Page 41 - CHIRP annual digest 2016.pdf

-CHIRPAnnual Digest 2016

Scenario 1: Overtaking It follows that apart from the right to stand on provided
Vessel A – a VLCC or Cape Size bulk carrier proceeding at in Rule 13(a), A should not be relied upon to take rapid
around 12 knots in or approaching a routing system and/or avoiding action.
a deep draught restricted channel; being overtaken by
Vessel B – a medium sized or large container vessel It is often reported that B makes an alteration of course
proceeding at 20 knots overtaking Vessel A. to port to leave A on the starboard side. The two vessels
then very quickly draw level but then they are often
navigating in disconcertingly close proximity. The large
The large differential between the two vessels’ speeds
means that this scenario can develop very quickly. differential of speed rapidly causes B to draw ahead but it
is also possible that the two large hulls might be close
enough to experience hydrodynamic interaction. It is
Besides being the stand on vessel the large vessel A is suspected that this may be the reality where reports of
encumbered by its speed, its draught and the need to
“aggressive” actions by vessels in this situation have been
maintain sufficient under-keel clearance. Its large displace - submitted. Interaction can become dangerous in that the
ment also causes a sizeable delay on any manoeuvring,
effect of the rudder is increasingly nullified and can
especially since the ratio of engine power to displacement ultimately be lost completely with consequential loss of
is likely to be much smaller in A than it is in B.
control, usually of the faster vessel, followed by the
drawing together of the hulls into a collision.
The overtaking vessel could also be encumbered by
draught although it is unlikely to be as critical as it is for The ongoing situation however also presents problems as
A. the overtaking vessel, which remains responsible for

D
C
E

WPA

A

✗ ✔

B

Figure 1: Situation involving multiple encounters

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