22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-3.11.2

AN AGILE AIRCRAFT NON-LINEAR DYNAMICS BY CONTINUATION METHODS AND BIFURCATION THEORY

K. Sibilski
Military University of Technology, Warsaw, Poland

Keywords: flight dynamics, flight at high angle of attack, bifurcation theory

The paper provides a brief description of the modern methods for investigation of non-linear problems in flight dynamics. A study is presented of aircraft high angles of attack dynamic. Results from dynamical systems theory are used to predict the nature of the instabilities caused by bifurcations and the response of the aircraft after a bifurcation is studied. A non-linear dynamic model is considered which enables to determine the aircraft’s motion. The aerodynamic model used includes nonlinearities, hysteresis of aerodynamic coefficients (unsteady aerodynamics), and dynamic stall effect. Aerodynamic model includes also a region of higher angles-of-attack including deep stall phenomena. In the paper continuation method is used to determine the steady states of the MiG-29 fighter aircraft as functions of the elevator deflections, and bifurcations of these steady states are encountered. Bifurcations of the steady states are used to predict the onset of wing rock, and “Cobra” manoeuvres. Dynamics of spatial motion of a supersonic combat aircraft with a straked wing is considered for post stall manoeuvres, and observations of chaotic motion in post stall manoeuvres are guided.

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