How Birds Take Flight With Such Ease
New research breaks down the fundamentals required to smoothly go from perched to airborne.
Ben Parslewhad a problem: His robots weren't very good at jumping.Parslew,anaerospace engineering researcherand lecturer at theUniversity of Manchester, studies the mechanics of flight. Along with his research team, he had turned to robots to better understand how flying machines mightbe able to launch themselves into the sky like birds. Butwhile avians seem to effortlesslybecome airborne, Parslew'srobots, which wererelatively simpleconstructions, didn’t find it quite so easy.Some wouldflip over in the air andland upside-down. Others remained stable in the air but jumped in the wrong direction. And still others fell over before they got off the ground in the first place.
Something was clearly not working here. So Parslew and histeam decided they needed to back up and first study how exactlya bird launches itself into the air.“That was kind of motivation for doing this study, to understand why our robots are failing and why birds succeed with such apparent ease,” Parslew says.
conductedwaspublished last month in the journalOpen Science. Using computer analysis, the researchers found that whenbirds take off, they simultaneously control two motions: the direction they’re jumping in and the amount theyrotate (pitch) their body as they accelerate, Parslew says.Such coordination allows them to remain balanced during launch.
To conduct thestudy, Parslew’s team created computer models usingdata from two studies of birds with different takeoff styles: one was led by Pauline Provini, who researches evolutionary biology at the French National Museum of Natural History in Paris, using, and another wasled by Havalee Henry, now an orthopaedic surgery resident at Yale New Haven Hospital, on.
"That’s the kind of approach we took," Parslew says, "looking at birds in nature as a sort of dataset, but then also building our own theoretical models and computational models.”
In addition to discovering the importance of pitch and direction, the researchers foundthat birds are speciallybuilt for this kind of takeoff because ofa certain sponginess, or cushioning, in their leg joints that lets them extend theirlegs for a smooth and fluid movement during the jump.This extra flexibilityin combination with their jump direction and proper rotation allows for a stable takeoff, he says.
Diamond Dove taking off.Video:Dr. Pauline Provini/Functional Morphology Lab/Muséum National d'Histoire Naturelle
The teamalso confirmed that the wingsdon’t contribute at all to the physics of the initialjump—it’s all about the legs. Thiscan be seen inProvini’svideo of a Diamond Dove taking off. The bird lowersits trunk by flexing its legs, and then extends itship, knee, and ankle to push the body in the direction of takeoff.
“What is interesting is the fact that the wings are still up when the bird leaves the perch,"Provini says, "meaning that they are not involved in the first propulsion.”
Parslew’s modeling also showed that a bird'sability to grip a perch is beneficial fortaking off: It allows them to launchat more anglesthan when they are standing with their feet on flat ground.
"The big impact of having a perch to apply torque to is that it means you can jump in many more directions—from very shallow to very steep," Parslew says."Without a perch you have a much narrower window of jump directions, and if you try anything outside of this window you tip over."
TheDiamond Doves, for instance,jumped at angles around 20 degrees shallower than birds with feet that aren't made for gripping, Parslew says.Contrast that with the Guinea Fowl: With their fee flat on the ground, they have a much more limited range of jumping angles.
While thisnew research helps scientists understandbird flightand takeoff better,Parslew hopes thatit will also translate to robotics research.These findings could make drones more efficient, he says, andperhaps one daythey willeven be able to perch and take off themselves—without doing any unexpected flips.
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