Abstract: 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.

Abstract: A flight system capable of passively stable hover comprises an apparatus defining a vertical axis, and including multiple upright ducts spaced about the axis; fluid momentum generators in the ducts to effect flow of fluid downwardly in the ducts; and fluid flow deflector structure in the path of the downwardly flowing fluid, and angled to deflect the fluid flow away from the axis, in such manner as to provide stability in hover of the apparatus.

Abstract: A flight system capable of passively stable hover and horizontal translatory flight, comprises an apparatus defining a vertical axis, and including multiple ducts with substantially vertical axes in hover mode, spaced the axis; fluid momentum generators in the ducts to effect flow of fluid downwardly in the ducts in hover; and fluid flow deflector structure in the path of the flowing duct fluid, and angled to deflect the fluid flow away from the axis, in such manner as to provide stability in hover of the apparatus, as well as stability when the entire device is tilted through approximately 90.degree. to execute horizontal translatory flight.

Abstract: A terrain surveillance, powered aircraft is disclosed to have an on-board video camera that is not gimballed relative to the aircraft, the aircraft typically comprising multiple components; the method of the invention including: assembling the components into aircraft configuration at or near a launch site; launching the aircraft at that site with no human pilot on board same; remotely controlling the flight path of the aircraft by radio or cable link, to fly to a location for terrain surveillance; operating the on-board video camera to survey the terrain while varying yaw of the aircraft to provide sweep viewing of the terrain; and recovering the aircraft by controlling its flight to steeply descend to a landing zone.