Near collision example

[jonjo]

The TSS sub debate in the "Near Collision" thread is interesting, so I thought the following example might help us all.

A small yacht is crossing a TSS on a southerly heading at right angles in daylight sailing at 5 knots.

A merchant vessel is noticed approaching at 70 degrees off to starboard at about 6 miles distant. By the time the distance has reduced to 3 miles the yacht skipper has decided he will cross ahead by 1/2 a mile and so maintains a steady course.

At 2 miles the captain of the merchant vessel, making 15 knots, also thinks the yacht will pass just head by a 1/4 of a mile but to make sure he alters course 5 degrees to port. <Event 1>

At a distance of 1/4 of a mile nearly ahead of the merchant vessel the yacht skipper panics, turns 180 degrees and engages his engine, this prompts the merchant captain to turn 20 degrees to starboard. The action by the merchant vessel has to be short lived because 2 miles behind on his aft starboard quarter another merchant vessel is slowly over taking. <Event 2>


I think some on Scuttlebutt would interpret both events as impeding another vessel in a TSS, others would claim that Event 1 is routine and not significant.

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[boatmike]

If I read you right there is no argument. Both vessels had decided there was no risk and should stand on. Bravo the ship for making it even more safe by a slight change of course. In coming about the yacht was totally at fault. Don't see how it could be interpreted differently. If he wanted to start his engine to increase his speed OK thats fine. Going about was wrong TSS or not. Key issue as far as colregs is concerned is that risk of collision did not exist therefore no need to give way. Prudent action was taken by the ship. Prudent action by the yacht could be argued increase speed to ensure well clear by motor sailing (probably what I would do as the wind could die at any time) No action was actually called for by either vessel technically though if a risk of collision did not exist.

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[bedouin]

As I'm sure you realise, my view on the impeding issue is that in the absence of other factors limiting the ability of the merchant vessel to manouevre then the yacht by standing on has met it's requirement to give the other vessel sufficient sea room for safe passage. So IMHO, up to the end of event 1 everyone seems to have been behaving correctly.

IMHO the yacht skipper is totally wrong in making a 180, as it would be an inappropriate action even without it being a TSS and a 2nd ship limiting the actions of the 1st. (My advice for a "panic" response is to turn on to the same heading as the other vessel.)

NB if the figures you give are correct, then by the time the merchant ship was within 1/4 mile of the yacht then the yacht should have been 5 degrees on the starboard bow - which makes the yacht skipper's action even worse.

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[kimhollamby]

Added thoughts

a) any turn to port potentially suspect as an action (please don't read my post in other thread!)

b) many merchant ships consider a CPA of 1nm or less as a potential collision risk.

c) an estmated pass ahead of a commercial ship by just half-a-mile is a potentially risky judgement at the best of times?

One way perhaps of intepreting 'do not impede' in Rules 9 and 10 is to never place your boat in a position where a watch officer in a ship is considering any kind of action on your behalf (assuming he is not on the loo or making coffee) and therefore holding course but slowing the boat, or turning 360°s (to present a static ARPA target), well before issues about passing close ahead present themselves, might be better?

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[Koeketiene]

Re: Added thoughts

Very sensible comments. To this I would like to add: above all - DON'T PANIC!!!

Whilst, all IMHO of course, regularly recurring discussions on the subject of crossing any TSS may heighten people's awareness on this subject; it may also have a certain adverse effect. It may cause less adventurous skippers to "freak out" in the TSS when faced with such a, let's face it', relatively straightforward situation.

After all, how many accidents happen in a TTS? Last year there was one - well publicised. The main cause of the accident was the yacht's skipper’s wrong interpretation of his radar picture. Just goes to show that all the modern gizmos in the world won't save you if you don't know how to use them. Get trained, people!!!


<hr width=100% size=1>Experience is a good teacher, but she sends in terrific bills.

 

[peterb]

Re: Added thoughts

With respect, that accident was not in a TSS.

I always suspect that the IMO were aware of the Solent standard of Colregs awareness, so arranged a gap in the TSS just where Solent sailors would be crossing the shipping lanes. /forums/images/icons/wink.gif

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[Talbot]

I think your scenario is a tad suspect, in the last phase of it when the yacht is at 1/4 mile right ahead, you reckon that the merchant vessel will notice the alteration and make a 20 degree alteration. The bridges on most big merchant ships are so well placed that most of them would not even see you at 1/2 mile right ahead unless they were on their bridge wing (pretty unlikely).

Regardless of this, any yacht that places himself inside 1/2 mile right ahead of a merchant vessel must have a death wish or some enormous engine ready to start and whizz out of the way .

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[peterb]

Have a look at <A target="_blank" HREF=http://www.dft.gov.uk/stellent/groups/dft_maritimesafety/documents/page/dft_masafety_030084.pdf>this</A> and you'll realise that it may all be a bit theoretical. The examples on pages 19, 20 and 22 are particularly interesting.

