Etienne Oemichen, a young engineer with the Peugeot motor car company, began to experiment with rotating-wing designs in 1920, and in all designed and built six different vertical take-off machines. When the first of these failed to develop enough lift from its twin rotors and 25hp engine to rise off the ground, he added a hydrogen-filled balloon on top of it to give it added stability and lift. The most noteworthy - and most striking - of his aircraft was the helicopter No.2, which had no less than 4 rotors and 8 propellers, all driven by a single 120hp Le Rhone rotary engine when it flew for the first time on 11 November 1922. A 180hp Gnome engine was substituted later. The Oemichen No.2 was basically a steel-tube framework of cruciform layout, with 2-blade paddle-shaped rotors at the extremities of the four arms. The angle of these blades could be varied by warping. Five of the propellers, turning in a horizontal plane, served to stabilise the machine laterally; another propeller mounted at the nose was for steering the helicopter; and the remaining pair acted as pusher propellers for forward propulsion. The opposing pairs of rotors were of slightly different diameters. The Oemichen No.2 exhibited, for its time, a considerable degree of stability and controllability, and in all made more than a thousand test flights during the middle 1920s. By 1923 it was able to remain airborne for several minutes at a time, and on 14 April 1924 it established the first-ever FAI distance record for helicopters of 360m. Three days later it increased this to 525m and on 4 May was airborne for 14 min, flying more than a mile and completing in the process the first 1km closed-circuit flight by a helicopter in 7 min. 40 sec. Oemichen was, however, dissatisfied with the modest heights to which No.2 was able to fly, and from the third machine onward he adopted a single main rotor layout, accompanied by two smaller anti-torque rotors. His last design, in 1938, reverted to the balloon-assisted principle of his first aircraft.
K.Munson "Helicopters And Other Rotorcraft Since 1907", 1968
In France, Etienne Oemichen, a young engineer at Peugeot, began rotary wing experiments in 1920, building a total of six different machines. His second machine flew unassisted on 11 November 1922. The Oemichen No. 2 had an "X"- shaped, tubular frame with a wide two-bladed rotor at the end of each arm. For control and lateral movement, eight small propellers were used: five horizontal propellers with variable and reversible pitch for lateral stability, another propeller at the nose for steering, and another pair of pushers for forward motion. By 1923, the Oemichen No. 2 was able to remain airborne for several minutes and on 14 April 1924, it established the first rotary wing distance record: 360m. On 4 May, it completed the first 1km closed circuit flight by a rotary wing vehicle in 7 minutes 40 seconds to win a 90,000 franc prize. Maximum endurance was 14 minutes. Despite the fact that it was able to demonstrate sufficient controllability and power in ground effect for this historic flight, it was not a practical flying machine. In recognition of the impracticality of the machine, Oemichen began pursuing a series of aircraft with a single-main rotor and two anti-torque rotors, but had little success.
Technical data for Oemichen No.2
Engine: 1 x Gnome Rhone rated at 135kW, rotor diameter: 2 x 7.60m + 2 x 6.40m, empty weight: 800kg