Prey carrying and passive wing load alleviation reconfigure longitudinal stabilization in a gliding barn owl

An experimentally informed model of gliding barn-owl flight with prey carriage and passive wing load alleviation is developed to examine trim, static stability, and dynamic response. Baseline trim predictions agree with prior owl data and are shown to be more consistent with a minimum-sink condition than with minimum drag coefficient or maximum lift-to-drag ratio. A generalized static-stability analysis demonstrates that vertical center-of-gravity offset and drag-induced moments, including those associated with prey carriage, contribute directly to the pitching-moment balance, so that the pitching-moment slope is not determined by fore-aft center-of-gravity position alone. Prey carriage is found to drive the generalized static margin further into the unstable region and to shorten the time to double amplitude of the dominant mode. In the dynamic model, passive wing load alleviation attenuates the dominant unstable mode and shifts its character, as measured by unit-invariant modal participation factors, from a fast short-period-like response to a slower, more phugoid-like response as compliance increases. With passive alleviation present, modest proportional wing-pitch feedback is sufficient to place the system poles in the stable left-half plane. These results indicate that load carriage and passive compliance can reshape the stability properties of gliding flight, reducing the control required to maintain steady trajectories without requiring a classically stable configuration.