Similar in appearance to the Douglas B-18 Bolo, but intended to achieve significantly improved performance, the North American NA-21 bomber was developed at the company's Inglewood, California plant during 1935-3, the prototype being completed in March 1937. Powered by two 895kW Pratt & Whitney R-218.0 Twin Hornet engines with F-10 turbo-superchargers, the XB-21 carried a six-man crew and armament comprised single 7.62mm machine-guns in nose and dorsal turrets, plus a similar weapon in each of the ventral and two waist positions. Short-range bomb load was 4536kg, reducing to 998kg over 3058km.
Only the prototype was built.
