HIGH-VOLTAGE LABORATORY TEST simulates lightning, allowing engineers to assess aircraft safety. COURTESY OF EDWARD J. RUPKE
The aircraft's radome,the nose cone that contains radar and other flight instruments,is another area to which lightning protection engineers pay special attention. In order to function, radar cannot be contained within a conductive enclosure. Instead, lightning diverter strips applied along the outer surface of the radome protect this area. These strips can consist of solid metal bars or a series of closely spaced buttons of conductive material affixed to a plastic strip that is bonded adhesively to the radome. In many ways, diverter strips function like a lightning rod on a building.
Private general aviation planes should avoid flying through or near thunderstorms. The severe turbulence found in storm cells alone should make the pilot of a small plane very wary. The FAA has a separate set of regulations governing the lightning protection of private aircraft that do not transport passengers. A basic level of protection is provided for the airframe, fuel system and engines. Traditionally, most small, commercially made aircraft have aluminum skins and do not contain computerized engine and flight controls, and they are thus inherently less susceptible to lightning; however, numerous reports of noncatastrophic damage to wing tips, propellers and navigation lights have been recorded.
The growing class of kit-built composite aircraft also raises some concerns. Because the FAA considers owner-assembled, kit-built aircraft "experimental," they are not subject to lightning protection regulations. Many kit-built planes are made of fiberglass or graphite-reinforced composites. At LTI we routinely test protected fiberglass and composite panels with simulated lightning currents. The results of these tests show that lightning can damage inadequately protected composites. Pilots of unprotected fiberglass or composite aircraft should not fly anywhere near a lightning storm or in other types of clouds, because nonthunderstorm clouds may contain sufficient electric charge to produce lightning.
