When Convair built the single XB-46 prototype medium bomber during the late stages of World War II it was designed to become the Air Force’s first jet-propelled medium bomber and to compete with the German Arado AR 234 Blitz jet bombers then in development. But when the war ended the program fell victim to budget cuts. Eventually Convair had to choose between two development programs. The XB-46 program lost that decision to the XA-44- a smaller design featuring swept-forward wings that was also unsuccessful in the end. Here’s a video of featuring some clips of the graceful and shapely XB-46 uploaded by airailimages.
The XB-46, together with the North American XB-45 and the Martin XB-48, were referred to as the “Class of 45” at the time of their development. North American eventually produced 145 short-lived B-45 Tornado bombers for the Air Force. Martin’s 6 jet-engine straight-wing design never got past the prototype stage. Boeing…well Boeing was working on the B-47, which as we know eventually became the Air Force’s choice for the role, but not before it morphed several times during development.
The XB-46 (Air Force serial number 45-59582) was completed in 1947 as a stripped-down prototype lacking mission equipment. It flew for the first time on April 2nd 1947. Shoulder-mounted Davis (high-aspect) wings spanning 113 feet (roughly the same span as the B-24 Liberator) supported a tapered fuselage 105 feet long. Powered by four Allison J35-C3 axial-flow turbojets (built by Chevrolet) and mounted in pairs in wing-mounted nacelles, the aircraft was striking in appearance. The bomber carried a crew of three in its pressurized fuselage- pilot and co-pilot seated in tandem under a forward-fuselage fighter-type canopy and a bombardier-navigator-radio operator behind a B-26 Maruader-esque transparent nose.
Had the bomber been ordered into production it would have been armed with a pair of .50 caliber machine guns mounted in an Emerson tail turret controlled by the APG-27 remote fire control system. The J-35 engines powering the prototype airframe would have been swapped for the improved General Electric J47 engines. As it was the airframe was used primarily for testing of the unique aerodynamic and system engineering contained in the design. Specifically the flight control system utilized pneumatic rather than hydraulic, manual, or electrical control lines and systems.
In flight the bomber was praised by its test pilots, both Convair and Army Air Force alike, for its handling qualities. But though stability and control were excellent during 64 flight totaling 127 hours, engine de-icing and cabin air systems required additional engineering work. It seems the most serious problem was likely the vertical oscillations caused by harmonic resonance between the wing and spoilers. Actually installing the fire control system probably would have forced a major redesign of that shapely fuselage too. In the end the program was cancelled before flight testing was even completed. The B-45 had already been ordered into production and the B-47…well we know the rest of that story!
44 additional hours of Convair flight testing was flown from Palm Beach Air Force Base (AFB) in Florida during 1948 and 1949. Investigation into excessive noise, tail vibration, and stability and control issues took place during this final period of flight testing. Taken out of service in 1949, the aircraft spent a year on the ground before heading to Eglin AFB in Florida to have its unique pneumatic control systems tested at that base’s the large climate facility. The aircraft was finally scrapped in February of 1952.