From: Reuters
Published February 28, 2008 02:01 PM

Bats use same flying trick as insects: study

By Michael Kahn

LONDON (Reuters) - Bats stay aloft by employing an aerodynamic trick previously thought unique to insects, researchers said on Thursday.

Using a wind tunnel to study the wake bats leave as they fly, they found that a tiny cyclone of air over each wing called a leading edge vortex provided as much as 40 percent of the lift required to keep the animals in the air.

"It wasn't known that vertebrates can do it too," Anders Hedenstrom, a biologist at the University of Lund in Sweden who led the study, said in a telephone interview. "Now we have found bats have used a similar mechanism."

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The shape of the wings of planes and birds produce lift by utilizing a more steady stream of air, Hedenstrom said. Bats take advantage of additional lift created in the downstroke of the wing that allows them to hover and fly more nimbly.

The researchers filled the wind tunnel with an aerosol fog to help capture images of the bats as they flew towards a tube of honey water, then analyzed the images on a computer.

When the bats hovered they created a vortex above each wing.

"This is the mechanism behind this high lift force during hovering flight," Hedenstrom said.

The findings, published in the journal Science, have practical implications. Engineers, for example, can use this knowledge when developing micro-air vehicles, Hedenstrom added.

Such robotic machines -- with potential uses for surveillance -- might be able to fly in and out of buildings and confined areas because their flapping wings would permit hairpin turns and hovering, he added.

"To really make them work this is an important piece of information, because it shows how we control the wing's structure during a wing stroke," Hedenstrom said. "With fixed wings they can't turn on a dime."

(Reporting by Michael Kahn; editing by Maggie Fox and Andrew Roche)

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