Excerpts from the report on the dynamic behavior of the cross, dated July 29, 1994, by the CTICM (reference 94.01)

Introduction : Assessment of the dynamic behavior of the Cross aims at..."discovering the effects of the relative flexibility of the cross and possibly to obtain a coefficient for the overall dynamics of the entire cross".

Method of Calculation : Starting from the results of the Statics study, ... "we can therefore know the flexibility (notice taken, too, of the shear forces) of the cross at these points. Flexibilities at intermediate levels may be obtained, at the present stage of the study, by linear interpolation.

For that, we study the spatial deformability of the structure on a given length. Then, we deduce the characteristics to give to a finite-element model of the cross in order to obtain the same deformations under the same loading.

The study of the methods necessary for applying CECM rules is done on this finite-element model. For that, we give this model a linear density which allows the restoration of the law of distribution of masses along the length of its neutral axis."

Conclusion : "Eddies of KARMAN may be produced. Moreover, elastic stability, in pure torsion as well as in torsional flexion coupling, is not completely assured.

...However, the fact that we are far from a long list of results which would permit us to say that there is no risk of instability leads one to be prudent and to recommend aerodynamic tunnel trials.

Messrs Remy, Lelache, Engineers

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