Design considerations for D-C aircraft generators

Engine-mounted aircraft generators must fit within an envelope 6 1/2 inches in diameter by 14 inches long. Electric-power requirements on military airplanes are increasing so rapidly that the most urgent assignment confronting designers of aircraft generators is that of achieving the ultimate output possible from this envelope. In 1939 the maximum rating was 1,500 watts; in 1940 the maximum rating jumped to 3,000 watts; in 1942 to 6,000 watts. A rating of 9,000 is coming into use, and a rating of 12,000 watts is likely to be possible in 1944. A rating of 15,000 watts has been mentioned. New materials, new military demands, new design ingenuity, new manufacturing techniques, and new operating experiences have all had a part in introducing more advances in this field during the past four years than were made during the approximate 20 years of generator history prior to 1938. Methods by which these advances have been accomplished are described, and possibilities for future progress are indicated.