Damaged stability

Damaged stability is the assessment of a ship’s residual buoyancy and stability after one or more compartments flood. For cargo ships of 80 m and over and all passenger ships, SOLAS Chapter II-1 (the harmonized 2009 regulations) uses the probabilistic method: the attained subdivision index A, the sum of survival probabilities over all postulated damage cases, must be at least the required index R, which scales with ship length and persons carried. Each flooded case is checked for residual GZ range, maximum righting arm, and equilibrium heel against the equilibrium and intermediate-stage criteria. Permeability of each space sets how much volume floods. Older and smaller ships may still use deterministic floodable-length rules.