Vessel Stability & Structural Integrity Flashcards

To reconstruct a vessel's loading condition at the time of a sinking, a CMI investigator should obtain which combination of evidence?

Answer: Cargo manifests, tank sounding logs, fuel consumption records, and witness accounts of the vessel's loading

Reconstructing the actual loading condition requires synthesizing multiple operational records—cargo documentation, tank soundings, consumable logs, and witness observations—because design documents reflect approved conditions, not what was actually aboard.

In a marine investigation, 'progressive flooding' is defined as:

Answer: Sequential flooding of compartments as watertight boundaries successively fail

Progressive flooding describes the sequential loss of compartments as water breaches successive watertight boundaries—bulkheads, doors, hatches, and pipes—ultimately overwhelming the vessel's reserve buoyancy and stability.

What is the significance of the 'angle of loll' in a stability investigation?

Answer: It is the angle at which a vessel with negative initial GM reaches a precarious stable equilibrium on its side

A vessel with negative initial GM is unstable when upright and will heel until it reaches the angle of loll, where the righting lever from increasing waterplane area restores momentary equilibrium—but this equilibrium is fragile and the vessel may capsize to either side.

In capsizing investigations, the 'angle of vanishing stability' (AVS) is a critical threshold because:

Answer: Beyond this angle the righting lever becomes negative, meaning the vessel cannot self-right and capsize is inevitable

The AVS (the second zero crossing of the GZ curve) is the point of no return—beyond it, the GZ lever is negative and gravity assists capsizing rather than resisting it, so the vessel cannot recover without external intervention.

Damage stability calculations performed during a marine investigation are used to determine:

Answer: Whether the vessel could remain afloat and maintain positive stability with flooding in one or more specified compartments

Damage stability calculations model the vessel's floatability and residual stability after flooding designated compartments, which is essential for determining whether the vessel's design met survivability standards and whether the actual casualty was predictable.

When a vessel's cargo suddenly shifts transversely during heavy weather, the immediate stability consequence is:

Answer: A permanent list toward the shifted cargo as the center of gravity moves off-centerline

A transverse cargo shift moves the vessel's center of gravity toward the low side, creating a static heeling moment that results in a permanent list, reducing the righting arm on the listing side and increasing capsize risk in subsequent rolling.

Under the ISM Code, what stability-related documentation should a CMI investigator expect to find aboard a well-managed vessel?

Answer: Approved stability booklets, loading computer records, and stability management procedures within the Safety Management System (SMS)

The ISM Code requires a documented Safety Management System covering all critical operational aspects; for stability, this means approved stability booklets, records from any loading computer, and SMS procedures describing how loading and stability are verified before departure.