There has been increasing interest into the performance of electric vertical takeoff and landing (eVTOL) aircraft. The propellers used for the eVTOL propulsion systems experience a broad range of aerodynamic conditions, not typically experienced by propellers in forward flight, that includes large incidence angles relative to the oncoming airflow. Formal experiment design and analysis techniques featuring response surface methods were applied to a subscale, tilt-rotor wind tunnel test for three, four, five, and six blade, 16-inch diameter, propeller configurations in support of development of the NASA LA-8 aircraft. Investigation of low-speed performance included a maximum speed of 12 m/s and a maximum RPM of 6800 tested over a range of incidence angles from 0° to 100°. High-speed testing achieved a maximum speed of 30 m/s and maximum RPM of 6000 while incidence angle was varied from 0° to 20°. Results were compared for each propeller configuration using nondimensional aerodynamic coefficients, including performance of off-axis forces and moments. The outcome of this research describes important behavior of propellers operating in conditions experienced by eVTOL vehicles as well as provides a general testing approach to performance characterization that includes empirical model building with uncertainty estimates
