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Image of the 25 hp helicopter with balloon, used as a stabiliser but later discarded from design.
"Some extremely interesting and possibly epoch making experiments in vertical flying are being conducted at Valentigny, in the French Department of Doube, by M Etienne Oehmichen, a French engineer. A small experimental machine, fitted with a motor, has proved able to carry Oehmichen a distance of 4 feet from the ground for 1 min.
The small balloon attached to the machine serves as a stabiliser, being of substantial construction, has but little lifting power, the real work being done by horizontal twin propellers.
The inventor intends to do away with the balloon during further experiments with a larger machine, fitted with a more powerful motor. The balloon will be replaced by a stabilised of small size having no lifting power whatever. M Oehmichen then hopes to make a flight of at least 1 hr
Additional- this machine is now stated to have accomplished 8 seconds of flight in one day, rising at the last trial to 13 feet", 4 Apr 1921.