The stability implications of drag minimization by tail action modelled in the gliding barn owl (<em>Tyto alba</em>)

Tail posture influences lift, drag, trim, and stability for birds, yet the interaction between them as the tail spreads and pitches remains unclear, even during steady gliding. In this study, we investigated the aerodynamic consequences of tail morphing, exploring the interactions between weight support, drag, longitudinal trim, and stability using data obtained from computational fluid dynamics (CFD) simulations of high-fidelity, photogrammetry-derived geometry of a free-gliding barn owl. Assuming drag to be minimized over a range of speeds, the tail should be more spread and pitched at low speeds, and less so at high speeds. This influences the proportion of weight supported by the tail; in order to prevent net aerodynamic pitching moment and maintain longitudinal moment equilibrium, the relative position of the center of gravity must shift. These effects shorten the negative static margin at higher speeds, making the model bird less unstable, limiting the reduction in pitch divergenc..., , # The stability implications of drag minimization by tail action modelled in the gliding barn owl (*Tyto alba*) Dataset DOI: [10.5061/dryad.tmpg4f59f](10.5061/dryad.tmpg4f59f) ## Description of the data This data includes the original points cloud used to reconstruct the high-fidelity geometry of the CFD simulation, as well as the data we obtained from CFD simulation for the analysis. With these data, readers can reproduce the trim states (tail spread, pitch and center of gravity shift) of the barn owl, and validate the conclusions of this paper. ### Files and variables **File: Geometrical_variables.zip** Description: This zip file includes four csv data files. (1) \"data_spanwise_leading_AR_t.csv\" indicates the aspect ratio of the BARN OWL variation with tail spread and pitch, the data structure is 5 X 3, row number indicates the pitching angle changing from 46 degrees to -46 degrees, column number indicates the spread angle changing from 0 to 35 degrees. (2) \"data_spanwise_leadi...,