Investigation of the High Angle of Attack Dynamics of the F-15B Using Bifurcation Analysis

Abstract : Previous studies predicted the F-15B high angle of attack and flat spin behavior using bifurcation analysis. These studies varied control surface deflections to find equilibrium and periodic solutions. The purpose of this research was to use bifurcation analysis to predict the F-15B high angle attack and flat spin behavior as a result of variable thrust, asymmetric thrust, and thrust vectoring. Using a previously developed model of the F-15, bifurcation analysis and continuation methods were used to map out the equilibrium and periodic solutions of the model as a function of the thrust parameters. A baseline bifurcation diagram,, as a function of alpha and elevator deflection angel, of the equilibrium solutions for the F-15 was developed. Thrust was varied and changes were identified. Thrust asymmetries were introduced and their effect on entering and recovering from spins was identified. Thrust vectoring was introduced to see how pitch and yaw vectoring can aid in the entry and recovery from spins. Where deemed necessary, time history simulations were presented to further explain F-15 behavior. Keywords: Spinning motion; Aerodynamic stability; Jet fighters; Equations of motion; Bifurcation mathematics; Angle of attack; Aerodynamic control surfaces.

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