Instructions for Improving the Shape of Long-range Subsonic Airplanes and Gliders

Optimizing airplanes and gliders requires improving their shapes to reduce aerodynamic drag. In particular, the high weight-to-drag ratio (commercial efficiency) increases the range of the vehicles. Corresponding ideas and results are well-known. Nevertheless, high interest in unmanned vehicles requires simple instructions for engineers and managers. Analytic formulae for the drag-to-lift ratio of the optimal wing for the laminar and turbulent flow patterns are presented. The lift-to-drag ratio, angle of attack, and chord length of the optimal wings, drag on the optimal fuselage, commercial efficiency, engine power, and maximum range were estimated for subsonic airplanes and gliders with the given mass, cruise speed, wing aspect ratio, and fuselage volume. The wing aspect ratio must be as high as possible to achieve the maximum range. For certain combinations of the given parameters, the drag on the special-shaped, unseparated fuselages can be neglected in comparison to the drag on the optimal wing. The characteristics of the optimal aircraft with desirable values of range are estimated. The range of gliders can be comparable to the range of small electrical airplanes of the same commercial efficiency.