Recent videos from Joby Aviation have sought to illustrate just how quiet its eVTOL air taxi prototype is compared to conventional airplanes and helicopters. Now, the company is teaming up with NASA to quantify the difference in a rigorous way.
During a two-week test campaign that launched this week, NASA engineers will use their Mobile Acoustics Facility and more than 50 pressure ground-plate microphones to obtain multi-directional measurements of sound emissions from Joby’s fully electric aircraft. The data will be used to evaluate how the intensity and character of its sound compare to existing aircraft, as well as how the eVTOL will blend into the background noise of urban communities.
NASA and Joby researchers expect to share the results of their analysis later this year. The exercise is part of NASA’s Advanced Air Mobility (AAM) National Campaign, which is currently in a developmental testing phase prior to its full launch in 2022. Joby is the first company to fly an eVTOL aircraft as part of the effort.
“NASA is proud to continue our relationship with Joby by gathering highly valuable aircraft safety and noise data that will contribute towards an aviation future that includes [AAM] operations,” stated Davis Hackenberg, NASA AAM mission integration manager, in a press release. “Data from industry leaders like Joby is critical for NASA’s research activities and future standardization of emerging aircraft configurations.”
Joby has collaborated with NASA on a number of electric propulsion projects over the past decade, including a long-endurance eVTOL demonstrator called Lotus, the Leading Edge Asynchronous Propeller Technology (LEAPTech) project, and the design of the X-57 Maxwell experimental airplane. According to Joby founder and CEO JoeBen Bevirt, “NASA has been a critical catalyst in the transition to electric aviation, and we’re proud to have partnered with them on multiple groundbreaking projects since our first collaboration in 2012.”
Joby’s eVTOL design uses six tilting propellers for vertical take-offs and landings and wing-borne cruise flight. The company said the number of blades, blade radius, tip speeds, and disc loading were all selected to minimize the aircraft’s acoustic footprint while also improving the character of its sound.
Additionally, the propellers can individually adjust their tilt, rotational speed, and blade pitch, helping to avoid the blade vortex interactions that contribute to the distinctive noise signature of conventional helicopters. The result, Bevirt claims, is “an aircraft that not only has an extremely low noise profile, but blends seamlessly into the natural environment” — features that will be critical for public acceptance of urban air mobility vehicles.