Convair XB - 46 The Convair XB - 46 was a single example of an experimental medium jet bomber which was developed in the mid - 1940s but which never saw production or active duty . It competed with similar designs , the North American XB - 45 and Martin XB - 48 , all of which saw little use after the successful development of the Boeing XB - 47 . Development . In 1944 , the War Department was aware of aviation advances in Germany and issued a requirement for a range of designs for medium bombers weighing from 80 , 000 lb ( 36 , 287 kg ) to more than 200 , 000 lb ( 90 , 718 kg ) . Other designs resulting from this competition , sometimes named the " class of ' 45 " , included the North American XB - 45 and the Convair XB - 46 . Procurement began with a letter contract ( cost - plus - fixed - fee ) on 17 January 1945 with mock - up inspection and approval in early February . Orders for three prototypes followed on 27 February 1945 with certain changes recommended by the board . Serials " 45 - 59582 " to " 59584 " were assigned . Budgetary concerns also led to the contract being changed to a fixed - price type . In the fall of 1945 , Convair found it was competing with itself when the USAAF became interested in an unorthodox canard jet attack design , the XA - 44 - CO that the company had also been working on . With the end of World War II severely curtailing budgets , the company considered canceling the XB - 46 in favor of the other project as there was insufficient funding for both . Company officials argued that it made more sense to allow them to complete the XB - 46 prototype as a stripped - down testbed omitting armament and other equipment and for the AAF to allow them to proceed with two XA - 44 airframes in lieu of the other two XB - 46s on contract . In June 1946 , the AAF agreed to the substitution but that project was ultimately cancelled in December 1946 before the prototypes were completed . The B - 46 would be completed with only the equipment necessary to prove its airworthiness and handling characteristics . The XB - 46 was a graceful design and had a long streamlined oval torpedo - shaped fuselage , long narrow straight shoulder - mounted wings with four Chevrolet - built J35 - C3 axial - flow eleven stage turbojets of static thrust paired in an integral nacelle under each wing . The fuselage turned out to be a problem , as it distorted under flight loads . The pilots sat in tandem in a pressurized fighter - style cockpit under a single Plexiglas teardrop canopy with the bombardier - navigator - radio operator in a transparent Plexiglas nose section . The straight wing had an aspect ratio of 11 . 6 , and was equipped with Fowler flaps which extended over 90 percent of the span , in four sections . The flaps extended via electrical actuators , and had very small ailerons . Each wing had five spoilers made of perforated magnesium alloy . The engine air intakes were flat oval inlets , with a duct curving downward in a flat “ S ” to the engines , which were mounted behind the trailing edge of the wing . Production versions were to be equipped with a pair of . 50 caliber machine guns in a tail turret designed by Emerson Electric Company and provision was made for an APG - 27 remote control optics and sighting system , but no weaponry was fitted into the prototype . Likewise , production aircraft were intended to be built with the General Electric J47 engines with static thrust rather than the J35s used on the prototype . Testing . The XB - 46 ' s first flight occurred 2 April 1947 after a month of taxi testing , and lasted ninety minutes as the bomber departed the Convair plant in San Diego , California for Muroc Army Airfield in the high desert . The pilot praised its handling qualities . Basic flight testing took place for five months and by September 1947 it was concluded after 127 hours aloft on 64 flights by both Convair company and AAF test pilots . Stability and control were excellent but there were engineering problems with engine de - icing , the cabin air system , and vertical oscillations caused by harmonic resonance between the wing and spoilers . There was also concern regarding the ability of the three man crew to exit the aircraft in case of an emergency , since the exit plan relied on the pneumatic system to hold the main door open against the airstream . The aircraft was accepted on 7 November and delivered on 12 November 1947 . Cancellation . The B - 46 program was cancelled in August 1947 , even before flight testing had been completed , because it was already obsolete . The North American B - 45 Tornado already had production orders , and even it would be eclipsed by the Boeing B - 47 Stratojet ' s superior performance . Furthermore , the bulky radar fire - control system which was not installed in the XB - 46 prototype would have undoubtedly forced an expensive redesign of the slender fuselage . Subsequent testing investigated excessive noise , tail vibration , and stability and control issues , and was conducted at Palm Beach Air Force Base , Florida between August 1948 and August 1949 . After 44 additional flight hours , the XB - 46 was taken out of service , since the cost of support and maintenance , coupled with a lack of spare parts , had become prohibitive . After sitting idle for a year , it was flown to Eglin Air Force Base , Florida , in July 1950 , where its pneumatic system was tested under the coldest conditions in the large climatic facility there . Most jet aircraft of this period used hydraulic or electrical systems , so the pneumatic control system of this aircraft offered a unique opportunity for investigation . When this testing program was concluded in November 1950 , the Air Force no longer had need for the XB - 46 , a fact acknowledged in the press as early as August , and on 13 January 1951 the nose section was sent to the U . S . Air Force Museum at Wright - Patterson Air Force Base , Ohio , although it appears that the airframe section has not survived in the collection . The rest of the airframe was scrapped on 28 February 1952 .