97002 Closest Point of Approach

Closest Point of Approach
Singapore Straits
Report No. 97002

I am a keen reader of your MARS reports which regrettably appear to mirrorthe lowering abilities of ships' staff we are now facing. I also frequentlytransit the Singapore Straits where these lowering abilities of not onlyOfficers of the Watch but also certain Shipmasters are all too evident.On a routine visit to the bridge, I noticed a gas tanker overtaking ownship quite close on the starboard quarter. A glance at the ARPA revealeda CPA of 0.5 miles. The OOW said he had tried to call the offending vesselbut had not had any response. After several calls by myself on the VHF,the person in charge on the other vessel answered. I requested that he altercourse to achieve a CPA of at least 1 mile. This he readily agreed to do.I might have been mistaken but I got the impression that he was quite gladto have someone to tell him what to do! At the time, it was broad daylightwith a calm sea and perfect visibility with no other vessels in the nearvicinity. In fact both vessels had a large area in which to manoeuvre. Thiswas possibly a case of trying to adhere to a course line no matter whathappened. This phenomenon seems to be a direct result of widespread GPSusage.

The second incident concerned much the same thing but in this case itwas my own vessel which was very much in the wrong. We were steering almostdue east at about 1930 and it was dark. I happened to look out of my cabinwindow and saw the red sidelight and three vertical white lights of a vesseltowing close on the port bow. I was soon on the bridge and told the OOWput the wheel to starboard. A glance at the radar showed the tug to be steeringabout 300 degrees and with a CPA of about 0.5 miles. The vessel which wasbeing towed was virtually unlit and could only vaguely be seen. My OOW seemedsurprised by my actions and did not show any concern that a CPA of 0.5 mileswas anything to worry about. I pointed out to him that this tow was crossingour bow, that there was a good chance that the tow was yawing about considerably,that we were yawing due to a quarterly sea, and that in these circumstancesa CPA of 0.5 miles was unacceptable. Surprisingly the tug carried on regardlessand neither signalled or tried to contact us on VHF. Perhaps he felt thatthis small CPA was acceptable as well.

ARPA is an excellent tool for the navigator but regrettably similar incidentsare all too common today. To some navigators it would appear that any CPAabove zero is acceptable. They do not appear to take into account any possibleinaccuracies in the ARPA system or the possibilities of failure in the shipspropulsion or steering systems. This ship's Standing Orders include thestatement "an ARPA CPA of less than 1 mile is to be considered a collisionsituation and a CPA of less than three miles a close quarters situationand appropriate action taken". These Standing Orders were re-iteratedto the other watchkeeping officers. A "blackout" occurred on thisvessel not long after the above incidents. This served as a very good exampleto all concerned as to why we need to keep to a reasonable CPA wheneverpossible.