添付資料：MSC.1/Circ. 1228（11 January 2007）を掲載

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Ref. T1/2.04

MSC.1/Circ.1228
11 January 2007
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1
The Maritime Safety Committee, at its eighty-second session (29 November
to 8 December 2006), approved the Revised Guidance to the master for avoiding dangerous
situations in adverse weather and sea conditions, set out in the annex, with a view to providing
masters with a basis for decision making on ship handling in adverse weather and sea conditions,thus assisting them to avoid dangerous phenomena that they may encounter in suchcircumstances.
2
Member Governments are invited to bring the annexed Revised Guidance to the attentionof interested parties as they deem appropriate.
3This Revised Guidance supersedes the Guidance to the master for avoiding dangerous
situations in following and quartering seas (MSC/Circ.707).

***

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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 undercertain 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 shipmaster 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 ofdangerous phenomena, which may lead to capsizing or severe roll motions causing damage tocargo, 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 ofoccurrence 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, andwhich 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 bemeasured by means of a stop watch as the time span between the generation of a foam patch by abreaking wave and its reappearance after passing the wave trough. The wave length O isdetermined either by visual observation in comparison with the ship length or by reading themean distance between successive wave crests on the radar images of waves.
1.5

The wave period and the wave length O are related as follows:
O = 1.56  TW2 [m] or TW

0.8 Ȝ [s]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:

TE

3TW2
3TW  Vcos Į[s]where V = ship’s speed [knots]; andD ҏ= angle between keel direction and wave direction (D = 0° means head sea)
1.7
The diagram in figure 1 may as well be used for the determination of the period of
encounter.

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MSC.1/Circ.1228
ANNEX
Page 2
1.8

The height of significant waves should also be estimated.
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2.1
It should be noted that this guidance to the master has been designed to accommodate forall types of merchant ships. Therefore, being of a general nature, the guidance may be too
restrictive for certain ships with more favourable dynamic properties, or too generous for certain
other ships. A ship could be unsafe even outside the dangerous zones defined in this guidance if
the stability of the ship is insufficient. Masters are requested to use this guidance with fairobservation of the particular features of the ship and her behaviour in heavy weather.
2.2
It should further be noted that this guidance is restricted to hazards in adverse weather
conditions that may cause capsizing of the vessel or heavy rolling with a risk of damage. Other
hazards and risks in adverse weather conditions, like damage through slamming, longitudinal or
torsional stresses, special effects of waves in shallow water or current, risk of collision or
stranding, are not addressed in this guidance and must be additionally considered when deciding
on an appropriate course and speed in adverse weather conditions.
2.3
The master should ascertain that his ship complies with the stability criteria specified in
the IS Code or an equivalent thereto. Appropriate measures should be taken to assure the ship’s
watertight integrity. Securing of cargo and equipment should be re-checked. The ship’s natural
period of roll TR should be estimated by observing roll motions in calm sea.
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MSC.1/Circ.1228
ANNEX
Page 3'$1*(52863+(120(1$

3KHQRPHQDRFFXUULQJLQIROORZLQJDQGTXDUWHULQJVHDVA ship sailing in following or stern quartering seas encounters the waves with a longer period
than in beam, head or bow waves, and principal dangers caused in such situation are as follows: 6XUIULGLQJDQGEURDFKLQJWRWhen a ship is situated on the steep forefront of a high wave in following or quartering sea
conditions, the ship can be accelerated to ride on the wave. This is known as surf-riding. In thissituation the so-called broaching-to phenomenon may occur, which endangers the ship to
capsizing as a result of a sudden change of the ship’s heading and unexpected large heeling.
 5HGXFWLRQRILQWDFWVWDELOLW\ZKHQULGLQJDZDYHFUHVWDPLGVKLSVWhen a ship is riding on the wave crest, the intact stability can be decreased substantiallyaccording to changes of the submerged hull form. This stability reduction may become criticalfor wave lengths within the range of 0.6 L up to 2.3 L, where L is the ship’s length in metres.
Within this range the amount of stability reduction is nearly proportional to the wave height.
This situation is particularly dangerous in following and quartering seas, because the duration ofriding on the wave crest, which corresponds to the time interval of reduced stability, becomes
longer.
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6\QFKURQRXVUROOLQJPRWLRQLarge rolling motions may be excited when the natural rolling period of a ship coincides with theencounter wave period. In case of navigation in following and quartering seas this may happen
when the transverse stability of the ship is marginal and therefore the natural roll period becomes
longer.
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3.3.1 Parametric roll motions with large and dangerous roll amplitudes in waves are due to thevariation of stability between the position on the wave crest and the position in the wave trough.
Parametric rolling may occur in two different situations:
.1

