Minimizing Fixed-Wing Flight Costs in Turbulence through Passive Stability: Insights from the Avian Wing Aerodynamics

Birds rely on active high-acceleration morphing and flapping to navigate complex airflows, but they can also maintain stable fixed-wing postures under persistent atmospheric disturbances. Here, we show that avian wings exhibit aerodynamic adaptivity to incoming flow variations, characterized by a gentler lift curve slope, a wider operative angle of attack range, and turbulence insensitivity, compared to engineered airfoil wings across varying angles of attack and turbulence intensities. This adaptivity stems from the consistent flow structures around avian wings under different turbulence intensities and their ability to suppress flow separation at high angles of attack. Longitudinal dynamic stability analysis further reveals that avian aerodynamic characteristics enable the corresponding modeled rigid flyers to maintain a broader stability envelope. This stability supports stable fixed-wing flight in real turbulent environments while reducing the need for active control, thereby minimizing flight cost.