| • Science | • People | • Locations | • Timeline |
| Martin XB-51 | ||
|---|---|---|
| Description | ||
| Role | ground attack | |
| Crew | two; pilot and navigator in tandem | |
| First Flight | April 17, 1950 | |
| Manufacturer | Martin | |
| Dimensions | ||
| Length | 85 ft 1 in | 25.9 m |
| Wingspan | 53 ft 1 in | 16.2 m |
| Height | 17 ft 4 in | 5.3 m |
| Wing area | 548 ft² | 50.9 m² |
| Weights | ||
| Empty | 29,584 lb | 13,419 kg |
| Loaded | 55,923 lb | 25,366 kg |
| Maximum takeoff | 62,457 lb | 28,330 kg |
| Powerplant | ||
| Engines | 3 × General Electric J47-GE-13 turbojets | |
| Thrust | 5200 lb | 23 kN |
| Performance | ||
| Maximum speed | 645 mph | 1038 km/h |
| Combat range | 1075 miles | 1,730 km |
| Ferry range | 1613 miles | 2,596 km |
| Service ceiling | 40,500 ft | 12,300 m |
| Rate of climb | 6980 ft/min | 2,130 m/min |
| Wing loading | lb/ft² | kg/m² |
| Thrust/Weight | ||
| Avionics | ||
| Avionics | ||
| Armament | ||
| Guns | 8 × 20 mm cannon with 1280 rounds | |
| Bombs | 4 × 1600 lb (730 kg) bomb internally, or 2 × 2000 lb (900 kg) bombs externally. Maximum bombload 10,400 lb (4,700 kg). | |
| Rockets | 8 × High Velocity Aerial Rockets (HVAR) | |
The Martin XB-51 was a ground attack aircraft designed to a 1945 United States Army Air Force requirement, and originally designated XA-45. The "A" ground attack classification was eliminated the next year, and the XB-51 designation was assigned instead. The requirement was for low-level bombing and close support.
The resulting design, first flying on October 28, 1949 was (unusually for a combat aircraft) fitted with three engines, General Electric J47 s in this case; one at the extreme tail with an intake at the base of the tailfin, and two underneath the forward fuselage. The wings, swept at 35° and with 6° anhedral, were equipped with variable incidence , leading-edge slots, full-width flaps and spoilers instead of ailerons. The main landing gear was dual sets of wheels in tandem in the fuselage, similar to the B-47 Stratojet, with outrigger wheels at the wingtips. The aircraft was fitted with a rotating bomb bay , a Martin trademark; bombs could also be carried externally up to a maximum load of 10,400 lb (4,700 kg), although the specified basic mission only required a 4,000 lb (1,800 kg) bombload.
In 1950, the United States Air Force issued a new requirement based on early Korean war experience for a night intruder/bomber to replace the A-26 Invader. The XB-51 was entered, as well as the Avro Canada CF-100 and the English Electric Canberra. The Canberra and XB-51 emerged as the favorites. The XB-51 was a highly maneuverable aircraft at low level, and substantially faster than the Canberra. However, its load limiting factor of only 3.67G restricted tight turns, and the XB-51's endurance was substantially poorer than the Canberra's; this latter proved to be the deciding factor. Additionally, the tandem main gear plus outriggers of the XB-51 was thought unsuitable for the requirement to fly from emergency forward airfields. The Canberra was selected for procurement and the XB-51 program ended. Martin did not end up the loser, however, for they were selected to build the 250 Canberras ordered under the designation B-57A.
Flight testing for research purposes continued after program cancellation. The second prototype crashed on May 9, 1952 during low-level aerobatics. The other aircraft continued to fly, including appearing in the film Towards the Unknown , until it crashed on takeoff on March 25, 1956.