Vought V-173

https://en.wikipedia.org/wiki/Vought_V-173

and also its more developed version https://en.wikipedia.org/wiki/Vought_XF5U

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

Both the V-173 and the XF5U featured an unorthodox "all-wing" design consisting
of flat, somewhat disk-shaped bodies (hence the name) serving as the lifting
surface. Two piston engines buried in the body drove propellers located on the
leading edge at the wingtips.

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 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 cancelling 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.

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.


Role
Experimental aircraft

Manufacturer
Vought

First flight
23 November 1942

Retired
15 March 1947

Number built
1

Developed into
Vought XF5U

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. 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. 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.

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.

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 ft2 (44.2 m2)
Loaded 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)
Rate of climb: to 5,000 ft in 7 min (1,100 m in 5 min)




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