Northrop XP-56 Black Bullet

https://en.wikipedia.org/wiki/Northr...6_Black_Bullet

The Northrop XP-56 Black Bullet was a unique prototype fighter interceptor built
by the Northrop Corporation. It was one of the most radical of the experimental
aircraft built during World War II. Ultimately, it was unsuccessful and did not
enter production.

The initial idea for the XP-56 was quite radical for 1939. It was to have no
horizontal tail, only a small vertical tail, used an experimental engine, and be
produced using a novel metal. The aircraft was to be a wing with a small central
fuselage added to house the engine and pilot. It was hoped that this
configuration would have less aerodynamic drag than a conventional airplane.

The idea for this single-seat aircraft originated in 1939 as the Northrop N2B
model. It was designed around the Pratt & Whitney liquid-cooled X-1800 engine in
a pusher configuration driving contra-rotating propellers. The U.S. Army ordered
Northrop to begin design work on 22 June 1940, and after reviewing the design
ordered a prototype aircraft on 26 September 1940. Shortly after design work had
begun, Pratt & Whitney, however, stopped development of the X-1800. The Pratt &
Whitney R-2800 engine was substituted, although it was considered not entirely
suitable. Although the new engine was more powerful (2,000 hp vs 1,800 hp) it
had a larger diameter and required a larger fuselage to house it. This change
delayed the program by five months. It was expected that the new engine would
require a 2,000 lb weight increase and cost 14 mph in top speed. Since this
tailless design was novel and considered high risk, it was decided to construct
a small, lightweight plane of similar configuration for testing called the Model
N-1M. In parallel with the design of the XP-56, successful flight trials of the
configuration were conducted utilizing this airframe, confirming the basic
layout. Two small Lycoming engines powered this aircraft. These trials confirmed
the stability of the radical design and, upon review, the Army decided to
construct a second prototype, which was ordered on 13 February 1942.

Northrop constructed the XP-56 using magnesium alloy for the airframe and skin,
because aluminium was forecast to be in short supply due to wartime demands. At
the time there was little experience with magnesium aircraft construction.
Because magnesium cannot be easily welded using conventional techniques,
Northrop hired Vladimir Pavlecka to develop the heliarc welding technique for
magnesium alloy. (Later it was discovered that in the 1920s General Electric had
already developed similar techniques.)


Role
Fighter

Manufacturer
Northrop Corporation

First flight
30 September 1943

Status
Canceled

Number built
2

First prototype

First engine runs in the aircraft were conducted in late March 1943, but
excessive propeller shaft flex caused the engine to fail. Pratt & Whitney did
not send another engine until August, causing a five-month delay.

Taxi tests of the XP-56 began on 6 April 1943 and showed a serious yaw problem.
At first, it was thought to be caused by uneven wheel brakes, and considerable
effort was placed into fixing this problem. Manual hydraulic brakes were
installed and the aircraft flew on 30 September 1943 at Muroc Air Base in
southern California. Eventually, the yaw problem was traced to a lack of
aerodynamic stability, and to fix this the upper vertical stabilizer was
enlarged from a mere stub, to one virtually matching the ventral unit in shape
and area.

After a number of flights, the first XP-56 was destroyed 8 October 1943 when the
tire on the left gear blew out during a high-speed (~130 mph) taxi across Muroc
Dry Lake. The pilot, John Myers, survived with minor injuries which he credited
to his innovative wearing of a polo player's helmet. Myers was the test pilot
for several of Northrop's radical designs during the war.

Second prototype

A number of changes were made to the second prototype, including re-ballasting
to move the center-of-gravity forward, increasing the size of the upper vertical
tail, and reworking the rudder control linkages. This second prototype was not
completed until January 1944. The aircraft flew on 23 March 1944. The pilot had
difficulty lifting the nose wheel below 160 mph (257 km/h). He also reported
extreme yaw sensitivity. This flight lasted less than eight minutes, but
subsequent flights were longer, and the nose heaviness disappeared when the
landing gear was retracted. Only relatively low speeds were attained, however.
While urging NACA to investigate the inability to attain designed speeds,
further flight tests were made. On the 10th flight, the pilot noted extreme tail
heaviness, lack of power, and excessive fuel consumption. Flight testing was
then 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-powered
fighters, and had no need for a new propeller-driven fighter aircraft.

Specifications (XP-56 estimates)

General characteristics
Crew: one, pilot
Length: 27 ft 6 in (8.38 m)
Wingspan: 42 ft 6 in (12.96 m)
Height: 11 ft 0 in (3.35 m)
Wing area: 306 ft² (28.44 m²)
Empty weight: 8,700 lb (3,955 kg)
Loaded weight: 11,350 lb (5,159 kg)
Max. takeoff weight: 12,145 lb (5,520 kg)
Powerplant: 1 × Pratt & Whitney R-2800-29 radial, 2,000 hp (1,492 kW)

Performance
Maximum speed: 465 mph at 25,000 ft (749 km/h)
Range: 660 miles (1,063 km)
Service ceiling: 33,000 ft (10,061 m)
Rate of climb: 3,125 ft/min at 15,000 ft (953 m/min)
Wing loading: 37 lb/ft² (181 kg/m²)
Power/mass: 0.18 hp/lb (0.96 kW/kg)

Armament

2 × 20 mm (.79 in) cannons
4 × .50 in (12.7 mm) machine guns



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