Modal Analysis of Helicopter Blades with Lumped Mass Method and Experimental Test

Modal analysis is done periodically to ensure blades performance for non-occurrence of resonance obtained under various operating conditions. Since metal or composite helicopter blades have a certain flexibility at different speeds in different planes can lead to deformation of the structure that can have a great effect on the aerodynamic performance of the helicopter. In this paper, modal analysis of helicopter blade has been carried out by the lumped mass methods (myklestad and finite element method) and modal test on the rotor structure. The finite element analysis has been developed by two approach of analytical and software method. Modal testing was also performed in both static and dynamic states, with constant speed, to validate the lumped mass methods. Finally, the results of both methods are compared with each other. After ensuring there correspondence between lumped mass methods and experimental results, an analysis was done according to the operating conditions of the rotor and finally Campbell diagram has been generated. According to this diagram became clear there was not any problem with the resonance of the rotor blades, while the numerical result of case has an acceptable match with the experimental results.