A bending motion equation of a tilting helicopter drive shaft with elastic multi-supports was derived by the theorem of motion for center of mass

Galerkin method and Dirac function.A bifurcation equation of the steady state main resonance was obtained based on the multiple scales method.The motion stability

topology structure of amplitude-frequency response curves etc.were analyzed.The results show that elastic intermediate supports plays the role of the limiters

which can improve the motion stability and increase frequency range of non-bifurcation between adjacent orders of main resonance.The bifurcation of main resonance can be removed by reducing the eccentricity and the order of main resonance and increasing damping of the driving shaft and intermediate supports.