An airfoil designed for a high-altitude, long endurance remotely piloted vehicle

Currently, there is interest in the development of high-altitude, long-endurance remotely piloted vehicles for a number of proposed missions including communications relaying, weather monitoring, and providing targeting information for cruise missiles. The preliminary design and sizing of such aircraft is complicated, however, by the fact that data regarding suitable airfoils are limited. This is due to the fact that such vehicles, unlike those for which the majority of airfoils have been developed in the past, operate at fairly high lift coefficients and at relatively low Reynolds numbers. Thus, to provide realistic airfoil performance information for preliminary design efforts, a generic airfoil has been designed which is suited for use on aircraft with missions similar to those noted. The airfoil is unflapped and has a thickness of 15-percent chord. The design Reynolds-number range is 7x10⁵ to 2x10⁶. Low drag is predicted for lift coefficients ranging from 0.4, the lift coefficient providing high-speed dash capability, up to 1.5, the maximum endurance design condition. Further, the airfoil is designed specifically such that the maximum lift coefficient, approximately 1.8, is unaffected by surface contamination. Consequently, take-off and landing in rain, or with insect residue on the wings, should present no special difficulties.