Collision course, radio and procedures

[Pelagic]

Those are really good questions and indicate perhaps an evolution in IMO recommendations.

When I was getting my various commercial Master licensing 1982 to 86 ....the bible in SEN and simulator examination was this

http://www.amazon.com/gp/aw/d/008097...564676-9410758

Somewhere in the 2nd to 4th edition he provided a guideline.... Something like this:

12 to 10 nm ...Detection
10 to 6nm..... Assessment
6 to 3 mm..... Action

Inside 3nm with too close a CPA was considered a dangerous situation tempered by the relative closing speed and TCPA.

Remember this was in the days when ARPA was in its infancy, no MARPA or AIS
Paper charts and Radar plotting sheets were the norm and dependable radar assessments at longer ranges were questionable so they wanted the standing vessel to remain a consistent target if possible.

Modern equipment has now made this plotting info more universally available with quicker updates.

I'm curious... Has anyone read in his 7th edition, if Cocroft has changed his explanation of IMO recommendation?

[Dockhead]

Originally Posted by Richard_W

My first question is … why wait? At the point when the OP's situation started developing, 30 minutes and 8 miles apart, it was the perfectly safe time for a stand-on vessel to take Colregs sanctioned action. Correct?

My second question is … if so, what would be wrong with making, then and there, a few degree course change (oh no, to port!?) to pass to stern of the give-way vessel?

On the first question: 10 miles, in open water, is a typical decision point for the give-way vessel, but between 5 and 10 miles is still reasonable. Furthermore, 5 miles is still comfortable for you to make your own move. So although it is a judgment call, most experienced mariners would call 8 miles too soon. You need to give the give-way vessel a decent chance to do his thing. It's not "perfectly safe" to maneuver early, when you're the stand-on vessel -- see the answer to the next question for why.

On the second: Don't ever make a "few degrees" course change, when a risk of collision already exists (but this is ok before that -- so 10 to 15 miles out), and especially don't make a series of small course changes. All course changes should be large and obvious. Alteration to port is not good if the crossing angle is obtuse, and in any case, if you must alter to port, then the alteration should be especially large and especially obvious.

The reason we don't alter to port in collision risk situations is because in a real crisis where both vessels are maneuvering -- in extremis, everyone alters to starboard. If he alters to starboard and you alter to port - crunch.

The same thing can happen in exactly this situation -- you prematurely give up standing-on at 8 miles and start maneuvering yourself. But at the same time, the give-way vessel starts doing what he is supposed to do -- and alters course. He expects you to be standing-on, and alters to starboard to pass behind you. But you alter to port to pass behind him! You have changed course by just "a few degrees", so he doesn't immediately perceive that you've maneuvered. And what has happened is that you two have maneuvered onto a collision course, and by the time you figure that out, you're now dangerously close and in extremis!

Lots of collisions in real life have happened in just this way! And that's why it does not add to your safety to maneuver early, when you're the stand on vessel.

[Richard_W]

Thanks, your reply started precise but went quickly into generalities and lectures about small course changes and extremes that are not applicable (yet) at the distance the vessels at hand were apart.

If you stay in context of the situation and your initial explanations, and perhaps draw a scaled model of the situation, you will see that some argument are not applicable and are not likely to happen when the distance between the ships is 8 miles or so.

For example, while still 8 miles apart, if both vessels make 20 degree turn, give-way to starboard and stand-on to port, in all likelihood they will still safely pass starboard to starboard with plenty of water between them. There could be a quite different outcome if the vessels were 1 or 2 miles apart and confused. That's the difference ... why wait until then?

[four winds]

Amazing. Someone actually thinks the "Law of Gross Tonnage" might possibly actually be real.

I've always taken the "Big boats have the right of way." statements as a sure sign of naive inexperience.

[Stu Jackson]

Originally Posted by Dockhead

The same thing can happen in exactly this situation -- you prematurely give up standing-on at 8 miles and start maneuvering yourself. But at the same time, the give-way vessel starts doing what he is supposed to do -- and alters course. He expects you to be standing-on, and alters to starboard to pass behind you. But you alter to port to pass behind him! You have changed course by just "a few degrees", so he doesn't immediately perceive that you've maneuvered. And what has happened is that you two have maneuvered onto a collision course, and by the time you figure that out, you're now dangerously close and in extremis!

Lots of collisions in real life have happened in just this way! And that's why it does not add to your safety to maneuver early, when you're the stand on vessel.

Thanks again for your repeated discussion of these issues.

This large paragraph, whether a repeat from previous discussions or brand new, is one of the best well presented reasons you've written, and your material is extremely helpful.

Thanks again.

[Richard_W]

Originally Posted by Pelagic

...

Somewhere in the 2nd to 4th edition he provided a guideline.... Something like this:

12 to 10 nm ...Detection
10 to 6nm..... Assessment
6 to 3 mm..... Action

Inside 3nm with too close a CPA was considered a dangerous situation tempered by the relative closing speed and TCPA.

...

I'm curious... Has anyone read in his 7th edition, if Cocroft has changed his explanation of IMO recommendation?

Looks to me that this situation assessment and proper course of action depends on these (updated) guidelines.

