Effect of changes in some design parameters on the dynamic properties of aircraft

The aim of the study presented in the paper was to examine the impact of changes related to aircraft modernization, the dynamic properties of an aircraft on the basis of five cases studied experimentally. Which changes in the dynamics of an aircraft structure occurred as a result of modernization can be experimentally tested by resonance tests. For this purpose, resonance tests should be carried out before the aircraft modernization and after its completion. In order to mapping the conditions of free flight the objects were suspended flexibly. The electrodynamics actuators were used to induce vibrations, piezoelectric transducers were used for the measurement of vibrations. The size and phase of extortion forces and their application points were selected individually for each resonance in order to get the best separation of it. The first stage of the study was based on recordings the frequency - amplitude characteristics. The second stage of the study was the Identification of individual frequencies and mode shapes of each resonance, which was implemented by choosing the size and the proportion of mutual phase shifts between the extortion forces. In the selection the criteria based on minimizing the phase difference of vibrations measured at several points of the structure were used. The final stage of this study was to register the frequency and shapes mode of the tested resonance and the resonance generalized masses and damping coefficients.