Fault tolerant control of a small helicopter with Tail Rotor Failures in hovering mode

Tail rotor failure is one of the major failures occurring frequently and causing accidents. In this paper we investigate Tail Rotor Control Failure(TRCF) based on helicopter dynamic models. There is no notable work reported in the literature on control of a small helicopter with TRCF. In contrast to hover mode, forward flight improves yaw damping naturally. So it is a challenging task to retain the control during TRCF in hovering mode. Multi-loop PID controller is designed as per ADS-33PRF requirements to control the helicopter when the tail rotor control failure occurs in hovering flight. Robustness in terms of stabilizing ability of developed controllers is also analyzed. All developed control schemes are tested in Matlab/Simulink environment including linear as well as non-linear simulations.