A methodology of identification of the aircraft translational dynamic stability derivatives in water tunnel experiments

Abstract

The aircraft dynamic stability derivatives (DSD) describe the variation of aerodynamics forces and moments with respect to disturbances of kinematic parameters (translational or rotational). The knowledge of DSD is important due to determination of aircraft dynamic stability characteristics. Thus, the identification of DSD is an issue of analytical or numerical analysis and experimental researches. Experimental methods use air or water tunnel tests. The investigated model is submitted to forced oscillations with relatively low amplitude, which simulates the disturbances around steady state flight parameters. The variation of forces and moments are measured by strain balance system, which allows identifying DSD. This work is focused on development the methodology of experimental identification the aircraft translational DSD in water tunnel tests. Study of available publications shows that model manipulator system usually provides rotational movements around three axes. Therefore, the measurements can be performed with respect to rotational velocity disturbances. However, by addition the translational manipulator with one degree of freedom the measurements can be expanded into translational velocity disturbances (normal and sideslip). It is necessary to point that axial velocity disturbance is omitted due to lack of axial force component in strain balance construction. The proposed modification does not affect the construction of rotational manipulator or balance. The article contains translational manipulator scheme, modification of data acquisition system and mathematical process of identification the aircraft translational dynamic stability derivatives.