a close up of the nose of an airplane

The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Sperry and Emerson Electric each developed a ball turret, and the designs were similar in the nose turret version. The Sperry ball turret was very small[clarification needed] in order to reduce drag, and was typically operated by the smallest man of the crew. To enter the turret, the turret was moved until the guns were pointed straight down. The gunner placed his feet in the heel rests and occupied his cramped station.