Airplane feathers could be aviation’s next big thing.
The bird’s wings are outlined with overlapping rows of tufts of feathers, which flare out from near the shoulders. These “covert feathers” help the bird move through the air. Aircraft performance could also be improved. Lining the aircraft wing with a row of lightweight flaps. imitate hidden feathers It can increase lift, reduce drag and prevent stalls, researchers reported Oct. 28. Proceedings of the National Academy of Sciences.
Many airplanes already have flaps and spoilers on their wings. But unlike those components, the biologically inspired flaps deploy passively when the wing hits oncoming airflow at a high angle. This is a scenario known as high angle of attack (SN: 1/12/24). “They’re not controlled by motors or hydraulic actuators,” says Amy Wissa, an engineer at Princeton University. Plus, “They’re all over the wing, not just the back or the front.”
In wind tunnel experiments, Wissa and her colleagues studied how multiple rows of flaps affect airflow around the wing. They found that the flaps affected flow in two ways. Flaps placed near the front of the airfoil helped direct airflow around the wing closer to the wing, helping to improve lift and reduce drag. Adding more rows of flaps enhanced the effect.
They also found that by installing a row of flaps near the rear of the airfoil, they blocked high-pressure air near the trailing edge from creeping toward the front of the wing. This is important, Wissa said, because low pressure in the area is needed to create lift. Wissa’s team found that adding five rows of flaps to the airfoil can increase lift by up to 45 percent and reduce drag by 31 percent.
Subsequent tests with remotely piloted aircraft also found that the flaps reduced stall (the sudden loss of lift at high angles of attack) and increased the aircraft’s angle of attack range by 9%. The flaps also improved flight stability, Wissa noted.
This range increase can be especially useful when flying in heavy gusts or landing on very short runways. Without the flap, such operations may not be able to be completed safely, Wissa says. “But you can do it now.”
