Northrop XP-56 Black Bullet
Radical tailless prototype fighter built from magnesium.
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The Northrop XP-56 Black Bullet was a prototype fighter interceptor developed by the Northrop Corporation. It ranks among the most unconventional experimental aircraft of World War II. The project ultimately failed and never reached production.
Design and development
The concept originated in 1939 as the Northrop N2B model. The design was radical for its time: it had no horizontal tail, only a small vertical tail, used an experimental engine, and was built from magnesium. The aircraft was essentially a wing with a small central fuselage for the engine and pilot, intended to reduce aerodynamic drag compared to conventional planes.
It was designed around the Pratt & Whitney X-1800 liquid-cooled engine in a pusher layout with contra-rotating propellers. The U.S. Army ordered design work to begin on 22 June 1940, and after reviewing the plans, ordered a prototype on 26 September 1940. Shortly after work started, Pratt & Whitney halted development of the X-1800.
The Pratt & Whitney R-2800 engine was substituted, though it was not fully suitable. The new engine produced 200 more horsepower (2,000 hp total) but had a larger diameter, requiring a bigger fuselage. This change delayed the program by five months and was expected to add 2,000 pounds in weight and reduce top speed by 14 mph.
Because the tailless design was novel and high-risk, a smaller, lightweight test aircraft of similar configuration, the Model N-1M, was built. Powered by two small Lycoming engines, it flew successfully alongside the XP-56's design phase, confirming the basic layout's stability. Based on these trials, the Army ordered a second prototype on 13 February 1942.
Northrop built the XP-56 using magnesium alloy for both the airframe and skin, as aluminum was expected to be in short supply due to wartime demand. At the time, experience with magnesium aircraft construction was limited. Since magnesium cannot be easily welded with conventional methods, a team including Vladimir Pavlecka, Tom Piper, and Russell Meredith developed the heliarc welding technique for magnesium alloy. This process resembled earlier GMAW methods from the 1920s by General Electric but used inert gas shielding.
First prototype
First engine runs in the aircraft began in late March 1943, but excessive propeller shaft flex caused the engine to fail. Pratt & Whitney did not send a replacement until August, causing another five-month delay.
Lore & Background
The XP-56 originated in 1939 as the Northrop N2B model, designed around the Pratt & Whitney X-1800 engine in a pusher configuration with contra-rotating propellers. The U.S. Army ordered design work on 22 June 1940 and a prototype on 26 September 1940.
When Pratt & Whitney stopped development of the X-1800, the R-2800 engine was substituted, causing a five-month delay and requiring a larger fuselage. To test the novel tailless layout, Northrop built the smaller N-1M, which confirmed the configuration's stability. The Army then ordered a second prototype on 13 February 1942.
Northrop used magnesium alloy for the airframe and skin due to anticipated aluminum shortages. Because magnesium could not be easily welded with conventional techniques, a team developed the heliarc welding technique using inert gas shielding. The first prototype's engine runs began in late March 1943, but propeller shaft flex caused engine failure; a replacement arrived in August. Taxi tests on 6 April 1943 revealed a serious yaw problem, initially attributed to uneven brakes.
The aircraft first flew on 30 September 1943 at Muroc Air Base. The yaw issue was later traced to aerodynamic instability, and the upper vertical stabilizer was enlarged. On 8 October 1943, the first prototype was destroyed when a tire blew out during a high-speed taxi; pilot John Myers survived.
Second prototype
The second prototype incorporated changes including re-ballasting, a larger upper vertical tail, and reworked rudder linkages. It flew on 23 March 1944. The pilot had difficulty lifting the nose wheel below 160 mph and reported extreme yaw sensitivity. Subsequent flights were longer, but only low speeds were attained.
On the 10th flight, the pilot noted extreme tail heaviness, lack of power, and excessive fuel consumption. Flight testing was ceased as too hazardous, and the project was abandoned after a year of inactivity. By 1946, the U.S. Army Air Forces was developing jet fighters and had no need for a new propeller-driven fighter.
Reader's Guide
The XP-56 Black Bullet represents a bold but ultimately unsuccessful attempt to push fighter design into uncharted territory during World War II. Its tailless, pusher-propeller configuration was intended to reduce aerodynamic drag, but the design introduced severe stability and control problems that could not be overcome with the technology of the time. The use of magnesium for the airframe was driven by wartime material shortages and required the development of a new welding technique, heliarc welding, which later found broader applications.
The aircraft's failure to achieve its performance goals, combined with the rapid advance of jet propulsion, led to the project's abandonment. The second prototype survives in the collection of the Smithsonian Institution's National Air and Space Museum, preserved as a testament to the experimental extremes explored during the war. The XP-56's legacy lies not in combat service but in the lessons learned about tailless aircraft stability and the challenges of alternative materials.
Did You Know?
- Pilot John Myers survived the crash of the first prototype and credited his wearing of a polo player's helmet for his minor injuries.
Frequently Asked Questions
What is the Northrop XP-56 Black Bullet?
It was a single-seat, tailless prototype interceptor that Northrop Corporation built during World War II. Only two airframes were ever completed, and the project was shelved before it could enter production.
What made the XP-56's design so radical for its time?
The aircraft was essentially a wing with a tiny central pod housing the pilot and engine, and it carried no horizontal stabilizer at all. Its airframe was also constructed from magnesium, a material far more experimental for airframes in that era.
What engine powered the XP-56 Black Bullet?
It was fitted with a Pratt & Whitney R-2800 radial engine producing roughly 2,000 horsepower, a substantial output for a single-seat interceptor of the period.
When did the XP-56 first fly, and how long had the concept been in development?
Its maiden flight took place on 30 September 1943, though the design had been in gestation since the concept was first sketched as the N2B back in 1939.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Northrop XP-56 Black Bullet (CC BY-SA 4.0).
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