The Peregrine Falcon's Dive: On the Pull-Out Maneuver and Flight Control Through Wing-Morphing

TL;DR

This study investigates the aerodynamic mechanisms behind the Peregrine falcon's pull-out maneuver, revealing how wing-morphing and vortex lift contribute to high maneuverability and stability during rapid dives.

Contribution

It combines flight analysis, wind-tunnel experiments, and high-fidelity simulations to elucidate the aerodynamic effects of wing-morphing in falcons, a novel approach in avian flight research.

Findings

Falcons experience load factors up to 3g, potentially reaching 10g during high-speed pull-outs.

Wing-morphing generates vortex lift similar to combat aircraft delta wings.

Falcons fly unstably in pitch but use wing configurations to enhance responsiveness and stability.

Abstract

During the pull-out maneuver, Peregrine falcons were observed to adopt specific flight configurations which are thought to offer an aerodynamic advantage over aerial prey. Analysis of the flight trajectory of a falcon in a controlled environment shows it experiencing load factors up to 3 and further predictions suggest this could be increased up to almost 10g during high-speed pull-out. This can be attributed to the high maneuverability promoted by lift-generating vortical structures over the wing. Wind-tunnel experiments on life-sized models together with high fidelity simulations on idealized models, which are based on taxidermy falcons in different configurations, show that deploying the hand-wing in a pull-out creates extra vortex-lift, similar to that of combat aircraft with delta wings. The aerodynamic forces and the position of aerodynamic center were calculated from Large Eddy Simulations of the flow around the model. This allowed for an analysis of the longitudinal static stability in a pull-out, confirming that the falcon is flying unstably in pitch with a positive slope in the pitching moment and a trim angle of attack of about 5$^\circ$, possibly to maximize responsiveness. The hand-wings/primaries were seen to contribute to the augmented stability acting as `elevons' would on a tailless blended-wing-body aircraft.