Effect of thrust vectoring on aircraft post - Stall trims, stability, and maneuvers

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 flight envelope. In recent times, the urge to expand the flight 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, effectiveness 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 effect 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 effectiveness of closed-loop in stabilizing otherwise unstable open-loop turn trims. Instantaneous turn maneuver has been remodeled to incorporate realistic effects of throttle saturation and negative specific excess power on maximum achievable turn rate. Improvement in the instantaneous turn rate with thrust vectoring is qualified and quantified. Finally, using thrust vectoring, controlled departure and subsequent recovery to level flight is simulated for flight instabilities as pitch bucking and oscillatory spin.