Around 1902, Viscount Decazes and G. Besancon had conducted tests of a 6m diameter vertically mounted propeller in Paris for a planned concept that would have used two of these vertical thrusting propellers, in addition to fixed wings and a propeller for forward thrust. The "rotor" tested produced 67kg of lift at 60 rpm, requiring 10hp. Without a flight weight engine, however, Decazes would have to weight ten more years to build his idea. In 1912, Decazes built his prototype "Helicoplane" at the Loire et Olivier Aircraft plant, and it was tested the following year by Commandant Dorand at Villacoublay. It used two 50hp Gnome rotary engines, one for the co-axial four-bladed rotors and one for the propeller. Two wings in tandem had approximately 25m² surface area each. Although it was not intended to hover without a head wind, it was planned to have minimum speed of 18km/h. A transmission failure, however, ended the tests prematurely, prior to flight.

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