The coupled rotor/fuselage system was developed using multibody dynamics approach. The undercarriage of helicopter comprised the oleo and tyre as a nonlinear system. The ship had the roll and pitch motion in the form of harmonic oscillation. Under different rotor speeds and excited frequencies

the response and dynamic stability of the rotor/fuselage system had been investigated. The result shows that the fuselage and the rotor oscillations may generate limit cycle oscillations under the excitement of ship. When the rotor oscillation is equal to the excited frequency of ship

the response of regressing lag will bring about limit cycle oscillations

and the center of gravity of rotor will shift from the hub

leading to ship resonance.