Question 1

Your vessel has a calculated GM of 0.4m at the start of a winter North Atlantic passage in ballast condition. A weather routing service advises significant gale force conditions en route. Is 0.4m GM adequate and what additional stability considerations apply?

Accepted Answer

GM 0.4M WINTER NORTH ATLANTIC — STABILITY ASSESSMENT: 0.4m GM is a LOW GM for a winter North Atlantic passage. IS IT ADEQUATE? The SOLAS Intact Stability Code (MSC.267(85)) requires: minimum initial GM of 0.15m. 0.4m exceeds the minimum. BUT THE MINIMUM IS NOT THE TARGET. ADDITIONAL FACTORS FOR THIS VOYAGE: (1) STATIC vs DYNAMIC STABILITY: static GM is the initial resistance to inclination. Dynamic stability is the WORK DONE by the righting arm as the vessel heels — the area under the GZ curve. A vessel with GM = 0.4m but a narrow GZ curve (peak GZ at 15° only) may be less safe than a vessel with GM = 0.3m and a wide, flat GZ curve reaching 45°; (2) WAVE HEELING MOMENT: in Force 10-11 conditions, wind heeling moment must be assessed. The IS Code requires a heeling moment calculation for the maximum wind speed expected. At 0.4m GM and full ballast windage area — this calculation must be made and the stability must remain adequate; (3) ICE ACCRETION: in the North Atlantic in winter — ice formation on superstructure and deck equipment is possible. Ice raises G. Even 10-15 tonnes of ice on the upper works can significantly affect a vessel with 0.4m GM; (4) WATER ABSORPTION: if timber or other water-absorbing cargo on deck — water absorption increases weight at height; (5) HEAVY WEATHER BALLASTING: consider increasing ballast to improve GM before departure. Many vessels in ballast condition can increase ballast to improve stability at the cost of extra fuel consumption; (6) WEATHER ROUTING: request a route that minimises exposure to the worst conditions. A slightly longer route in safer weather may be preferable to a direct route in severe weather with marginal stability. SOLAS minimum GM (option B): the 0.15m minimum is a regulatory floor — not a seagoing standard. Vessels operating in severe weather require significantly more. Many classification societies and organisations recommend 0.30m minimum for ocean voyages and higher for high-latitude winter passages. The "minimum" protects against total instability; professional seamanship requires a safety margin above the minimum. Ballast is safest? (option C): not necessarily. A vessel in high ballast with a high centre of gravity (ballast tanks at top of double bottom) may have worse stability than the same vessel in loaded condition with a lower G. Ballast condition stability must be calculated — it is not automatically "safer." Some vessels have very poor stability in high ballast condition and require additional ballast or redistributed ballast. Trim correction (option D): trim (difference in draught fore and aft) affects the metacentre position (KM) — but the effect is typically small and complex. "2-metre trim improves GM" is not a reliable rule and is not an approved method for correcting low GM. The correct approach is to ballast more tanks (lower G) or depart with cargo that provides adequate stability. Ice accretion: the IS Code Appendix covers icing allowances. In areas with icing risk, the stability calculation must include the estimated ice weight. For North Atlantic winter voyages north of 60°N, icing allowance should be applied. This can significantly reduce the available GM.

Question 2

You are Master of a 35,000 GT bulk carrier in the North Atlantic in a Force 11 storm. The vessel is experiencing heavy slamming and two deck crew have been injured. Speed has been reduced to 5 knots. Charterer is demanding continued passage. What is your command decision?

