Research on the Longitudinal Stability of Fighter Aircraft using Computational Fluid Dynamics Based Method

Stability is the most important factor of a certain aircraft model, especially fighter ones due to its strong effect on the ability to control and maneuver. Therefore, stability research is crucial in developing and validating flight simulator. In the scope of this work, the longitudinal stability of Flanker-C-Like model was numerically assessed based on MIL-F8785C standard to confirm that its longitudinal behaviors are similar between the numerical model and real aircraft. Specifically, Computational Fluid Dynamics (CFD) method was utilized to generate the aero-lookup table in the aerodynamic model. This is the reason why, the flight dynamics model was developed to describe the six Degrees of Freedom (DOF) motion based on the forces and moments generating on the aircraft. The aero-lookup table contains static and dynamic coefficients calculated by Ansys Fluent and Athena Vortex Lattice respectively. The flight dynamics model continuously calculated the states of aircraft by solving a system of differential equations which represents the effect of gravity, engine and aerodynamic forces. The longitudinal stability was analyzed by introducing a disturbance of control signal into “trim” flight condition and then, observing the response of aircraft in the angle of attack, velocity, and altitude. The result showed that the present model was successfully described as the high maneuverability airplane which is in good agreement with Flanker-C-Like's classification. The result also proved practical application of the CFD-based method in building the aerodynamic and flight dynamics model to access the longitudinal stability of flight objects.