Abstract: A rotor is mounted to an aircraft wing to recover induced drag associated with a wingtip vortex. When the rotor is placed in the vortex stream, the transverse component of relative wind encountered at selected increasing spanwise locations along the blade changes sign due to an increasing transverse component of blade velocity and decreasing transverse component of vortex velocity with increasing distance from the axis of rotation. In order to maximize induced drag recovery, the blade is twisted in a spanwise direction so that the inner portion of the blade drives the blade, while the radially outward portion acts as a propeller to resist rotation. The induced drag recovery is in the form of thrust generated by the rotor blade.

Abstract: Disclosed are telescopic gunsights for aiding shooters to achieve proper "hold-over" when shooting at targets of estimatable heights at long ranges. The reticles in the preferred telescopic gunsights comprise two or more superjacent target-spanning and aiming apertures of differing heights. By comparing the height of a target image viewed through the sight to the height of one or more of the apertures, the shooter can determine the aiming sight picture which produces the hold-over necessary to strike the target. Using the preferred variable power scopes of this invention the shooter can rapidly make adjustments so that the scope will be "calibrated" for any one of a plurality of target heights and/or trajectories, and for trajectory variations caused by altitude and ambient temperature variations and for angles of fire differing substantially from horizontal.