Simone Zuccher Simone Zuccher

Airplane spin

Can the spin of an airplane be considered a chaotic motion? The origin of such a doubt resides in the fact that in certain cases the spin motion turns out to be very complex (the so-called anomalous spin) and the recovery of the aircraft is very difficult or even not possible. Moreover, since it happens at angles of attack for which nonlinear effects are important, the spin could introduce chaotic aspects.

In order to find an answer, wind tunnel tests are carried out on a model of a fighter aircraft attached to its center of gravity through an universal joint that allows only the three rotations. The angles that define the three degrees of freedom are analyzed using the typical tools of the theory of the chaos, such as power spectra, projections of the attractor in the phase space, reconstruction in the embedding space and Poincare sections.

From the analysis of the data, it can be deduced that increasing the wind tunnel velocity, i.e. the Reynolds number, successive bifurcations in the frequencies of the motion, a more complex structure of the attractor with fractal aspects and sensitivity to initial conditions are found. These hints could make one think about an evolution towards chaos, however true chaotic motion is not fully observed.

Other configurations are also analyzed, by changing the nose of the model or the wings, so as to verify the influence of these particulars on the motion. The conclusion is that, for certain configurations, a development of the motion towards chaos is observed; for others the motion turns out be very regular. Visualizations with smoke confirm the hypotheses concerning the aerodynamic interaction between the wings and the vortices produced from the nose and between the tail-planes and the wake due to the wings.

For more details, see the following related publications.

Zuccher, S. & De Ponte, S. 2007 Post-Stall Motions Evolving Toward Chaos. Journal of Aircraft, 44, No. 3, 833-844.

Zuccher, S. 1997 Moti Caotici Post-Stallo, Master Thesis, Politecnico di Milano, Milano.

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Last updated: 03 Mar 2022. Webmaster