How swifts control their glide performance with morphing wings.

Area of Science:

• Avian biomechanics
• Aerodynamics
• Flight dynamics

Background:

• Birds dynamically alter wing shape and size to optimize aerodynamic performance.
• Analytical models predict birds adjust wing sweep based on glide speed, derived from aerodynamic theory.

Purpose of the Study:

• To investigate the aerodynamic and structural performance of swift wings.
• To develop a semi-empirical glide model based on empirical swift wing data.
• To determine how wing sweep affects glide speed, turning rate, and flight efficiency.

Main Methods:

• Wind tunnel measurements of swift wing aerodynamic and structural performance.
• Development of a semi-empirical glide model incorporating empirical data.
• Analysis of wing morphing effects within and beyond the behavioral envelope.

Main Results:

• Wing sweep significantly impacts glide speed and turning rate; optimal sweep can halve sink speed or triple turning rate.
• Extended wings are advantageous for slow glides and turns; swept wings are superior for fast glides and turns.
• Swept wings offer reduced lift generation during high-speed turns but can withstand higher loads; glide model predicts cost-effective gliding at 8-10 m/s.

Conclusions:

• Wing morphing allows birds to tailor wing performance to specific flight tasks, such as efficient gliding or agile maneuvering.
• The study explains why swifts maintain low flight speeds (8-10 m/s) for roosting, aligning with cost-effective gliding predictions.
• Understanding avian wing morphing can inform the design of future aircraft with adaptive flight capabilities.