The XB-21 of the mid-1930s was North American Aviation's first venture into the bomber field. It was a twin-engined six-place heavy bomber powered by a pair of 1200 hp Pratt & Whitney R-2180-1 Twin Hornet radial engines equipped with F-10 turbosuperchargers. The XB-21 was a mid-wing monoplane armed with five 0.30-inch machine guns. One gun was mounted in each of power turrets installed in the nose and in the rear dorsal positions, plus one 0.30-inch machine gun firing from a ventral hatch and from left and right waist positions.
The aircraft was known by the company as the NA-21, and work on the project was begun in January 1936. The prototype took to the air on its maiden flight on December 22, 1936. After some rework, it was accepted by the Air Force as the XB-21. The serial number 38-485 was assigned. Two 1100-pound bombs could be carried 1960 miles, or eight 1100 pound bombs for a 660 mile range. During testing, the nose turret was removed and replaced by a solid shell, and the ventral turret was removed completely.
The XB-21 aircraft found itself in competition with the Douglas B-18A for production orders. Price was the determining factor, the two aircraft having roughly similar performances. North American was asking $122,600 for each plane, whereas Douglas was asking only $63,977. Consequently, Douglas got the order, and a contract for 177 B-18As was issued on June 10, 1937. No further XB-21s were built.
Serial number of North American XB-21: 38-485.
Specification of North American XB-21:
Two Pratt & Whitney R-2180-1 radials, rated at 1200 hp for takeoff. Performance: Maximum speed 220 mph at 10,000 feet. Cruising speed 190 mph. Service ceiling 25,000 feet. An altitude of 10,000 feet could be attained in 10 minutes. Range was 1960 miles with 2200 pounds of bombs, 660 miles with 10,000 pounds of bombs. Maximum range 3100 miles. Weights: 19,082 pounds empty, 27,253 pounds gross, 40,000 pounds maximum. Dimensions: Wingspan 95 feet, length 61 feet 9 inches, height 14 feet 9 inches, wing area 1120 square feet. Armed with a 0.30-inch machine gun mounted in power turrets in the nose and in the rear dorsal positions, plus one 0.30-inch machine gun firing from a ventral hatch and from left and right waist positions.