Keystone LB-6

The Keystone LB‑6 was a twin‑engine, all‑metal bomber built by Keystone Aircraft for the United States Army Air Corps in the early 1930s. Derived from the earlier LB‑5, the LB‑6 incorporated a strengthened airframe, upgraded Wright R‑1820 Cyclone radial engines delivering 650 horsepower each, and an enlarged bomb bay capable of carrying up to 2,000 pounds of ordnance. Its crew of four—pilot, co‑pilot, bombardier, and gunner—operated defensive armament consisting of two .30‑caliber machine guns mounted in dorsal and ventral positions. First flown in 1930, the LB‑6 entered service in 1931, serving primarily in the continental United States for training and tactical development. Although it saw no combat, the aircraft played a pivotal role in the evolution of American bomber design, bridging the gap between the fabric‑covered biplanes of World War I and the all‑metal, high‑performance monoplanes that would dominate World War II. The LB‑6’s emphasis on durability, increased payload, and more powerful engines informed later designs such as the Martin B‑10, cementing Keystone’s contribution to the United States’ transition to modern strategic bombing capabilities.

Keystone Aircraft

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