Lightning strikes to an airplane in a thunderstorm

Abstract

The analysis of radar echoes from lightning at the moments of strikes to the NASA Langley Research Center's F-106B instrumented airplane proves that the airplane itself triggers the lightning, rather than intercepting naturally occurring flashes. In 1982 the UHF band radar at the NASA Goddard Space Flight Center/Wallops Flight Facility was used to guide the F 106B through the upper regions of thunderstorms so that the airplane might be struck by lightning. The UHF band radar data was analyzed to determine the nature and characteristics of direct lightning strikes to the airplane, and the airborne data was used to document the environmental con ditions favorable for such strikes The echo characteristics of the strikes were similar to those of intracloud flashes, and indicated that most of the time the airplane was part of the lighting channel. The probability of a direct strike to the F-106B during storm penetrations (PDS) is defined here as the ratio of the number of direct strikes to the airplane to the total number of flashes occurring in the radar resolution volume containing the airplane Correlations between the PDS and the intensity of rain, the intensity of turbulence, the ambient temperature, and the lightning flash rate in the storms penetrated were obtained The correlations indicated that the highest risk for the F-106B to be struck by lightning during penetrations in the upper regions of thun derstorms occurred under the following conditions: 1) ambient temperatures of -40 C and colder; 2) negligible to light precipitation; 3) negligible to light turbulence; and 4) lightning flash rates of < 10 per minute