This month’s featured artifact is the K-11 compensating gunsight, part #655441 serial # 1611 made by the Sperry Gyroscope Company of Brooklyn, New York.
The K-11 was used primarily in the nose turret of the Consolidated B-24 Heavy Bomber during WW2. The K-11 Compensating Gun Sight was a late war innovation that used the aircraft’s altitude and speed with the direct correlation of where the weapon was pointed to calculate the reticle. The aircraft altitude and speed was programmed into the dial shown on the rear of the sight. The correlation was determined by drive lines that connected the K-11 Sight to the turret.
A compensating sight offsets the line of sight only to compensate for the speed of the firing aircraft. These sights did not take into account target range, but based their calculation on the angle between the gun line and the aircraft axis, using two dimensional cams.
The museum’s piece is a nice clean example and shows the bore sighting instructions on the side as well as front and rear folding sights. It also features the rear sun shield, which you don’t find on many surviving examples. This could also be folded down rearward and out of the way when not required. Note the placard that states that it can only be used in the nose cone position only. The K-11’s sister sight, the K-13 was another compensating gun sight that could be used in the side and waist gun positions and was mounted directly on the rear housing of the .50 caliber machine guns in those positions.
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