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Martin XB-51

Jet-Powered Bomber Prototype Aircraft

Martin XB-51

Jet-Powered Bomber Prototype Aircraft

OVERVIEW
SPECIFICATIONS
ARMAMENT
VARIANTS
HISTORY
MEDIA
OVERVIEW



Developed for a USAAF low-level bombing requirement, the Martin XB-51 existed in only two prototype examples before being canceled in 1952.
National Flag Graphic
ORIGIN: United States
YEAR: 1949
MANUFACTURER(S): Glenn L. Martin Company (Martin) - USA
PRODUCTION: 2
OPERATORS: United States (cancelled)
SPECIFICATIONS



Unless otherwise noted the presented statistics below pertain to the Martin XB-51 model. Common measurements, and their respective conversions, are shown when possible.
CREW: 2
LENGTH: 84.97 feet (25.9 meters)
WIDTH: 53.15 feet (16.2 meters)
HEIGHT: 17.39 feet (5.3 meters)
WEIGHT (EMPTY): 29,586 pounds (13,420 kilograms)
WEIGHT (MTOW): 62,457 pounds (28,330 kilograms)
ENGINE: 3 x General Electric J47-GE-13 turbojet engines.
SPEED (MAX): 646 miles-per-hour (1040 kilometers-per-hour; 562 knots)
RANGE: 1,075 miles (1,730 kilometers; 934 nautical miles)
CEILING: 40,354 feet (12,300 meters; 7.64 miles)
RATE-OF-CLIMB: 6,980 feet-per-minute (2,128 meters-per-minute)




ARMAMENT



STANDARD:
8 x 20mm cannons in nose assembly

OPTIONAL (internal rotary launcher):
Up to 10,400lb of conventional drop ordnance OR 8 x High-Velocity Aerial Rocket (HVAR) rockets.
VARIANTS



Series Model Variants
• XB-51 - Base Project Designation
• XA-45 - USAAF designation for attack requirement


HISTORY



Detailing the development and operational history of the Martin XB-51 Jet-Powered Bomber Prototype Aircraft.  Entry last updated on 4/3/2017. Authored by Staff Writer. Content ©www.MilitaryFactory.com.
Developed as a low-level bomber and ground attack platform for the then-United States Army Air Forces (USAAF), the Martin XB-51 proved itself a failed development, producing just a pair of prototypes. First flight was recorded on October 28th, 1949 and the program ran until 1952 when it was officially cancelled and then formally retired in March of 1956 with a price tag of $12.6 million USD. Both prototypes were eventually lost in crashes which ended any notion of them ending as museum showpieces. The renamed United States Air Force (1947 onwards) eventually selected the British English Electric Canberra bomber in its place.

The XB-51 was intended to fulfill a USAAF requirement in replacing its aging line of Douglas A-26 Invaders in the light bombing / ground attack role. Martin engineers returned with a unique turbojet-powered design in which the aircraft utilized three engines - the primary pair set along nacelles held away from the forward lower fuselage with the third engine buried in the tail section. The fuselage also took on a unique appearance with its slab sides. The finish was of all silver, consistent with American aircraft of the period. The main wing elements were mid-mounted and swept at 35-degree angles for aerodynamic efficiency. Each element showcased variable incidence for take-off and landing actions and an anti-icing capability was built-in. Dive brakes were added for glide controlling during combat diving actions envisioned for the aircraft. The empennage was made up of a "T-style" tail unit which utilized the vertical fin as the support for the high-mounted horizontal planes. The third engine was aspirated at the fuselage spine at the base of the tail system and exhausted through a port at rear. The cockpit was held well-forward in the design, aft of the nose cone assembly which sloped downwards to provide the necessary out-of-the-cockpit vision for the pilot. The crew included the primary pilot and a systems officer in a pressurized, air conditioned cockpit that featuring ejection seats and a bulletproof windshield. However, only the pilot sat under the provided canopy for the systems officer was hidden away in his shrouded position nearby. The undercarriage was of a "bicycle" arrangement which utilized two main, double-tired landing gear legs in line with small, single-wheeled supporting legs at the wingtips - the latter for controlling lateral stability. When at rest, the aircraft exhibited a noticeable "nose-up" appearance. Landing was aided by release of a drag chute at rear.




