In 1930, seven Keystone bombers were ordered under the designation LB-13. They were to be equipped with single vertical tails and were to be powered by a pair of 525 hp Pratt & Whitney GR-1690 geared radials. Serials were 30-344/353.
In 1930, the USAAC abandoned its separate designation categories for light (LB) and heavy (HB) bombers, and classified them both under the B category. Of the seven LB-13s that were ordered, five were completed as Y1B-4s with 575 hp R-1860-7 engines (30-344/348) and the other two as Y1B-6 with 575 hp R-1820-1 engines (30-349/350). Three more Y1B-6s were converted from B-3As (30-351/353)
Specification of the Keystone Y1B-4:
Two 575 hp Pratt & Whitney R-1860-7 alr-cooled radial engines. Maximum speed 121 mph at sea level Weight: 13,011 pounds gross. Wingspan 74 feet 9 inches, length 48 feet 10 inches, height 15 feet 9 inches, wing area 1145 square feet. Two Lewis machine guns in an open gunner's position in the nose, two Lewis machine guns in an open dorsal gunner's position, one Lewis gun firing downward through an opening in the lower fuselage.
Specification of the Keystone Y1B-6:
Two 575 hp Wright R-1820-1 air-cooled radial engines. Maximum speed 120 mph at sea level Weight: 13,300 pounds gross. Wingspan 74 feet 9 inches, length 48 feet 10 inches, height 15 feet 9 inches, wing area 1145 square feet. Two Lewis machine guns in an open gunner's position in the nose, two Lewis machine guns in an open dorsal gunner's position, one Lewis gun firing downward through an opening in the lower fuselage.
Sources:
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United States Military Aircraft Since 1909, Gordon Swanborough and
Peter M. Bowers, Smithsonian, 1989.
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American Combat Planes, Ray Wagner, Third Edition, Doubleday, 1982.
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American Warplanes, Bill Gunston
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Jane's Encyclopedia of Aviation
- U.S. Army Aircraft, 1908-1946, James C. Fahey
