Bifurcation Analysis and Simulation of Stall and Spin Recovery for Large Transport Aircraft

Abstract

The nonlinear dynamics of a large transport aircraft are analyzed to determine how the natural stability of the aircraft could be used for stall and spin recovery. The analysis is performed using the wide-envelope nonlinear simulation model for the Generic Transport Model (GTM). A bifurcation analysis is performed with respect to elevator to find the desirable stable equilibria of the aircraft inside the aerodynamic envelope, and to check for undesirable stable equilibria outside the envelope. For control surface deflections near zero, only one stable equilibrium branch is found, corresponding to the aircraft gliding with the steady-state angle of attack and sideslip angle well within the envelope. For excessive elevator deflections, two stable branches are found corresponding to stall and spin conditions. Simulations are performed to confirm the results of the bifurcation analysis and to analyze the transient behavior during the stall and spin departure and recovery. The results confirm that the aircraft enters stall and spin when excessive elevator is commanded, and recovers from stall and spin when the elevator is returned to zero deflection. The stall and spin recovery of a large transport aircraft can therefore be performed by setting the throttle to idle, returning the control surfaces to their neutral values, and relying on the aircraft’s natural stability. The natural rate damping of the aircraft is sufficient to quickly recover the aircraft from spin, and the natural tendency of the aircraft to point its nose into the airstream is sufficient to recover the aircraft from stall.