B-60

The YB-60 program started in August 1950 after the Consolidated Vultee Aircraft Corporation (Convair) offered to re-design the B-36G into a turboprop bomber.

Existing B-36s were swept-wing, all-jet aircrafts. Earlier, a letter issued by the Air Force supplemented the basic B-36 contract and authorized Convair to convert two B-36Fs into prototype B-36Gs, entirely outfitted with turbojets but capable of accommodating turboprop engines.

The proposed B-36G however had very little in common with the B-36F, forcing the Air Force to determined that the B-60 level would be assigned to the aircraft, because of the striking change in physical appearance and upgrading in performance over that of the conventional B-36 aircraft. 

In August 1951, confusion about the configuration of the B-60 prototypes obliged the manufacturer to recommend that at first only two stripped aircrafts will be developed. Accepting responsibility for the error, the manufacturer also proposed that the second YB-60 later be completed as a full tactical model. This meant that separate specifications would have to be developed for each prototype aircraft. The Air Force agreed to this proposal. 

The B-60 prototype differed significantly from the B-36 by featuring swept-back wings and swept-back tail surfaces, a new needle-nose radome, a new type of support power system, and 8 Pratt & Whitney J57-P-3 jet engines, fit in pairs inside pods suspended below and forward of the leading edge of the wings. Another special feature of the YB-60 was that its extended tail, which enabled the aircraft to remain in a level position for a considerable period of time during takeoff, with a gross weight of 280,000 pounds, after only 4,000 feet of ground roll.

Convair was able to use the J57-P-3 Boeing designed nacelles and engine pods, which seemed to be a distinct advantage over other aircrafts of the time. This was particularly true, since the J57 engine was itself the product of an intensive effort to develop a high-thrust turbojet with low fuel consumption. In 1952, production of the aircraft started but the engines were in short supply. The prototype’s eighth J57-P-3 engine finally arrived at the Convair’s Fort Worth plant in April 1952. 

On 18 April 1952, B-60 first flew from the Convair’s Fort Worth plant. The 66 minute flight was hampered by bad weather, but two subsequent flights proved successful. The B-60 displayed excellent handling characteristics. Convair test-flew the first YB-60 for 66 hours, accumulated in 20 flights; the Air Force, some 15 hours, in 4 flights. This encouraging start however, did not prevail in the long run. Flight testing of the aircraft ended on 20 January in the following year as the second YB-60, although 93 percent complete, was not flown at all. This was due to worrisome test results and a number of deficiencies including engine surge, control system buffet, rudder flutter, and problems with the electrical engine-control system.

The US Air Force canceled the B-60 program as it could not compete with similar aircrafts of the same time. The project’s sole purpose was to be a B-36 successor. The YB-52 demonstrated better performance and greater improvement potential than the YB-60. The YB-52’s first flight on 15 April 1952; 3 days ahead of the YB-60’s; was an impressive success and generated great enthusiasm. The Convair prototype’s stability was unsatisfactory because of the high aerodynamic forces acting upon the control surfaces and the low aileron effectiveness of the plane.

The B-60 program was canceled in 1952, and testing of the stripped prototype ended in January 1953. Convair even though tried to convince the Air Force, that the YB-60s should be used as experimental test-beds for turbo propeller engines. Budget constrains and the YB-60’s several unsafe characteristics forced the Air Force to turn down Convair’s tempting proposal.

The cost of the two B-60 prototypes was set at $14,366,022. This figure, included Convair’s fee, the contract termination cost, and the amount spent on the necessary minimum of spare parts.

The Air Force destroyed the two YB-60s in June 1954.