Republic XF-12 Rainbow Strategic Reconnaissance Aircraft
The Republic XF-12 Rainbow squared off against the Hughes XF-11 with both losing out thanks to the end of World War 2 and the American shift to jet-powered types.
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During World War 2, the Republic Aviation name was primarily tied to the excellent P-47 "Thunderbolt" fighter-bomber which proved so popular with its pilots and so valuable to warplanners for her multi-faceted capabilities. One of Republic's lesser-known projects during the war became the XF-12 "Rainbow" reconnaissance platform which appeared only in a pair of prototype forms but these were only made available after the war had come to a close. The XF-12 was born from a mid-war requirement brought about by the USAAC (United States Army Air Corps) ATSC (Air Technical Service Command) describing a high-performance, high-altitude long-range platform to assist in photography and reconnaissance of potential vital enemy targets - primarily in the Pacific Theater of war against the likes of the Japanese Empire.
The war front of the Pacific was a very different sort of beast than that as found in Africa, Europe and Asia. There were miles and miles of ocean surface to contend with and the war effort on this side of the globe would ultimately involve all types of available weaponry - warships, submarines, aircraft carriers, bombers, fighters, soldiers and marines - often fighting in the worst possible environments imaginable (despite the images of palm trees and beaches). The primary challenge for aircraft in the theater was managing the vast expanse of ocean - a challenge that would soon allow the aircraft carrier to replace the battleship as "king of the seas". However, aircraft carriers were realistically designed for small-class fighters and torpedo dive bombers - not multi-engined bombers. As such, the need was there for a long-range, land-based bomber to reach the heart of the Japanese Empire.
As the theater grew to encapsulate more fronts than original envisioned, there was a definite need for aircraft that could manage longer distances - which is where aircraft like the Lockheed P-38 Lightning and Consolidated B-24 Liberator shined (among many flying boats as well). Regardless, a dedicated need was required and the formal specifications called for an airframe possessing a 400 mile per hour maximum speed with a range out to 4,600 miles and a service ceiling of 40,000 feet to help keep it out of the reach of enemy fighters and ground-based "flak" artillery. The design would therefore have to have high-performance engines built for both speed and high-altitude operation. The fuselage would be pressurized for the safety of the crew operating in high-level flight and possess an internal fuel load and fuel efficiency to help meet the mission demand. Mission equipment would include a bevy of photographic cameras and applicable systems.
Two firms proved up to the challenge - these being Howard Hughes's Hughes Aircraft and competing Republic Aviation. The Hughes design was designated as the "XF-11" and was a large, twin-engine, twin-boom design with a crew of three. It was powered by a pair of Pratt & Whitney R-4360-31 "Wasp Major" series radial piston engines each delivering 3,000 horsepower. The design promised a top speed of 450 miles per hour, a range of 5,000 miles and a service ceiling of 44,000 feet - all specifications exceeding the original US military requirement. The Republic submission became the "XF-12" and this proved more of a conventional, large-scale bomber design sporting four radial engines, a tubular fuselage and a conventional tail section with a crew of seven. The engines were the same as on the Hughes XF-11 while performance promised a top speed of over 470 miles per hour, a range of 4,500 miles and a service ceiling in excess of 45,000 feet with output rated at 3,250 horsepower. Design of this aircraft was attributed to Alexander Kartveli, a Georgian-American who had previously worked for Alexander de Seversky's "Seversky Aircraft Company" founded in 1931 (having since reorganized under its new name of "Republic Aviation" beginning in 1939). Comparatively the USAAC itself would become known as the United States Army Air Force (USAAF) in World War 2 before becoming the United States Air Force (USAF) of today - fully separated from its Army origins. Contra-rotating propellers were initially intended for both the XF-11 and XF-12 design but the latter never implemented them. The first Hughes XF-11 prototype did fly with its contra-rotating propellers (lost in the famous Howard Hughes crash) but the second was completed with conventional propellers.