Overview

The metal skin of a modern airplane can be considered a good approximation both to a Faraday cage and to the outer surface of a topological shielded system (see Section 3.1). As such, the skin provides the primary lightning protection for the aircraft. Generally, when lightning strikes a metal airplane, the lightning current remains in the skin of the plane as it flows between entrance and exit points. If the shielding by the plane's skin were perfect, there would be no danger to the interior electronics or to the fuel in the wings of the airplane. Unfortunately, there are openings (apertures) such as windows in the metal skin and antennas that project through insulated areas in the skin, both of which may serve as entry points for lightning electromagnetic fields. Additionally, the plane's aluminum skin is not always thick enough to avoid direct damage by a severe lightning charge flowing into the skin (see Section 2.3). Lightning often disables interior aircraft electronics, as we shall discuss in Section 9.2, and occasionally lightning can burn through the aircraft's skin, igniting fuel or releasing hydraulic fluids, examples of which are given in Section 9.3. In Section 9.4, we will briefly consider the standards for testing aircraft to make more certain they can withstand a lightning strike without serious consequences.

Contrary to the common view, most lightning discharges that strike airplanes in flight are initiated by the planes themselves. The lightning would not have occurred if the plane had not been present.