Structural Dynamic Aspects Of Rotor Antiresonant Isolation

In the last years increasing efforts have been made in practical testing of antiresonance isolation systems (ARIS) for helicopters. The prediction of the vibration control performance of these systems is essential for the design and the costs of the whole helicopter. The feature of the passive nodal isolation system is the antiresonant frequency tuned to the main rotor passage frequency to prevent the transmission of the oscillatory hub forces and moments to the fuselage. The investigation of this paper demonstrates that the nodal rotor isolation system may be strongly influenced by the structural dynamics of the helicopter. Due to the numerous eigenvalues it may happen, that the antiresonant frequency of the isolation system is compensated by an adjacent natural frequency. In this case the desired isolating effect disappears. The complexity of the three dimensional structure aggravates the understanding and prediction of vibration system.