Republic XF-12 Rainbow Color Photographs

The Republic Rainbow was designed to fulfill a 1943 requirement for a reconnaissance aircraft able to reach an altitude of 40,000 feet (12,000 meters), a speed of 400 mph (640 kph), and a range of 4,000 miles (7,400 km). All these criteria were exceeded. The design used four Pratt & Whitney R-4360 Wasp Major 28-cylinder engines, each developing 3,250 horsepower. The prototype made its maiden flight on 04FEB46. (NASM Rudy Arnold collection)
The Rainbow’s design emphasis was on minimizing drag, and the result is considered by many to be one the most beautiful aircraft of the time. Cooling air and turbocharger exhaust was discharged through the back of each engine nacelle, the resulting thrust was calculated to produce the equivalent of an extra 250 horsepower per engine. Pictured is an unmarked Rainbow prototype along with a P-47 Thunderbolt and RC-3 Seabee for comparison.
The Rainbow lacked cowl flaps, which would have increased drag. When additional engine cooling was needed the entire cowling moved to open a slot to increase airflow. Another novel feature seen in this photograph is the pressurized cockpit visible behind the clear aerodynamic nosecone, which was unpressurized.
Two aircraft were built, serials 44-91002 and 44-91003. The fuselage contained a fully-equipped photo lab so that photographs could be developed on the return leg of a reconnaissance flight. The second prototype performed a mapping demonstration dubbed Operation Bird’s Eye, which mapped a swath of the continental United States from coast to coast in less than seven hours. The finished photo mosaic was 325 feet (99 meters) long. (NASM Rudy Arnold collection)
The Rainbow came too late to serve in the Second World War. Despite its impressive performance, jet-powered designs held greater promise and the USAAF decided to make due with modifications of existing types until the jets entered service. The second prototype was lost after an engine explosion on 07NOV48, while the first was retired in June 1952 and expended as a target.
No Rainbows survive today. For those wishing to add a Rainbow to their model collection, Anigrand produces a resin kit in 1/72 scale. While a little pricy, it is a large model. (NASM Rudy Arnold collection)