Dynamic flight stability in the desert locust Schistocerca gregaria

Area of Science:

• Biomechanics
• Animal Flight Dynamics
• Insect Physiology

Background:

• Dynamic stability in flying animals is not well understood.
• Previous hypotheses suggested a 'constant-lift reaction' in locusts.
• Locusts' ability to correct pitch disturbances within a wingbeat is key.

Purpose of the Study:

• To perform the first quantitative analysis of dynamic stability in flying animals.
• To analyze longitudinal static stability derivatives and mass distribution in desert locusts.
• To investigate the role of pitch attitude and aerodynamic incidence sensitivity in locust flight.

Main Methods:

• Quantitative analysis of longitudinal static stability derivatives.
• Measurement of mass distribution in desert locusts (Schistocerca gregaria).
• Identification of natural longitudinal modes of motion.

Main Results:

• Locust static stability and control are insufficient for dynamic stability without pitch attitude and aerodynamic incidence sensitivity.
• No evidence for a 'constant-lift reaction' was found.
• Three natural longitudinal modes identified: stable subsidence, unstable divergence, and a stable short period oscillatory mode.

Conclusions:

• Pitch rate damping is essential for stabilizing locust flight, particularly at insect scales.
• The short period mode, similar to aircraft, involves rapid pitch oscillations.
• Balancing short period mode frequency with wingbeat frequency is critical for effective, single-wingbeat control inputs in flying animals.