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Rotary aircraft passively stable in hover

Image Number 3 for United States Patent #5297759.

A rotary aircraft includes a cylindrically tubular hub mounting a plurality of outwardly extending, resiliently flexible blades. The blades are uniformly spaced around the hub and its central axis and fixed in pitch. Outer tips on each of the blades are downwardly turned and outwardly turned sufficiently to balance the lift generated by the blades from air striking the aircraft horizontally when the aircraft is in hover to provide passive stability to the aircraft. A pair of propellered electric motors are mounted on a diametrically opposing pair of the blades, pitched transversely to the central axis of the hub and to a plane perpendicular to the central axis, to simultaneously provide both lift and rotation. A battery supplies all power used by the aircraft while radio control circuitry in the hub permits variation of the power supplied to the motors for altitude control of the aircraft.

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