Shroud geometry for unmanned aerial vehicles

An unmanned aerial vehicle, comprising:

• a toroidal fuselage having a coaxial fuselage axis, said toroidal fuselage defining an inner duct flow channel;
• and
• rotor assembly means for providing collective and cyclic pitch to control flight operations of said unmanned aerial vehicle, said rotor assembly means including a pair of multi-bladed, counter-rotating rotors coaxially mounted in said inner duct flow channel to provide high hover efficiency, said multi-bladed, counter-rotating rotors having an axis of rotation coaxial with said fuselage axis;
• said toroidal fuselage having an outer aerodynamic surface optimized to retain said high hover efficiency provided by said pair of multi-bladed, counter-rotating rotors coaxially mounted in said inner duct flow channel, to produce a pressure distribution that provides high lift forces in translational flight, to counteract the undesirable nose-up pitching moment produced by lift generated by said rotor assembly means by reducing lift required from said rotor assembly means in translational flight, and to reduce the need for superimposed cyclic pitch for trimmed translational flight;
• said outer aerodynamic surface including a leading edge and a trailing edge defined by the lower edge of said inner duct flow channel wherein said trailing edge lies in a plane above the plane of said leading edge.