In 1907 military engineer K.A.Antonov applied for, and in 1912 obtained a patent for his Helicoplane. The helicoplane was built and tested in St.Petersburg during 1910.
It was a coaxial helicopter with an additional propeller for horizontal movement. All rotors were driven by single 35hp engine. Aircraft had a collective pitch control of main rotors. It was supposed that 0° pitch will be used for parachuting or gliding.
Despite all systems working as expected, the Helicoplane failed to takeoff.