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The Martin XB-51 was an American trijet ground-attack aircraft. It was designed in 1945 and made its maiden flight in 1949. It was originally designed as a bomber for the United States Army Air Forces under specification V-8237-1 and was 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 XB-51 lost out in evaluation to the English Electric Canberra which — built by Martin — entered service as the Martin B-57 Canberra.

Design and development

thumb|left|Martin's two XB-51 prototypes, seen low over the runway on a high-speed pass

This unorthodox design, first flying on 28 October 1949, was fitted with three General Electric J47 engines — an unusual number for a combat aircraft — two underneath the forward fuselage in pods, and one at the extreme tail with the intake at the base of the tailfin. The combination of variable incidence and slotted flaps gave a shorter takeoff run.

thumb|Testing RATO

The main landing gear consisted of dual wheel sets in tandem in the fuselage, similar to the Boeing B-47 Stratojet, with outrigger wheels at the wingtips (originally proved on a modified Martin B-26 Marauder named "Middle River Stump Jumper"). The XB-51 was a large but aerodynamically "clean" design which incorporated nearly all major systems internally. Eight 20&nbsp;mm cannon mounted in the nose would have been installed in production aircraft. The cockpit was a pressurized, air-conditioned environment, equipped with upward-firing ejection seats. The XB-51 was the first Martin aircraft equipped with ejection seats, these being of their own design.

Operational history

thumb|46-685 on approach

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 Douglas A-26 Invader. The XB-51 was entered, as well as the Avro Canada CF-100 and English Electric Canberra; the XB-51 and Canberra emerged from these as the favorites.

Test flights showed the XB-51 to be highly maneuverable at low altitudes and substantially faster than the Canberra and faster than most fighter aircraft of the era. The surviving prototype was en route to Eglin AFB to shoot additional footage when it crashed during takeoff, following a refueling stop in El Paso, Texas, on 25 March 1956.

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General characteristics

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|wing area sqft=548

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|airfoil=NACA 63A010

|empty weight lb=30906

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|gross weight lb=57874

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|max takeoff weight lb=62452

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Powerplant

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|eng1 number=3

|eng1 name=General Electric J47-GE-13

|eng1 type=turbojet engines

|eng1 lbf=5200

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Performance

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|max speed mph=644

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|range miles=1075

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|ferry range miles=1444

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|ceiling ft=41750

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|climb rate ftmin=6600

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|wing loading lb/sqft=105.6

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|thrust/weight=0.27

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Armament

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|guns=8 × 20 mm M24 cannon (0.79 in) cannon with 1,280 rounds

|rockets=8 × High Velocity Aerial Rockets (HVAR) or

|bombs= Up to 10,400 lb (4,720 kg) carried internally

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See also

References

Notes

Citations

Bibliography

  • Andrade, John M. U.S. Military Aircraft Designations and Serials since 1909. Earl Shilton, Leicester, UK: Midland Counties Publications, 1979. .
  • Boyne, Walter. "Attack, The Story of the XB-51, Martin's Phantom Strike Ship!" Airpower, Volume 8, No. 4, July 1978.
  • Jones, Lloyd S. U.S. Bombers, B-1 1928 to B-1 1980s. Fallbrook, California: Aero Publishers, 1962, second edition 1974. .
  • Mikesh, Robert C. B-57 Canberra At War 1964-1972. London: Ian Allan, 1980. .
  • Winchester, Jim. "Martin XB-51." Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft. Kent, UK: Grange Books plc., 2005. .
  • USAF Museum: XB-51
  • Several photographs of the Martin 234 XB-51 46-685