Post critical analysis of helicopter ground resonance
Résumé
In helicopter with hinged blades, an unstable dynamic phenomenon known as ground resonance may occur during take-off and landing phase leading to the possible destruction of the aircraft. The prediction of the stability boundary has been addressed for various helicopter configuration and by using different methods. However, in order to study the behavior of the system when the rotor speed is in the range of instability, an analysis of the post-critical behavior is needed. To do this, the behavior of a helicopter with isotropic blades and fuselage properties is investigated. The nonlinear terms due to large blades rotation are kept up to cubic order and a coordinate array transformation is used to simplify the equation of motion. The resulting nonlinear system is analyzed using the method of multiple scales and the normal form of the bifurcation is obtained. The results are compared and validated with numerical simulations.