Origins and Context
Charles H. Zimmerman developed the Flying Pancake concept from 1933-1937 while working at NACA Langley Field.1 The design featured a circular wing with propellers at the wingtips to minimize drag and enable extremely short takeoff and landing capabilities.2
Program Structure
The program consisted of two phases: the wooden V-173 proof-of-concept aircraft and the all-metal XF5U-1 fighter prototype.3 The V-173 first flew on November 23, 1942, powered by two 80-hp Continental A-80 engines, while the XF5U-1 used more powerful 1,600-hp Pratt & Whitney R-2000-7 engines.4
Legacy
The V-173 completed 131 flight hours across 199 flights, proving the viability of Zimmerman's circular wing concept.5 Though the XF5U-1 showed promise with projected speeds of 425 mph, the Navy canceled the program in March 1947 as jet technology superseded propeller-driven aircraft.6
References
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Patent #2,108,093 granted February 14, 1938 for Zimmerman's circular wing aircraft design. ↩
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The propeller placement was designed to reduce wingtip vortices and recover energy normally lost in propeller slipstream. ↩
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The V-173 was constructed of wood and fabric, while the XF5U-1 used a metalite construction of aluminum-balsa sandwich material. ↩
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Test pilots included Boone T. Guyton, Richard Burroughs, and Charles Lindbergh. ↩
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The aircraft demonstrated remarkable low-speed handling, with no tendency to stall or spin. ↩
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The XF5U-1 prototype was scrapped before its first flight, though ground testing had been completed. ↩