Aircraft protection from thunderstorm discharges to antennas

The transport aircraft is inherently provided nearly complete thunderstorm-discharge protection by the metal fuselage, which forms a safe path for discharge currents that the aircraft may intercept. External elements such as movable surfaces and antennas can be protected. Airline experiences have shown that antennas frequently intercept discharges; a current surge conducted along the antenna lead-in frequently damages radio equipment and, in some cases, has resulted in fires. An effective antenna-protection unit was consequently developed, which besides protecting the ratio equipment, also records the bypassed current and charge magnitudes. Analysis of the sphere-gap pitting indicates the total-charge transfer, and small magnetic links indicate the peak currents by their magnetization. Because of the research importance of the data, these experimental units have been made available to airlines interested in cooperating with the Lightning and Transients Research Institute's program of protection researches. The discharge-current records and supplementary information from questionnaires are providing data for improved protection, and also help resolve statistically such questions as discharge-probability variations to be expected with various operating factors of geographical location, altitude, temperature, and size and speed of the aircraft.