Curtiss-Wright XP-71 Heavy Fighter / Bomber Escort
The Curtiss XP-71 was developed along the lines of a heavy fighter with solely cannon armament - though the need for such an aircraft type was over by the end of 1943.
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Prior to America's entry into World War 2 (1939-1945) in 1941, the war was viewed from an "outside-looking-in" perspective. Observations were keenly focused on the evolving (and deteriorating) situation in Europe where quick-bombing strikes paralyzed military forces and populations alike. German and Axis elements made their way across Poland, Norway, the Low Countries and, finally, France to give real rise to the threat of American soil being attacked once Britain had fallen. Such thinking then spurred development into heavy fighter types designed to meet the threat of bomber formations head on and one such accepted submission by the United States Army was from Curtiss-Wright who sold them on the idea of its two-seat XP-71 heavy concept.
The primary role for the new aircraft was in intercepting bomber formations, cutting through their ranks with cannon fire while avoiding enemy guns and escort fighters. Its secondary role would see the mount used as an escort for Allied bombers in turn for when the battle turned against the invader. The design would have to possess the necessary speed, agility, firepower and range to meet the challenges it would eventually face. As proved common practice during the war, the Army contracted for two working prototypes in the XP-71 mold based on the company's "Model CW-29" proposal. The contract appeared on October 28th, 1941 - just months before the Japanese surprise attack on Pearl Harbor, Hawaii.
A mockup of the XP-71 was completed and reviewed during November 1942 and the interesting design decision was made to make the XP-71 a single-seat heavy fighter. This allowed for more internal space to be maximized for components such as avionics, fuel and electronics but also increased the pilot's workload in flight. Overall dimensions produced a very large fighter aircraft with a wingspan reaching 82.25 feet, a length of 61.8 feet and a height of 19 feet. Engineers elected for a conventional arrangement in which the fuselage made up most of the continuous length of the aircraft. Wings were shoulder-mounted amidships and each held an engine nacelle running ahead of the leading edge and through the trailing edge. The cockpit sat just forward of the main wing element which offered excellent vision forward, to the sides and to the rear thanks to a lightly-framed bubble-style canopy. The cockpit sat well aft of the nose cone assembly which was to house a potent cannon armament. The fuselage then tapered at the empennage which was capped by a rounded single vertical tail fin and low horizontal planes. The undercarriage was of the tricycle arrangement which made ground running easier for the pilot to handle while offering the necessary clearance for the spinning propeller blades selected. A first flight was tentatively scheduled for June of 1944.
Power for the XP-71 came from a pair of large and powerful Pratt & Whitney R-4360-13 "Wasp Major" radial piston engines developing 3,450 horsepower each while coupled to General Electric turbochargers. This became 6,900 total horsepower when combined which required a stiff mounting structure and large propeller blades for optimal thrust output. As such, Hamilton Standard 13.5-foot diameter blades were installed and each engine drove these in a contra-rotating configuration set within a "pusher" arrangement. That is, the propellers were fitted at the wing trailing edges as opposed to a position ahead of the wing leading edges - common to many other aircraft. In this fashion, the engines "pushed" the aircraft through the air instead of "pulling" it. Undoubtedly, this was one of the more unique design qualities of the Curtiss design. The twin engine installation provided the airframe with a maximum reported speed of 430 miles per hour with a range out to 3,000 miles. Its service ceiling was 40,000 feet which necessitated a fully-pressurized cockpit for the pilot.
At the heart of this "bomber destroyer" was its armament - led by a 75mm cannon in the nose. This was supplemented by 2 x 37mm cannons in the nose as well, giving the XP-71 a potent "one-two" punch against all known bomber targets in service with Axis forces - primarily those of Germany. The 75mm cannon was fed through an automated feeder which supplied 20 projectiles while the 37mm guns were afforded 60 rounds each. This ammunition stock was rather limiting, requiring the pilot to utilized short, controlled bursts to good effect.
Work on the Curtiss aircraft continued into 1943 and its technological edge was becoming a greater issue for engineers to overcome than originally envisioned. During testing in February of 1943, the gun arrangement in the nose proved problematic and applicable gun systems were revealing their own issues. Add to this the changing face of the war during 1943 which did not see the emergence of large scores of German bombers but, in turn, the rise of long-range bomber formations fielded by the Allies - limiting the potential tactical appeal of the XP-71 in the heavy fighter / bomber escort role, particularly when other fighters such as the North American P-51 and Republic P-47 Thunderbolt were equally up to the task.
As such, the XP-71 program - as promising as the heavy fighter was - was officially cancelled during October of 1943. The Army briefly toyed with the idea of converting the XP-71 into a reconnaissance-minded platform but this endeavor turned to naught and no other service branches took serious consideration of the XP-71. It therefore joined the many other American efforts to produce the perfect aircraft for the job during World War 2.
Curtiss factories continued in their support of the war effort through aircraft production of other types.