Focke Rochen

The Focke Rochen (English: Focke Stingray), also known as the Focke-Wulf Schnellflugzeug or Focke-Wulf VTOL, was a German VTOL aircraft project designed by Heinrich Focke of the Focke-Wulf company toward the end of World War II. The source dossier page that is the source for this article reproduces a Wikipedia summary of the project and links five patent documents.

Status

The project "remained unbuilt before the surrender of Nazi Germany, but saw some development in the postwar years." The page states that "the information about this project is limited" and that the aircraft "was named after the ray owing to its unusual shape." It was never built.

Configuration

The aircraft is described as having "an airfoil section with two huge propellers in the center" — a Circular-Wing Annular-Duct Configuration in which the open center of a circular airfoil-section body acts as a duct for Contra-Rotating Propellers. The propellers were to be driven by "a projected Focke-Wulf designed turbojet engine via an axle and gearbox."

Claimed flight mechanisms

• Forward flight by vectoring propeller downwash rearward through a series of louvers below the propellers; the louvers could be fully closed for gliding flight after engine failure (Downwash Vectoring Louvers).
• Auxiliary combustion chambers on the trailing edges of the circular wing, fed by a forked exhaust nozzle, acting as "primitive afterburners" when fuel was added, to provide horizontal flight (Auxiliary Combustion Chambers (Rochen)).
• Low-speed control by varying power to each auxiliary chamber through two small nozzles.
• Landing gear: two main gear legs either side of the central propellers and a small tailwheel.
• Stability: a single fin and rudder for lateral stability at higher speeds.
• Cockpit: a nacelle protruding from the front of the circular airfoil-section fuselage.

Development and testing

The page states that Focke patented the circular-aircraft concept in 1939, that a wooden 1/10 scale model was built in Bremen after the war and subjected to wind tunnel tests, and that Focke filed for a patent of the aircraft in 1957. No wind-tunnel results, dimensions or performance figures are given.

Patents associated with the project

The page header says "4 patents" while listing five identifiers. See DE953938 — Kombiniertes Hubschrauber-Drachenflugzeug, US2978037 — Stabilizing Means for Helicopter Aircraft, CA587730 — Flying Machines for Vertical and Horizontal Flight, GB768190 — Improvements in Flying Machines for Vertical and Horizontal Flight, DE950169 — Hubschrauber mit Schraubenblaettern.

Limitations

All design detail in the source is stated in the conditional mood and describes an unbuilt project. The source is a secondary encyclopedia summary with no test data; the patents are the only primary artifacts.