The Gyroplanes, Helicopters and Convertiplanes of Raoul Hafner

Raoul Hafner's work played an important role in the successful development of the gyroplane and the helicopter. His pioneering work on a helicopter with Bruno Nagler in Austria during the late 1920s led to its further development in Britain during the early 1930s. Hafner's first main breakthrough was the development of the "spider" system for both collective and cyclic blade pitch control on the rotor. First tested on the AR.III gyroplane in 1935, the design gave the gyroplane a new level of performance that was to eclipse the Cierva Autogiro designs. A series of larger gyroplanes were designed but they were not to be built, and Hafner focused more on helicopters. These concepts were all unique in the use of airfoil shaped fuselages for anti-torque and directional control. The World War 2 years saw Hafner focus on the development of the innovative Rotachute and Rotabuggy concepts. Although both projects were technically successful, neither was to see operational service. In 1945, Hafner became Chief Designer for the helicopter division of Bristol Aeroplane Co., with the single rotor Bristol Type-171 Sycamore being his first production design. The Sycamore was flying as early as 1947, and became the first civil certified British helicopter. Other Bristol helicopter designs followed, with an emphasis on large tandem rotor concepts with elements of lift compounding. The Type-192 Belvedere saw successful service with the Royal Air Force. In later years, after Hafner was appointed Technical Director (Research) at Westland Helicopters, he was to focus on the design of numerous convertiplane and tiltwing concepts that could combine the merits of helicopters and airplanes. Hafner was to write many significant papers and reports on the theory and practice of the helicopter. He was also to win many honors and awards for his innovative contributions to the development of the modern helicopter