Industry Looking at Reductions in Rotor Tip Speed for Quieter Urban Mobility

By Frank Wolfe | October 11, 2018
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Uber's future air taxi design. Image courtesy of Uber

While demonstrating safety will be key for urban mobility providers, industry is also examining ways to reduce rotor noise to make the concept of urban mobility more palatable to the general public.

"We are looking at a number of things, like getting tip speed down, which is the biggest driver of noise," Zach Lovering, project executive of Airbus Group's Vahana, said at an Aero Club luncheon Oct. 10 in Washington, D.C.


Airbus will capitalize on its experience in noise reduction technologies, Lovering said, adding that changing RPMs selectively on each electric motor and selecting routes for minimal noise impact are also under consideration.

In January, Vahana held brief test flights of its self-piloted electric-vertical-takeoff-and-landing (EVTOL) aircraft at the Pendleton UAS Range in Pendleton, Oregon.

Vahana aims to develop the aircraft for individual autonomous passenger and cargo transport and hopes to launch a product demonstrator in 2020.

Michael Thacker, EVP of technology and innovation at Bell, agreed with Lovering that reducing noise is a major issue for future urban mobility providers.

"If you look at major cities' vertiports, many have been shut down because of noise," he said. "If you can get the public acceptance and tackle the noise issue so you're a good neighbor, we may be able to open some of those up and increase capacity relatively quickly before we start building new infrastructure."

Within the last decade, computational speed has progressed to permit distributed propulsion with a higher number of rotors — an increase that will allow electric motors to control the EVTOL vehicles and retain lift simultaneously under lower rotor tip speeds, Thacker said.

Bell is teaming with Garmin International to develop and integrate autonomous vehicle management computer systems on Bell VTOL aircraft.

While Bell personnel will focus on developing and producing VTOL systems, Garmin is to lead the avionics effort needed for on-demand mobility vehicle management, including primary flight information, navigation/communication, flight guidance and flight management systems. Safran will provide the hybrid-propulsion system for Bell’s VTOL aircraft.

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