The XB-35 Flying Wing
The contract for the XB-35 was approved November 22, 1941, while the war was in full swing. The contract called for an operational range of 10,000 miles with 10,000 pounds of bombs. This was such a long mission that a relief crew of six people was provided with sleeping areas. Twenty 0.50 caliber machine guns were to protect the plane with seven remotely controlled turrets, four on the wing itself, two in the crew nacelle, and one in the tail stinger.
To power the behemoth, four Pratt & Whitney Wasp Major engines (each composed of one pair of a R-4360-17 and R-4360-21) were to provide 3000 hp each to a four-bladed, contra-rotating Hamilton Standard propellor via a government furnished equipment (GFE) gearbox. This was to prove to be a crippling weakness in the bomber, as the gearboxes were a constant source of trouble.
First flight of the design was to be June 25, 1946, a measure of the complexity of the project. Many other planes were able to go from contract to first flight in a year or two, the Wing was allocated almost five. As engineering work continued, a contract for a backup plane test was awarded, as well as a contract for 14 test models, the YB-35. In June of 1943, a contract for 200 B-35s was anticipated. The problem with all this was that Northrop's construction facilities were already heavily taxed in current production of the P-61 Black Widow night fighters. Someone else's plant would have to help build the bombers. The Glenn L. Martin Company was contracted to assist Northrop in engineering the XB-35 and YB-35, as well as manufacture the 200 B-35s.
Unfortunately, the relationship did not help the program. Lack of cooperation and coordination, as well as too many engineers having left for military duty, left the program 18 months behind schedule by early 1944.
In May, the AAF conducted a program review. It was decided that Martin's production contract was to be canceled, although they were to continue to give Northrop engineering assistance on the X and Y models. As a result of this, it became clear that the B-35 would not be in service before the end of the war. This had significant implications for the B-35. Jets were being developed, and new fighters and bombers designed to use the new powerplants. Faster was better, even if range shrunk dramatically.
As a result of the jet age, it was obvious that the B-35 would be just too slow. On the other hand, it was an extremely aerodynamic airplane to start with, and could easily be converted to jet power. A series of programs were begin to study how to best implement a jet powered Wing.
On June 25 1946, after a successful taxi test program which reached taxi speeds of 115 mph, the Wing underwent it's first flight. In true Dilbertian management style, employees were forbidden to attend, as there were so many of them that crowd control would be a problem.
The Wing, piloted by Max Stanley, became airborne at 120 mph. This first flight was just a ferry flight from Northrop airport to Muroc Army Air Base (now Edwards AFB). During this flight the gear was cycled, and maximum airspeed reached was 200 mph. The flight lasted 44 minutes.
The test program revealed major problems with the GFE gearboxes and governors. Vibration caused gearbox failures. The governors failed to perform adequately. The second XB-35 flew almost a year after the first, and had similar problems. It was decided to remove the contra- rotating propellers and replace them with single rotation propellers, but this decreased performance considerably.
Two of the XB-35s were converted to the YB-49 configuration by replacing the piston engines with eight 4000 pound thrust TG-180 (J35) engines. Because of the decreased ventral area, small fins were added for stability at the trailing edges.
In November 1949, the Air Force ordered all XB-35s scrapped. Scrapping of the XB-35s began in January 1950, the only flying YB-49 was destroyed on March 1950 during a failure of the nose landing gear. See the Northrop and Symington article for more details.