Douglas proposed a number of modifications designed to improve the performance of the B-18. Initially considered a redesign, the XB-22 featured 1,600 hp Wright R-2600-1 Twin Cyclone radial engines. The complete B-18 redesign was considered promising enough by the USAAC to alter the original contract to produce the last 38 B-18As ordered under Contract AC9977 as the B-23] The design incorporated a larger wingspan with a wing design very similar to that of the DC-3, a fully retractable undercarriage, and improved defensive armament. The B-23 was the first operational American bomber equipped with a glazed tail gun position. The tail gun was a .50 calibre (12.7 mm) machine gun, which was fired from the prone position by a gunner using a telescopic sight. The first B-23 flew on July 27, 1939 with the production series of 38 B-23s manufactured between July 1939 and September 1940. For the operational history of the B-23 and details of the three variants, click here.
