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Posted 7/7/2009 Printable Fact Sheet
Boeing/Pratt & Whitney XB-44
Boeing/Pratt & Whitney XB-44. Original photo caption reads "XB-44 oblique front view of completed airplane during ground shakedown runs." Note that the No. 3 engine is running. (U.S. Air Force photo)
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The XB-44 was a modification of a Boeing B-29A-5-BN (S/N 42-93845) done by Pratt & Whitney to adapt the aircraft for R-4360 supercharged radial engines. The larger and more powerful engines required a complete redesign of the engine nacelles which featured a distinctive scoop air inlet on the underside. The XB-44 was never intended to be anything except an engine test bed, but it carried minimal defensive armament -- two .50-cal. machine guns in the tail.

The XB-44 program was initiated in mid-1943 when Pratt & Whitney offered to modify a B-29 with larger engines. A contract was awarded in July 1944, and the first flight of the aircraft occurred in May 1945. The XB-44 was capable of cruising speeds about 50-60 mph faster than a production B-29.

Although the XB-44 was superior to the B-29, the entire program was near cancellation because of the approaching end of World War II and rapid demobilization. The Army Air Forces needed a very heavy bomber and lobbied for continuation of the program. Initially, a production version design was designated B-29D, but because Boeing engineers had modified the basic B-29 design extensively, the aircraft was redesignated B-50. The first production versions were produced as B-50A. Ironically, the aircraft initially classified as a very heavy bomber in the mid-1940s was, by the end of its service life, classified as a medium bomber. Aircraft like the B-36 and B-52 dwarfed the last of the USAF's propeller-driven bombers.

Type Number built/
XB-44 1 (cv) B-50 prototype; a.k.a. XB-29D

Armament: Two .50-cal. machine guns in the tail
Engines: Four Pratt & Whitney R-4360-33 Wasp Major supercharged radials of 3,000 hp each (takeoff power)
Maximum speed: 392 mph at 25,000 ft.
Cruising speed: 282 mph
Range: 2,400 miles
Service ceiling: 39,000 ft.
Span: 141 ft. 3 in.
Length: 99 ft. 0 in.
Height: 29 ft. 7 in.
Weight: 140,000 lbs. (maximum gross weight)
Crew: 11 maximum, although it usually flew with a smaller test crew
Serial numbers: 42-93845 (originally B-29A-5-BN)

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