Interim Standards for Ship Manoeuvrability was adopted at 18th IMO Assembly in Nov. 1993, and ship manoeuvrability becomes important from the viewpoint of human life safety and ocean environmental protection. In relation to these conditions, it is necessary to examine manoeuvring performance under the external force of waves.
In this report, Fujii-Takahashi's semi-empirical equation which can calculate the added resistance in short wavelength region is extended to calculate the surge and sway forces and yaw monent caused by directional spectrum waves having short wavelength. By introducing these forces to M. M. G. model, simulation for zigzag test in short wavelength waves is carried out and compared with the free running model experiment in the towing tank of Yokohama National University, in which directional spectrum waves can be generated. Further, manoeuvrability indices are obtained by K-T analysis of simulation results using 1st order approximate equation.