Influence of flight control law on spin dynamics of aerodynamically asymmetric aircraft
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Avionics Department, Institute of Avionics and Aeronautics, Air University, Islamabad
Department of Avionics Engineering, CAE, NUST, Rislapur
Mechanical Engineering Department, Institute of Avionics and Aeronautics, Air University, Islamabad
Publication date: 2017-07-15
Journal of Theoretical and Applied Mechanics 2017;55(3):963–975
In this paper, we analyze the spin dynamics of an aerodynamically asymmetric aircraft in open-loop configuration and also evaluate the performance of gain scheduled flight control law in improving dynamic characteristics of aircraft spin. A look-up tables based aerodynamic model is developed from static, coning and oscillatory coning rotary balance wind tunnel test data. As a starting point, all possible steady spin modes are identified by solving the aircraft dynamic model comprising moment equations. The influence of high-alpha yawing moment asymmetry on predicted right and left spin modes is discussed. Six degree of freedom simulations of left and right flat spins are performed in open-loop and closed-loop configurations with the flight control law. Our studies reveal that large amplitude oscillations in the angle of attack and sideslip observed in the open-loop configuration are significantly damped by the control law. The control law reduces the recovery time of the left flat spin. However, the aircraft natural tendency to rotate rightwards due to yawing moment asymmetry at high angles of attack renders flight control law ineffective in aiding the recovery of the right flat spin.