Martin XB-51 (Cont'd)

Jet-Powered Bomber Prototype Aircraft

Martin XB-51 (Cont'd)

Jet-Powered Bomber Prototype Aircraft



The XB-51 was completed with 3 x General Electric J47-GE-13 turbojet engines of 5,200lbs thrust each. These included a water-alcohol thrust quality which was used to support short/quick take-off actions beyond the normal thrust power output of the turbojets. Also, 4 x rocket pods could be installed at the rear of the fuselage for 14-seconds of take-off assistance (Rocket-Assisted Take-Off = "RATO"), each canister producing 954lbs of additional thrust each. The engines were protected in armor against ground-based artillery fire (FlaK type) and their combined output power gave the airframe a maximum speed of 645 miles per hour with a cruising speed of around 530 miles per hour. Ferry range was out to 1,600 miles with an operational service ceiling of 40,500 feet (hence the cockpit pressurization for the crew).

Dimensions included a wingspan of 53 feet, a length of 85 feet and a height of 17.3 feet. Empty weight was listed at 29,590lb with a Maximum Take-Off Weight of 62,560lb.

Proposed armament for the XB-51 line was to include 8 x 20mm cannons with a total of 1,280 x 20mm projectiles carried. All of the cannon were to be fitted in the nose assembly and used for strafing runs against land-based or naval targets. An internal bomb bay was nestled in the fuselage complete with a rotary-style delivery system and cleared to carry up to 10,400lbs of internal stores. This would have included conventional drop bombs or 8 x 5" High-Velocity Aerial Rockets (HVAR). Aiming systems for the aircraft included an A-1-B gun-bomb rocket sighting device with radar ranging capability. All gun actions would be recorded on an onboard camera and a rear-facing camera would record the ground for damage assessment during strafing/bombing rungs. Still another camera was installed for high-altitude attack work or general reconnaissance. The XB-51made use of the SHORAN (SHOrt RAnge Navigation) bombing system already proven in the Korean War (1950-1953) through the Douglas A-26/B-26 Invader light bombers and Boeing B-29 Superfortress heavy bombers. The SHORAN system used the AN/APN-3 radar set and K-1A bombing computer in conjunction with a pair of AN/CPN-2/2A ground stations for improved bombing effectiveness over that seen in World War 2 (1939-1945).

The prototype XB-51 aircraft were assigned serial numbers 46-685 and 46-686. Its original attack-minded approach begat the little-known, short-lived "XA-45" designation before the bomber-minded classification was introduced to produce the "XB-51" designation. The original USAAF requirement was met by submissions from Martin as well as Avro Canada (the CF-100) and English Electric (the Canberra). While the XB-51 proposal was favored ahead of the two competing types for its inherent speed and agility, it eventually lost out to the British Canberra for its vastly superior operational range which was highly coveted. The Canberra was procured by the now-renamed USAF as the "B-57" and was, ironically, produced in 250 examples by Glenn L. Martin Company facilities.

Despite the XB-51 program setback, the prototypes continued in flight testing after their formal, potential USAF run had ended. Both prototypes were then lost in separate crashes - the second during maneuvers in May of 1952 and the first on a flight to Elgin AFB during March of 1956. Such ended the short-lived tenure of the Martin XB-51.




MEDIA









Our Data Modules allow for quick visual reference when comparing a single entry against contemporary designs. Areas covered include general ratings, speed assessments, and relative ranges based on distances between major cities.

Image of collection of graph types

Relative Maximum Speed Rating
Hi: 750mph
Lo: 375mph
    This entry's maximum listed speed (646mph).

    Graph average of 562.5 miles-per-hour.
City-to-City Ranges
NYC
 
  LDN
LDN
 
  PAR
PAR
 
  BER
BER
 
  MSK
MSK
 
  TKY
TKY
 
  SYD
SYD
 
  LAX
LAX
 
  NYC
Graph showcases the Martin XB-51's operational range (on internal fuel) when compared to distances between major cities.
Aviation Era
Pie graph section
Pie graph section
Pie graph section
Pie graph section
Pie graph section
Useful in showcasing the era cross-over of particular aircraft/aerospace designs.
Unit Production Comparison
Comm. Market HI*: 44,000 units
Military Market HI**: 36,183 units
2
2

  * Commercial Market High belongs to Cessna 172.

  ** Military Market High belongs to Ilyushin Il-2.


Altitude Visualization
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Supported Roles
A2A
Interception
UAV
Ground Attack
CAS
Training
ASW
Anti-Ship
AEW
MEDEVAC
EW
Maritime/Navy
SAR
Aerial Tanker
Utility/Transport
VIP
Passenger
Business
Recon
SPECOPS
X-Plane/Development
A2A=Air-to-Air; UAV=Unmanned; CAS=Close Support; ASW=Anti-Submarine; AEW=Airborne Early Warning; MEDEVAC=Medical Evac; EW=Electronic Warfare; SAR=Search-Rescue
Supported Arsenal
Graphical image of an aircraft Gatling-style rotating gun
Graphical image of an aircrat automatic cannon
Graphical image of aircraft aerial rockets
Graphical image of an aircraft conventional drop bomb munition
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