Collision Avoidance, Cones of Uncertainty, and Appropriate CPA

[David M]

I AM a commercial mariner and I communicate by radio numerous times every time I get underway. Much of these communications are for making passing arrangement so there is no doubt whatsoever which side we plan to pass, cross or overtake.

Communicating and making a definite plan is the most predictable and therefore the safest way of passing. Creating angles so as to make it (hopefully) clear which side we wish to pass and figuring out CPA's is less predictable although that can be safe as well. We are not ignoring the Rules at all when making passing arrangement. For example we will typically pass port to port when it is close. Making passing arrangements by radio is also in the Rules!...it is indeed.

I don't know what an MCA is. So I went to an acronym finder and went through hundreds of acronyms with MCA. (Maritime & Coast Guard Agency in the UK?) Avoiding acronyms when everyone who reads this may not know what the acronym means is always helpful. It only takes a few extra seconds to fully spell out what you wish to communicate. I am sometimes guilty of it as well with all my oceanography acronyms. I can forget that those not in the business may not know what the hell I am talking about

[Quebramar]

Originally Posted by conachair

Not always though - the MCA would rather you didn't and stuck to the colregs as much as possible -
https://www.gov.uk/government/upload...io_and_AIS.pdf



Stick to colregs and calling VHF shouldn't be needed much anyway. In the channel they'll sometimes ignore you anyway - I'm sure there was a link ages ago regarding one shipping line telling crew to keep off the VHF unless really necessary. Can't find it now.

Calling on the VHF in open seas may not be a big deal, but try in anything less than 50NM of Dover.... So better go for prevention (Colregs) rather than cure (radio), no?

[Dockhead]

Originally Posted by David M

Communicating and making a definite plan is the most predictable and therefore the safest way of passing.

I don't know what an MCA is. Avoiding acronyms when everyone who reads this may not know what the acronym means is always helpful. It only takes a few extra seconds to fully spell out what you wish to communicate.

The MCA is the Maritime and Coastguard Agency of the United Kingdom, the world's preeminent maritime authority, whose guidance notes are studied all over the world. One of the vestiges of Britannia's ruling the waves. We Yanks have nothing to compare with it.

[conachair]

Originally Posted by David M

I don't know what an MCA is.

Link was a bit of a giveaway

I AM a commercial mariner and I communicate by radio numerous times every time I get underway. Much of these communications are for making passing arrangement so there is no doubt whatsoever which side we plan to pass, cross or overtake.

Is that more in pilotage waters? Sort of thing you'll her all the time in the Thames estuary (You happy with green to green ) but not nearly so much out in more open waters like the channel.

[Jim Cate]

I wonder if the MCA's aversion to radio contact was formed in pre AIS days, when it was often completely unclear what vessel was calling what other vessel? When calling by specific vessel name, this uncertainty is eliminated and confusion reduced.

Sailing in pilotage waters in Australia, VHF communictions are often initiated by the merchant vessel. I suspect the pilots know how ignorant WAFIs are about COLREGS and wish to circumvent close calls well in advance.

Jim

[Dockhead]

Originally Posted by Jim Cate

I wonder if the MCA's aversion to radio contact was formed in pre AIS days, when it was often completely unclear what vessel was calling what other vessel? When calling by specific vessel name, this uncertainty is eliminated and confusion reduced.

Sailing in pilotage waters in Australia, VHF communictions are often initiated by the merchant vessel. I suspect the pilots know how ignorant WAFIs are about COLREGS and wish to circumvent close calls well in advance.

Jim

Yes, the MCA note certainly has the danger of communicating with the wrong vessel, front and center. That danger is much less now.

But still -- you have to agree with the basic point -- why call and make up an ad hoc crossing arrangement, if everyone could just follow the rules?

The point is that yakking on the radio shouldn't be a SUBSTITUTE for knowing the rules.

But in case of doubt or something not clear or typical -- I'm all in favor of it.

