Manoeuvrability in adverse conditions: rational criteria and standards

The importance of norming manoeuvrability of ships in adverse weather conditions increased after the introduction of EEDI regulations, which raised concerns that manoeuvrability of ships in adverse conditions may become insufficient if EEDI requirements are achieved by simple reduction of the installed engine power. This paper addresses the definition of the required criteria (i.e. ship’s abilities, relevant for the considered problem), measures (values quantifying ship’s performance with respect to the criteria) and standards (acceptance limits for the measures). It is proposed to combine criteria that are based on the physics of the problem with standards that are empirical to some degree to reflect the existing safety level and operational practice and, at the same time, compensate for inevitable simplifications in the practical criteria. The paper reviews existing proposals, interviews of ship masters and accident data to define criteria for manoeuvrability in adverse conditions and summarises experience with their application, particularly addressing their practicality and redundancy with respect to each other. A practical assessment procedure is proposed, illustrated in examples and validated. A rational approach to fine-tune the standards, based on benchmarking of existing ships with respect to the new criteria, is proposed and tested on bulk carriers and tankers.