Airbus Helicopters is tapping in-house efforts to reduce helicopter noise with both technology and new operating methods to influence its design work for its planned eVTOL aircraft. The European manufacturer feels that achieving acceptable noise levels will be critical to winning public acceptance for future urban air mobility operations.
While the company’s Fenestron tail rotor and Blue Edge main rotor blades can reduce a helicopter’s overall noise signature, Airbus is continuing to explore ways to minimize other variables that can be irritants to the human ear including impulsive, tonal, and high-frequency sounds, as well as the duration of the sound exposure. An example of impulsive sound includes the common “blade slap” generated by the intersection of the main blades’ vortex trail with subsequent blades.
Possible solutions to further lower rotorcraft noise include “improving the Fenestron, working on blade profiles, reducing rotor speed, integrating hybridization, exploring low-sound flight procedures, and inventing very specific solutions for reducing a helicopter’s perceived sound footprint in urban areas,” said Julien Caillet, a sound expert at Airbus Helicopters.
Earlier this year, Airbus Helicopters’ innovation and acoustics teams, supported by France's DGAC civil aviation authority, conducted a study to measure the sound levels of Airbus helicopters as perceived by urban residents to positively influence the design of future eVTOLs. The project’s objective was to measure how buildings can filter or amplify sound.
After some disruption from the Covid-19 crisis, Airbus has resumed flight testing of its CityAirbus technology demonstrator at its Manching facility near Munich in southern Germany. The results from this project, and also its evaluation of the smaller Vahana demonstrator last year, are expected to inform the company's plans for an eVTOL prototype aircraft. In recent months, Airbus has increasingly signalled that it view hydrogen propulsion as more promising than all-electric options.