23857122-0457-180273-0366

wo Saw Pd to the crew and passengers. Just preceding t} ~ : .& 18 ONSSU of a lightning stroke tq an aircraft, pilots havs re- ’ ported observing a streamer of corona dischar up on the nose, propellers or other extremity craft? of the aircraft and depends on the passage of ning stroke nearly or through the aircraft. Co . The movement of the streamer accompan ge build of the ies that gene ht rona discharges on sharply convex surfaces of aircraft have also been observed during flight between masses o clouds strongly charged with electrical charges o : . opposite sign (positive and nesative). pares charging of the aircraft by tribo-electr and other effects during flight through sn or nies precipi-~ tation particles intensifies a corona discharvos. These are of the same nature as St. llmots Fire. St. Elmo's Fire has been observed numerous times on the mastheads of ships and generally moves with them during passage beneath thun derclouds or other me teor= legical conditions where intense electrical potential rradients exist. (e) &ffect on Surrounding Atmosphere 1. Clouds ne Lightning of any kind can ocour in clouds only a Vv e dl if the dielectric properties of the air are broken down when f the sparking potential eradient is reached. air this amounts to about 30,000 volts per cm. level and about 21,000 vo ve per cm. at 10,000 altitude. In ol tion particles the sparking potential rradient n clear o> a AG §$@ea fap os Le ouds, or in the presence of precipita- is less depending on the size of the particles. For example, in the presence of raindrops 1/6 inch in diame is about 10,000 volts/on. ter it. ‘ Le Pa | co ° ry A shown by Macky“, droplets of water suspended in an electrical field sufficiently intense to induce break- down will display sparkingeover phenomena and will coe 2 yee ON en tO HN He tn rag Ls Ba 1. Harrison, L. P., “Lightning Discharges to Aircraft and la Associated Meteorolorical Bynstbione * NACA nical Note 1001 (19h,6) " r) y oe ww) 7 oo e Tech 2. Macky, W. Aes Proc, Roy. Soc. London, Ser. A, vol. 133, pp. 565-587, (1931). Declassification Authority: NND 57565