Chronological Development of Rotary Wing Aircraft

1483  –   LEONARDO da VINCI’S sketch of his non-operative helicopter, of a fixed-wing design, corkscrew-type, was designed around a vertical shaft. The bottom of this shaft was to be mounted on two bearings on a conical base. The corkscrew was meant to revolve in the same manner as a merry-go-round. It is not clear what he intended to use for power. No controls of any kind are shown. 

1908  –   KIMBALL – "The helicopter consisted of a light framework in which are 24 small wooden propellers set in a horizontal plane and run by a single motor." (The helicopter closely resembled a rocket launcher and as the three photographs, with the inventor inside, show it is standing fast on the ground with "ceiling underground.") (POPULAR MECHANICS, December 1908, volume 10, number 12, page 802, "THE KIMBALL HELICOPTER") 

1908/1910  –  
IGOR SIKORSKY, in Kiev, Russia, built a helicopter with a 25-hp Ansani engine. It was the second helicopter he built at that time. The first and second helicopter never rose from the ground. The picture of his helicopter does not show any means of control for free flight and has no provision for a pilot’s space. "Sikorsky’s first helicopter rotors, therefore, were contra-rotating and coaxial. He employed vanes, as in the Cornu design, for control. The machine was found incapable of lifting its own weight from the ground, so Sikorsky redesigned it to remove a hundred pounds of weight and to increase the length of the rotor blades. When the tests were resumed, the craft could rise into the air, but it was beset by the basic helicopter illnesses of insufficient control and stability." (HELICOPTER GUIDE, April 1951, Charles Lester Morris) 

1912  –  JENS CHRISTIAN ELLEHAMMER, the Danish
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