4.30 Enhanced Survivability for Vessels provided with Davit Launched Liferafts or Davit Launched Liferafts and Marine Evacuation Systems in lieu of Lifeboats in accordance with Annex 3:

(1) In addition to meeting the requirements of SOLAS II-1 Part B-1 Regulation 6 and 7 and the requirements of Part II or of Part VI of this Chapter, as appropriate, the following additional requirements should be met in all loading conditions following the flooding of any two adjacent compartments-

• (a) Except where paragraph 4.30(1)(b) applies,_in the final stage of flooding and also after equalisation measures, if any. have been taken shall be as follows-

  • (i) the residual stability should be such that any angle of equilibrium does not exceed 7° from the upright, the resulting righting lever (GZ) curve has a range to down-flooding of at least 7° beyond any angle of equilibrium; and

  • (ii) the residual stability should be such that the vessel has a positive GZ of not less than 0.05 metres and a GM of not less than 0.05 metres; and

  • (iii) the margin line should not be immersed in the final stage of flooding except where (b) is complied with,

• (b) the Administration may permit the margin line to be immersed in the final stage of flooding provided that the following conditions are satisfied-

  • (i) with the exception of subparagraph 4.30(1)(a)(iii), all other provisions of this section are complied with in full;

  • (ii) no progressive flooding can occur;

  • (iii) no escape routes, muster stations or survival craft locations are immersed;

  • (iv) all essential services, such as survival craft launching appliances, emergency generators,, bilge systems, fire fighting systems and communications are available at all stages of flooding; and

  • (v) no controls intended for the operation of watertight doors, equalisation devices, or valves on piping or on ventilation ducts intended to maintain the integrity of watertight bulkheads from above the bulkhead deck, become inaccessible or inoperable,

• (c) in intermediate stages of flooding the angle of heel should not exceed 20° and the maximum GZ shall be at least 0.03 metres and the range of positive righting levers shall be at least 5° and progressive flooding is not to take place within this positive range; and

• (d) for the purposes of this section damage should be assumed to occur anywhere in the length of the vessel.

(2) The assumed extent of damage shall be as follows-

• (a) in the longitudinal extent, 3 metres plus 3% of the length (L) of the ship but need not exceed 10% of length, or 11 metres, whichever is the less, provided that where the required factor of subdivision is 0.33 or less the assumed longitudinal extent of damage shall be increased as necessary so as to include any two consecutive main transverse watertight bulkheads;

• (b) in the transverse extent (measured inboard from the ship's side, at right angles to the centreline at the level of the deepest subdivision load line) a distance of one fifth of the breadth of the ship, as defined in section 1.3; and

• (c) in the vertical extent: from the base line upwards without limit,

• provided that if any damage of lesser extent than that indicated in this paragraph would result in a more severe condition regarding heel or loss of metacentric height, such damage shall be assumed in the calculations.