When it comes to drone use in communities like widespread drone delivery, one of the primary concerns is noise. At a panel held at AUVSI’s Xponential today, drone manufacturer Eurolink talked about the importance of mitigating UAS noise – and how it’s done.
Pietro Lapiana is founder of Italian drone company Eurolink, manufacturers of the Beluga drone. In Europe, he explains, EASA is not formally addressing noise concerns of small UAS, but is thinking in terms of urban air mobility. “Drones are a new noise,” he says. “Human beings react differently to new noises, and you have to consider the spectrum – becuase it is not only the level of the sound, but the composition of the sound that matters.” Comparing noise from known sources like helicopters to noise created from drones, for example, Pietro points out that public perception is different – because humans identify new noises as “extremely annoying.” For a dual use aircraft like the Beluga, however, stealth can be critically important for mission success: far beyond concerns about public perception.
Eurolink developed their Beluga drones to mimic the shape of a whale, which moves gracefully through the water despite its weight. “Human subtlety will never devise an invention more beautiful, more simple, or more direct than does nature becasue in her inventions nothing is lacking, and nothing is superfluous,” said Leonardo DaVinci, and Lapiana and the Eurolink engineers took a “biomimic” approach for both profile optimization and noise reduction in its Beluga fleet.
“Instead of reinventing the wheel, we set out to see how mother nature has solved the problem,” says Lapiana. In nature, large birds of prey like owls fly silently through the air in order to approach unnoticed: and Eurolink’s scientists took owls as a model for developing a unique propeller design that reduces the sound of drone flight.
“An owl’s wings have 3 basic characteristics to support an owl to catch prey,” Lapiana explains. “They have a soft coating on the belly of the wing, a comb of stiff feathers at the leading edge, and they have a fringe of flexible filaments at the trailing edge of the wing feathers.”
Those observations led to the development of a toothed propeller blade that mimics the features of an owl’s wings – and has a major effect on UAS noise considerations. Testing shows that the Beluga drone, utilizing the toothed propeller, is significantly quieter than a standard commercial off the shelf drone like the DJI Matrice 300 – even though the Matrice is heavier. In fact, says Lapiana, testing shows that the Beluga is 9x quieter than the DJI Matrice 300.
The propeller design does have a slight cost in thrust, from 5 – 10%: but there are other performance benefits that outweigh the cost.
While the Beluga has already achieved significant gains in noise reduction, the company is still working to develop quiet flight. “I think that after aeronautics, the next step will be active noise cancellation – we’re working on that now,” says Lapiana.
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Article source: Dronelife.com