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The Boeing XB-39 Superfortress was a United States prototype bomber aircraft, a single example of the B-29 Superfortress converted to fly with alternative powerplants. It was intended to demonstrate that the B-29 could still be put into service even if the first choice of engine, the air-cooled Wright R-3350 radial engine, ran into development or production difficulties.
Fisher finally focused again on the B-39. The first flight of the B-39 was made on 9 December 1944 at Cleveland, Ohio. The initial flight tests of the B-39, without turbosuperchargers installed, were impressive. However, the B-39 program was by now seriously delayed, and the flawed R-3350 B-29s had already been rushed into combat in June 1944.
Despite continuing problems with the B-29s, the aircraft was functioning well enough in combat that it no longer made any sense to shift resources in the manufacturing base to a new engine for the B-29 and so the B-39 was not ordered into production.
XB-39 on USAF Museum site
{{USAF bomber aircraft B-39 Superfortress Boeing B-39 Superfortress Four-engined tractor aircraft
Design and development
Starting life as the first YB-29 delivered to the United States Army Air Forces, it was sent in November 1943 to theFisher Body
Fisher Body was an automobile coachbuilder founded by the Fisher brothers in 1908 in Detroit, Michigan. A division of General Motors for many years, in 1984 it was dissolved to form other General Motors divisions. Fisher & Company (originally Allo ...
Aircraft Development Section of General Motors
The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
to be converted to use Allison V-3420-17 liquid-cooled W24 (twin- V12, common crankcase) inline engines.''Flying Magazine,''August 1945, p. 51. Fisher was chosen for the modification as it was familiar with the engine, as it was to power the P-75 Eagle that they were then developing. Testing on it began in early 1944.
Further development of the engine and the aircraft was delayed by a series of changes in the planned turbosuperchargers, as the originally specified GE Type CM-2 two-stage turbosupercharger became unavailable due to demands on GE's production of its other turbosuperchargers. Other turbosuperchargers were considered, but the end result was that the first flights of the B-39 had to be made without any turbosuperchargers at all.
Operational history
Fisher finally focused again on the B-39. The first flight of the B-39 was made on 9 December 1944 at Cleveland, Ohio. The initial flight tests of the B-39, without turbosuperchargers installed, were impressive. However, the B-39 program was by now seriously delayed, and the flawed R-3350 B-29s had already been rushed into combat in June 1944.
Despite continuing problems with the B-29s, the aircraft was functioning well enough in combat that it no longer made any sense to shift resources in the manufacturing base to a new engine for the B-29 and so the B-39 was not ordered into production.
Specifications (XB-39)
See also
References
Notes
Bibliography
* Jones, Lloyd S. ''U.S. Bombers, B-1 1928 to B-1 1980s''. Fallbrook, California: Aero Publishers, 1962, second edition 1974. . * Whitney, Daniel. ''Vee's For Victory!''. Atglen, Pennsylvania: Schiffer Military History, 1998.External links
XB-39 on USAF Museum site
{{USAF bomber aircraft B-39 Superfortress Boeing B-39 Superfortress Four-engined tractor aircraft
XB-39
The Boeing XB-39 Superfortress was a United States prototype bomber aircraft, a single example of the B-29 Superfortress converted to fly with alternative powerplants. It was intended to demonstrate that the B-29 could still be put into service ...
Mid-wing aircraft
Aircraft first flown in 1944
Four-engined piston aircraft