Overview of Wind Tunnel Testing of the Joby Aviation eVTOL Isolated Propeller System

Abstract:
In 2023, Joby Aviation conducted a test of a prototype propeller for an electric vertical takeoff and landing (eVTOL) tilt-propeller aircraft in the 40- by 80-Foot Wind Tunnel at the National Full-Scale Aerodynamics Complex (NFAC). The propeller differed from rotors found on typical helicopters and tiltrotors in having rigid blades and no cyclic pitch variation, and from airplane propellers in operating in an edgewise flow environment. This wind tunnel test was intended to study the behavior of the propeller in the transition regime experienced during conversion from thrust-borne, through semi-thrust-borne, to wing-borne flight and back. There were three objectives of the test: measuring 1) propeller performance, 2) dynamic blade loads, particularly in resonance, and 3) aeroacoustics. The propeller was instrumented with rotating-frame blade load sensors and mounted to a fixed-frame balance. Testing was performed at a range of wind speed, propeller angle of attack, propeller speed, and collective blade pitch points. Sample results are provided in the paper, including a look at the high propeller pitch and roll moments in edgewise flight, a demonstration of blade resonance due to variable RPM operation, and a comparison of overall sound pressure levels showing expected increases in noise with high propeller angles of attack and high tip speeds. This paper is part of a trio, with companion papers cited in the text presenting detailed analysis of measurements and comparisons to analytical predictions of performance, loads, and aeroacoustics.

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