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Above: Vought VS-315. This was an intermediate concept between the V-173 and XF5U-1, produced =p by Charles Zimmerman. The idea of a prone cockpit layout was not adopted by the US Navy. via Bill Rose ele) | o Left: Comparison drawings between the Vought | V-173 and XF5U-1 aircraft. Bill Rose oS Below left: Vought XF5U-1 with 4-blade propellers. 2 US Navy The four-bladed propellers continued to be used for engine and taxying trials, while Zim- merman took another look at an idea he had proposed in 1943, finally deciding that heavy- duty articulated flapping helicopter types were needed, with two blades mounted slightly ahead of the others. Vought’s heli- copter specialist Ralph Lightfoot also sug- i The four-bladed propellers continued to be used for engine and taxying trials, while Zim- merman took another look at an idea he had proposed in 1943, finally deciding that heavy- duty articulated flapping helicopter types were needed, with two blades mounted slightly ahead of the others. Vought’s heli- copter specialist Ralph Lightfoot also sug- gested fitting extended fairings on the outer sides of the propeller nacelles to improve aerodynamic performance, but this option was never taken up. By late 1945, the static XF5U-1 had been destroyed during tests to determine load lim- its, but flights of the original V-173 continued, with the famous aviator Charles Lindbergh piloting the aircraft on at least one occasion. The XF5U-1 was scheduled to begin flight-test- ing in 1947 and preparations had been drawn up to ship the XF5U-1 to Muroc Field in Cali- fornia (now Edwards AFB) via the Panama Canal. The choice of Muroc Field remains somewhat mysterious, as it would have been much easier to conduct trials at Patuxent River Naval Air Station in Maryland, as is nor- mally the case with new Navy aircraft. However, the Navy had concluded that pro- peller-driven combat aircraft had reached their performance limits as far back as 1944 30 Below left: Vought XF5U-1 with 4-blade propellers. US Navy Secret Projects: Flying Saucer Aircraft