In a study comparing the hovering prowess of hummingbirds with that of one of the most advanced micro-helicopters in the world, it was no contest, researchers say; nature -- and the hummingbird -- won out.
In a measure of how much energy was required to lift themselves into the air, expressed as a power-to-weight ratio, the best hummingbird hoverers were 20 percent more efficient at sustained hovering than the helicopter, researchers at Stanford University reported.
However, they noted, the helicopter was able to match more average hummingbirds in flight efficiency, demonstrating how far flight engineering has come.
The study, reported in the Journal of the Royal Society Interface, pitted hummingbird performance with that of a small drone known as the Black Hornet, a tiny micro-drone weighing less that an ounce used by British ground troops serving in Afghanistan for surveillance.
Using both studies of hummingbirds in the wild, using high-speed video, and lab tests on hummingbird wings taken from museum specimens, the Stanford scientists, working with colleagues from the University of British Columbia in Canada and in the Netherlands, were able to determine the flapping power a hummingbird needs to be able to to exert to lift its own weight into the air.
"By combining the wings' motion with the drag [that we measured in the lab], we were able to calculate the aerodynamic power hummingbird muscles need to provide to sustain hover," study leader David Lentink of Stanford said.
One species, Anna's hummingbird, proved the hovering champion, far outdoing the efficiency of the micro-helicopter, but if the performance of a number of hummingbird species was averaged their performance was "on par with the helicopter," the researchers said.
They acknowledged that straight hovering flight was not the only consideration for helicopters -- or for hummingbirds, for that matter.
"Clearly we are not even close to hummingbirds in many other design metrics, such as wind gust tolerance, visual flight control through clutter, to name a few," Lentink says.
"But if we focus on aerodynamic efficiency, we are closer than we perhaps ever imagined possible."
Scientists have learned it pays to take a intense interest in what can be discovered if studies of natural biology and human engineering come together, and say they're humbled by what they see in the animal kingdom.
Recreating those natural skills using engineering technology is a challenge they're happy to take on, Lentink says.
"There is still a ton we can learn from nature," he says.
