Feather-inspired aircraft flaps can enhance flight performance

The aircraft wing may be the next big thing in aviation.

The wings of the birds are contoured with overlapping rows of tufts of feathers, spreading from near the shoulder. These “stealth feathers” help birds maneuver through the air. They can also increase aircraft performance. Lining aircraft wings with rows of light circles that mimic stealth feathers can increase lift, reduce drag and prevent stalling, researchers report Oct. 28 in Proceedings of the National Academy of Sciences.

Many aircraft already have flaps and spoilers on their wings. But unlike those components, bio-inspired flaps would passively deploy when the wings meet oncoming airflow at a high angle, a scenario known as a high angle of attack (SN: 1/12/24). “They are not controlled by any motors or any hydraulic actuators,” says engineer Aimy Wissa of Princeton University. Furthermore, “they are all over the wings, not just the back or the front.”

In wind tunnel experiments, Wissa and her colleagues studied how multiple rows of flaps affected the airflow around airfoils. They found that the flaps affected the flow in two ways. Flaps placed near the front of an airfoil helped the air flow around it closer to the wing, which helped improve lift and reduce drag. Adding more rows of collisions increased the effect.

They also found that installing a single row of hoops near the trailing edge of an airfoil blocked high-pressure air near the trailing edge from creeping toward the front of the wing. That’s important because low pressure in that area is needed to produce lift, Wissa says. Wissa’s team found that adding five rows of blades to the airfoil improved lift by up to 45 percent and reduced drag by 31 percent.

Later tests with remote-controlled aircraft also showed that the flaps mitigated stall, a phenomenon that involves a sudden loss of lift at high angles of attack, expanding the craft’s angle-of-attack range by 9 percent. The flaps also improved flight stability, Wissa notes.

This increased range can be especially useful when flying through hard glides or during very short landings on the runway. Without collisions, you may not be able to safely complete such maneuvers, Wissa says. “But now you can.”