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The sign on the turret display. It reads

B-17 Upper Machine Gun Turret Type A-1A

This turret was one of the first fully powered machine gun turret designs used to equip American aircraft and was used initially on the B-17E "Flying Fortress." It is operated by an electro-hydraulic system which powers both elevation and traverse of the turret's two .50 caliber M-2 Browning machine guns, and has a rate of fire of 1400-1600 rounds per minute. Turrets of this and later types gradually replaced manually operated machine guns introduced for bomber defense during the First World War, and so made the bomber a more formidable opponent to attacking fighters. This turret was manufactured by the Emerson Electric Manufacturing Company to a Sperry Gyroscope Company design, and was donated to the Museum by the Hobart Corporation of Troy, Ohio.