Vought V-173 Flying Pancake

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

Only one prototype was built.

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 manoeuvrability with greater structural strength.

The empennage consisted of two vertical fins with rudders, all-moving stabilizers with anti-servo tabs, and two large elevator/trim surfaces on either side of centreline on the trailing edge of the wing planform.

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.

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.

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.

Although a prototype was constructed, it only performed brief hops on the runway, it never entered true controlled flight.

Specifications

Crew

One

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.

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