Accepted Answer

COMMAND DECISION — FORCE 11 HEAVY WEATHER: SOLAS V/34 and ISM Code Section 5.3 give the master OVERRIDING AUTHORITY on safety decisions. The charterer cannot override this. ASSESSMENT: (1) STRUCTURAL INTEGRITY: at 35,000 GT bulk carrier in Force 11 — slamming at 5 knots indicates the vessel is taking green water over the bow. Slamming causes cumulative structural fatigue and can cause hatch cover failure — potentially fatal for a bulk carrier. Inspect hatch covers and deck plating; (2) CREW SAFETY: two crew injured — this is already a safety failure. Continuing in Force 11 with injuries risks further crew harm. The master must cease activities that are causing injury; (3) CARGO INTEGRITY: bulk cargo shift risk in extreme rolling. Check cargo for signs of movement or liquefaction; (4) STABILITY: check the stability situation — in heavy weather, free surface effects from ballast movement and deck water may affect GM; COMMAND OPTIONS: (a) HEAVE-TO: turn the vessel into the sea (head-to-sea or bow slightly off) and reduce speed to minimum steerage. This dramatically reduces slamming and deck cargo stress. The vessel makes minimal progress but safety is maximised; (b) RUN WITH THE SEA: in some sea states, running before the sea at controlled speed reduces slamming but risks broaching; (c) SEEK PORT OF REFUGE: assess the nearest available port of refuge and request entry. The port of refuge decision involves: vessel structural condition; crew condition; weather forecast (will it moderate?); port availability and shelter quality; (4) COMMUNICATION: inform the charterer in writing. State the safety grounds under ISM Section 5.3. Document everything. The charterer's commercial demands do not override the master's safety authority. The command decision in heavy weather is one of the most important tests of professional judgment. It is not binary (proceed vs stop) — it requires a continuous, dynamic assessment. The key factors: (1) structural condition of the vessel; (2) crew safety and welfare; (3) cargo condition; (4) weather forecast; (5) proximity to shelter; (6) vessel's sea-keeping characteristics. Charterer authority (option B): the charterer has NO authority over safety decisions. This is stated explicitly in ISM Section 5.3 and backed by SOLAS V/34. A master who proceeds in conditions causing structural damage and crew injury at the charterer's insistence has abandoned their STCW and ISM responsibilities. The forced heave-to (option C): not necessarily the right decision either. A well-found vessel with experienced crew in open sea may be able to make headway in Force 11. The decision depends on: (a) the vessel's actual condition; (b) the forecast trend; (c) whether heaving-to creates its own hazards (proximity to lee shore, traffic). MAYDAY (option D): Force 11 + slamming + two injuries is NOT automatically a MAYDAY situation. The vessel is navigating and not in immediate danger of sinking. A MAYDAY is appropriate only when the vessel is in imminent danger of sinking or a life is in immediate danger. The correct communication is: UKMTO/MRCC notification if seeking assistance; the passage/condition report to company; MAYDAY only if the situation genuinely becomes life-threatening. Documentation of the command decision: write every assessment, every communication with the charterer, and every action taken in the log. If a formal inquiry follows — this documentation demonstrates the master's professional decision-making.

Question 3

After 36 hours in Force 10-11 conditions, your vessel has shifted cargo and developed a 7° permanent list to starboard. You are 200nm from the Azores. What is your port of refuge decision process?

Accepted Answer

PORT OF REFUGE DECISION — MASTER: A 7° permanent list indicates the centre of gravity has shifted — either cargo movement or flooding. This is a SERIOUS STABILITY SITUATION requiring immediate port of refuge consideration. DECISION PROCESS: (1) ASSESS THE CAUSE: is the list from: (a) Cargo shift (if so — is it getting worse? Can it shift further in continuing heavy weather?); (b) Flooding (is water making its way in?); (c) Free surface from shifted ballast or tank changes? (2) ASSESS THE TREND: is the list stable at 7° or worsening? A stable 7° list may be survivable in moderate conditions. A worsening list in Force 10-11 may lead to capsize; (3) STABILITY CALCULATION: run the loadicator with the assumed shifted cargo weight and position. What is the current effective GM? What is the righting arm (GZ) at current heel? Does the vessel have adequate stability reserve?; (4) WEATHER FORECAST: will the storm moderate within 6-12 hours? If yes — can the vessel safely ride it out? If no or uncertain — proceed to port of refuge; (5) ASSESS THE REFUGE PORT: (a) Can the Azores (Horta, Terceira) receive a vessel with 7° list in the current sea state? (b) Is there adequate shelter in the port? (c) Can cargo be restowed there? (d) Is a tug available for assistance if manoeuvring is compromised by the list?; (6) DECLARATION TO COASTAL STATE: contact the Portuguese maritime authority (MRCC Delgada) — request port of refuge entry. Provide vessel condition, stability status, list, cargo shift; (7) PAN PAN: in a vessel with compromised stability, transmit a PAN PAN (urgency) signal. This alerts maritime authorities without the formality of MAYDAY. 7° list from cargo shift: this is a serious situation requiring IMMEDIATE action — but not necessarily abandon ship. The master's response must be measured and analytical. At 7° list, the vessel's GZ curve has been shifted. The question is: what is the residual stability reserve? A vessel with 1.5m GM shifted to 7° may have adequate reserve. A vessel with 0.3m GM shifted to 7° is dangerously close to capsizing. The loadicator gives this answer. The worsening trend: if the list is worsening (was 3°, now 7°, still rolling heavily) — immediate port of refuge is required. The cargo will continue to shift in heavy weather until equilibrium at the new angle or until the vessel capsizes. 7° being "manageable" (option B): depends entirely on the stability reserve. This is not a generic answer — it requires calculation. Oral examiners want to see that the master uses the loadicator and makes a data-driven decision, not a "seems OK" assessment. Abandon ship (option C): premature. A 7° list in heavy weather is dangerous but not necessarily a capsizing situation. Abandoning ship in Force 10-11 seas is enormously dangerous — survival craft in these conditions have capsized. The master does not abandon the vessel unless the remaining-on-board option is worse than abandonment. Counter-ballasting (option D): this addresses the list symptom but not the cause. If the cargo has shifted — adding starboard ballast may correct the list angle but it adds weight and reduces freeboard. In continuing heavy weather, the cargo may shift further, making the next correction impossible. The longer-term solution is port of refuge and cargo restowage.