The Boeing B-54 was an American strategic bomber designed by Boeing for use by the United States Air Force. Derived from the YB-50C Superfortress, construction of the prototype was canceled before completion, and the aircraft was never flown. Design and development Begun in 1947, the B-54 was the planned production version of the YB-50C prototype. The standard Pratt & Whitney R-4360 engines of the normal B-50 bomber were replaced with R-4360-51 Variable Discharge Turbine (VDT) turbo-compound engine, the fuselage was lengthened by over and the wingspan was extended by , which required the installation of outrigger landing gear in the first and fourth engine nacelles. Large fuel tanks under the outboard wing section were required to carry an additional of fuel to reach the intended range; 14 .50-caliber machine guns comprised the specified defensive armament. On May 29, 1948, contracts were placed by the Air Force for 21 B-54A bombers and 52 RB-54A reconnaissance aircraft; However, on April 18, 1949, the B-54 project was cancelled due to the development of better-performing jet aircraft; construction of the prototype B-54A had started at Seattle but was never completed. The cancellation was lambasted by the Seattle press, who claimed that it was a political decision instead of a military one. Variants B-54A Intended production version of the YB-50C RB-54A Reconnaissance version Specifications See also References Notes Citations Bibliography . Swanborough, F. G. and Peter M. Bowers. United States Military Aircraft since 1909. Washington, DC: Smithsonian Institution Press, 1989. . B-54 Cancelled military aircraft projects of the United States Four-engined tractor aircraft B-54 Mid-wing aircraft Four-engined piston aircraft