Fruit flies modulate passive wing pitching to generate in-flight turns

TL;DR

This study reveals how fruit flies subtly adjust passive wing pitching by modulating hinge spring angles to perform sharp in-flight turns with minimal active effort.

Contribution

It uncovers the passive mechanical role of the wing hinge spring and how insects exploit it for maneuvering, advancing understanding of insect flight control mechanisms.

Findings

Wing hinge acts as a torsional spring resisting wing flip.

Insects asymmetrically change spring rest angles to turn.

Passive wing pitching modulations enable sharp turns with minimal actuation.

Abstract

Flying insects execute aerial maneuvers through subtle manipulations of their wing motions. Here, we measure the free flight kinematics of fruit flies and determine how they modulate their wing pitching to induce sharp turns. By analyzing the torques these insects exert to pitch their wings, we infer that the wing hinge acts as a torsional spring that passively resists the wing's tendency to flip in response to aerodynamic and inertial forces. To turn, the insects asymmetrically change the spring rest angles to generate rowing motions of their wings. Thus, insects can generate these maneuvers using only a slight active actuation that biases their wing motion.