- XB-44 Superfortress
name = XB-44 Superfortress
type = Test Plane
caption = Boeing XB-44
first flight =
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BoeingXB-44 Superfortress was a United States B-29 Superfortress bomberaircraft upgraded with Pratt & WhitneyR-4360-33 Wasp Major radial enginesof convert|3000|hp takeoff rating, in place of the production engines rated at convert|2200|hp|abbr=on takeoff rating.
The program began in mid-1943, when Pratt & Whitney proposed to the
United States Army Air Forces(USAAF) that the B-29 be modified with larger engines. In July 1944, a contract was signed and one B-29A-5-BN (s/n 42-93845) was made available to P & W for developmental work. Modification involved complete redesign of the four engine nacelles, including the addition of a large airscoop below each cowling.
Because the aircraft was intended to be only a testbed for the engine installation, most of its defensive equipment was removed before testing. Two machine guns in the rear
fuselagewere left in place.
Only the one aircraft was used in the B-44 flight test program. [ [http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2656 National Museum XB-44 Superfortress Factsheet] ]
First flying in May 1945, the XB-44 proved 50-60 mph faster than the B-29 (available sources do not indicate how much of this increased speed was due to differing aircraft weight or to deleted armament).
Production of the re-engined bomber was initially planned as the B-29D, but it was decided to change the aircraft designation in military inventory because of the extensive airframe changes that would be required (this design work would have to be performed by the aircraft manufacturer, Boeing; it was not performed on the B-44 prototype except for the engine nacelle rework). The upgrade program became the "
B-50 Superfortress" in December 1945. Officially, the aircraft's new designation was justified by the changes separating the proposed B-29D from its predecessors:
*New engine nacelles and engine mounts
*Larger vertical tail required for engine-out stability
*Wing reinforcing due to greater engine weight
*Revised routing for combustion and exhaust gases
*Upgraded armament-control equipment
*Increases in landing gear capability
*Added fuel capacity
However, according to
Peter M. Bowers, a long-time Boeing employee and small aircraft designer, and a well-known authority on Boeing aircraft, "the redesignation was an outright military ruse to win appropriations for the procurement of an aeroplane that by its designation appeared to be merely a later version of an existing model that was being canceled wholesale, with many existing examples being put into dead storage." [Knaack, Marcelle Size. "Post-World War II Bombers". Washington, D.C.: Office of Air Force History, 1988. ISBN 0-912799-59-5. p. 163.] [ [http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2656 Fact Sheets : Boeing/Pratt & Whitney XB-44 : Boeing/Pratt & Whitney XB-44 ] ]
When the R-4360 was first developed, its takeoff power rating was 3000 horsepower. [ [http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=850 National Museum Fact Sheet for Pratt & Whitney R-4360] .] By the time it was incorporated into the B-50, its MTO rating was convert|3500|hp, and even higher when used in other aircraft ("e.g.", 3800 in the
Convair B-36). Much of the difference is due to differing turbochargers installed in the different aircraft (the engine also contains a supercharger, gear-driven by the crankshaft).
XB-38 Flying Fortress
List of bomber aircraft
List of military aircraft of the United States
* Jones, Lloyd S. "U.S. Bombers, B-1 1928 to B-1 1980s". Fallbrook, CA: Aero Publishers, 1962, second edition 1974. ISBN 0-8168-9126-5.
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