Alternating versus direct current for aircraft-radio power supply

Recent designs of aircraft-radio equipment have provided for operation from existing aircraft electric systems, and little attention has been given to providing the electric system that is best suited for radio equipment use. This has been a natural and proper approach, because of the relatively small load requirements of aircraft radio. Accordingly, comparatively little attention has been given to the effects of the type of power supply on the characteristics of aircraft radio equipment. It is the authors´ belief that a review of the subject is desirable at this time to assist aircraft designers in making a proper choice of the electric system to be provided on future aircraft designs, as well as possible modifications to the electric systems on aircraft now in use. This paper considers the effects of the various types of aircraft electric systems on the characteristics of the radio equipment, from the standpoints of weight, efficiency, reliability, simplicity, flexibility, and emergency operation. The various types of a-c and d-c power supplies are discussed, and consideration is given to the effects of frequency and number of phases on a-c power supplies.