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ANNEX D

(This annex and its Appendices I to IV reproduce the text of the Recommendation on Intact Stability for Passenger and Cargo Ships under 100 Metres in Length, adopted by the 4th Extraordinary Session of the IMCO Assembly (Resolution A.167(ES.IV), as amended with respect to ships carrying deck cargoes by Resolution A.206(VII), adopted by the 7th Ordinary Session of the IMCO Assembly).

RECOMMENDATIONS ON INTACT STABILITY FOR PASSENGER AND CARGO SHIPS UNDER 100 METRES IN LENGTH AS AMENDED WITH RESPECT TO SHIPS CARRYING DECK CARGOES

 1. Scope ^

1. The provisions given hereunder are recommended for new decked sea-going passenger and cargo ships (other than fishing vessels) under 100 metres in length.
   
   

2. Administrations are invited to adopt, for all conditions of loading, the stability criteria given in paragraph 5 unless they are satisfied that operating experience justifies departure therefrom.

 2. General precautions against capsizing ^

1.  Compliance with the stability criteria does not ensure immunity against capsizing regardless of the circumstances or absolve the master from his responsibilities. Masters should therefore exercise prudence and good seamanship having regard to the season of the year, weather forecasts and the navigational zone and should take the appropriate action as to speed and course warranted by the prevailing circumstances.
   
   

2. Care should be taken that the cargo allocated to the ship is capable of being stowed so that compliance with the criteria can be achieved. If necessary the amount should be limited to the extent that ballast weight may be required.
   
   
3. Before a voyage commences care should be taken to ensure that the cargo and sizeable pieces of equipment have been properly stowed or lashed so as to minimize the possibility of both longitudinal and lateral shifting while at sea, under the effect of acceleration caused by rolling and pitching.

3. Calculation of stability curves ^

The methods and procedures employed for calculating stability righting arms should be in accordance with Appendix I, and the degree of accuracy obtained should be acceptable to the Administration.

 4. Assessment of compliance with criteria ^

1.  For the purpose of assessing in general whether the criteria are met, stability curves should be drawn for the main loading conditions intended by the owner in respect of the ship’s operations.
   
   

2. If the owner does not supply sufficiently detailed information regarding such loading conditions, calculations should be made for the standard conditions given in Appendix II.
   
   
3. In all cases calculations should be based on the assumptions shown in Appendix II.

 5. Recommended criteria ^

1. The following criteria are recommended for passenger and cargo ships.
    

   1. The area under the righting lever curve (GZ curve) should not be less than 0.055 metre-radians up to q = 30° angle of heel and not less than 0.09 metres-radians up to q = 40° or the angle of flooding q _f^* if this angle is less than 40°.
      
      Additionally, the area under the righting lever curve (GZ curve) between the angles of heel of 30° and 40° or between 30° and q _f, if this angle is less than 40°, should not be less than 0.03 metre-radians.
   2. The righting lever GZ should be at least 0.20 m at an angle of heel equal to or greater than 30°.
   3. The maximum righting arm should occur at an angle of heel preferably exceeding 30° but not less than 25°.
   4. The initial metacentric height GM_o should not be less than 0.15 m.
      
      

2. For ships loaded with timber deck cargoes and provided that the cargo extends longitudinally between superstructures^** transversely for the full beam of the ship after due allowance for a rounded gunwale not exceeding 4 per cent of the breadth of the ship and/or securing the supporting uprights and which remains securely fixed at large angle of heel, an Administration may apply the following criteria in substitution for criteria given in 5.1 above:
   
   

   1. The area under the righting lever (GZ curve) should not be less than 0.08 metre-radians up to q = 40° or the angle of flooding if this angle is less than 40°.
   2. The maximum value of the righting lever (GZ) should be at least 0.25 m.
   3. At all times during a voyage the metacentric height GM_o should be positive after correction for the free surface effects of liquid in tanks and, where appropriate, the absorption of water by the deck cargo and/or ice accretion on the exposed surfaces. Additionally, in the departure condition the metacentric height should be not less than 0.10 m.
   
   
   

3. The following additional criteria are recommended for passenger ships:
   
   

   1. The angle of heel on account of crowding of passengers to one side as defined in Appendix II 2.(II) should not exceed 10°.
   2. The angle of heel on account of turning should not exceed 10° when calculated using the following formula:
      
      D
      
      Where:
      MR = heeling moment in metre-tons
      
       V_o = service speed in metres/second
      
      L = length of ship at waterline in metres
      
      D = displacement in metric tons
      
      d = mean draught in metres
      
      KG = height of centre of gravity above keel in metres
      
      

1.  The criteria mentioned in 5.1, 5.2 and 5.3 above fix minimum values, but no maximum values are recommended. It is advisable to avoid excessive values, since these might lead to acceleration forces which could be prejudicial to the ship, its complement, its equipment and to the safe carriage of the cargo.
   
   

2. Where anti-rolling devices are installed in a ship the Administration should be satisfied that the above criteria can be maintained when the devices are in operation.
   
   
3. A number of influences such as beam wind on ships with large windage area, icing of topsides, water trapped on deck, rolling characteristics, following seas, etc., adversely affect stability and the Administration is advised to take these into account so far as is deemed necessary.
   
   
4. Regard should be paid to the possible adverse effects on stability where certain bulk cargoes are carried. In this connexion attention should be paid to the Code of Safe Practice for Bulk Cargoes. Ships carrying grain in bulk should comply with the criteria mentioned in 5.1 above in addition to the stability requirements in Chapter VI of the International Convention for the Safety of Life at Sea, 1960.

 6. Inclining test ^

1. When construction is finished, each ship should undergo an inclining test, actual displacement and co-ordinates of gravity being determined for the light ship conditions.
   
   

2. The Administration may allow the inclining test of an individual ship to be dispensed with, provided basic stability data are available from the inclining test of a sister ship.

 7. Stability information ^

1.  The master of any ship to which the present Recommendation applies should receive information which will enable him to assess with ease and certainty the stability of his ship in different service conditions. A duplicate of this information should be communicated to the Administration.
   
   

2. Stability information should comprise:
   
   
   1. Stability characteristics of typical loading conditions;
      
      
   2. Information in the form of tables or diagrams which will enable the master to assess the stability of his ship and verify whether it is sufficient in all loading conditions differing from the standard ones. This information should include, in particular, a curve or table giving as a function of the draughts, the required initial metacentric height GM_o (or any other stability parameter) which ensures that the stability is in compliance with the criteria given in 5.1 above;
   
   
   
   3. Information on the proper use of anti-rolling devices if these are installed in the ship;
   
   
   
   4. Additionally, information enabling the ship’s master to determine the initial metacentric height GM_o by means of rolling test as described in the Annex to the Memorandum to Administrations reproduced at Appendix III would be desirable;
   
   
   
   5. Notes on the corrections to be made to the initial metacentric height GM_o to take account of free surface liquids;
   
   
   
   6. For ships carrying timber deck cargoes the Administration may deem it necessary that the master be given information setting out the changes in deck cargo from that shown in the loading conditions, when the permeability of the deck cargo is significantly different from 25 per cent;
   
   
   
   7. For ships carrying timber deck cargoes conditions should be shown indicating the maximum permissible amount of deck cargo having regard to the lightest stowage rate likely to be met in service.

* qf is an angle of heel at which openings in the hull, superstructures or deckhouses which cannot be closed
weathertight immerse. In applying this criterion, small openings through which progressive flooding cannot
take place need not be considered as open.

** Where there is no limiting superstructure at the after end, the timber deck cargo shall extend at least to
the after end of the aftermost hatchway.

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