It's a pdf document; you'll need Adobe Acrobat and it's not very fast in loading. Don't bother with the annexes, there's nothing there worth reading for yachtsmen.

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[TerryG]

Personally, I always turn towards the ship when on a collision course and then keep pointing towards them until i'm back on my original course. Can anyone find anything wrong with this manouvre (ie: it's always worked in 30 years sailing But . . . . . . .?)

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[jonjo]

This sounds effective but would it be legal in a TSS?

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[TerryG]

Dunno, i've never sailed one.

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[TheBoatman]

I always turn towards them as well but I tend to run parallel to their course and don't close them, then when it's obvious that we are going to miss I return to course.

On a slightly different note isn't it a shame that there is no sound /light signal in the ColRegs that could be used by vessels that means "I've seen and understand your intentions keep going like you are"

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[MrG]

We will adapt our course to whatever suits the situation best, whether that be
running parallel, aiming for the stern until back on course, etc.

However this previous comment
"I've seen and understand your intentions keep going like you are"

I thought we already had that in place - we make clear and discernable course changes - this leaves no doubt as to our intentions.



<hr width=100% size=1><font color=blue>Regards Mark

 

[Bergman]

Sounds more a question of when rather than what

I cannot believe that an estimate of passing within half a mile can be sensibly made at a range of 7 miles. I also doubt that the 5 degree course change would have been visible to the yacht

Event one was really the last point at which something should have been done. A plan which involves passing 400 yards across the front of a ship doing 15 knots cannot be the right decision. Almost anything else would have been a safer choice. Perhaps heave to and put the kettle on or dump the main for a few seconds, anything really but not so close in front of him. Even with electronic gear you cannot predict variations in wind strength, distraction of helmsman (highly probable in the circumstances) or anything else which may slow the yacht fractionally.

Any subsequent decision is really little less than a panic move to save the yacht and has little to do with colregs.

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[jonjo]

I agree with your comments but unfortunately you did not read my scenario properly.

The yacht skipper makes the 1/2 mile pass ahead estimate at 3 miles.

The scenario does not involve the yacht skipper noticing the 5 degree course change.

The merchant vessel captain makes the 1/4 estimate, the yacht skipper proceeds on the basis of his 1/2 mile estimate.

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[Its_Only_Money]

"On a slightly different note isn't it a shame that there is no sound /light signal in the ColRegs that could be used by vessels that means "I've seen and understand your intentions keep going like you are" "

I suspect that it would be based on a false assumption (ie that you truly know what the other vessels intentions are - he may be about to crash stop because of yet another vessel coming up on his opposite side from you, out of your visual angles and in your radar blind spot for all you know), and to issue that signal may lead the other skipper into a false comfort zone by indicating to him that you think you know what his intentions are......

<hr width=100% size=1>Rgds

Simon
Its Only Money
Fairline Sprint
Solent-based

 

[Bergman]

Ooops - always read the question!

But you did say by the time he's 2 miles away.

I didn't intend to say the 5 deg change affected the yachts decision making. My thoughts were that it demonstrates why a significant course change is necessary to indicate intention.

The more I think about it the more puzzled I get by this course change. If my mental arithmatic is right a 5 deg change at a range of 2 miles will make a difference of around 5/30ths of a mile or 333 yards.

This would indicate that the original passing distance was only about 100yds rather than 1/4 mile

If this is the case then the ships original estimate of 1/4 mile was somewhat optmistic and the yachts estimate of 1/2 a mile was a long way out.

Had the ship held his course the point of collision would have been 1/3 mile further along the yachts course than was the case. This would represent some 4 minutes sailing time for the yacht.

The yacht did the panic turn 1/4 mile ahead of the ship or 1 minutes sailing time ahead of him.

Had the ship held course I would suggest the ship would have sailed 3 minutes before the courses crossed. Or to put it another way would have been 3/4 mile to port of the yacht.

( Best check these numbers, its all done in me head)

Not sure what this demonstrates except perhaps why a turn to starboard by the ship is a better bet although I suppose in a mirror image situation that would not be true.

I suppose we can agree that:

1 making very clear very early that you are passing astern is the safest bet even if you are stand on vessel (although I am uncomfortable with this)

2 accurate estimate by eye at 6 miles range is virtually impossible

3 even at 2 miles accuracy is limited particularly where there is a significant speed differential



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[waverider]

Jonjo I remember this scenario being similar to an incident in a recent MAIB report that was printed in PBO No448 pg 68!..........Losing The Plot....PBO titled it!

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[jonjo]

> PBO No448 pg 68!..........Losing The Plot....PBO titled it

This is a surprise I thought I was being original and had a future as the internet’s alternative to Tom Cunliffe, I will look up the PBO aritcle. Thanks.

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[waverider]

Yep straight up jonjo....I'm not pulling your leg either m8.

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