The early versions of the Stratojet were all severely underpowered, and in pursuit of a more powerful Stratojet the Air Force proposed a version of the B-47 powered by four 10,090 lb.s.t. Allison J71-A-5 turbojets. The designation YB-56 was assigned to this project, since the different engine configuration was thought to justify a change in designation. A reconnaissance version known as RB-56A was also planned. According to the original planning, the 88th B-47B (50-092) was scheduled be converted to YB-56 configuration as a testbed for the concept.
For a time, the YB-56 was intended to be the "definitive" Stratojet. However, since the airframe was basically that of a "stock" B-47B, the designation of the YB-56 was changed to YB-47C. The J71 engine was later found to be unsuitable for the Stratojet, and a decision was made to switch to the new Pratt & Whitney YJ57 turbojet. However, these engines were not yet available, and in any case they were already earmarked for the B-52. Consequently, the YB-47C program was cancelled in December of 1952, and no four-jet Stratojet was ever built.
Sources:
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American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday,
1982.
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Post World War II Bombers, Marcelle Size Knaack, Office of Air Force
History, 1988.
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The Boeing B-47, Peter Bowers, Aircraft in Profile, Doubleday, 1968.
-
Boeing Aircraft Since 1916, Peter M. Bowers, Naval Institute Press,
1989.
- United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.
