The XB-46's development originated in 1944, when the War Department called for bids and proposals on an entire family of jet bombers, with gross weight ranging from 80,000 to more than 200,000 pounds. Consolidated Vultee Aircraft (Convair) Corporation answered the War Department's requirements with the design study of a 90,000 pound, jet propelled bomber. The design, submitted and accepted in November 1944, was labeled by the Army Air Force (AAF) as the XB-46.
The AAF initiated the XB-46's procurement with Letter Contract W33-038-ac-7674, which was approved on 17 January 1945. This first document covered preliminary engineering, wind tunnel, model, tests, mockup, and data that were to be based on the contractor's proposal of November 1944.
The letter contract of January was supplemented on 12 February by a definitive contract of the standard cost plus fixed fee type. This contract followed by 1 week completion of the XB-46's first mockup inspection. As was usually the case, the contract satisfied the inspection board's essential recommendations. In short, 3 experimental B-46s were ordered and required to incorporate the necessary changes identified by the board. A supplemental agreement on 3 March provided for data and spare parts for the 3 XB-46s. Because of fiscal restrictions, the AAF also altered the terms of the basic contract, changing it to the fixed price type.
By the fall of 1945, the AAF had become particularly interested in a Convair jet attack design, identified as the XA-44. The AAF actually considered canceling the XB-46 in favor of the XA-44, since there was not enough money for both projects. The contractor, however, firmly believed a better solution would be to complete 1 XB-46 in a stripped but flyable condition and to develop 2 XA-44s in lieu of the 2 other XB-46s remaining under contract. Although the AAF ratified the suggested substitution in June 1946, the XA-44 program did not materialize. AAF support of the XA-44 did not last long. The program was ended in December 1946, when the design was converted to a light bomber design and redesignated the XB-53. The XB-53 project was given up soon afterwards. The XA-44 program was reinstated in February 1949, but only for a short while. Similarly, the special testing of a TG-180 engine, due to be installed in a B-24J airplane as an added requirement related to the XB-46 development, was also subsequently abandoned.
A distinguishing feature of the XB-46 was the tail turret, designed by the Emerson Electric Company Also, the pilot rode in a fighter style cockpit with a teardrop canopy (The XB-46's cockpit design was selected for study by other aircraft manufacturers). In other respects, despite its extremely thin wings and long, oval fuselage, the graceful airplane did display a few conventional features. Its wings were straight, and it was powered by 4 J35 axial flow engines, which were paired in low slung nacelles, 1 on each side of the fuselage, a typical arrangement.
The XB-46's first flight on 2 April 1947, from San Diego, California, to Muroc Army Airfield lasted over 1 hour and a half. The contractor's test pilot praised the functioning and handling of the airplane which, as completed, contained only the equipment considered necessary to prove its air worthiness and handling characteristics.
The basic flight tests (Phases I and II) of the single XB-46 (Serial No. 45-59582) were concluded in September 1947, within 5 months of the aircraft's first flight. Convair test pilots accumulated more than 26 hours of testing in 16 flights; the AAF's pilots, about 101 hours in 46 flights. Although stability and control were for the most part excellent, engineering problems included engine troubles as well as difficulties with the spoiler clutch installation and with the lateral control surfaces when the aircraft flew at high speeds. All in all, the XB-46 appeared to meet the contractor's only guarantee that it would be safe for experimental test purposes.
The Air Force accepted the sole XB-46 on 7 November 1947 and took delivery of the aircraft on the 12th.
The B-46 program was officially canceled in August 1947, several months before the experimental aircraft was formally accepted and exactly 1 year after the AAF had endorsed the immediate production of the North American XB-45. Still, only a small quantity of B-45s would be bought because, in the final analysis, the performance characteristics of the XB-47, being developed by the Boeing Airplane Company, were sure to exceed those of the future B-45 and of the unfortunate B-46. The AAF selected the XB-45 over the XB-46 for a number of reasons. Weight was one of them. Being at the time slightly heavier than the XB-45, the XB-46 could not be expected to match the future B-45's performance. Another factor against the XB-46 was the size of the necessary radar equipment. Most likely, the installation of such equipment would have required an extensive modification of the aircraft's thin fuselage.
As agreed upon in mid 1946, completion of only 1 stripped version of the XB-46 was intended to provide "a very realistic approach to the problem of development with relatively low cost." Just the same, when completed 1 year later, the experimental program nearly reached the $5 million mark.
Like most strictly experimental airplanes, once accepted by the Air Force, the XB-46 participated in a variety of extra tests such as noise measurements, tail vibration investigations, and the like. Additional stability and control tests were also conducted at West Palm Beach AFB, Florida, between August 1948 and August 1949. However, after 44 hours of flight, these tests were stopped because "maintenance difficulties, aggravated by lack of spare parts, required a prohibitive number of manhours to keep the aircraft in flying condition." Actually, no additional testing was done on the airplane for almost a year. The XB-46 was flown to nearby Eglin AFB in July 1950, where its pneumatic system was tested at low temperatures in the base's climatic hangar. Completion of the climatic tests in November 1950 marked the bomber's end, since the Air Force had no more use for it. Except for its nose section, which was sent to the Air Force Museum at Wright-Patterson AFB, Ohio, on 13 January 1951, the XB-46 was scrapped on 28 February 1952.
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