Convair XC-99

The Convair XC-99, 43-52436, 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 23 November 1947 in San Diego, California, and after testing it was delivered to the Air Force on 23 November 1949.

Design capacity of the XC-99 was 100,000 lb (45,000 kg) of cargo or 400 fully equipped troops on its double cargo decks; a cargo lift was installed for easier loading.

Operational history:

In July 1950 the XC-99 flew its first cargo mission, "Operation Elephant." It transported 101,266 pounds (45,933 kg) 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 lb (47,200 kg) from an airfield at 5,000 ft (1,500 m) elevation. In August 1953, the XC-99 would make its longest flight, 12,000 mi (19,000 km), to Rhein-Main Air Base, Germany, by way of Bermuda and the Azores. It carried more than 60,000 lb (27,000 kg) each way. It attracted much attention everywhere it flew.

The US 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.

Retirement and display

The XC-99 landing during trials.The aircraft was put on display at Kelly Air Force Base near San Antonio, Texas. During the 1960s, it was considered for restoration by the San Antonio Air Logistics Center at Kelly AFB, but the deterioration of the airframe due to the high magnesium content led to the abandonment of that plan. The airplane was later moved to a grassy field near the base. In 1993, the USAF moved it back to the Kelly AFB tarmac (29°22'27.37"N 98°35'13.74"W). It was planned to move the XC-99 via road to the National Museum of the United States Air Force at Wright-Patterson Air Force Base, Ohio, 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 Kelly Field in April 2004. Portions of the airframe were then airlifted from Kelly to Wright-Patterson Air Force Base near Dayton, Ohio. Upon arrival at Wright-Patterson's active base, the parts had to be further moved by truck several miles to the Museum side of the base. Transporting the XC-99 components taxed the C-5A's cargo capacity, as the largest piece moved intact was over 75 feet by 13 feet. By the summer of 2008, the XC-99 had been completely transferred to Dayton and was laying on the ramp outside the Museum's restoration facility. Upon examination, the aircraft was found to have suffered from considerable corrosion, which was not unexpected considering it had remained outside for over fifty years. The wing spar was found to be too badly corroded to restore, and a new replacement would need to be fabricated. A full restoration is being performed by the restoration crew of the Air Force Museum, though no timetable exists at this time. As of May 2011, the corrosion control of the center wing boxes was nearing completion. Once this portion of the project is finished, the XC-99 will be reassembled and the restoration work started.

Following 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. Once all aircraft have been moved from the Museum's current "Research and Development Hangar" to a new display hangar planned to be added onto the main Museum buildings, the XC-99 restoration project will move into the former R&D Hangar where visitors will be able to watch the restoration in progress.Upon completion, the XC-99 will remain on display in the former R&D hangar.Pending the restoration and display of the XC-99, in an effort to educate visitors about the aircraft the Air Force Museum has placed a model of the XC-99 on display in its Post-Cold War Gallery. The model, in approximately 1/72 scale, was constructed by a member of the Museum's restoration staff. An explanation of the Museum's plans for the restoration and display of the XC-99 is located in the case with the model.

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 (55.63 m) length, 230 ft (70 m) wingspan, and a high-capacity, double-deck fuselage. The projected passenger load was to be 204, and the effective range 4,200 mi (6,800 km).15 aircraft were ordered by Pan American for transatlantic service.Unfortunately for the project, the fuel and oil consumption of the six 3,500 hp (2,600 kW) 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. 15 orders were not sufficient for production, and the project was abandoned.

Specifications XC-99. Data from General Dynamics Aircraft and their Predecessors

General characteristics:

Crew: Five duty + five reserve crew

Capacity: 400 troops
Payload: 100,000 lb (45,000 kg)
Length: 182 ft 6 in (55.64 m)
Wingspan: 230 ft 0 in (70.12 m)
Height: 57 ft 6 in (17.53 m)
Wing area: 4,772 ft² (443.5 m²)
Empty weight: 135,232 lb (61,469 kg)
Loaded weight: 265,000 lb (120,455 kg)
Max takeoff weight: 320,000 lb (145,455 kg)
Powerplant: 6 × Pratt & Whitney R-4360-41 Wasp Major

28-cylinder air-cooled radial engine, 3,500 hp (2,611 kW) each

Performance:

Maximum speed: 307 mph (267 knots, 494 km/h)

Range: 8,100 mi (7,043 nmi, 13,041 km)
Service ceiling: 30,000 ft (9,150 m)

From Wikipedia