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Posted 6/26/2009 Printable Fact Sheet
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Boeing YB-29
Boeing YB-29. (U.S. Air Force photo)
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The YB-29 was an improved version of the XB-29 used for service testing. The engines were upgraded to the -21 model of the Wright Cyclone, and three-blade propellers of the XB-29 were changed to a four-blade type for the YB-29. The YB-29 featured an improved fire control system and turret-mounted .50-cal. machine gun pairs.

The first flight of the YB-29 took place in the summer of 1943, and as testing proceeded, a wide variety of modifications were tried on one or more of the 14 aircraft ordered. The first YB-29 (S/N 41-36954) was modified by replacing the Wright Cyclone radial engines with Allison V-3420-17 inline engines and was redesignated XB-39. The fourth YB-29 (S/N 41-36957) was extensively modified to test defensive armament. One arrangement had a nose-mounted Erco ball turret and fixed forward fuselage blisters housing dual .50-cal. machine guns. Other YB-29s were fitted with manned dorsal and ball turrets (similar to the B-17 arrangement), waist gunner positions and remote-controlled ball turrets mounted in the cheeks (lower forward nose).

Because of the urgent need for the long-range B-29, production aircraft were developed and built in parallel with the service test program. The first of more than 1,600 B-29-BWs built at Boeing's Wichita, Kan., plant was delivered in September -- just two months after the initial YB-29 was delivered.

Type Number built/
YB-29 14 Improved XB-29 for service test

Armament: 10 .50-cal. machine guns (standard) plus 20,000 lbs. of bombs
Engines: Four Wright R-3350-21 Cyclone radials of 2,200 hp each (takeoff power)
Maximum speed: 368 mph at 25,000 ft.
Cruising speed: 247 mph
Range: 5,850 miles
Service ceiling: 32,100 ft.
Span: 141 ft. 3 in.
Length: 98 ft. 2 in.
Height: 27 ft. 9 in.
Weight: 120,000 lbs. (gross)
Crew: 11
Serial numbers: 41-36954 to 41-36967

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