The experimental Northrop XP-56 fighter design program was one of many unusual aircraft design to come out of World War Two. Many nations throughout War World Two encouraged aircraft manufacturers to think outside normal convention and come up with an aircraft design that was a war winner. Faster, higher, more fire power was the axiom of the day. The search was on for anything that would help bring any nation air superiority in a war that seemed to spreading like wild fire.

During the early days of World War Two the military was keeping an eye at what was transpiring in Europe and were deeply concerned. If the United States was to go to war against the Axis powers they would be outclassed in many areas especially in aircraft design and performance. The Army Air Corps’ response was to draft and put forth the FY 1940 (R-40C) proposal. This proposal called for a fighter design that would be faster, climb higher, quicker, and be better armed than any of its contemporaries. The proposal also encouraged the “unconventional configuration” to be applied to the new aircraft design. Many companies took the challenge but only a few provided plans for a viable design. The Army Air Corp selected four designs for further studies; Bell XP-52, Vultee XP-54, Curtis XP-55, and the Northrop XP-56.

 

Even though Jack Northrop was designing planes since the 1920’s the XP-56 would be the company’s first official attempt at a fighter aircraft design. The XP-56 concept could be traced back to the N1M “Jeep” full scale flying test bed. Built and flown in 1940 the N1M flying model was build to study the feasibility of an all wing tailless aircraft. Also the N1M was the first truly all wing tailless American aircraft to take to the air. Early flights were satisfactory and confirmed that the idea of a tailless aircraft could be possible. Between 1940 and 1941 over 200 flights were made in the N1M to study stability and control of the tailless aircraft. The N1M also had the ability to adjust the wing tips on the ground to study various wing configurations.

The engineers at Northrop, building on data obtained from the N1M, came up with a truly unconventional aircraft design. This new aircraft was to be a tailless craft with swept back wings, with two rear facing contra-rotating propellers, powered by a single engine located behind the pilot who would sit in an unpressurized cockpit well situated forward of the craft. The design would be built around the experimental Pratt and Whitney X-1800 H-type liquid cooled engine and it was to be constructed entirely of magnesium alloy. The X-1800 allowed designers to fit the engine in any configuration. This new aircraft was designated the N2B.

Since the beginning development of the XP-56 was plagued by problems and it would continue throughout its short history. As soon as development of the XP-56 began Pratt and Whitney cancelled the X-1800 engine program, the engine that was to equip the new aircraft. As a result Northrop had to scramble to find a replacement engine. Their alternative, but less desirable choice, was the Pratt & Whitney R-2800-29 air-cooled radial engine.

Though the new engine was more powerful than the X-1800 and had a much simpler cooling system, the new radial engine had a large diameter, which meant the aircraft would have to be modified to accommodate it. The aircraft now took a more rounded stubby look, which added more weight.

The next major engineering hurdle was the welding process for welding magnesium. Magnesium is unlike most metals and when enough heat was applied this metal can ignite and burn very hot and bright. To make the aircraft lighter Magnesium was used for the construction. Magnesium is lighter then aluminum so that meant the skin could be made thicker and help distribute loads better.

In initial testing it was discovered that the aircraft tended to yaw to the left. And so the decision was made to add a dorsal fin in order to stabilize the aircraft. This combined with the larger radial engine increased the total weight of the aircraft.
Problems persisted for the XP-56. Nose heaviness made control of the aircraft difficult. Nose wheel could not leave the ground at speeds less then 160 mph, thus also increasing the amount of runway needed for lift off.

There were two variants of the 41-786 prototype fighter. The main recognizable difference between the two was an added dorsal fin. The dorsal fin was found to be needed when during early high speed taxis and low level flights reveal stability problems with the aircraft.

 

Northrop’s first attempt at a fighter design could be considered to be a dismal and complete failure. Flight tests reveal there was no significant improvement in performance over existing fighters of the day. Engineering challenges, mechanical failures, the end of the war, and the advent of the jet age help to end the quest of the unconventional high performance piston driven fighter. But not all was a complete loss as data obtained from the XP-56 program help contribute to the design of the XB-35, XB-49, and the B-2 Stealth Bomber, some 60 years later.