Martin XB-51

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.

Martin XB-51 46-585 in flight
First prototype, 46-685 during testing
Role Bomber
Manufacturer Glenn L. Martin Company
First flight 28 October 1949
Retired 25 March 1956
Status Canceled in 1952
Primary user United States Air Force
Number built 2
Unit cost
US$12.6 million for the program[1]

Design and development

Twin XB-51
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.[2] The innovative, variable incidence wings, swept at 35° and with 6° anhedral, were equipped with leading edge slats and full-width flaps. Spoilers gave most of the roll control and undersized ailerons provided feel for the pilot.[3] The combination of variable incidence and slotted flaps gave a shorter takeoff run.[4] Four 954 lb (4.24 kN) thrust Rocket-Assisted Take Off (RATO) bottles with a 14-second burn duration could be fitted to the rear fuselage to improve takeoff performance. Spectacular launches were a feature of later test flights.[2]

Martin XB-51 rocket-assisted take off 061026-F-1234S-013
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"[2]). The B-51 was a large but aerodynamically "clean" design which incorporated nearly all major systems internally.[4] 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 required only a 4,000 lb (1,814 kg) bombload.[5] Eight 20 mm cannon mounted in the nose would have been installed in production aircraft.[4]

Crew was a pilot under a "fighter"-type bubble canopy and a Short-range navigation and bombing system (SHORAN) operator/navigator in a compartment located lower than and to the rear of the cockpit (only a small observation window was provided).[4] Both crew members were provided with a pressurized, air conditioned environment, equipped with upward-firing ejection seats.[4] The XB-51 was the first Martin aircraft equipped with ejection seats, these being of their own design.[6]

Operational history

A shot of 46-685 on approach, from the archives of the National Museum of the U.S. Air Force

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.[4] However, the XB-51's endurance was significantly lower than that of the Canberra and this factor was decisive in its cancellation. In addition, a load limiting factor of only 3.67 g (36 m/s2) meant that the general strength of the airframe was relatively low and would prevent tight turns while fully loaded. Additionally, the tandem main gear plus outriggers of the XB-51 were thought unsuitable for the requirement to fly from emergency forward airfields.

While the XB-51 was not selected for procurement, it was decided that Martin would build 250 Canberras under license, under the designation B-57. Furthermore, Martin's rotating bomb bay would be incorporated into production variants of the B-57. A "Super Canberra", incorporating other XB-51 features, such as swept wings and tail-planes, was also proposed. This aircraft – although it promised much better speed and performance than the B-57 – never reached the prototype stage, mainly because the many changes would have taken too long to implement and test, before it could be put into production.[2]

Flights by the XB-51 prototype, 46-685, continued, for general research purposes, following the project's official cancellation by the USAF. A second prototype, 46-686, which first flew in 1950, crashed during low-level aerobatics on 9 May 1952. 46-685 continued to fly, including an appearance in the film Toward the Unknown as the "Gilbert XF-120" fighter.[note 1] 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.[4]

Specifications (XB-51)

Data from U.S. Standard Aircraft Characteristics[7]

General characteristics

  • Crew: 2
  • Length: 85 ft 1 in (25.93 m)
  • Wingspan: 53 ft 1 in (16.18 m)
  • Height: 17 ft 4 in (5.28 m)
  • Wing area: 548 sq ft (50.9 m2)
  • Airfoil: NACA 63A010[8]
  • Empty weight: 30,906 lb (14,019 kg)
  • Gross weight: 57,874 lb (26,251 kg)
  • Max takeoff weight: 62,452 lb (28,328 kg)
  • Powerplant: 3 × General Electric J47-GE-13 turbojet engines, 5,200 lbf (23 kN) thrust each


  • Maximum speed: 644 mph (1,036 km/h, 560 kn)
  • Range: 1,075 mi (1,730 km, 934 nmi)
  • Ferry range: 1,444 mi (2,324 km, 1,255 nmi)
  • Service ceiling: 41,750 ft (12,730 m)
  • Rate of climb: 6,600 ft/min (34 m/s)
  • Wing loading: 105.6 lb/sq ft (516 kg/m2)
  • Thrust/weight: 0.27


