In the 1930s, Charles H. Zimmerman was a noted aeronautical engineer who advocated the concept of "discoidal" aircraft, the so-called "Zimmer Skimmer" and worked on a variety of projects on his own and with the Vought company. After testing using scale models, including a remotely controlled, electrically powered large-scale model, designated the Vought V-162, the US Navy approached Zimmerman and offered to fund further development. Data and concept documentation was given to the Navy in 1939, with wind tunnel tests on full-scale models being completed in 1940-1941.
The original prototype, designated the V-173 (Flying Pancake), was built of wood and canvas and featured a conventional, fully symmetrical aerofoil section (NACA 0015). Designed as a "proof-of-concept" prototype, the initial configuration V-173 was built as a lightweight test model powered by two 80 hp (60 kW) Continental A-80 engines turning F4U Corsair propellers. These were replaced by a pair of specially modified 16 ft 6 in three-bladed units. A tall, fixed main undercarriage combined with a small tailwheel gave the aircraft a 22° "nose-high" angle.
The first flight of the V-173 was on 23 November 1942 with Vought Chief Test Pilot Boone Guyton at the controls. The aircraft's most significant problem concerned its complicated gearbox that routed power from the engines to its two long propeller shafts. The gearbox produced unacceptable amounts of vibration in ground testing, delaying the aircraft's first test flight for months. This contributed to the aircraft feeling much too heavy when maneuvering for its light weight. In addition to this on the first few flights, the pilot was never able to achieve enough speed to achieve the correct amount of airflow over the control surfaces to pull the aircraft into level flight. The test pilot Guyton discussed these issues with Zimmerman and they worked to eliminate these issues. In addition to this Guyton commented that the cockpit design was poor. He explained that in addition to the poor comfort the pilot had limited to no use for the clear bottom panels of the cockpit. He explained that the pilot sat too high in the cockpit to effectively use these lower panels for takeoff or landing. Flight testing of the V-173 went on through 1942 and 1943 with 190 flights, resulting in reports of UFOs from surprised Connecticut locals. Charles Lindbergh piloted the V-173 during this time and found it surprisingly easy to handle and exhibiting impressive low-speed capabilities. Both Lindbergh and Guyton found that they were almost unable to stall the aircraft. Guyton was able to keep the aircraft in flight no matter how hard he pulled the stick in low-speed flight ranges at any altitude under 20,000 ft. On one occasion, the V-173 was forced to make an emergency landing on a beach. As the pilot made his final approach, he noticed two bathers directly in his path. The pilot locked the aircraft's brakes on landing, causing the aircraft to flip over onto its back. Remarkably, the airframe proved so strong that neither the plane nor the pilot sustained any significant damage. Despite their inability to stall the aircraft they did find low speed handling to be a persistent issue largely due to the shape of the lifting body. They found that the aircraft acted as an airbrake when it was pulled into a high angle of attack. This meant that the control surfaces, the horizontal stabilizers, in particular, would become very hard to operate at low speeds such as stalls, takeoff, and landing.
The developmental V-173 made its last flight 31 March 1947. In 131.8 hours of flying over 190 flights, Zimmerman's theory of a near-vertical takeoff- and landing-capable fighter had been proven. This project would be improved upon including the addition of potential armament with the Chance Vought XF5U. This project would improve on many of the weaknesses discovered during the testing of the V-173 prototype.
Both the V-173 and the XF5U featured an unorthodox "all-wing" design consisting of a flat, somewhat disk-shaped body (like a pancake flying, hence the nickname) serving as the lifting surface. Two piston engines buried in the body drove propellers located on the leading edge, at the wingtips.
Photo-Description:
Aircraft: Vought V173
Reg: 02978 photos
Serial #:
Airline: United States - US Navy (USN)
Photo Date: Mar 28, 2013
Uploaded: May 05, 2013
Dallas Love Field - KDAL, USA - Texas
Notes:
A/C on loan from the Smithsonian. After an 8 year restoration, it is currently displayed at the Frontiers of Flight Museum, Love Field, Dallas, Texas.
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