Recent marine disaster of large ships often causes serious oil pollution. To prevent or reduce such a disaster, International Maritime Organization(IMO) has been endeavoring to increase ships manoeuvrability, and adopted the interim standards for ship manoeuvrability A751(18) in 1993. These standards cover the typical manoeuvrability including turning ability, initial turning ability, yaw-checking and course-keeping ability, and stopping ability. Yaw-checking and course-keeping ability in IMO's ship manoeuvrability standards is reviewed from the viewpoint of safe operation.
In this paper the authors review the manoeuvrability standards particularly focussing the criterion for the yaw-checking and course-keeping ability. Three types of actual-ship (the authors take three types of original actual-ship built in Korea recently) are taken as tested model. Assumed series-ships which have different instability on course systematically, are generated from the actual-ships. The numerical simulation on Z-test is carried out in order to examine the correlation between known manoeuvrability and various kinds of overshoot angle. Next, using the assumed series-ships, simulator experiments are executed in situation of curved, narrow waterway by five pilots in order to examine the correlation between known manoeuvrability and subjective rating scale evaluated by pilots. Three kinds of IMO's criterion concerning yaw-checking and course-keeping ability are discussed in view of degree of manoeuvring difficulty.