An application is studied of the outboard horizontal stabilizer (OHS) aircraft design concept to a high-altitude, long endurance (HALE) mission, uninhabited air vehicle (UAV). It was found that the OHS concept appears to be very well suited for the suggested mission because of the relative advantage, compared with a conventional UAV design, due to an improved lift/drag ratio over a wide range of lift coefficients implying that the benefits of improved performance, in lift/drag terms, would be available during both cruise to and from the surveillance site and during the loiter phase of the mission. A simplified, approximate, design process is presented that allows the expected lift/drag ratio of the aerodynamic surfaces to be estimated in an elementary manner. The all-important flow fields around the tail surfaces of a wind-tunnel model of the suggested OHS vehicle were explored using twodimensional PIV equipment. It was shown by this means, that the flows around the horizontal stabilizer surfaces generated by the wing-tip vortices, made it possible for the horizontal stabilizers to generate lift and, due to the upwash approaching these surfaces, this lift was obtained efficiently with offset of both the fictional and induced drags of the horizontal tails. In-flows about the vertical stabilizer surfaces generated, in a horizontal plane, lift forces acting primarily towards the vehicle vertical plane of symmetry but also inclined upwind. As a direct consequence of this a thrust component of the horizontally directed lift force also served to counteract the drag forces associated with the vertical tails.