Circular-Wing Annular-Duct Configuration

The circular-wing annular-duct configuration is the defining geometry of the Focke Rochen as described in the source dossier. The source states that in 1939 Heinrich Focke "patented the idea of a circular aircraft with a large airfoil section and an open center that acted as a huge propeller duct for twin contra-rotating propellers."

Geometry

• A circular body of airfoil section forms the wing.
• The open center of the circle acts as an annular duct for the propellers.
• Two large Contra-Rotating Propellers sit in that duct.
• A cockpit nacelle protrudes from the front of the circular airfoil-section fuselage.
• A single fin and rudder are provided for lateral stability at higher speeds.

The source states that the aircraft "was named after the ray owing to its unusual shape" — the planform is what gives the project its name, Rochen / Stingray.

Function as claimed

The ducted center is the lift-producing element for vertical flight, and the same propellers feed the Downwash Vectoring Louvers used for the transition to forward flight. The source describes the arrangement in the conditional mood and gives no aerodynamic data, so the configuration is recorded here as a design proposal rather than a measured result.

Related mechanisms

• VTOL Aircraft — the operational category the configuration serves.
• Downwash Vectoring Louvers — how the ducted flow is redirected for forward flight.
• Auxiliary Combustion Chambers (Rochen) — the trailing-edge thrust augmentation described for the same aircraft.