1 General
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC.1/Circular.1228 – Revised Guidance to the Master for Avoiding Dangerous Situations in Adverse Weather and Sea Conditions – (11 January 2007) - Annex - Revised Guidance to the Master for Avoiding Dangerous Situations in Adverse Weather and Sea Conditions - 1 General

1 General

  1.1 Adverse weather conditions, for the purpose of the following guidelines, include wind induced waves or heavy swell. Some combinations of wave length and wave height under certain operation conditions may lead to dangerous situations for ships complying with the IS Code. However, description of adverse weather conditions below shall not preclude a ship master from taking reasonable action in less severe conditions if it appears necessary.

  1.2 When sailing in adverse weather conditions, a ship is likely to encounter various kinds of dangerous phenomena, which may lead to capsizing or severe roll motions causing damage to cargo, equipment and persons on board. The sensitivity of a ship to dangerous phenomena will depend on the actual stability parameters, hull geometry, ship size and ship speed. This implies that the vulnerability to dangerous responses, including capsizing, and its probability of occurrence in a particular sea state may differ for each ship.

  1.3 On ships which are equipped with an on-board computer for stability evaluations, and which use specially developed software which takes into account the main particulars, actual stability and dynamic characteristics of the individual ship in the real voyage conditions, such software should be approved by the Administration. Results derived from such calculations should only be regarded as a supporting tool during the decision making process.

  1.4 Waves should be observed regularly. In particular, the wave period TW should be measured by means of a stop watch as the time span between the generation of a foam patch by a breaking wave and its reappearance after passing the wave trough. The wave length λ is determined either by visual observation in comparison with the ship length or by reading the mean distance between successive wave crests on the radar images of waves.

  1.5 The wave period and the wave length λ are related as follows:

  1.6 The period of encounter TE could be either measured as the period of pitching by using stop watch or calculated by the formula:

where

V = ship's speed [knots]; and
α = angle between keel direction and wave direction (α = 0° means head sea)

  1.7 The diagram in figure 1 may as well be used for the determination of the period of encounter.

  1.8 The height of significant waves should also be estimated.

Determination of the period of encounter TE

Parent topic: Annex - Revised Guidance to the Master for Avoiding Dangerous Situations in Adverse Weather and Sea Conditions
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