aircraft skin thickness are all contributing factors in lightning swept stroke damage in aircraft lightning Zone 2A. Paint thickness is not always under direct control of the manufacturer and the maximum paint thickness that could safely be applied on an aircraft skin with very low risk of puncture due to lightning is still a controversial matter. This paper introduces the analysis and investigation performed by the Bombardier Aerospace Core Engineering Electromagnetics team through several test campaigns.