The Focke Helicopter
This is a 1938 NASA technical report, a translated memorandum on the Focke helicopter, a rotorcraft design, with photographs, diagrams and performance charts for engineers and aviation researchers. Its pictures show propeller hubs and bevel gear drives, a stepped row of rotor-motion sketches, a power-versus-speed chart comparing autogiro and airplane, and the D-EKRA test aircraft in flight and on the ground, giving designers a plain technical record of early rotary-wing machines.
