Gliding birds can perforin maneuvers that surpass the capabilities of the most advanced aircraft. Modern aircraft maneuver by using discrete control surfaces such as ailerons and flaps to control their flight. However, birds do not have discrete controls and instead can change the shape of their wings in flight, known as wing morphing. Due to the large disparities between these control methods, the effectiveness of biological wing morphing controls is not well understood. To examine how wing morphing contributes to flight path control, we used a numerical approach to investigate the static pitch control effectiveness of the elbow and wrist during gliding flight for four distinct avian species; glaucous-winged gulls, common nighthawks, red-tailed hawks and bald eagles. For each species, we first identified the wing shapes associated with the skeletal joint angles across the range of motion. Next, we evaluated the aerodynamic characteristics of the biologically viable wing shapes using a numerical lifting line method. This analysis revealed that the avian wrist and elbow are effective in pitch control, and that the magnitude of this effect varies across species. For all species, the elbow was most effective when the wrist angle was fixed at high angles and vice versa. Nighthawk wings demonstrated a divergent trend from the other species for both wrist and elbow effectiveness. These findings confirm that different avian species' wing configurations can yield substantially different control mechanisms in flight. Understanding these species-specific differences helps set effective bio-inspired target designs for future experimental evaluations.
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