|The sole XC-99 in its early days of operation, before a nose radome was fitted.|
|Maiden flight||23 November 1947|
|Introduced||23 November 1949|
|Primary user||United States Air Force|
|Developed from||Convair B-36|
The Convair XC-99 was a prototype heavy cargo aircraft built by Convair for the United States Air Force. It was the largest piston-engined land-based transport aircraft ever built, and was developed from the B-36 bomber, sharing the wings and some other structures with it. The first flight was on November 23, 1947 in San Diego, California, and after testing it was delivered to the Air Force on November 23, 1949.
Design capacity of the XC-99 was 100,000 pounds of cargo or 400 fully equipped troops on its double cargo decks; a cargo lift was installed for easier loading. In July 1950 the XC-99 flew its first cargo mission, "Operation Elephant." It transported 101,266 pounds of cargo, including engines and propellers for the B-36, from San Diego to Kelly Air Force Base in San Antonio, Texas, a record it would later break when it lifted 104,000 pounds from an airfield at 5,000 ft elevation. In August 1953 the XC-99 would make its longest flight-12,000 miles-to Rhein-Main Air Base, Germany, by way of Bermuda and the Azores. It carried more than 60,000 pounds each way. It attracted much attention everywhere it flew.
The U.S. Air Force determined that it had no need for such a large, long-range transport at that time, and no more were ordered. The sole XC-99 served until 1957, including much use during the Korean War. It made twice weekly trips from Kelly AFB to the aircraft depot at McClellan AFB, California, transporting supplies and parts for the B-36 bomber while returning by way of other bases or depots making pick-ups and deliveries along the way. During its operational life the XC-99 logged over 7,400 hours total time, the most of any X-Plane in U.S. history.
The aircraft was put on display at Kelly Air Force Base near San Antonio, Texas. During the 1960s it was considered for restoration, but the deterioration of the airframe due to the high magnesium content led to the abandonment of that plan. The airplane was later on moved to a grassy field near the base. In 1993 the USAF re-acquired the plane and moved it back to the Kelly AFB tarmac. It was planned to move it via road to the National Museum of the United States Air Force at Wright-Patterson Air Force Base, restore and reassemble it, and put it on display in the USAF Museum's collection of experimental aircraft. Ultimately, transporting the massive aircraft by ground proved impractical and too expensive.
Disassembly of the aircraft began at the former Kelly AFB in April 2004. Portions of the airframe were airlifted from the Kelly Annex at Lackland Air Force Base to Wright-Patterson Air Force Base near Dayton, Ohio. The remaining parts will be airlifted as opportunity permits. A full restoration is expected to be performed by the restoration crew of the Air Force Museum, though no timetable exists at this time. Following a complete restoration the aircraft is expected to be displayed inside in one of the Museum's new hangars. Like its relative the B-36, it is expected to become a showpiece of the Museum.
A civil variant of the XC-99, the Convair Model 37 was a large passenger aircraft which was planned but never built. The Model 37 was to be of similar proportions to the XC-99; 182 ft 6" in length, 230 ft wingspan, and a high-capacity, double-deck fuselage. The projected passenger load was to be 204, and the effective range 4,200 miles.
Fifteen aircraft were ordered by Pan American for transatlantic service.
Unfortunately for the project, the fuel and oil consumption of the six 3,500 hp Wasp Major radials powering the XC-99 and B-36 meant that the design was not economically viable, and hoped-for turboprop powerplants did not materialise fast enough. Fifteen orders were not sufficient for production, and the project was abandoned.
- Crew: 5
- Capacity: 100,000 lb (45,000 kg) or 400 troops
- Length: 185 ft (56.4 m)
- Wingspan: 230 ft (70.10 m)
- Height: 57 ft 5 in (17.50 m)
- Wing area: 4,772 ft² (443.3 m²)
- Maximum takeoff: 320,000 lb (145,000 kg)
- Powerplant: 6 × Pratt & Whitney Wasp Major, 3,500 hp (2,600 kW) each, 21,000 hp (15,600 kW) total
- Range: 13,000 km (8,000 miles)
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