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The Boeing Y1B-20 (Model 316) was a development of the XB-15 design proposed by Boeing as a long-range heavy bomber. About the same size as the XB-15, the Y1B-20 design was primarily done to increase the performance of the large bomber by using more powerful engines. The design was presented to the Army in early 1938 and two aircraft were ordered later that year. The Army leadership reversed its decision and canceled the order before construction began.
Although the Army General Staff still considered the four-engine bomber a luxury into the late 1930s, the experience gained by Boeing engineers designing the XB-15 and Y1B-20 led directly to the development of the B-29 -- one of the premiere U.S. bombers of World War II.
||Development of XB-15; canceled
TECHNICAL NOTES (as designed):
Armament: Four .50-cal. and three .30-cal. machine guns and 17,600 lbs. of bombs (max)
Engines: Four Wright GR-2600-A73 geared radials of 1,350 hp each or four Pratt & Whitney R-2180-5 radials of 1,400 hp each
Maximum speed: 258 mph
Cruising speed: 242 mph
Range: 4,000 miles with 4,000 lbs. of bombs
Span: 157 ft. 0 in.
Length: 109 ft. 2 in.
Height: 23 ft. 4 in.
Weight: 87,500 lbs. gross weight
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