[TJ D]

Originally Posted by Dockhead

Yes, the MCA note certainly has the danger of communicating with the wrong vessel, front and center. That danger is much less now.

But still -- you have to agree with the basic point -- why call and make up an ad hoc crossing arrangement, if everyone could just follow the rules?

The point is that yakking on the radio shouldn't be a SUBSTITUTE for knowing the rules.

But in case of doubt or something not clear or typical -- I'm all in favor of it.

I agree with this, but I think that the VHF is getting short shrift here. I call commercial vessels (while sailing) relatively frequently, in one situation in particular.

When I'm the stand-on vessel, under sail, I'm not really meeting the colregs requirement to maintain my course and speed, particularly speed. My boat speed in variable winds, with some surfing thrown in, may vary from 7 knots into the teens. Not everyone has variations like this, but we all do to some degree.

Therefore, it makes the watchstander's job on the ship pretty hard. In a lull, he might be passing ahead just fine, then I catch a 20 minute increase in wind, and his solution is right out the window.

In these cases, I'll often call them and invite them to just maintain their course and speed, since I'm all over the road, so to speak. It makes them happy, and I now have the freedom to chase puffs and waves that I'm looking for.

That is something to consider- are you ever really properly 'standing on' when you're sailing and your speed varies a lot?

Under power, I typically don't do this, or when sailing in very steady conditions, but there are times when it's much easier for all involved to just make a call to the poor guy watching his ARPA and let him know you've got it under control and not to worry about you.

[Lodesman]

Originally Posted by Dockhead

One of the fast Brittany Ferry cats -- monstrous huge things making 40 knots -- ran down a fishing boat and killed a bunch of fishermen, a couple of years ago, somewhere in the Channel Islands. I haven't seen the incident report, but I'm willing to bet dollars to doughnuts that this would be one of those rare cases where the ferry was 100% responsible, due to the total lack of any practical thing the fishermen could have done. Who was stand on and who give way would have been completely irrelevant.

Look here: https://web.archive.org/web/20120820...nt/pdf_289.pdf

The back half is the English version.

[Lodesman]

Originally Posted by David M

I AM a commercial mariner and I communicate by radio numerous times every time I get underway. Much of these communications are for making passing arrangement so there is no doubt whatsoever which side we plan to pass, cross or overtake.

The MCA's guidance has to be taken in context. If you read the circular, they actually don't say "don't use VHF", but warn of situations where the language or intentions may be misunderstood. In US waters, you generally won't have too much of an issue with language barriers, but it should probably be hoisted in that one ought to be careful using local terms or colloquialisms.

[Lodesman]

Originally Posted by markpierce

during my thirty years of boating experience in limited waters , i've never observed a commercial vessel avoiding a recreational vessel. as a result, I avoid all commercial vessels.

I don't believe you. I'm going to assume you've been blithely unaware of the manoeuvres they've made to avoid recreational vessels, and/or you've probably caused a lot of professional mariners to mutter some choice words under their breath.

[Lodesman]

Originally Posted by Exile

I do the same, and would like to think it's also compliant with the Rules since there are provisions which explicitly mandate taking whatever appropriate actions are necessary under the circumstances to avoid collision. (Someone will chime in with the Rule no. & actual text I'm sure )

You're probably thinking of rule 2(b)

In construing and complying with these Rules due regard shall be had to all dangers of navigation and collision and to any special circumstances, including the limitations of the vessels involved, which may make a departure from these Rules necessary to avoid immediate danger.

I think it was brought up earlier that the rules are only meant for two-vessel scenarios - and of course, that point was argued. This rule covers that eventuality - take a situation where you are on collision course with 2 other vessels at the same or similar TCPA, where you are "stand on" to one and "give way" to the other. Logically both of them are at risk of collision and the same dynamic exists for them. You have to break one rule, in order to comply with the other, and ultimately to avoid collision.

