The Keystone B-3A was a bomber aircraft developed for the United States Army Air Corps by Keystone Aircraft in the late 1920s. Design and development The B-3 was originally ordered as the LB-10A (a single-tail modification of the Keystone LB-6), but the Army dropped the LB- 'light bomber' designation in 1930. Although the performance of the B-3A was hardly better than that of the bombers flown at the end of World War I, it had come a long way. In terms of its safety, it was far superior to its oldest predecessors. Operational history The B-3A was a member of the last family of biplanes operated by the US Army; it remained in service until 1940. A few years after it was first produced, the introduction of all-metal monoplanes rendered it almost completely obsolete. Variants LB-10 The last of the 17 LB-6s ordered (S/N 29-27) was converted with a re-designed single fin and rudder and two 525 hp Wright R-1750E engines. Delivered to Wright Field on 7 July 1929, it was wrecked on 12 November 1929. LB-10A This version used Pratt and Whitney R-1690-3 Hornet engines and was slightly smaller, in both wingspan and fuselage. A total of 63 were ordered (S/N 30-281/343). All were re-designated as the B-3A before any deliveries were made, with the final 27 built as B-5A with Wright engines. B-3A Ordered as LB-10A, 36 delivered as B-3A (S/N 30-281/316). The first aircraft was delivered in October 1930. B-5A Ordered as B-3A, re-engined with Wright R-1750-3 Cyclone engines, 27 built (S/N 30-317/343). Operators United States Army Air Corps 2d Bombardment Group, Langley Field, Virginia 20th Bomb Squadron – operated B-3A and B-5A 1931–1932 49th Bomb Squadron – operated B-3A and B-5A 1931–1932 96th Bomb Squadron – operated B-3A and B-5A 1931–1932 4th Composite Group, Nichols Field, Luzon, Philippines 28th Bomb Squadron – operated B-3A 1932–1937 2nd Observation Squadron- operated B-3A 1938–1940 5th Composite Group, Luke Field, Territory of Hawaii 23d Bomb Squadron – operated B-5A 1932–1937 72d Bomb Squadron – operated B-5A 1932–1936 6th Composite Group, France Field, Panama Canal Zone 25th Bomb Squadron – operated B-3A 1932–1936 7th Bombardment Group, March Field, California 9th Bomb Squadron – operated B-3A 1931–1934 11th Bomb Squadron – operated B-3A 1931–1934 31st Bomb Squadron – operated B-3A 1931–1934 19th Bombardment Group, Rockwell Field, California 30th Bomb Squadron – operated B-3A 1932–1936 32d Bomb Squadron – operated B-3A 1932–1935 Air