The YB-49 Flying Wing
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.
First flight of the YB-49 was on October 21, 1947. The aircraft logged as much flight time in the next two months as the troublesome XB-35's had in two years. Unfortunately, the jet technology was very new, and a series of problems with auxiliary power units, and the jets themselves, gave the YB-49 less than spectacular reliability.
After logging almost 57 hours of flight time, disaster struck when the second YB-49 crashed, killing all aboard, including copilot Captain Glenn Edwards, for whom Edwards AFB was named. "Black boxes" were not in existence in those days, and the cause of the crash was not known. This flight was the 25th for that aircraft. The major portion of the aircraft landed inverted with little horizontal velocity, and much of the aircraft was destroyed in the fire that followed the crash.
The investigation observed that a major structural failure had occurred in flight, although the cause was not clear. It appeared that the outer wing panels had failed during a positive load condition, possibly as a result of a high-G pullout, perhaps during recovery from a stall.
In September, 1948, a contract for 30 reconnaissance versions, the RB-49A, was awarded. The planes were to be produced at the Fort Worth government owned plant of Consolidated Vultee Aircraft Corporation (Convair).
In November, a devastating blow to the bomber program was received when Major Robert Cardenas, an Air Force test pilot, delivered a report which stated that the YB-49 was "extremely unstable and very difficult to fly on a bombing mission... because of the continual yawing and the pitching with was evident upon application of the rudders, undoubtedly due to the control arrangements or elevons peculiar to the YB-49." Subsequently, Major Cardenas stated the bomber was only "marginally" stable, rather than "extremely". These problems could be corrected through the use of an autopilot.
In December, a Board of Senior Officers recommended cancellation of the RB-49. In January, Northrop received direction to terminate all work on the RB-49, except for completion of one YRB-49A.
In the early part of 1949, Max Stanley conducted autopilot test on the YB-49. After an evaluation by the Air Force, the aircraft was declared suitable for its mission. In April and June, a series of bomb drop tests were performed, which showed problems with bomb delivery. Footage from chase planes showed that as the bombs exited the bomb bays, they acquired a pitching and oscillation movement, attributed to turbulence in the bomb bay.
During this time period, a proposed merger of Northrop and Convair was rejected as unsuitable. Since then, John Northrop has expressed his views of what really happened.
In November 1949, the Air Force ordered all YB-49s scrapped (See the article on Northrop and Symington for details). 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.