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.2

The stability varies with an encounter period TE that is about equal to the rollperiod TR of the ship (encounter ratio 1:1). The stability attains a minimum once
during each roll period. This situation is characterized by asymmetric rolling,i.e. the amplitude with the wave crest amidships is much greater than theamplitude to the other side. Due to the tendency of retarded up-righting from thelarge amplitude, the roll period TR may adapt to the encounter period to a certain
extent, so that this kind of parametric rolling may occur with a wide bandwidth ofencounter periods. In quartering seas a transition to harmonic resonance may
become noticeable.
The stability varies with an encounter period TE that is approximately equal to half
the roll period TR of the ship (encounter ratio 1:0.5). The stability attains aminimum twice during each roll period. In following or quartering seas, where
the encounter period becomes larger than the wave period, this may only occur

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MSC.1/Circ.1228
ANNEX
Page 4
with very large roll periods TR, indicating a marginal intact stability. The result issymmetric rolling with large amplitudes, again with the tendency of adapting theship response to the period of encounter due to reduction of stability on the wave
crest. Parametric rolling with encounter ratio 1:0.5 may also occur in head andbow seas.
3.3.2 Other than in following or quartering seas, where the variation of stability is solely
effected by the waves passing along the vessel, the frequently heavy heaving and/or pitching inhead or bow seas may contribute to the magnitude of the stability variation, in particular due tothe periodical immersion and emersion of the flared stern frames and bow flare of modern ships.
This may lead to severe parametric roll motions even with small wave induced stability
variations.
3.3.3 The ship’s pitching and heaving periods usually equals the encounter period with thewaves. How much the pitching motion contributes to the parametric roll motion depends on thetiming (coupling) between the pitching and rolling motion.
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The dynamic behaviour of a ship in following and quartering seas is very complex. Ship motionis three-dimensional and various detrimental factors or dangerous phenomena like additionalheeling moments due to deck-edge submerging, water shipping and trapping on deck or cargo
shift due to large roll motions may occur in combination with the above mentioned phenomena,
simultaneously or consecutively. This may create extremely dangerous combinations, which
may cause ship capsize.
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23(5$7,21$/*8,'$1&(The shipmaster is recommended to take the following procedures of ship handling to avoid thedangerous situations when navigating in severe weather conditions.
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6KLSFRQGLWLRQThis guidance is applicable to all types of conventional ships navigating in rough seas, provided
the stability criteria specified in resolution A.749(18), as amended by resolution MSC.75(69), aresatisfied.
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Surf-riding and broaching-to may occur when the angle of encounter is in therange 135°<Į<225° and the ship speed is higher than 1.8 L cos 180  D (knots). To avoid
surf riding, and possible broaching the ship speed, the course or both should be taken outside thedangerous region reported in figure 2.

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MSC.1/Circ.1228
ANNEX
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4.2.2.1 When the average wave length is larger than 0.8 L and the significant wave height islarger than 0.04 L, and at the same time some indices of dangerous behaviour of the ship can beclearly seen, the master should pay attention not to enter in the dangerous zone as indicated infigure 3. When the ship is situated in this dangerous zone, the ship speed should be reduced or
the ship course should be changed to prevent successive attack of high waves, which could
induce the danger due to the reduction of intact stability, synchronous rolling motions, parametricrolling motions or combination of various phenomena.
4.2.2.2 The dangerous zone indicated in figure 3 corresponds to such conditions for which theencounter wave period (TE) is nearly equal to double (i.e., about 1.8-3.0 times) of the wave
period (TW) (according to figure 1 or paragraph 1.4).
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4.2.3.1 The master should prevent a synchronous rolling motion which will occur when theencounter wave period TE is nearly equal to the natural rolling period of ship TR.

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MSC.1/Circ.1228
ANNEX
Page 64.2.3.2 For avoiding parametric rolling in following, quartering, head, bow or beam seas thecourse and speed of the ship should be selected in a way to avoid conditions for which theencounter period is close to the ship roll period ( 7( | 75 ) or the encounter period is close to one
7 | 0.5  75
half of the ship roll period ( ().
4.2.3.3 The period of encounter TE may be determined from figure 1 by entering with the ship’s
speed in knots, the encounter angle Į and the wave period TW.

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MEMO

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日本船主責任相互保険組合
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