Professor
Henrich Focke, through his development of the
Fw 186, and through the efforts of producing the
C.19 and
C.30 autogyros under licence, came to the conclusion that the limitations of
autogyros could be eliminated only by an aircraft with a powered rotor, the helicopter. He and engineer
Gerd Achgelis started the design for this helicopter in 1932. A free-flying model, built in 1934 and propelled by a small two-stroke engine, brought the promise of success. Today, the model can be seen in the
Deutsches Museum in
Munich. On 9 February 1935, Focke received an order for the building of a
prototype, which was designated the Fw 61; Focke referred to it as the F 61. Roluf Lucht of the technical office of the
RLM extended the order for a second aircraft on 19 December 1935. The
airframe was based on that of a well-tried training aircraft, the
Focke-Wulf Fw 44 Stieglitz. Using rotor technology licensed from the
Cierva Autogiro Company, a single
radial engine drove twin rotors, set on tubular steel outriggers to the left and right of the
fuselage. The
counter-rotation of the two rotors solved the problem of
torque-reaction as also shown by
Louis Bréguet. The small horizontal-axis propeller directly driven by the engine was purely to provide the necessary airflow to cool the engine during low-speed or hovering flight and provided negligible forward thrust. On 10 May 1937, it accomplished its first
autorotation landing with the engine turned off. Focke-Achgelis began work on a two-seat sports version of the Fw 61, the
Fa 224, which would have used an Argus As 10C engine and had greater performance. However, the Fa 224 never left the drawing board at the outbreak of World War II. ==Operational history==