  • 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

See also

Aircraft of comparable role, configuration and era

Related lists



  1. ^ A few seconds of test flight footage of an XB-51 also appeared in the 1951 Tales of Tomorrow episode "Plague From Space". Note: Although the XB-51 did not receive an official name, "Panther" had been suggested by the company.
  1. ^ Knaack, Marcelle Size. Post-World War II bombers, 1945-1973. Washington, DC: Office of Air Force History, 1988. ISBN 0-16-002260-6.
  2. ^ a b c d Winchester 2005, p. 144.
  3. ^ The Martin XB-51, Air Force Legends Number 201, Scott Libis, published by Steve Ginter 1998, ISBN 0-942612-00-0, p.5
  4. ^ a b c d e f g Winchester 2005, p. 145.
  5. ^ "Pivoting Bomb-bay Door Permits Accurate Drops at High-Speeds." Popular Mechanics, February 1954, p. 126.
  6. ^ Tuttle, Jim. Eject! The Complete History of U.S. Aircraft Escape Systems. St. Paul, Minnesota: MBI Publishing Company, 2002. ISBN 0-7603-1185-4.
  7. ^ "Standard Aircraft Characteristics: XB-51" (PDF). US Air Force. 11 July 1952. Retrieved 8 June 2017.
  8. ^ Lednicer, David. "The Incomplete Guide to Airfoil Usage". Retrieved 16 April 2019.


  • Andrade, John M. U.S. Military Aircraft Designations and Serials since 1909. Earl Shilton, Leicester, UK: Midland Counties Publications, 1979. ISBN 0-904597-22-9.
  • 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. ISBN 0-8168-9126-5.
  • Mikesh, Robert C. 'B-57 Canberra At War 1964-1972. London: Ian Allan, 1980. ISBN 0-7110-1004-8.
  • Winchester, Jim. "Martin XB-51." Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft. Kent, UK: Grange Books plc., 2005. ISBN 978-1-84013-809-2.

External links

Aircraft in fiction

Aircraft in fiction covers various real-world aircraft that have made significant appearances in fiction over the decades, including in books, films, toys, TV programs, video games, and other media. These appearances spotlight the popularity of different models of aircraft, and showcase the different types for the general public.


B51 or B-51 may be:

HLA-B51, an HLA-B serotype

Bundesstraße 51, a road in western Germany

Martin XB-51, an American airplane

Sicilian Defence in the Encyclopaedia of Chess Openings

B51 (New York City bus)

English Electric Canberra

The English Electric Canberra is a British first-generation jet-powered medium bomber. It was developed by English Electric during the mid-to-late 1940s in response to a 1944 Air Ministry requirement for a successor to the wartime de Havilland Mosquito fast bomber. Among the performance requirements for the type was the demand for an outstanding high-altitude bombing capability and high speed. These were partly accomplished by making use of newly developed jet propulsion technology. When the Canberra was introduced to service with the Royal Air Force (RAF), the type's first operator, in May 1951, it became the service's first jet-powered bomber.

Throughout most of the 1950s, the Canberra could fly at a higher altitude than any other aircraft in the world. In 1957, a Canberra established a world altitude record of 70,310 feet (21,430 m). In February 1951, another Canberra set another world record when it became the first jet aircraft to make a non-stop transatlantic flight. Due to its ability to evade the early jet interceptor aircraft and its significant performance advancement over contemporary piston-engined bombers, the Canberra became a popular aircraft on the export market, being procured for service in the air forces of many nations both inside and outside of the Commonwealth of Nations. The type was also licence produced in Australia by the Government Aircraft Factories and in the US by Martin as the B-57 Canberra. The latter produced both slightly modified B-57A Canberra, and the significantly updated B-57B.

