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In this paper results of numerical analysis of the ground resonance are shown. This analysis is performed making use of the complete model of the one‐main rotor helicopter. This model is adopted from flight mechanics. For the basic analysis it is assumed that the helicopter fuselage is a rigid body and the main rotor consists of four rigid blades. Each blade performs motions about its horizontal flapping hinge and vertical lagging hinge. The tail rotor is treated as a hingeless and weightless source of thrust, which equilibrates the drag moment and ensures directional control of the helicopter. For analysis of the ground resonance phenomenon, forces and moments produced by the landing gear are taken into account – their rigidity and damping are included into consideration.

The supercritical propulsion shaft equipped with a dry friction damper has been designed for a polish ultra light helicopter named IS‐2. Models of the shaft and the damper and some results of analysis of the shaft flexural vibrations are presented.As it turned out the shaft vibrations strongly depend on parameters of the damper (especially on the damper gap) and can be regular or chaotic. There are two main cases: the damper with a small gap and the damper with a big gap, when compared to shaft eccentricity.