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(ii) Additional subdivision is provided in way of the step to maintain the same measure of safety as that secured by a plane bulkhead. (iii) The compartment over which the step extends does not exceed the permissible length corresponding to a margin line taken 3 inches (or 76 millimetres) below the step. (/) Where a main transverse bulkhead is recessed or stepped, an equivalent plane bulkhead shall be used in determining the subdivision. (g) If the distance between two adjacent main transverse bulkheads. or their equivalent plane bulkheads, or the distance between the transverse planes passing through the nearest stepped portions of the bulkheads, is less than 10 feet (or 3-05 metres) plus 3 per cent, of the length of the ship, or 35 feet (or 10-67 metres) whichever is the less, only one of these bulkheads shall be regarded as forming part of the subdivision of the ship in accordance with the provisions of Regulation 5. (h) Where a main transverse watertight compartment contains local subdivision and it can be shown to the satisfaction of the Administration that, after any assumed side damage extending over a length of 10 feet (or 3-05 metres) plus 3 per cent, of the length of the ship, or 35 feet (or 10-67 metres) whichever is the less, the whole volume of the main compartment will not be flooded, a proportionate allowance may be made in the permissible length otherwise required for such compartment. In such a case the volume of effective buoyancy assumed on the undamaged side shall not be greater than that assumed on the damaged side. Regulation 7 Stability of Ships in Damaged Condition (a) Sufficient intact stability shall be provided in all service conditions so as to enable the ship to withstand the final stage of flooding of any one main compartment which is required to be within the floodable length. Where two adjacent main compartments are separated by a bulkhead which is stepped under the conditions of subparagraph (e) (i) of Regulation 6, the intact stability shall be adequate to withstand the flooding of those two adjacent main compartments. Where the required factor of subdivision is -50 or less the intact stability shall be adequate to withstand the flooding of any two adjacent main compartments. (b) (i) The requirements of paragraph (a) of this regulation shall be determined by calculations which are in accordance with paragraphs (c), (d) and (/), following, and which take into consideration the proportions and design characteristics of the ship and the arrangement and configuration of the damaged compartments. In making these calculations the ship is to be assumed in the worst anticipated service condition as regards stability. (ii) Where it is proposed to fit decks, inner skins or longitudinal bulkheads of sufficient tightness to seriously restrict the flow of water, the Administration shall be satisfied that proper consideration is given to such restrictions in the calculations.

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