In addition to being a tactical nuclear strike aircraft, the Canberra proved to be highly adaptable, serving in varied roles such as tactical bombing and photographic and electronic reconnaissance. Canberras served in the Suez Crisis, the Vietnam War, the Falklands War, the Indo-Pakistani wars, and numerous African conflicts. In several wars, each of the opposing sides had Canberras in their air forces. The Canberra had a lengthy service life, serving for more than 50 years with some operators. In June 2006, the RAF retired the last of its Canberras, 57 years after its first flight. Three of the Martin B-57 variant remain in service, performing meteorological work for NASA, as well as providing electronic communication (Battlefield Airborne Communications Node or BACN) testing for deployment to Afghanistan.

General Electric J47

The General Electric J47 turbojet (GE company designation TG-190) was developed by General Electric from its earlier J35. It first flew in May 1948. The J47 was the first axial-flow turbojet approved for commercial use in the United States. It was used in many types of aircraft, and more than 30,000 were manufactured before production ceased in 1956. It saw continued service in the US military until 1978. Packard built 3,025 of the engines under license.

Glenn L. Martin Company

The Glenn L. Martin Company was an American aircraft and aerospace manufacturing company founded by aviation pioneer Glenn L. Martin. The Martin Company produced many important aircraft for the defense of the US and allies, especially during World War II and the Cold War. During the 1950s and 60s, the Martin Company moved from the aircraft industry into the guided missile, space exploration, and space utilization industries.

In 1961, the Martin Company merged with American-Marietta Corporation, a large sand and gravel mining company, forming Martin Marietta Corporation. In 1995, Martin Marietta merged with aerospace giant Lockheed to form the Lockheed Martin Corporation.

Guy M. Townsend

Guy Mannering Townsend III (October 25, 1920 – March 28, 2011) was a retired United States Air Force brigadier general, test pilot, and combat veteran. As an Air Force officer, he served as chief of bomber test at Wright-Patterson Air Force Base, flew as co-pilot on the first flight of the B-52 Stratofortress, was test force director for the XB-70 Valkyrie, and served as program director for the C-5 Galaxy and B-1 Lancer. He was the first military pilot to fly the B-47 Stratojet, B-50 Superfortress, B-52 Stratofortress, and the prototype of the KC-135 Stratotanker. During his years at Boeing, he was the head of the Supersonic Transport operations organization.

Hans Multhopp

Hans Multhopp (17 May 1913 – 30 October 1972) was a German aeronautical engineer/designer. Receiving a degree from the University of Göttingen, Multhopp worked with the famous designer Kurt Tank at the Focke-Wulf Flugzeugbau AG during World War II, and was the leader of the team responsible for the design of the Focke-Wulf Ta 183 lightweight jet fighter, which was the winner of the 1945 Emergency Fighter Competition. Emigrating to the United Kingdom after the war, he assisted in the advancement of British aeronautic science before moving to the United States, where his work for Martin Marietta on lifting bodies provided aerodynamic experience that proved instrumental in the development of the Space Shuttle.

Landing gear

Landing gear is the undercarriage of an aircraft or spacecraft and may be used for either takeoff or landing. For aircraft it is generally both. It was also formerly called alighting gear by some manufacturers, such as the Glenn L. Martin Company.

For aircraft, the landing gear supports the craft when it is not flying, allowing it to take off, land, and taxi without damage. Wheels are typically used but skids, skis, floats or a combination of these and other elements can be deployed depending both on the surface and on whether the craft only operates vertically (VTOL) or is able to taxi along the surface. Faster aircraft usually have retractable undercarriages, which fold away during flight to reduce drag.

For launch vehicles and spacecraft landers, the landing gear is typically designed to support the vehicle only post-flight, and are typically not used for takeoff or surface movement.

List of United States bomber aircraft

This is a list of United States bomber aircraft

List of accidents and incidents involving military aircraft (1950–1954)

This is a list of notable accidents and incidents involving military aircraft grouped by the year in which the accident or incident occurred. Not all of the aircraft were in operation at the time. Combat losses are not included except for a very few cases denoted by singular circumstances.

