Control and stabilization were key elements for the Wright brothers to overcome for the first airplane to take flight. While technology has evolved significantly when it comes to aviation, the effort to enhance flight hasn’t stopped. University of British Columbia (UBC) researchers looked to a flying expert for insight: gulls.
“While we know birds frequently alter their wing shape, this is the first empirical evidence demonstrating how that wing morphing affects avian stability,” said Douglas Altshuler, UBC zoologist and senior author on the team’s recently published paper. “In this case, the gull’s wing design points to a novel, and fairly simple, avian-inspired joint that may enable aircraft to adjust dynamically to challenging conditions.”
The UBC team sought the help of aviation expert Professor Philippe Lavoie, University of Toronto, and his wind tunnel lab to gain insight into the ability of gulls to morph their wings to stabilize their flight. The team honed in on gulls specifically since these birds typically navigate unsteady turbulence while flying over open water. To counter increased wing speeds and gusts, gulls can alter the angle of their elbow joint from extended wing configurations to a flexed configuration. The ability to pull the tips of their wings in and back gives them more control.
“If you can change the shape of the wings, you can create more stable configurations with lower drag when you want more endurance,” Lavoie said. “Gulls can use updrafts to increase altitude so they don’t have to flap their wings as much to conserve energy. But if they need to make quick maneuvers, like diving to catch fish, they can change the shape of the wing for that particular purpose.”
Altshuler and fellow UBC researchers Christina Harvey and Vikram Baliga studied the anatomical elbow range of gull wings and measured performance of 12 wing shapes in the wind tunnel, as well as observed the birds in their natural habitat. Their research demonstrated that a simple elbow adjustment to expand wings in or out allows gulls to create a range of wing shapes that stabilize their glide.
When soaring, gulls fully extend their wings to be more planar with increased static stability. When wind speed picks up, they tend to reduce the elbow angle to create a more rounded configuration with reduced static stability. According to the study, the range of the pitch stability derivative achieved by a gull morphing its elbow angle is approximately −0.03 to −0.75, which is substantially more than a rigid wing’s static pitch stability derivative range of −0.01 to −0.26.
“The benefit of morphing is that you don’t need bulky control surfaces during flight,” Lavoie said. “It makes it easier to take advantage of energy harvesting through soaring.”
The team’s research has the potential to be used for creating more efficient aircraft, especially drones. Lavoie believes that drones could be engineered to soar on thermal updrafts to scan pipelines, inspect farms, or monitor animal herd movements, as well as track forest fires.
Interested in more ways that researchers are looking to nature for enhancing flight technology? Check out AI Helps Gliders Soar Like Eagles and Wireless Robotic Fly Takes Flight.