Nonlinear Modeling and Flight Validation of a Small-Scale Compound Helicopter

The compound configuration is a good option for helicopters to break through speed limitation and improve maneuverability. However, the compound configuration applied on the small-scale helicopter has not been investigated in detail. In this study, an 11-state nonlinear dynamics model of a small-scale compound helicopter was established with the help of first physical principles and linear modification method. The ducted fan, free-rotate wing and horizontal stabilizer were considered in the compound configurations. To validate the accuracy of the model, high-quality flight data were obtained in hover and forward flights from 15 m/s to 32 m/s. Results show that the overall responses of the developed nonlinear model matched the hover data. In forward flight, it was proved that the nonlinear model has high accuracy in agreement with trim results and time-domain simulations. The wing model works well below 27 m/s. Furthermore, the effectiveness of the elevator and aileron in high speed was also verified in the simulation of a coordinated turn.