Pilot Workload Investigation for Rotorcraft Operation in Low-Altitude Atmospheric Turbulence

This paper aims to investigate pilot workload for rotorcraft operations in low-altitude atmospheric turbulence. A novel low-altitude turbulence model derived through the prewarped Tustin transformation is used to modify the classic distributed turbulence model. The distributed model is then validated against the von Kármán spectra and is integrated into a flight simulation environment that consists of a high-fidelity nonlinear flight dynamics model and a multi-loop compensatory pilot model. The simulation responses and pilot controls in turbulence have been compared against flight test data for operations in bluff-body and freestream turbulence conditions. The effect of terrain roughness on pilot workload is analyzed. The results show that low-altitude turbulence becomes more intense and has smaller length scales over rougher terrain for the same conditions of the reference wind speed and altitude. Moreover, the effect of terrain roughness can increase pilot workload with increasing airspeed and decreasing flight altitude