this is from Joe Baugher, one of the few people I actually trust for aviation info sice he seems to be a research junkie LOL
http://home.att.net/~jbaugher2/b49_1.html
The reasons for the abrupt cancellation of the B-49 project remain uncertain even today, and many of the details are still classified. The chronic stability problems, plus the series of accidents that seem to dog the project at every step along the way certainly must have played a role. In addition, the YB-49 carried its bomb load in a series of bomb bay cells, each of which was too small to accommodate the Mk III and Mk 4 atomic bombs of the day, which were 5 feet in diameter, 10 feet long, and weighed 10,000 pounds. In contrast, the weapons bay in the B-36 was cavernous and could carry almost anything.
Many deficiencies turned up in the second series of tests. The J35 turbojets of the YB-49 were extremely thirsty for fuel, and the jet-powered YB-49 had only half the range of the YB-35 that preceded it. The test pilots complained that the aircraft was extremely unstable and difficult to fly. They also maintained that the YB-49 was completely unsuitable as a bombing platform-- it could not hold a steady course or a constant airspeed and altitude, and that here was a persistent rocking motion in yaw, which tended to upset the bomb sights. In comparison with the B-29, the YB-49 had a much poorer circular average error and range error during bombing trials. In retrospect, many of the stability problems with the flying wing may have been insoluble with the technology available in the late 1940s, requiring the fly-by-wire technology that was developed much later for their solution.
On March 15, 1950, the cancellation of the entire YB-49 program became official. On that very same day, the first YB-49 (42-102367) got itself involved in a ground taxiing accident at Edwards AFB. There were no fatalities, but crewmen were injured and the aircraft was totally destroyed by fire. Excessive shimmy of the nosewheel followed by total gear collapse were blamed for the mishap.
---the "sabotage" rumor-----
On the way back to California, 42-102367 stopped off at Wright Field in Dayton so that the Air Force could take a look at the new plane. On February 23, the YB-49 took off to return to Muroc, but during the flight three of the J35 engines on the left and one on the right side caught fire, forcing an emergency landing at Winslow, Arizona. There were hints of sabotage, since it was later determined that the cause of the engine fires was that the turbine oil reserves had not been filled in any of the J35 engines during refuelling at Wright Field. The FBI was called in to investigate, but a blanket of security was thrown over the entire affair and the incident was all but forgotten.
"We sleep safely in our beds because rough men stand ready in the night to visit violence on those who would harm us". George Orwell
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<img src="http://www.fas.org/man/dod-101/sys/ac/atengun2X.GIF" border=0>