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.

Investigation of Poststall Pitch Oscillations of an Aircraft Wind-Tunnel Model

“…With this model, it was proven that, given a sufficiently negative lift curve slope, a limit cycle will occur. More recently, limit cycles and evidence of chaotic behavior were shown through numerical experimentation with an F-18 aircraft model [18]. In this model, standard flight dynamics equations were used together with tabulated aircraft data, and no attempt was made to develop a more detailed stall model.…”

“…This figure was obtained by multiplying the friction moment [Eq. (18)] by a coefficient, known in mathematical texts as a homotopy parameter k f , so that friction is off when k f 0 and fully on when k f 1. The figure illustrates how the single stable limit cycle, which occurs when k f 0, splits into the small-amplitude limit cycle and the larger one.…”

Aeronautics and astronautics: Recent progress and future trends

“…If this situation evolves without adequate control, it may become more and more critical, and can lead into chaos. Detecting such abnormal behaviour is crucial for aircraft safety, particularly for high-performance combat aeroplanes that frequently undergo high angle of attack manoeuvres [197]. Overcoming these problems can be achieved by the development of intelligent decision and control algorithms based on a strategy of systems integration.…”