Flight Performance with Respect to Rotor Rotation Directions of Multirotor Aircraft

Abstract

A multirotor electric vertical takeoff and landing (EVTOL) aircraft is specialized for intracity point-to-point urban air mobility services due to its advantages of efficient hover performance, high gust resistance, and relatively low noise. Because of its multiple rotors, rotor–rotor interference inevitably affects flight performance, mainly depending on inter-rotor distance and rotor rotation directions. It is assumed that there exists an optimal rotation direction for a given lot of multiple rotors. In this study, the aim is to investigate rotor–rotor interference for various rotation directions and the resulting flight performance. We propose a concept of rotor rotation direction that achieves the desirable flight performance in forward flight. The concept is called front-retreating/rear-advancing (FRRA), in which the retreating side of the front rotor and the advancing side of the rear rotor are aligned in a straight line. To this end, a multidisciplinary flight simulation framework was developed to predict the flight performance of a general multirotor EVTOL aircraft. It was found that the FRRA concept minimizes thrust loss due to rotor–rotor interference in high-speed forward flight. For a generic mission profile, the rotation direction set by the FRRA concept reduces the battery energy consumption by 7% in comparison to the rotation direction of unfavorable rotor–rotor interference in operation.