Your examiner asks: "What must a vessel's Stability Booklet contain, and when must it be reapproved?" Give the SOLAS Chapter II-1 requirements.

A. The Stability Booklet must contain: lightship particulars (displacement, KG, LCG) from the inclining experiment; hydrostatic curves and cross-curves of stability; GZ curves for loaded conditions including departure and arrival, full load, partial load, and ballast; draught and trim tables; loading guidance and maximum permissible KG or minimum GM curves; any special restrictions. It must be reapproved by the flag state or RO after: major structural alteration; conversion; or when the lightship particulars differ significantly from the approved booklet.

B. The Stability Booklet is reissued every 5 years as part of the class renewal survey. It only needs to contain calculations for the full load condition.

C. The Stability Booklet must be submitted to the port state authority at each port of call. PSC officers retain a copy at each port.

D. Stability Booklets are produced by the ship designer only. The master is not required to update or verify the booklet during the vessel's life.

A. GM is the distance between the keel and the metacentre. A higher GM always means a safer, more stable vessel regardless of its magnitude.

B. GM is always a positive value. A negative GM means the ship is overloaded and must discharge cargo immediately.

C. GM (metacentric height) is the distance between the centre of gravity (G) and the metacentre (M). A positive GM (M above G) indicates stable equilibrium — the vessel will right itself when heeled. A very low GM risks loll, slow period of roll, and potential capsize. A very high GM (stiff ship) causes a rapid, violent rolling motion that can create excessive dynamic loads on cargo, structures, and crew — which can be as dangerous as low stability.

D. GM only applies to loaded conditions. In ballast, stability is assessed using only the KG value.

A. The IMO IS Code applies to new vessels only. Older vessels built before 2010 comply with the 1966 Load Lines convention stability requirements only.

B. The minimum GM under all criteria is 0.5 metres. The GZ curve must reach a maximum of at least 0.5m at any angle between 20 and 60 degrees.

C. The only IMO requirement is that the angle of vanishing stability must exceed 60 degrees. Area under the curve and initial GM are national flag state requirements only.

D. Key GZ curve features: range of stability (angle at which GZ returns to zero); maximum GZ and angle of maximum GZ; area under the curve (dynamical stability). IMO IS Code 2008 criteria: area 0-30 degrees minimum 0.055 metre-radians; area 0-40 degrees (or to flooding angle if less than 40) minimum 0.090 metre-radians; area 30-40 degrees minimum 0.030 metre-radians; maximum GZ at least 0.200 metres at 30 degrees or greater; initial GM not less than 0.150 metres.