Ellehammer's first studies of rotary-winged flight began in 1910, and various experiments were carried out in 1911 with a scale model helicopter. The full-sized machine that he built in the following year was a compound helicopter, as its 6hp engine (also designed by Ellehammer) drove both the rotor system and a conventional propeller. The lifting rotors were two contra-rotating rings, each of 5.97m diameter, the lower one being covered with fabric to increase the lift. At regular intervals round the perimeter of the wings were six vanes, each about 1.50m long and 0.66m wide and pivoting about its horizontal axis. The rotor system was driven via a hydraulic clutch and gearbox, all designed by Ellehammer, and the rotor vanes' angle could be altered in flight by the pilot as an early example of cyclic pitch control. After several successful indoor take-off tests, during which the machine was probably tethered, Ellehammer's machine made a free vertical take-off later in 1912, in front of witnesses who included H.R.H. Prince Axel. Tests with the 1912 helicopter continued until late in September 1916, when it overturned after a take-off and the machine was wrecked when the rotors spun into the ground.
Engine; 1 x Ellehammer air-cooled radial, 25kW
Rotor diameter: 7.47m