Northrop XP-56

The experimental Northrop XP-56 flying wing fighter of 1943 was one of the most unusual fighter aircraft to be evolved by any of the combatants during World War II. Although unsuccessful in attaining production, the XP-56 gained a lot of valuable data on flying wing designs, some of which was ultimately used in the design of the Northrop B-2 Spirit stealth bomber of the 1990s.

The founder of Northrop Aircraft Inc. was John Knudsen "Jack" Northrop, who at one time worked for Loughead Aircraft Manufacturing Company (later changed in spelling to Lockheed) as well as for Douglas Aircraft. It is not widely known, but there were actually THREE separate and distinct aircraft companies that carried Jack Northrop's name.

The first one of these companies ("Northrop I") had been founded by Jack Northrop in 1927, initially under the name of the Avion Corporation. For the first couple of years as head of the California-based Avion Corp., Jack Northrop spent his time experimenting with ideas for all-metal construction and for flying-wing designs. Unfortunately for the bottom line, nothing actually got built or sold by Avion in the first two years of its existence, and economic reality eventually made itself felt. Lacking sufficient capital to carry on by itself, the Avion Corporation was absorbed in 1929 by the United Aircraft and Transport Corporation, and operated until 1931 as the Northrop Aircraft Corporation, a division of UA&T Corp. During this period, Northrop built the Alpha (a single-engined passenger- and mail-carrying aircraft) and the Beta (a two-seat sports aircraft).

In 1931, UA&T consolidated its two subsidiaries--Northrop Aircraft Corp and Stearman Aircraft--into a single unit and moved everything to Wichita, Kansas. Jack Northrop was a dyed-in-the-wool Californian, and found the prospect of facing Kansas winters unpalatable. Consequently, he left UA&T and tried once again to establish another California-based aircraft company. He got together with his old friend and former employer, Donald Douglas, to found the Northrop Corporation ("Northrop II"), with Douglas retaining 51 percent of the stock and Jack being named as its president. The main factory was located at El Segundo, California, ensuring that Jack could remain living in the state that he loved. The Northrop Corporation was responsible for the famous Gamma and Delta commercial monoplanes which were so successful during the 1930s. The Northrop Corporation was also responsible for the 3A monoplane fighter of 1935 and for the A-17 attack plane of 1935/36. Northrop was also responsible for the BT-1 attack bomber, which was to evolve into the famous SBD Dauntless of World War II fame.

However, the Northrop Corporation began to experience some serious labor strife in the late 1930s. The labor problems eventually got so bad that the Army refused to accept any further deliveries of A-17 attack planes until they were corrected. In an attempt to correct the labor problems, on April 5, 1937, Douglas decided to acquire the rest of the stock of the Northrop Corporation. Continued labor difficulties forced Douglas to dissolve the Northrop Corporation altogether on September 8, 1937. It was immediately reformed under the direct aegis of Douglas, the name of the company changing to the El Segundo Division of Douglas.

By 1939, the Northrop Corporation had become just another division of Douglas Aircraft, and Jack Northrop went out on his own for a third time to found yet another California-based aircraft company bearing his name, this one named Northrop Aircraft Inc. of Hawthorne, California ("Northrop III"), the forerunner of today's Northrop Corporation, the maker of the B-2 stealth bomber.

The Northrop XP-56 was the first USAAF fighter aircraft to be built by "Northrop III". The Northrop XP-56, like the Bell XP-52, the Vultee XP-54, and the Curtiss XP-55, was evolved as a response to Circular Proposal R-40C, which was issued on November 27, 1939. It called for a fighter that would be much more effective than any extant--with a top speed, rate of climb, maneuverability, armament, and pilot visibility, all of which would be far superior to those of any existing fighter. In addition, the fighter was required to have a low initial cost and had to be easy and inexpensive to maintain. The Army specifically mentioned in R-40C that they would consider aircraft with unconventional configurations.

The Northrop entry, designated N2B by the company, was nothing if it was not unconventional. It was a unique tailless interceptor made entirely of magnesium. The N2B was a swept-wing tailless flying-wing aircraft with no forward-mounted elevators. Northrop proposed to use the new and untried Pratt & Whitney X-1800-A3G (H-2600) liquid-cooled engine, mounted behind the pilot's cockpit and driving a pair of contrarotating pusher propeller.

Jack Northrop had actually been thinking about flying wing aircraft as far back as 1929 when he was with the Avion Corporation. In 1939, Northrop had, in fact, built a full-scale flying testbed to explore the possibility of all-wing designs. Designated N1M by the company, the flying testbed was powered by a pair of Lycoming engines driving pusher propellers. The N1M has survived to the present day and is in storage at the Paul Garber facility in Suitland, Maryland. I saw it there in November of 1992. It seems to be in pretty good shape.

On June 22, 1940, Northrop Aircraft, Inc. received a contract for preliminary engineering data and a powered wind tunnel model. The designation P-56 was reserved for the project. On September 26th, 1940, a single prototype was ordered as the XP-56. The serial number was 41-786.

