Republic XF-12 Rainbow / XR-12 / RC-12
Development of the XF-12 photo-reconnaissance airplane began in 1944 when it appeared that a fast, specialized reconnaissance airplane would be needed during the final stages of the war in the Pacific. The XF-12 was roughly the same size as the C-54, hut it was much heavier and had more than twice as much power. The four turbo-supercharged, 3,000hp (2,200kw) Pratt & Whitney Wasp Major engines were enclosed in long, slender nacelles that extended well beyond the wing trailing edges. The wing and empennage shared a resemblance with those of the F-84 Thunderjet. The fuselage was a slender teardrop shape, unbroken even by the windshield. Each main landing gear had a very large single wheel to fit inside the confines of the laminar flow wing. The Rainbow had its own darkroom in order to develop reconnaissance images on the way back from a long photo mission.
The first of two XF-12 prototypes was completed and flown on February 7, 1946. Subsequent experimental flight tests showed that it had lived up to its promise, and it passed into the service-test phase in June 1947. The XR-12 delivered to the Air Force crashed on its second test flight. The other Rainbow was sent to a gunnery range.
Unfortunately, the day of high-performance reciprocating engine-powered military airplanes had passed and the anticipated contract for 20 production F-l2As never materialized.
Republic still hoped to make the Rainbow into a 46-seat airliner, which they called the RC-2. Their selling point was speed, for which customers would pay a premium. Unfortunately, the expected postwar boom was not immediate and the airlines bought the slower but roomier DC-4 and Boeing 377 instead.
Engine: 4 x Pratt & Whitney R-4360 Wasp Major, 2250kW
Max take-off weight: 45950 kg / 101303 lb
Wingspan: 39.36 m / 129 ft 2 in
Length: 28.59 m / 94 ft 10 in
Height: 8.63 m / 28 ft 4 in
Wing area: 152.30 sq.m / 1639.34 sq ft
Max. speed: 684 km/h / 425 mph
Cruise speed: 640 km/h / 398 mph
Ceiling: 13000 m / 42650 ft
Range: 7000 km / 4350 miles