The quadruple 1.1-inch machine cannon, affectionately known as the “Chicago Piano,” was the first medium-range antiaircraft gun adopted by the U.S. Navy.1 Engineered and built by the Naval Gun Factory during the Great Depression, it was designed specifically to combat dive bombers. The four-barreled weapon fired a one-pound explosive shell that was fused to explode on contact with the thin doped fabric that covered the wings of the era’s biplanes. The resulting shrapnel would tear through the wing, causing loss of control.
Armaments and Innovations - A Gun to Counter the Dive Bomber
By Thomas Wildenberg