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Sperry Ball Turret

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It hard to imagine a worse place to go to war in then the ball turret position of the B-17 Flying Fortress.  Isolated from the rest of the ten man crew, the ball turret was extremely cramped quarters and required a man with a slight build. In almost every case, there was not enough room for the ball turret gunner to wear a parachute.  Ironically, post war analysis of B-17 crew fatality records revealed that the ball turret gunner had the safest job on the plane (with the pilot having the most dangerous).


     Towards the end of the war when fighter attacks became rare, there was a plan to remove all ball turrets from B-17's to save weight (1200 pounds including the gunner) but this was never initiated.

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Source: USAAC

Source: Author

Source: USAAC

Description of the Sperry Ball Turret

The Ball Turret was built by the Sperry Corporation (Model 645473E) and housed two 50 caliber machine guns. The associated ammunition (250 rounds per gun) fed down from boxes mounted on either side of the hoist. Located in the bottom of the fuselage just aft of the radio compartment, the ball turret was electrically powered. Unlike the ball turret installation on the B-24, the B-17 ball turret could not be retracted into the fuselage although it could be rotated manually using a hand crank to allow entry and exit without power. The whole unit was suspended on a gimbal with the central tube of the structure attached to the ceiling of the fuselage.  For elevation the ball hinged on the frame on each side of the guns while the yoke of the gimbal pivoted giving the turret free movement in azimuth.  On the backside was an entry hatch which also contained armor plate to protect the gunner from aircraft fire (backside only). Inside the ball was a small radio, a K-4 type computing gunsight, a breathing oxygen regulator, interior lighting, a first aid kit and the gun turret controls. The temperature in the tail section when the side ports were open was quite frigid at high altitudes, especially in the wintertime. A plug-in point for a electrically-heated flight suit was also located in the ball.

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Special Credit to Aero Detail Books

The gunner entered the ball turret via a door at its rear, which also served as an emergency exit in case of trouble. The gunner could enter the turret from inside the plane by having the turret rotated until the door opening faced the interior of the plane. However, since this required that the ball turret be positioned so that the guns were pointed downward, this meant that the turret could not be entered from inside the plane while it was on the ground. It was possible for the gunner to enter the turret from outside the plane while it was on the ground by having it rotated so that its door faced outside the plane. However, once he did this, he would
have to stay inside the turret during the takeoff. Since the turret was only 15 inches off the ground, it would take a bold soul to ride inside the belly turret during take off or landing, and most ball turret gunners chose to enter the turret while the plane was in the air. Normally, the guns were stowed facing rearward with the barrels horizontal for takeoffs and landings. feetup_butt down.jpg (31113 bytes)

Special Credit to Aero Detail Books

The Gunner

Once inside the ball, the gunner sat all curled up in the fetal position, swiveling the entire turret as he aimed the two guns. The turret had a full 360 degress of motion horizontally and 90 degrees of motion vertically. The gunner could be in any attitude from laying on his back to standing on his feet. The gunner sat between the guns with his feet in stirrups positioned on either side of the 13" diameter window in front. An optical gunsight hung in front of his face, his knees up around his ears and his flight suit his only padding. A pedal under the gunner's left foot adjusted a reticle on the gunsight glass.  When the target was framed therein, the gunner knew the range was correct.  Two post handles, pointing rearward above the sight worked valves in the self contained electro-hydraulic system to control the movement of the ball.   A firing button located at the end of each handle would fire both guns.  Empty shell casings were ejected through a port just below the gun barrel.

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