Characterization of state variables in post-stall dynamics of high-performance aircraft

Abstract

The behaviour of the state variables in post stall flight region of high-performance aircraft is presented in this paper. To demonstrate the state variables of aircraft in post-stall dynamics, the non-linear state equations of aircraft are solved. The numerical investigation has shown that a sufficiently negative lift slope can lead to limit cycle oscillation motion. The behaviour of limit cycle is demonstrated with the action attributed to relay action caused by decrement of lift coefficient jump at stall. The time-history of state variables and the effects of decrement of lift coefficient on limit-cycle amplitudes are achieved. A numerical model constructed for a high-performance aircraft F-18 is solved to illustrate the results. The effects of significant factors such as mass, thrust on limit cycle behaviour in post stall region are considered in this analysis. The couple of effects including the mass and velocity on limit-cycle amplitude of attack angle and pitch angle are obtained in this region. The results indicate that chaos behaviour of attack angle exists in the case of a 20 per cent decrease in mass and a 5—10 per cent increase in velocity. Multi-point attractor is predicted with the change in the values of attack angle. A good agreement between the numerical results and the published work is obtained for limit cycle oscillation existence at different values of lift coefficient decrement.