List of accidents and incidents involving military aircraft (1955–1959)

This is a list of notable accidents and incidents involving military aircraft grouped by the year in which the accident or incident occurred. Not all of the aircraft were in operation at the time. Combat losses are not included except for a very few cases denoted by singular circumstances.

List of aircraft accidents at Eglin Air Force Base

This is a partial list of aviation accidents at Eglin Field/Eglin Air Force Base, Florida or involving Eglin-based aircraft.

List of bomber aircraft

The following is a list of bomber airplanes and does not include bomber airships, organized by era and manufacturer. A bomber is a military aircraft designed to attack ground or sea targets.

Martin B-57 Canberra

The Martin B-57 Canberra is an American-built, twinjet tactical bomber and reconnaissance aircraft that entered service with the United States Air Force (USAF) in 1953. The B-57 is a license-built version of the British English Electric Canberra, manufactured by the Glenn L. Martin Company. Initial Martin-build models were virtually identical to their British-built counterparts; Martin later modified the design to incorporate larger quantities of US-sourced components and produced the aircraft in several different variants.

The B-57 Canberra holds the distinction of being the first jet bomber in U.S. service to drop bombs during combat. The Canberra was used extensively during the Vietnam War in a bombing capacity; dedicated versions of the type were also produced and served as high-altitude aerial reconnaissance platforms (the Martin RB-57D Canberra), and as electronic warfare aircraft. The B-57 Canberra was also sold to export customers abroad; further combat use was seen by the Pakistani Air Force during the Indo-Pakistani War of 1965 and the Indo-Pakistani War of 1971.

In 1983, the USAF opted to retire the type; the B-57 Canberra's retirement marked the ending of the era of the tactical bomber. The three remaining flightworthy WB-57Fs are technically assigned to the NASA Johnson Space Center, next to Ellington Field in Houston, as high-altitude scientific research aircraft, but are also used for testing and communications in the U.S. and Afghanistan.

OKB-1 EF 131

The OKB-1/Junkers EF-131 was a jet bomber produced in Germany and the USSR from 1944.

Sud-Est Grognard

The SNCASE Grognard was designed as a single-seat, low-level ground-attack aircraft. Although in development in the 1950s for the French Armée de l'Air, the program was cancelled in favor of the Sud-Ouest Vautour II.

Toward the Unknown

Toward the Unknown (also titled Brink of Hell in its UK release) is a 1956 film about the dawn of supersonic flight filmed on location at Edwards Air Force Base. Starring William Holden, Lloyd Nolan and Virginia Leith, the film features the screen debut of James Garner.

Toward the Unknown was directed by Mervyn LeRoy and written by Beirne Lay, Jr. who had also penned the novel and screenplay for Twelve O'Clock High (1949), and later screenplays for Above and Beyond (1952) and Strategic Air Command (1955). The film's title is derived from the motto of the Air Force Flight Test Center, Ad Inexplorata.


A trijet is a jet aircraft powered by three jet engines. In general, passenger airline trijets are considered to be second-generation jet airliners, due to their innovative engine locations, in addition to the advancement of turbofan technology.

Other variations of three-engine designs are trimotors, which are aircraft with three piston engines.

Variable-incidence wing

A variable-incidence wing has an adjustable angle of incidence relative to its fuselage. This allows adjustment of the wing's angle of attack to the airflow while the fuselage remains at a constant attitude. The pivot mechanism adds extra weight over a conventional wing and increases costs, however in some applications the benefits can outweigh the costs.

Martin and Martin Marietta aircraft
Model numbers
Attack aircraft
Maritime patrol
Military transports
Military trainers
Scout/Torpedo bombers
Reconnaissance aircraft
Martin Marietta
United States attack aircraft designations, Army/Air Force and Tri-Service systems
Army/Air Force sequence
Tri-service sequence
Related designations
USAAS/USAAC/USAAF/USAF bomber designations, Army/Air Force and Tri-Service systems
Original sequences
Main sequence
Long-range Bomber
Tri-Service sequence


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