Flight Performance and Acoustics of Asymmetric Propellers with Uneven Blade Spacing

Anexperimental campaign is conducted to characterise the acoustics and flight performance of asymmetric propellers with uneven blade spacing by taking field measurements of an unmanned aerial system in hover. Further, the study compares the acoustics and flight performance of asymmetric propellers with uneven blades with conventional propellers. The vehicle was equipped with bespoke on-board instrumentation to measure and record a range of flight parameters, including motor RPM. Wind conditions were measured and reported using an ultrasonic anemometer at the test site. Acoustic data was recorded with a ground mounted, free-field, microphone inverted over a steel plate. A test matrix was established with a range of emission angles and radii relative to the microphone. Asymmetric propellers exhibit a lower frequency dominant tone compared to conventional propellers. A-weighted overall sound pressure level was reduced for asymmetric propellers at a majority of test points. However, the aerial system experienced greater vibrations and increased electrical power draw when asymmetric propellers were installed.