Design and development On 25 August 1950, Convair issued a formal proposal for a swept-winged version of the B-36 with all-jet propulsion. The United States Air Force was sufficiently interested that on 15 March 1951, the USAF authorized Convair to convert two B-36Fs (49-2676 and 49-2684) as B-36Gs. Since the aircraft was so radically different from the existing B-36, the designation was soon changed to YB-60. The YB-60 had 72% parts commonality with its piston-engined predecessor. The fuselages of the two aircraft were largely identical, although the YB-60 had a longer, pointed nose with a needle-like instrument probe instead of the B-36's rounded nose, its tail surfaces were swept to match the wings and a with a wedge-shaped insert added at the wing root. The swept wings also used many of B-36 parts. The YB-60's unofficial competitor for an Air Force contract was Boeing's B-52 Stratofortress. Convair's proposal was substantially cheaper than Boeing's since it involved modifying an existing design rather than starting from scratch. Like the B-52, it was powered by eight Pratt & Whitney J57-P-3 turbojets mounted in pairs in four pods suspended below the wing. Instead of the B-36's crew of 15, the YB-60's crew numbered only ten. Production B-60s were to have defensive armament similar to the B-36. Convair YB-60 serial number 49-2676 made its maiden flight on 18 April 1952, piloted by Beryl Erickson. The Boeing YB-52 beat the Convair aircraft into the air by three days. The YB-60 was approximately 100 mph (160 km/h) slower than the YB-52 and also had severe handling problems. It carried a heavier bomb load—72,000 pounds against 43,000 pounds (20 t) for the YB-52—but the Air Force did not see the need for the extra capacity given the YB-60's other drawbacks. Later "big belly" modifications increased the B-52's bomb load to 60,000 lbs. The flight test program was canceled on 20 January 1953 with 66 flying hours accumulated, and a second prototype was never completed. The airframe was built, but it was not fitted with engines or much other equipment. Since Convair completed their prototype contract satisfactorily, both YB-60s were formally accepted by the Air Force in 1954. The operational aircraft never flew again, and both airframes were scrapped by July. [edit]Specifications (YB-60) A YB-60 in flight. General characteristics Crew: 5 (2 pilots ,navigator ,bombardier /radio operator ,radio operator/tail gunner ) Length: 171 ft (52.1 m) Wingspan: 206 ft (62.8 m) Height: 60 ft 6 in (18.4 m) Wing area: 5,239 ft2 (486.7 m2) Empty weight: 153,016 lb (69,407 kg) Loaded weight: 160,000 lb (73,000 kg) Max. takeoff weight: 300,000 lb (140,000 kg) Powerplant: 8 × Pratt & Whitney J57-P-3 turbojets, 8,700 lbf (38 kN) each Performance Maximum speed: 508 mph (411 knots, 818 km/h) at 29,250 ft (8,915 m) Stall speed: 115 knots (132 mph, 212 km/h) Combat radius: 2,920 mi (2,540 nm, 4,700 km) Ferry range: 8,000 mi (7,000 nm, 13,000 km) Service ceiling: 53,300 ft (16,200 m) Rate of climb: 1,060 ft/min (5.38 m/s) Wing loading: 31 lb/ft2 (150 kg/m2) Thrust/weight: 0.44 Armament Guns: 2× 20 mm (0.787 in) cannon in tail Bombs: 72,000 lb (33,000 kg)

johnbr, Mar 24, 2013
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