Flight Path Optimization for Brownout Mitigation Using a High-Fidelity Simulation Model

This paper presents a simulation study of helicopter brownout mitigation through the optimization of the approach and landing trajectory. A high-fidelity flight dynamics model is coupled to a free-vortex method and a particle tracking scheme to model the brownout cloud. The objective function is related to the cloud density in selected portions of the pilot field of view. The design variables describe the approach trajectory. The optimization has a local minimum for a shallow approach with the pilot trying to outrun the dust cloud, and a global minimum for a steeper approach with the pilot delaying the time when the rotor wake touches the ground. Brownout can be substantially mitigated through appropriate landing trajectories. The main mechanisms are position and intensity of the ground vortex associated with the rotor wake. The position of the aircraft center of gravity affects the position of the tip path plane, which in turn affects the ground vortex.