Vought V-173

V-173
Role	Experimental aircraft
Manufacturer	Vought
First flight	23 November 1942
Retired	15 March 1947
Number built	1
Developed into	Vought XF5U

The Vought V-173 "Flying Pancake" was an American experimental test aircraft built as part of the Vought XF5U program during World War II.

Both the V-173 and the XF5U featured an unorthodox "all-wing" design consisting of a flat, somewhat disk-shaped body (like a

propellers located on the leading edge, at the wingtips.^[2]

Design and development

In the 1930s, Charles H. Zimmerman was a noted aeronautical engineer who advocated the concept of "discoidal" aircraft, the so-called "Zimmer Skimmer"^[3] 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

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.^[4]

The disc wing design featured a low aspect ratio that overcame the built-in disadvantages of

induced drag created at the wingtips with the large propellers actively canceling the drag-causing tip vortices. The propellers were arranged to rotate in the opposite direction to the tip vortices, allowing the aircraft to fly with a much smaller wing area. The small wing provided high maneuverability with greater structural strength. The empennage consisted of two vertical fins with rudders, all-moving stabilizers with anti-servo tabs,^[5] and two large elevator/trim surfaces on either side of centerline on the trailing edge of the wing planform.^[6]

Zimmerman chose to include the all-moving stabilizer design because he realized that the increased drag, prop wash, and large wing area would make the aircraft difficult to control at low speeds.^[7] Wind tunnel tests would prove that this was a success to an extent. The aircraft would prove to require a lot of force to control at low speeds during in-flight testing but the tail design would prove to make the aircraft controllable.^[8]

In January 1942, BuAer requested a proposal for two prototype aircraft of an experimental version of the V-173, known as the VS-135. The development version, the Vought XF5U-1, was a larger aircraft with all-metal construction, and was almost five times heavier.^[9] Although a prototype was constructed, it only performed brief hops on the runway, it never entered true controlled flight.^[6]

Operational history

The first flight of the V-173 was on 23 November 1942 with Vought Chief Test Pilot

UFOs from surprised Connecticut locals.^[11] 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.^[12] 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.^[13]

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.

XF5U

. This project would improve on many of the weaknesses discovered during the testing of the V-173 prototype.

Aircraft on display

As of April 2012, after undergoing a long restoration by Vought Aircraft Heritage Foundation volunteers, the V-173 is on loan from the Smithsonian Institution to the Frontiers of Flight Museum in Dallas, Texas.^[15]^[16]^[17]^[18]

Specifications (V-173)

General characteristics

Crew: One, pilot
Length: 26 ft 8 in (8.128 m)
Wingspan: 23 ft 4 in (7.1 m)
Height: 14 ft 9 in (4.51 m)
Wing area: 427 sq ft (44.2 m²)
Gross weight: 2,258 lb (1,024 kg)
Powerplant: 2 ×
Continental A-80
horizontally opposed, four-cylinder engines, 80 hp (60 kW) each each

Performance

Maximum speed: 138 mph (222 km/h, 120 kn)
Climb time to 5,000 ft (1,500 m): 7 min

References

Notes

^ Chant 1984, p. 53.
^ Winchester X-Planes 2005, p. 223.
^ Pearson 2002, p. 50.
^ Schoeni 1975, p. 568.
^ Naval Fighters Number Twenty One Chance Vought V-173 and Xf5U-1 Flying Pancakes. Steve Ginter. 1992. pp. 1, 9, 10, 11.
^ ^a ^b "Vought V-173 "Flying Pancake"". National Air and Space Museum, Smithsonian Institution. 1998. Retrieved 27 September 2020.
^ Naval Fighters Number Twenty One Chance Vought V-173 and Xf5U-1 Flying Pancakes. Steve Ginter. 1992. pp. 3, 4, 6.
^ Naval Fighters Number Twenty One Chance Vought V-173 and Xf5U-1 Flying Pancakes. Steve Ginter. 1992. p. 8.
^ Winchester Concept Planes 2005, p. 247.
^ Schoeni, Thomason, Clendenin, Lawson, Williams, Swisher, Larkins, Jansson, Downey, Kawalsk, Art, Tomy, Ed, Bob, Nick, William, William, Clay, Ron, bob (1992). Naval Fighters Number Twenty One Chance Vought V-173 and Xf5U-1 Flying Pancakes (1 ed.). Steve Ginter. p. 8.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ Winchester X-Planes 2005, p. 222.
^ Ginter 1992, p. 11.
^ Ginter 1992, p. 8.
^ Guyton 1991, p. 29.
^ "Chance Vought V-173 "Flying Pancake" | Frontiers of Flight Museum". Flightmuseum.com. 23 November 1942. Archived from the original on 26 November 2013. Retrieved 29 May 2013.
^ "V-173 Flying Pancake". Vought Heritage. Retrieved 27 December 2016.
^ Lee, Russell (20 March 2012). "Vought Aircraft Heritage Foundation Retirees Finish Vought V-173 "Flying Pancake" Following 8-Year Restoration Effort". Smithsonian National Air and Space Museum. Retrieved 2 March 2017.
^ Wright, Tim (November 2013). "Restoration: Vought V-173". Air and Space. Retrieved 2 March 2017.