The Last Autogiro: Skyway Engineering AC-35 of 1961 -1966

摘要

It is generally assumed that the French SNCASE C.302 Autogiro which flew in 1946, was the last Cierva-derived and licensed Autogiro, but there were two other unsuccessful attempts to revive this form of autorotational aircraft. These, the Kellett "Cropmaster" and Skyway Engineering attempt to revive the Pitcairn AC-35 (also known as the PA-35), were truly the last Autogiros. Of these two, the former is the best documented - until now. Kellett Aircraft made one final attempt to revitalize the Autogiro, this time involving a reconstructed direct control KD-1 A, during the 1958 -1960 time period. The airframe came from the model originally sold to the Army, called the YG-1B and then reconfigured as the XR-3. It had been sold to General Electric after the war as surplus for use in the development of helicopter rotor blades at its flight testing facility in Schenectady, New York, and subsequently passed to a private owner in Harrisburg, PA who leased it back to Kellett. The XR-3 had not been maintained and Kellett was forced to refurbish the airframe and construct new rotor blades. The decision was also made to recreate a direct control tilting rotor head from the original specifications, which allowed certification under the original ATC No. 712. The recreated KD-1 A was called the "Cropmaster". intended for agricultural uses as well as "pipeline inspection, geological and mineral exploration duties that were being performed by helicopters that cost almost twice as much and had high maintenance costs." Bob Kenworthy served as project engineer with George Townson as assistant project engineer and test pilot along with Roland "Blackie" Maier. The Russians had previously used the Kamov A-7bis during April - May 1941 for agricultural spraying in the foothills of Tyan-Shan (Tien-Shan) in Kirgizia Central Asia, with claimed success, demonstrating agricultural utility as the Soviet tests proved that the rotor disk was highly effective in crop dusting and spraying insecticides and fungicides as the chem- icals were efficiently forced downward. It was estimated in the Soviet experiments that the A-7bis could achieve an efficiency twice that of the most effective contemporary fixed-wing agricultural aircraft, and an American author in 1939 concluded that "in many respects, the autogyro is an ideal machine for dusting. An experienced 'giro pilot can hover his ship at low altitudes and literally push his chemicals into the hollows."