B-35 Flying Wing
Northropís Flying Wing
Strategic Air Command (SAC) inherited a trio of bomber projects developed during World War II period. A radical Northrop flying wing, a six-engine Consolidated giant, and a more conventional Boeing all took advantage of the 3,000-hp Pratt & Whitney R-4360 Wasp Major.
The most unconventional bomber of this era was the XB-35 flying wing, designed by John K. Northrop. His light wooden experimental twin-engine N-1M, first flown in July 1940, had demonstrated the possibilities of aircraft carrying all loads and controls within the wing and dispensing with fuselage and tail sections. The larger the aircraft, the greater the savings in weight and drag reduction, so an Air Force request on April ll, 1941, for bomber designs that could carry a 10,000-pound load halfway across a 10,000-mile range gave Northrop a chance for a bold step.
Encouraged by Air Force leaders, his company proposed a four-engine flying wing bomber, design NS-9E, and procurement was endorsed in a September 9 conference with General Oliver P. Echols, AMD Chief. A contract for a 1/3-scale flying model (N-9M) was approved October 3, 1941, to test the configurationís characteristics before XB-35 construction actually began. The prototype contract approved November 22, 1941, ordered an XB-35 to be delivered in two years. A second XB-35 prototype added to that contract on January 2, 1942, was expected to be delivered in April 1944.
Engineers of Northropís small new factory at Hawthorne, California, began 1942 with three quite radical projects: the single-engine XP-56 interceptor, the twin-engine XP-61 night fighter, and the four-engine XB-35. Although Northrop would not guarantee any performance levels before the small-scale model was flight tested, the AAF was confidant enough to order 13 YB-35 service-test aircraft on December 17, 1942.
The first N-9M flew on December 27, 1942, powered by two Menasco engines. Although it crashed on its 45th flight, three more were built, resuming the flight program on June 24, 1943. Optimism about the early results led to a June 30, 1943, contract to have Martin engineer and build 200 B-35Bs at the Omaha plant, but this was canceled May 26, 1944, when it was realized that the flying wing could not be ready in time for that war. Despite many technical delays, the radical designís potential continued to spark Air Force interest.
The XB-35 was first flown by Max R. Stanley from Hawthorne to Muroc on June 25, 1946, 55 months after the contract was approved. The power plant consisted of Pratt & Whitney Wasp Majors (two R-4360-17s outboard and two R-4360-21s inboard) with double turbosuperchargers and extended drive shafts for co-axial counterrotating Hamilton four-bladed pusher propellers. These dual propellers proved unsatisfactory, and after 3 flights, the XB-35 was grounded until March 1947.
The second XB-35 began test flights on June 26, 1947, but after only 11 flights by the first prototype and four by the second, the big Northrops were grounded in August 1947 to replace the dual-rotation system with Curtiss single-rotation propellers. Seven more flights were made by the first XB-35 from February 12 to April 1, 1948, but it wasnít flown again until its return to the factory on October 7 for scrapping after less than 24 flight hours.
Single-rotation propellers were also fitted to the second XB-35 and to the first YB-35 flown May 12, 1948, which was the only flying wing actually fitted with gun turrets. The crew consisted of nine men in the pressurized center section (two pilots, with a bombardier, engineer, navigator, radioman, and three gunners), plus accommodations for six relief men. Northropís control system was the first fully-powered hydraulic system on an American airplane, and the NACA 65 wing section was thick enough (seven feet at the apex) to enclose the retracted double-wheel landing gear and all of the equipment.
The eight bomb bays held from 10,498 to 51,200 (thirty-two 1,600-pound) pounds of bombs, but none of those bays was large enough for an atomic bomb. Twenty .50-caliber M-2 guns were in seven remote-controlled turrets aimed from central sighting stations behind the pilot, on top and beneath a cone protruding from the trailing edge. Four-gun turrets were spotted above and below the center section, two-gun turrets were visible outboard of the engines, one pair on top, another below, and four guns could be placed in the tail cone.
All test flights had been made from Muroc, now Edwards Air Force Base, by company pilots, and the pre-test performance estimates were not verified. Jet propulsion had rendered the original concept obsolete, but interest in the flying-wing principle with jet propulsion continued. To save enough funds for that YB-49 program, both XB-35s and the YB-35 were scrapped in August 1949.