Researchers at Princeton University’s School of Engineering have looked to nature—specifically, birds—to enhance flight safety and efficiency in aircraft. Inspired by the covert feathers birds use for precise maneuvers, the team has designed multi-row flaps that deploy automatically to prevent aircraft from stalling.

Birds rely on covert feathers during complex aerial movements, like landing in high winds, to improve control and stability. While engineers have long used single-row flaps in aircraft to improve lift, they haven’t explored multi-row configurations that mimic how birds manage airflow in response to environmental changes. Assistant Professor Aimy Wissa and her team focused on the aerodynamics of deploying multiple rows of flaps and how this design could improve flight performance.

Airplane wings create “lift” by allowing air to flow faster over the top of the wing than below, producing a low-pressure area above that pulls the aircraft up. However, sudden changes in speed or wind can disrupt this flow, leading to a stall where lift is lost.

Princeton’s covert flap design responds to airflow pressure without requiring external control systems, automatically deploying as needed. In experiments conducted in a wind tunnel, the team found that adding up to five rows of covert flaps increased lift by 45%, reduced drag by 30%, and improved stability.

The researchers tested their findings by outfitting a remote-controlled aircraft with covert flaps and an onboard computer programmed to induce stalls. The flaps deployed during flight, reducing stall intensity and delaying stall onset.

“Our discoveries about airflow modulation with covert flaps could have broader applications beyond aircraft, including in car design, underwater vehicles, and even wind turbines,” said Girguis Sedky, a postdoctoral researcher involved in the study. The innovation could mark a new era in fluid dynamics, applying the science of covert feathers to improve stability and efficiency across various fields.

By Impact Lab