XB-33 The first version of the B-33 design, the
XB-33, was a twin-tailed medium bomber with two
Wright R-3350 engines and pressurised crew compartments; its design began in
1940. It would carry around 4,000 lb (1,814 kg) of bombs. Soon after design of the XB-33 began it became clear that a twin-engined aircraft would not achieve the performance requested by the army. The company moved on to developing a larger four-engined design, the XB-33A.
XB-33A Following the abandonment of the original twin-engined design, the company continued to design a larger four-engined aircraft, and two prototypes were ordered by the USAAF as the
XB-33A; its bombload was to have been 12,000 lb (5,443 kg), as much as that of the
B-24 Liberator, the heaviest US bomber flown in combat prior to the
B-29. The original XB-33 design was to have been powered by the R-3350, the redesigned XB-33A was to have used
Wright R-2600 engines. The main reason for this was the demand for R-3350s for the B-29, one of the most highly valued projects of the Army Air Forces. On January 17, 1942, the USAAF placed an order for 400 B-33As, to be built at the government-owned plant in
Omaha, Nebraska, operated by Martin. On November 25, 1942, the project was cancelled to allow the Omaha plant to concentrate on manufacturing B-29s. ==Variants==