Curtiss B-2 Condor
The B-2 was a large fabric-covered biplane aircraft. Its two engines sat in nacelles between the wings, flanking the fuselage. It had a twin set of rudders on a twin tail, a configuration which was becoming obsolete by that time. At the rear of each nacelle was a gunner position. In previous planes, the back-facing gunners had been in the fuselage, but their view there was obstructed. A similar arrangement (using nacelle-mounted gun platforms) was adopted in the competing Keystone XB-1 aircraft.
The XB-2 competed for a United States Army Air Corps production contract with the similar Keystone XB-1, Sikorsky S-37, and Fokker XLB-2. The other three were immediately ruled out, but the Army board appointed to make the contracts was strongly supportive of the smaller Keystone XLB-6, which cost a third as much as the B-2. Furthermore, the B-2 was large for the time and difficult to fit into existing hangars. However, the superior performance of the XB-2 soon wrought a policy change, and in 1928 a production run of 12 was ordered.