The report presents data on aircraft icing conditions, methods of preventing and removing ice on aircraft in flight, and methods of testing ice protection systems to ensure adequacy. The first section discusses statistical icing data to be used as design criteria for ice protection evaluations and systems. The second section is concerned with thephysics of ice collection, and presents formulas and charts for determination of the rate, size, and shape of ice formations on aircraft. The third section discusses the known methods of ice protection, and presents formulas and data to be used in design. The fourth section shows specific and typical applications of ice protection systems to light and heavy aircraft. The fifth section presents data on detection of icing by visual means and by ice detector and indicator systems. The final section discusses the various methods of testing aircraft for adequacy of icing protection with and without ice protection systems. Included are data on icing tunnel testing, dry air flight testing, flight testing in natural icing, and flight in simulated icing.