The R-40C Project

[Stryker]

In 1938‑39, the U.S. Army Air Corps began to realize just how far behind the international standards U.S. military aircraft design had fallen. The Seversky P‑35 was only just attaining operational service, and anyone who compared its performance with what was known of the German Bf‑109 and the British Spitfire and Hurricane could see just how far behind the U.S. was. The result was the creation of some fairly daring requirements, which resulted in such operational aircraft as the P‑38 ‑ the only US single‑seat twin‑engine fighter to see service during the Second World War ‑ and the P‑39, which introduced a novel position for the engine that allowed installation of a heavy nose armament. This period of aeronautical adventursomeness also resulted in some major failures, though these aircraft would be quite interesting in their design philosophies.
 
In February, 1940, the Air Corps issued Proposal R-40C, which called for a new fighters with a top speed of 525 m.p.h. at 15,000 feet, and a proposed armament of two 20mm cannon and four 50-caliber machine guns. Curtiss, Vultee and Northrop responded to the proposal with three very different yet essentially-similar aircraft.
 
The pusher fighter concept had been around since 1915. The advantage of the design was it allowed a heavy armament on the centerline, though the use of booms for the tail unit made the resulting airplane more fragile than the traditional tractor designs. Use of modern aeronautical knowledge gave the promise of higher performance than traditional designs. One, the Vultee XP‑54, was the most traditional, with a central nacelle holding the cockpit and engine, with tail surfaces supported by booms to either side of the propeller arc. The other two were more radical, these being the Curtiss XP‑55 and the Northrop XP‑56.
 
The Vultee Aircraft Corporation was very largely the brainchild of Gerard Vultee, formerly chief engineer at Lockheed Aircraft Corporation during the time that Lockheed was owned by Detroit Aircraft. Gerard Vultee and his wife were killed in a plane crash in January 1938 just prior to the USAAC issuing Circular Proposal R-40C. The XP-54 "Swoose Goose", Vultee Model 70, was designed as a fast interceptor using the Pratt & Whitney X-1800-4AG engine. When the engine program was canceled, the aircraft was redesigned for the Lycoming XH-2470 and redesignated Vultee Model 84. The first of two XP-54s built made its initial flight on 15 January 1943 and flew 86 times before it was grounded by engine problems. The second aircraft flew only once. The XP-54 nose section had a very unusual design--it tilted slightly upwards when firing its 37mm cannon to increase the firing range while the .50-cal. machine guns were tilted down at the same time.
 
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. 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 XP-56, Northrop Model N2B, was a radical design resulting from the R-40C proposal. The "Black Bullet", an all-magnesium aircraft, was first flown on 30 September 1943 but was destroyed during a taxi test. The second prototype was first flown on 23 March 1944 and had a bigger vertical stabilizer and an improved wingtip design incorporating a yaw control system. XP-56 flight tests revealed no significant performance improvement over conventional types already flying and the aircraft never entered production.
 
The Curtiss entry, designated CW-24 by the company, was perhaps the most unconventional of the three finalists. It was to be one of the last projects supervised by Donovan Berlin before he left the Curtiss company to go over to Fisher to work on the P-75. On June 22, 1940, the Curtiss-Wright company received an Army contract for preliminary engineering data and a powered wind tunnel model. The designation P-55 was reserved for the project. Since the USAAC was not completely satisfied with the results of the wind tunnel tests, Curtiss-Wright took it upon itself to build a flying full-scale model. It had a fabric-covered, welded steel tube fuselage and a wooden wing. The undercarriage was fixed. Like the XP-54, the Ascender was initially designed for the Pratt & Whitney X-1800 engine and had to be redesigned when the engine project was canceled. The XP-55 first flew on 13 July 1943 with an Allison V-1710 engine. The aircraft experienced stability problems and had modifications to increase the canard elevator surface, vertical stabilizer area, and eventually received wing tip extensions.
 

The performance of the 3 XP prototype aircraft built was roughly the same as conventional fighters of the time and never entered production.
 

The fighters in order,
Vultee XP-54 "Swoose Goose"
Curtiss XP-55 "Ascender"
Northrop XP-56 "Black Bullet"

[Jay Edward (deceased)]

Very interesting Stryker...thanks.