Owls find flying in gusts a breeze
Tom Whipple Science Editor The Times 20 Oct
When an owl swoops across a field on silent wings, it does not worry about being knocked off course by a gust of wind. Yet ask a drone operator to negotiate such conditions and their craft would struggle to stay in the air.
Now, thanks to a barn owl called Lily, scientists have uncovered one of the secrets of how birds cope so well with turbulence. They have, the researchers found, “preflexes” in their wings that provide suspension and respond mechanically to gusts, meaning that they can adjust their flight even before their brain has received a signal that anything is wrong.
Shane Windsor, from the University of Bristol, carried out the research because, as someone who works with drones, he was jealous of birds. “When you use unmanned aerial vehicles, you realise how challenging it is when it is gusty,” he said. “But birds make it look easy.”
By getting Lily, a trained bird of prey, to fly through artificial gusts, Dr Windsor’s team found. the answer. To the naked eye, as she passed through the gust it appeared as “just a flutter” but in slow motion, “the wings moved massively”. He wrote in the journal Proceed ings of the Royal Society B, “I thought, ‘I know what that is — it’s suspension.’ “
Just as a car responds to a bumpy road without any need for sensors, so the wings were doing the same, hinging and twisting to keep the body on course.
This is what Dr Windsor meant by a “preflex”. “A preflex is a mechanical response built in. The bird’s wings respond to the gust so quickly that it can’t be due to a response in the brain.”
They also seemed to be tuned to respond in such a way that the body would barely notice. “A tennis racket has a sweet spot where you don’t feel a judder. That’s the same with wings —they take the force but don’t transmit.”
These preflexes bought the bird time, so that its brain could respond with more sophisticated actions, flexing the wings to reduce lift.
Dr Windsor hopes to translate the idea for use in unmanned aircraft but said it was unlikely it would end turbulence in larger craft. “This wouldn’t scale up to a Boeing 747,” he said. You don’t want those wings rotating.”