Army-Navy Precipitation-Static Project: Part III-Electrification of Aircraft Flying in Precipitation Areas

The principal features and mechanisms responsible for the transfer of free electrical charge to aircraft, as it flies through various types of precipitation, are examined. The charging characteristics of a typical airplane flying through dry snow are given and correlated with reliable quantitative data secured on the ground. The critical dependence of charging processes upon the ambient temperature and the character of the airplane´s surface is noted, and the possibility of neutralizing this charging by special surfaces is demonstrated. The discharge characteristics of the aircraft are evaluated in terms of the charge carried away by the engine-exhaust ions and by corona discharge. It is concluded that under severe precipitation conditions most of the accumulated charge is carried off by corona processes. The differences between unipolar or autogenous electrification and bipolar or exogenous charging are emphasized. Both types produce serious radio interference and require different treatments for their mitigation.