In 1879 John Greenough came out with a patented design that was a slight improvement. Calling his machine an acrobat, this Syracuse inventor fashioned his helicopter in the form of a giant bird's wing. The craft's two lifting rotors whirled around in two large circular openings cut into the wings. A boat-shaped fuselage was suspended beneath the wing.

Frank Ross Jr. "Flying Windmills", 1953

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