Inherent Properties of Ship Manoeuvring Linear Models in View of the Full-mission Model Adjustment

The paper presents new results on the inherent properties of ship linear dynamics. The focus is made on the second-order formulation for the uncoupled equations of sway and yaw, and on their unique, unknown performance within the zigzag test. From the standpoint of application to full-mission model tuning, a very important loop in the drift-yaw domain of the zigzag behaviour, as governed by the rudder rate dependent time constants (of T3-type), is brought to the light. This and some other dependent effects, like overshoot angle performance, are likely to be lost, if the well-known, rather ambiguous, first-order approximations are deployed.