Electrically‐Heated Transparencies: Recent Developments in the Use of Plastics for Aircraft Windscreens and Canopies with Particular Reference to Transparencies Utilizing the Sierracote 3 Electrically Conductive Coating Produced by D. Napier and Son Ltd.

THE provision of suitable transparencies for both civil and military aircraft has posed some particularly difficult problems for windscreen and canopy designers during recent years. The relentless increase in the operational performance of fighters, bombers and transports has involved the production of transparencies capable of withstanding high outside air pressure loadings, severe thermal stresses due to extremes of temperature, kinetic heating effects and cabin pressurization changes as well as high bird impact forces. In addition to these and other problems, the transparent panels must often be equipped with a suitable system which will prevent the formation of ice on the outside of the window and prevent mist from forming on the inside. Any such heating device will probably involve temperature gradients in the laminated transparency inducing further stresses.