helicopter's main rotor, with a very limited ability to shift their center of lift up and down to aid the aircraft in maneuvering. Initially, the aircraft used propellers originally designed for the V-173 prototype. These propellers would be replaced with propellers taken from the Vought F4U-4 Corsair. An ejection seat was fitted to allow the pilot to clear the massive propellers in the event of an in-flight emergency. Although the prototype was unarmed, a combination of six M2 Browning 50-caliber machine guns or four M3 20 mm cannons would be mounted in the wing roots in service. Testing and evaluation The XF5U design was promising: specifications given at the time promised great maneuverability and speeds up to 452 mph (727 km/h). However, it came at the time when the United States Navy was switching from propeller driven to jet propelled aircraft. By 1946, the XF5U-1 project was already long over its expected development time, and well over budget. With jet aircraft coming into service, the Navy finally canceled the project on 17 March 1947, and the prototype aircraft (V-173) was transferred to the Smithsonian Museum for display. Although two aircraft were constructed, a lone XF5U-1 underwent ground runs but never overcame vibration problems. Taxi trials at Vought's Connecticut factory culminated in short "hops" that were not true flights. The only completed XF5U-1 proved to be so structurally solid that it had to be destroyed with a wrecking ball. Specifications (XF5U-1) See also References Notes Bibliography Chant, Christopher. Fantastic Aircraft. New York: Gallery Books, 1984. . Ginter, Steve. Chance Vought V-173 and XF5U-1 Flying Pancakes (Naval Fighters Number Twenty-one). Simi Valley, CA: Steve Ginter Publishing, 1992. . Guyton, Boone and Paul Marcus. "The Ups and Downs of The Flying Pancake." True, July 1951. Vol. 29, no. 170. Jerram, Michael E. Incredible Flying machines: An Anthology of Eccentric Aircraft. New York: Exeter Books, 1980. . Norton, Bill. U.S. Experimental & Prototype Aircraft Projects: Fighters 1939-1945. North Branch, Minnesota: Specialty Press, 2008, pp. 165–168. . XF5U Standard Aircraft Characteristics. Washington, DC: Naval Historical Center at the U.S. Navy Yard. Retrieved: 25 July 2009. Winchester, Jim. "Vought XF5U-1". Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft. Kent, UK: Grange Books plc., 2005. . Winchester, Jim. "Vought V-173 and XF5U-1 'Flapjack' (1942)". X-Planes and Prototypes. London: Amber Books Ltd., 2005. . External links The XF5U story Chance Vought Flying Flapjack Story and Photos at vought.org Chance