Convair XB-46
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| Convair XB-46 | |
|---|---|
 |
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| Type | Medium bomber |
| Manufacturer | Consolidated Vultee |
| Maiden flight | 1947-04-02 |
| Status | Cancelled in 1947 |
| Primary user | United States Air Force |
| Number built | 1 |
| Unit cost | US$4.9 million for the program[1] |
The Convair XB-46 was a single example of an experimental medium jet bomber developed in the mid-1940s but which never saw production or active duty. In 1944 the U.S. 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 to more than 200,000 pounds (36,000 to over 90,000 kg). Consolidated Vultee Aircraft (Convair) responded with their Model 109, a 90,000 pound (41,000 kg) design which was accepted by the Army Air Forces in November 1944 and designated the B-46. Other designs resulting from this competition included the North American XB-45, the Boeing XB-47 and the Martin XB-48.
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[edit] Development
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 12 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, and considered cancelling 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 air-worthiness and handling characteristics.
The XB-46 was a graceful design and had a long oval torpedo-shaped fuselage, long narrow straight shoulder-mounted wings with four J35-C3 axial-flow eleven stage turbojets of 3,820 lbf (17,000 newtons) static thrust paired in an integral nacelle under each wing. The fuselage turned out to be a problem, as it distorted in flight. The pilots sat in pressurized fighter-style cockpits under a single teardrop canopy with the bombardier-navigator in the glazed nose section. It was to be equipped with a pair of .50 caliber weapons in a tail turret designed by Emerson Electric Company and provision was made for an APG-27 remote control optics and sighting system.
[edit] Testing
The XB-46's first flight occurred 2 April 1947 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 they had 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 the engines, the spoiler clutch installation and the lateral control surfaces at high speeds. In short, it was suited to be a testbed. The aircraft was accepted on 7 November and delivered on 12 November 1947.
[edit] Cancellation
The B-46 program was cancelled in August 1947 even before flight testing had been completed as it was already obsolescent. 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 involved noise measurements, tail vibration investigation, and stability and control, and were conducted at West 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 as 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. When this concluded in November 1950 the Air Force no longer had need for it and on 13 January 1951 the nose section was sent to the U.S. Air Force Museum at Wright-Patterson Air Force Base, Ohio. The rest of the airframe was scrapped 28 February 1952.
[edit] Specifications (XB-46)
General characteristics
- Crew: 3
- Length: 105 ft 9 in (32.23 m)
- Wingspan: 113 ft 0 in (34.44 m)
- Height: 27 ft 11 in (8.51 m)
- Wing area: 1,285 ft² (119.4 m²)
- Empty weight: 48,000 lb (21,800 kg)
- Loaded weight: 75,200 lb (34,100 kg)
- Max takeoff weight: 94,400 lb (42,800 kg)
- Powerplant: 4× Allison J35-A-3 turbojets, 4,000 lbf (18 kN) each
Performance
- Maximum speed: 545 mph (473 knots, 877 km/h)
- Range: 2,870 mi (2,490 nm, 4,620 km)
- Service ceiling: 40,000 ft (12,000 m)
- Rate of climb: 1,315 ft/min (6.683 m/s)
- Wing loading: 59 lb/ft² (294 kg/m²)
- Thrust/weight: 0.21
Armament
- Guns: 2× .50 in (12.7 mm) M2 Browning machine guns
- Bombs: 22,000 lb (10,000 kg)
[edit] References
- ^ Knaack, Marcelle Size (1988). Post-World War II bombers, 1945-1973. Office of Air Force History. ISBN 0-16-002260-6.
- Andrade, John M. (1979). U.S. Military Aircraft Designations and Serials since 1909. Earl Shilton, Leicester: Midland Counties Publications. ISBN 0-904597-22-9.
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