SUB-COMMITTEE ON STABILITY AND LOAD LINES AND ON ...

Ref.: 391/09 and 520/09
BSU
Bundesstelle für Seeunfalluntersuchung
Federal Bureau of Maritime Casualty Investigation
The righting levers curve calculated by the TUHH with the load condition 'Ballast and
little cargo' on the day of the accident is shown below in Figure 17:
ACCIDENT
Figure 17: Righting lever curve
With a GM of more than 5.60 m, the vessel's stability in smooth water is more than
adequate.
To examine the overall risk of parametrically excited roll oscillations, too, by way of
example the righting levers were calculated at the midship section for the conditions
'trough' and 'crest' using an equivalent wave. For an equivalent wave which
corresponded approximately to the wave on the day of the accident, a sine wave of
140 m in length (about 9.5 s) and 7 m in height was chosen. The calculations
revealed that the differences between the crest and trough situation and also the
comparison with the smooth water calculation were very low and the curves do not
differ considerably. These slight variations are caused by the fact that the vessel was
underway with a draught which was much shallower than the moulded draught. In the
case of the crest, this results in a degree of additional hydrostatical stability; on the
other hand, this floating condition coupled with a prominent bow flare causes the
vessel to become prone to the effect of direct swell moments especially in the aft
area. However, the result shows that the parametrically induced roll moments are
relatively low. Therefore, the direct exciting moments from the swell in conjunction
with the particular sea-going behaviour of modern container vessels at very shallow
draught can be viewed as the actual cause of the accident.
3.2.8.2 Investigation of the roll oscillation
Based on witness statements, the vessel must have experienced a roll angle of 35°
and thus considerable transverse accelerations on the bridge. Therefore, in addition
to the present stability analysis, the roll behaviour was considered with the E4ROLLS
simulation program at TUHH. Based on the shape of the hull and the distribution of
ballast, the linear transfer functions were calculated. The cuboid in the diagram below
corresponds to an equivalent that has the same mass inertia.
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