Monday, April 26, 2010

Northrop XB-35

The Northrop XB-35 was an experimental heavy bomber aircraft developed for the United States Army Air Forces during and shortly after World War II by the Northrop Corporation. It used the radical and potentially very efficient flying wing design, in which the tail section and fuselage are eliminated and all payload is carried in a thick wing. Only prototype and pre-production aircraft were built, although interest remained strong enough to warrant further development of the aircraft as a jet bomber, under the designation YB-49.

The XB-35 was the brainchild of Jack Northrop, who made the Flying Wing the focus of his work during the 1930s. During World War II, Northrop had been commissioned to develop a large wing-only, long range bomber designated XB-35. Northrop advocated the "flying wing" as a means of reducing parasitic drag and eliminating structural weight not directly responsible for producing lift. In theory, the B-35 could carry a greater payload faster, farther, and cheaper than a conventional bomber. On 11 April 1941, the United States Army Air Corps sent out a request for a bomber that could carry 10,000 lb (4,536 kg) of bombs to a round-trip mission of 10,000 mi (16,093 km). Requested performance was a maximum speed of 450 mph (740 km/h), cruise speed of 275 mph (443 km/h), and service ceiling of 45,000 ft (13,716 m). This aircraft would be able to bomb Nazi-occupied Europe in the event that Britain fell. This proposal was originally submitted to Boeing and Consolidated Aircraft Company, and led to the production of the Convair B-36. In May, the contract was also extended to include Northrop, inviting them to submit a design along the lines they were already exploring.[2]

Since the new aircraft would require a significant amount of engineering work in untested waters, the first order placed was actually for a one-third scale version of the XB-35 dubbed the Northrop N-9M (M standing for model). This aircraft would be used to gather flight data on the Flying Wing design, which would then be used in designing the big XB-35. It would also be used to familiarize pilots with the radical, all-wing concept. Early in 1942, design work on the XB-35 itself began in earnest. Unlike conventional aircraft, Flying Wings cannot use a rudder for lateral control, so a set of butterfly-like, double split flaps on the trailing edge of the wingtips were used. When aileron control was input, they were deflected up or down as a single unit, just like an aileron. When rudder input was made, the two surfaces on one side opened, top and bottom, creating drag, and yawing the aircraft. By applying input to both rudder pedals, both sets of surfaces were deployed creating drag so that the airspeed or the glide angle could be manipulated.[2]

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