Wind Tunnel Testing and Analysis of a Rigid, Variable Speed Rotor for eVTOL Applications

Abstract

Many electric vertical take-off and landing (eVTOL) aircraft intended for the urban air mobility (UAM) market are currently being designed with multirotor configurations using variable speed fixed-pitch, rigid rotors for lift. These types of rotors, which are similar in construction to general aviation airplane propellers, are simpler than helicopter rotors and have no moving parts in the rotating frame. This paper discusses wind-tunnel testing of a full-scale, UAM multirotor size, fixed-pitch, rigid rotor with a focus on vibratory blade loads and on the ability to predict these loads with comprehensive analysis. Test results show that vibratory loads are very high, with peak-to-peak magnitudes up to three times greater than the steady component. Correlation of test data to comprehensive analysis using geometrically exact composite beam structural elements and dynamic inflow wake modeling captures the trends in the steady and vibratory loads though it underpredicts the magnitudes; an expected result with the level of wake modeling fidelity used. The paper also discusses the physical sources of the observed vibratory loads and suggests potential options for mitigating their magnitude.