Effect of Thrust Vectoring on Aircraft Post - Stall Trims, Stability, and Maneuvers

Abstract

High performance airplanes require maneuvering at high rates and under conditions of high incidence where the dynamics can be extremely nonlinear and is often accompanied by control input saturation, thereby limiting the igh t envelope. In recent times, the urge to expand the igh t envelope, beyond that achievable using aerodynamic control surfaces, has been addressed using thrust vectoring due to its superior characteristics at high angles of attack. In this paper, eectiv eness of thrust vectoring as a control input has been discussed in detail. Improvement in the post-stall angle of attack capture using thrust vectoring on saturation of aerodynamic controls has been demonstrated by extended bifurcation analysis. Furthermore, the eect of control input saturation on stability of closed-loop airplane dynamics has been illustrated. Key maneuvers, such as turns, have been analyzed in detail to demonstrate eectiv eness of closed-loop in stabilizing otherwise unstable openloop turn trims. Instantaneous turn maneuver has been remodeled to incorporate realistic eects of throttle saturation and negative specic excess power on maximum achievable turn rate. Improvement in the instantaneous turn rate with thrust vectoring is qualied and quantied. Finally, using thrust vectoring, controlled departure and subsequent recovery to level igh t is simulated for igh t instabilities as pitch bucking and oscillatory spin.