North American XB-21

The North American XB-21, which the manufacturer knew as the NA-21 and which is sometimes called the Dragon, was a twin-engined prototype bomber that North American Aviation built in Inglewood, California, in the late 1930s for evaluation by the United States Army Air Corps. It was the company's first twin-engined military aircraft, a mid-wing all-metal monoplane with two turbosupercharged Pratt & Whitney Twin Hornet radial engines and an unusually heavy defensive armament for its day. It first flew on 22 December 1936 and was tested against an improved Douglas B-18 Bolo. The XB-21 performed better, but at an estimated US$122,000 an aircraft against Douglas's US$64,000 it lost the contest on price, and the five YB-21 pre-production aircraft ordered afterwards were never built. The single prototype served as a research aircraft, and its experience fed into the NA-40 and so into the B-25 Mitchell.