The model produced by these two French workers had a "gunpowder engine", which may be regarded as the forerunner of modern rocket propulsion.

P.Lambermont "Helicopters and Autogyros of the World", 1958

Model by two Frenchmen, Pomes and de la Pauze, which anticipated rocket propulsion.

G.Apostolo "The Illustrated Encyclopedia of Helicopters", 1984