DEVELOPMENT OF A COMPUTER PROGRAM FOR PARAMETRIC SAILPLANE PERFORMANCE OPTIlMIZATION

Abstract

A computer program is presented for the analysis and synthesis of a sailplane speed polar and subsequent calculation of cross country performance in predefined meteorological conditions. Attention is focused on calculating the wing characteristics. Wlng induced drag, wing profile drag (including Reynolds number effects) and empennage drag are calculated. Either estimated miscellaneous drag data (i.e., fuselage drag, wing-fuselage interference drag, etc.) can be applied or data determined by analyzing the measured speed polar of an existing sailplane. For subsequent parametric studies, weight and/or wing parameters like span, aspect ratio, taper, twist or airfoil characteristics can be varied continuously. While the horizontal and vertical tailpline will be adjusted if necessary, the original miscellaneous drag area is taken constant at equal values of the lift coefficient. If required, computer plots of the spanwise lift distribution and local lift coefficient at maximum wing lift coefficient (to assess stalling characteristics), the sailplane drag polar (in which wing drag contributions are shown) and the speed polar are produced. Cross-country performance is calculated assuming that optimum flight techniques are employed in given meteorological conditions. Depending on these conditions the highest possible cross-sountry speed, while maintaining average height, is realized by thermalling (with maximum rate of ctimb) or straight dolphin flying. The meteorological conditions are modeled as two regions with arbitrary constant vertical velocity of the air within each region - to be interpreted as spatial average values - and a thermal with specified vertical velocity profile. If required, computer plots of cross country speeds are generated for systematic variation of meteorological conditions (fixed sailplane configuration) or weight and aspect ratio (fixed meteorological coniitions). Some capabilities of the program are illustrated, starting from the measured speed polar of the Astir CS.