However, shortly after development of the XP-56 began, Pratt & Whitney abandoned all work on its X-1800 liquid-cooled engine. This left the XP-56 (and the competing XP-54 and XP-55 along with it) out on a limb, without an engine. Northrop's design team reluctantly decided to switch to the less-suitable Pratt & Whitney R-2800 air-cooled radial engine. Although the R-2800 engine was more powerful (2000 hp as opposed to 1800 hp), it was also wider. The larger diameter of the radial engine required in turn that the fuselage be widened in order to accommodate it. These changes resulted in an increase in the weight.

The fuselage was stubby and rounded, with an unpressurized cockpit situated well forward. The plane had a short and stubby dorsal fin and a very large ventral fin, so large, in fact, that it very nearly scraped on the ground when the aircraft stood on its landing gear. The cantilever mid-mounted wing had elevons which functioned both as ailerons and wingflaps mounted on the trailing edge of the drooping wing tip. Air ducts for cooling of the radial engine were located on the wing leading edge. The mainwheels retracted into the wing, and the nosewheel retracted into the fuselage. Proposed armament was to be two 20-mm cannon and four 0.50-inch machine guns, all mounted in the nose.

On February 13, 1942, a USAAF contract was issued for a second XP-56 prototype. The serial number was 42-38353. The name *Black Bullet* has been attached to the project, but I don't know if this name was official.

The first XP-56 (41-786) was ready in April of 1943. It was shipped out to Muroc Dry Lake (later Edwards AFB) for tests. During initial ground handling trials, it was found that the aircraft tended to yaw sharply and dangerously while taxiing at high speeds. It was thought that this problem was caused by faulty wheel brakes, and trials were halted until the aircraft was re-equipped with manual hydraulic brakes. This delayed the first flight until September 30, 1943, when test pilot John Myers took the XP-56 into the air for the first time. An altitude of five feet was maintained, and the XP-56 appeared to fly normally. Several additional flights were undertaken, during which somewhat greater altitudes were attained. These test flights were not particularly encouraging. Nose-heaviness was a persistent problem, and lateral control was difficult to maintain in all flight regimes. However, before any of these aerodynamic problems could be addressed, the port mainwheel tire blew out during a high-speed taxiing run and the aircraft somersaulted over onto its back. It was totally wrecked.

In an attempt to correct the deficiencies encountered with the first XP-56, the second XP-56 (42-38353) underwent some major changes. The center of gravity was moved further forward. There was a major increase in the size of the upper vertical surface--it was enlarged from a mere stub into a surface larger in area than the ventral fin. A new form of rudder control was fitted which made use of air bellows at the wing tips which operated a set of split flaps for directional control. The control of the bellows was achieved by valving air to or from the bellows by means of wingtip venturis.

On March 23, 1944, test pilot Harry Crosby took the second XP-56 up for the first time. However, Crosby found it impossible to lift the nosewheel off the ground at speeds below 160 mph, and the test flight lasted only a few minutes. The second flight went better, and it was found that the nose heaviness went away after the landing gear was retracted. However, the aircraft was severely underpowered for its weight, and only relatively low speeds could be attained, much less than the projected maximum speed of 465 mph at 25,000 feet.

On May 39, 1944, it was decided that NACA would use their wind tunnel at Moffett Field, California to look into the causes of the XP-56s low performance. However, the higher priority of other projects led to postponement of the XP-56 wind tunnel tests until late October of 1944.

While awaiting the beginning of the wind tunnel testing, further flight test trials were undertaken with the XP-56. On the tenth test flight, the pilot complained of extreme tail heaviness on the ground, low power, and excessive fuel consumption. After consultations, it was concluded that the XP-56 was basically not airworthy , and that it was just too dangerous to continue flight tests with it. Shortly thereafter, the whole project was abandoned. The further development of higher-performance piston-engined fighters was futile in any case, since the advent of jet propulsion would soon bring the era of propeller-driven fighters to a close.

Although the XP-56 project was a failure, it was not a total loss for Northrop, since the company had learned a lot about flying wing designs. This data gained during the XP-56 project was put to good use in later Northrop designs such as the XB-35 piston- engined bomber, the YB-49 jet-powered bomber, and the B-2 stealth bomber.

Specs of the XP-56:

One 2000 hp Pratt & Whitney R-2800-29 eighteen-cylinder air-cooled radial engine. Proposed armament was to be two 20-mm cannon and four 0.50-inch machine guns, all mounted in the nose. No armament was, in fact, ever actually fitted. In view of the limited flight testing of the XP-56, the following performance figures are based on manufacturer's estimates and were never achieved during actual tests. Maximum speed 465 mph at 25,000 feet, 417 mph at sea level. Climb rate of 3125 feet per minute at 15,000 feet. Climb to 20,000 feet in 7.2 minutes. Normal range 445 miles at 396 mph. Maximum range 660 miles. Service ceiling 33,000 feet. Weights were 8700 pounds empty, 11,350 pounds normal loaded, and 12,145 pounds maximum. Dimensions (second prototype) were wingspan 42 feet 6 inches, length 27 feet 6 inches, height 11 feet, wing area 306 square feet. The length of the first prototype was 23 feet 6 inches and the height was 9 feet 8 inches.

Sources:

1. The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.
   
   
2. War Planes of the Second World War, Fighters, Volume Four, William Green, 1964.