Stability derivatives for a delta-wing X-31 aircraft validated using wind tunnel test data

Abstract

The calculation and validation of the aerodynamic coefficients and stability deriva- tives for the X-31 model aircraft are the focus of this study. To improve the stability derivative calculations for a delta-wing aircraft in the subsonic regime, a compendium of new methods is programmed into a new code, FDerivatives, and added to the classical DATCOM method. The FDerivatives code is described, as are the improvements achieved in the aircraft canard configu- ration. All the required geometrical data relative to the aerodynamic coefficient estimation of the X-31 aircraft are calculated for the wing-body-tail configuration. Digital DATCOM code was used to validate the geometry and the aerodynamic coefficients, as well as the implicit method and the Jorgensen method. Experimental results are provided for the X-31 model in the low-speed wind tunnel of the German-Dutch Wind Tunnels (DNW-NWB). The FDerivatives code gives very good results in comparison with experimental results. An analysis of longitudinal motion, based on FDerivatives results, is presented at the end.