Martin XB-51
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Martin_XB-51.jpg
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 J47s 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 3.67 G (36 m/s²) 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. Reference to this Aircraft is mentioned in the 2002 Motion Picture "Hart's War"
Specifications (XB-51)
General characteristics
- Crew: 2
- 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)
- Empty: 29,584 lb (13,419 kg)
- Loaded: 55,923 lb (25,366 kg)
- Maximum takeoff: 62,457 lb (28,330 kg)
- Powerplant: 3× General Electric J47-GE-13 turbojets; 5,200 lbf (23 kN) thrust
Performance
- Maximum speed: 645 mph (1,038 km/h)
- Combat range: 1,075 miles (1,730 km)
- Ferry range: 1,613 miles (2,596 km)
- Service ceiling: 40,500 ft (12,300 m)
- Rate of climb: 6,980 ft/min (2,130 m/min)
- Wing loading: 102 lb/ft² (498 kg/m²)
- Thrust/weight ratio: 0.28 lbf/lb (2.7 N/kg)
Armament
- 8× 20 mm cannon with 1,280 rounds
- 8× High Velocity Aerial Rockets (HVAR)
- 2,000 (900 kg) of bombs
External links
- USAF Museum: XB-51 (http://www.wpafb.af.mil/museum/research/bombers/b4/b4-58.htm)
Related content
Related development:
Comparable aircraft: English Electric Canberra
Designation sequence: XB-48 - YB-49 - B-50 - XB-51 - B-52 - XB-53 - B-54
Related lists: List of military aircraft of the United States - List of bomber aircraft
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