Flight performance of multi-rotor configuration tail rotors

Abstract

To better understand and predict the flight performance of multi-rotor configurations of tail rotors controlled via collective pitch or rotor speed, a flight performance tool is derived. The tool includes a tail rotor model, an aerodynamic interference model, and a trim method. The vertical configuration of a multi-rotor tail rotor can effectively take advantage of aerodynamic interference to reduce the required power. The five-rotor configuration with fixed rotor speed reduces the power by 36.7%. More rotors are preferable from the point of view of power consumption. Too many rotors are unnecessary, since the extra benefit obtained is very diminished. Varying the rotor speed is better for performance improvement compared with varying the collective pitch, since lower rotor speed leads to rotor power reduction. The five-rotor configuration with fixed collective pitch reduces the power by 53.3%. The severe aerodynamic interference between the rotors leads to the longitudinal configuration of multi-rotor configuration having much poorer performance. The four-rotor configuration in a “plus” arrangement achieves better performance than the cross four-rotor configuration or a vertical four-rotor configuration.