Martin XB-51 - Operational History

Operational History

In 1950, the United States Air Force issued a new requirement based on early Korean war experience for a night intruder/bomber to replace the A-26 Invader. The XB-51 was entered, as well as the Avro Canada CF-100 and the English Electric Canberra. The Canberra and XB-51 emerged as the favorites. The XB-51 was a highly maneuverable aircraft at low level, and substantially faster than the Canberra (its "turn-of-speed" was faster than most fighter aircraft of the era). However, its load limiting factor of only 3.67 g (36 m/s2) restricted tight turns, and the XB-51's endurance was substantially poorer than the Canberra's; this latter proved to be the deciding factor. Additionally, the tandem main gear plus outriggers of the XB-51 was thought unsuitable for the requirement to fly from emergency forward airfields.

The Canberra was selected for procurement and the XB-51 program ended. Martin did not end up the loser, however, for they were selected to build the 250 Canberras ordered under the designation B-57A. Furthermore, the rotating bomb bay was incorporated in the B-57. A proposed B-57 Super-Canberra also included XB-51 features, such as swept wing and tailplane. In the end it was never built, mainly because it was a new design and would have taken too long to put in production, although it promised much better speed and performance.

Flight testing for research purposes continued after program cancellation. The second prototype, 46-686, which first flew in 1950, crashed on 9 May 1952 during low-level aerobatics. The first prototype, 46-685 continued to fly, including appearing in the film Toward the Unknown as the "Gilbert XF-120" fighter. The surviving prototype was en route to Eglin AFB to shoot additional footage when it crashed during takeoff following a refueling stop in El Paso, Texas, on 25 March 1956.