Bat takes flight cue from insects [BBC 2008-02-29]
[Photo] Scientists studied the Pallas's long-tongued bat.
Bats use the same aerodynamic mechanism as insects to hover in one place, scientists have found.
Writing in Science, they said that as the animal flapped its wings downwards, the motion created a tiny cyclone of air known as a "leading edge vortex".
This provided enough lift force to keep the bat airborne while hovering or flying in slow motion.
The trick has been seen before in insects, but until now has not been shown in larger, heavier creatures.
A joint Swedish and US team set up honey-water feeding stations in a wind tunnel, then used fog, lasers and high speed cameras to study how the bats flew.
By tracking the fog particles, they deduced that leading edge vortices (LEVs) provide as much as 40% of the lift force that helped the bats stay aloft.
The animal uses thumbs and fingers embedded in the skin membrane of its wings like flaps on an aeroplane to alter the curve of the wing and create the lift force required to hover.
Insects have thicker wings than bats and cannot control the movement to the same extent, the team said.
But they are able to produce LEVs because they beat their wings very quickly.
The findings could be used to improve the design of tiny aeroplanes used in surveillance.
"It's an important piece of information to know how to generate the control of the wing shape," said lead author Anders Hedenstrom of Lund University.
"This shows we still have lots of engineering design inspiration to recover from nature."