scope:

Overview and ST Background

NNAG Maritime Capability Group 6 on Ship design includes ship design standards in their programme of work. STANAG 4154 covers Seakeeping and ship motion requirements for mission based scenarios from an operability perspective without consideration for manoeuvring in a seaway. Manoeuvrability requirements and guidance exist in ANEP-70 but are mostly limited to calm water environments. Issues of manoeuvring in following seas and controllability in heavy seas have been introduced in various NATO documents under the topic of safety without recommendations for design requirements or criteria to assess performance against.

A common default design requirement for a corvette/frigate size ship is that the ship shall be fully operational in conditions up to sea state 6 and survive the worst storms likely. Demonstration of such requirements typically only considers discrete headings relative to the waves without factoring in reduced manoeuvring capability due to the seaway conditions or that certain manoeuvers such as turning or holding station in a seaway can exacerbate ship motions, further degrading equipment and human performance. Recognizing that for the North Atlantic on an annual basis, approximately 30% of the time sea state 3 conditions or less exist, almost 50% of the time sea states 4 or 5 can be expected and around 20% of the time sea state 6 or above is likely and the requirement to remain functional as a war ship regardless of the seaway conditions, greater attention to the implications of manoeuvring and the ability to control the ship in a seaway is warranted.

The area of Seaway Controllability can be described as a combination of seakeeping and manoeuvrability factoring in operational implications, storm survival capabilities and mitigation tactics. The aim for the Specialist Team has been to bridge the current gap between existing NNAG standardisation documents in manoeuvrability and seakeeping.

Providing operator guidance on Seaway Mobility is also very much a priority of the MCG/6. Volume II of ANEP-70 has been submitted to the NATO and PfP Navies to support them in establishing Onboard Manoeuvring Information. It offers a basis for the standardised presentation of manoeuvring information primarily intended for use by operators onboard and can be used in various training environments. Information related to seaway mobility is very limited in ANEP-70. Bringing in aspects of the influence of operating in moderate and heavy seas better addresses the factors that needs to be considered in order to make informed tactical decisions and highlight the risks of potentially dangerous conditions and scenarios.