This rule DOES NOT allow you to choose willy-nilly whether you need to follow the rules or not. If fact rule 2(a) says as much:

Nothing in these Rules shall exonerate any vessel, or the owner, master or crew thereof, from the consequences of any neglect to comply with these Rules or of the neglect of any precaution which may be required by the ordinary practice of seamen, or by the special circumstances of the case.

You have to follow the rules until it is impossible to do so, while doing what you need to do, to avoid collision.

[Exile]

Originally Posted by Lodesman

You're probably thinking of rule 2(b)



I think it was brought up earlier that the rules are only meant for two-vessel scenarios - and of course, that point was argued. This rule covers that eventuality - take a situation where you are on collision course with 2 other vessels at the same or similar TCPA, where you are "stand on" to one and "give way" to the other. Logically both of them are at risk of collision and the same dynamic exists for them. You have to break one rule, in order to comply with the other, and ultimately to avoid collision.

This rule DOES NOT allow you to choose willy-nilly whether you need to follow the rules or not. If fact rule 2(a) says as much:



You have to follow the rules until it is impossible to do so, while doing what you need to do, to avoid collision.

Glad you chimed in since this is quite different than where my assumptions had lead me. Back to the tug/barge chugging northbound up the west side of Chesapeake Bay which is their norm, presumably because there's sufficient water, they're well clear of the shipping channel, and generally out of the way. I'm heading south under sail with a north wind at my back. In that scenario I'm pretty sure I'm stand on even if it was a long tug & tow. Makes a whole lot of sense to just give way by altering course further out into the bay & passing stbd-to-stbd. But assuming I am in fact the stand on vessel, I need to stand on under Rule 2?

[StuM]

Originally Posted by Exile

...Back to the tug/barge chugging northbound up the west side of Chesapeake Bay which is their norm, presumably because there's sufficient water, they're well clear of the shipping channel, and generally out of the way. I'm heading south under sail with a north wind at my back. In that scenario I'm pretty sure I'm stand on even if it was a long tug & tow.

Depends. Can they deviate from their course reasonably safely? Are they hemmed in between shallow water and the shipping channel? It may well be that the tug is restricted in her ability to manoueuvre.

"The term “vessel restricted in her ability to manoeuvre” means a vessel which from the nature of her work is restricted in her ability to manoeuvre as required by these Rules and is therefore unable to keep out of the way of another vessel. The term “vessels restricted in their ability to manoeuvre” shall include but not be limited to:
...
(vi) a vessel engaged in a towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course."

But assuming I am in fact the stand on vessel, I need to stand on under Rule 2?

Only once "risk of collision" exists. Up to that point you are free to make whatever moves you want if you intend to "avoid impeding" the tow.

[Lodesman]

Originally Posted by Exile

But assuming I am in fact the stand on vessel, I need to stand on under Rule 2?

Yes, but during stage 1 you would be free to manoeuvre, which given slow speeds for both vessels could be assumed to be about >5 miles (IMO). Inside that, the rules require you to stand on. That said, you can make an arrangement over VHF, to act contrary to the rules - it happens all the time, with "head-ons" agreeing to pass green to green, starboard offering a port turn and other such actions. If you call the tug on 13 and offer to stay out of the way, it would do a lot to alleviate the master's stress level. I assume these guys so frequently see recreational sailors fail to stand on, that they wait until later than normal to take action.

[Exile]

Originally Posted by StuM

Depends. Can they deviate from their course reasonably safely? Are they hemmed in between shallow water and the shipping channel? It may well be that the tug is restricted in her ability to manoueuvre.

"The term “vessel restricted in her ability to manoeuvre” means a vessel which from the nature of her work is restricted in her ability to manoeuvre as required by these Rules and is therefore unable to keep out of the way of another vessel. The term “vessels restricted in their ability to manoeuvre” shall include but not be limited to:
...
(vi) a vessel engaged in a towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course."




Only once "risk of collision" exists. Up to that point you are free to make whatever moves you want if you intend to "avoid impeding" the tow.

But can only be a RAM if showing proper symbols (and/or transmitting such on AIS).