The Solution of Helicopter Ground Resonance Instability

A centrifugal force occurs as a result of eccentricity between the rotor's center of gravity and the rotation axis due to the difference between the progressing and regressing blade speeds. Ground resonance occurs when the frequency of this force coincides with the fuselage frequency. Moment of inertia values and center of gravity are obtained by creating a finite element model of a selected sample helicopter. The stiffness matrix of the landing gear is created by the substructure method of the helicopter, whose center of gravity and landing gear are modeled. The equation of motion, which includes the six-degrees-of-freedom body and the two-degrees-of-freedom rotor model, is solved as an eigenvalue problem. The eigenvalue results obtained are graphed, and it is determined at which rotor speeds the structure is unstable, and then instability is tried to be prevented with damping ratio suggestion.