I can hardly believe that one should strictly apply Colregs stand-on/give-way designations and applicable rules when ships are still 8 miles apart ... that would really cripple a lot of marine traffic.

[Dockhead]

Originally Posted by Richard_W

Thanks, your reply started precise but went quickly into generalities and lectures about small course changes and extremes that are not applicable (yet) at the distance the vessels at hand were apart.

If you stay in context of the situation and your initial explanations, and perhaps draw a scaled model of the situation, you will see that some argument are not applicable and are not likely to happen when the distance between the ships is 8 miles or so.

For example, while still 8 miles apart, if both vessels make 20 degree turn, give-way to starboard and stand-on to port, in all likelihood they will still safely pass starboard to starboard with plenty of water between them. There could be a quite different outcome if the vessels were 1 or 2 miles apart and confused. That's the difference ... why wait until then?

Sorry if it was not clearly written, but the case of getting into extremis with someone turning to port was intended to illustrate how the same principle can apply at 8 miles. That was the point.

Because if the give-way vessel assumes that that the stand-on vessel is standing-on and turns to starboard to pass behind, but the stand-on vessel is in fact not standing-on, but is turning to port, then the vessels may well be maneuvering into one another.

Perhaps there will be plenty of water between them, but if so, that will be just luck -- because the premises upon which both maneuvers were made are invalid. So if the give-way vessel calculated that he could make an x degree turn to starboard to make a CPA of one mile passing behind, this will not be the result if the stand-on vessel turns to port -- towards him, narrowing the CPA.

And it may take some time for both vessels to realize what has happened, especially if the alterations are not that big. You can eat up those 8 miles in no time -- crossing roughly at right angles, with the ship making 16 knots and you're making 7, TCPA will be less than 30 minutes.

Just like in close quarters, at 8 miles, the simultaneous maneuvering, especially when one vessel alters to port, will create an unpredictable and possibly collision course, just like it does in close quarters. The only difference is that at 8 miles, you might still have a chance to correct it.

[Dockhead]

Originally Posted by Richard_W

Looks to me that this situation assessment and proper course of action depends on these (updated) guidelines.

I can hardly believe that one should strictly apply Colregs stand-on/give-way designations and applicable rules when ships are still 8 miles apart ... that would really cripple a lot of marine traffic.

You start applying these procedures when (a) vessels are in sight of one another; and (b) a risk of collision exists.

Pelagic is a real professional mariner, so he will have more knowledge and will correct me if this is wrong, but based on my experience (thousands of ship encounters sailing in the busiest seaways in the world), decision points are somewhat further than that. I think it might be that more precise methods of plotting and calculating crossings (AIS and really good ARPA) allow ships to maneuver earlier than they used to.

In my experience, most ships will have maneuvered already by 8 miles. I tend to give them until about 5 to be really sure.

If you want to take really early action, before any risk of collision exists, I would suggest doing it earlier -- more than 10 miles. Of course it's really good seamanship to avoid a Colregs situation from ever arising in the first place -- when you can detect the situation early enough. The only tool on a recreational craft which is really capable of doing that is an AIS set with a good antenna.

And remember we're talking about open water. It's obviously very different in approaches to ports, in bays, and other congested areas. Where ships are turning, obviously you can't apply these principles, and the acceptable CPAs and decision points are going to be much tighter. In such places the main collision avoidance technique is to figure out where the ships are going to go (if there's a marked channel, it's easy), and just stay out of those places.

[Pelagic]

Originally Posted by Richard_W

Looks to me that this situation assessment and proper course of action depends on these (updated) guidelines.

I can hardly believe that one should strictly apply Colregs stand-on/give-way designations and applicable rules when ships are still 8 miles apart ... that would really cripple a lot of marine traffic.

It will be interesting to find out if the target analysis recommendations have been updated by Cockcroft.

But in many ways it is a red herring.

In a simple 2 vessel scenerio you can make course adjustments anytime you want for many reasons....

1...Anticipate course change by one of you that you decide to identify and force early.

2...You want a clear solution before watch change

3... Your bored and want to see what the other vessel will do.

BUT... when it gets crowded with traffic funneling in and out of a Port going different speeds, different directions and perhaps vesseles overtaking and cutting corners because of schedule issues..... things can get a bit more complicated and the stand on philosophy makes more sense, as you establish priorities and pecking order in a quickly changing scene.

In the Simulator, if you decided to make an early change as the stand on vessel, the DOT would generate a few more "troublesome" targets to force you into serious avoidance maneuvers.

This is what Dockhead is trying to reinforce.

[Richard_W]

I have followed your link at look at some available pages at Amazon ... have not seen specific guideline, but some charts for recommended course changes seem to refer to 6 to 4 miles, and 3 miles and below. I am seriously considering buying the book just to learn a bit of practical application of collision avoidance rules.

I am not trying to be difficult, I am really curious ... and have no problem with Dockhead's explanations and examples that are based on the correct and puristic interpretation of Colregs but the practical application is what I would like to understand better.

So far, there is one Colregs rule that helps me to set context for the rules discussed here ... Rule 11, which sets a practical limitation to the following collision avoidance rules:

Rule 11 - Application
Rules 11-18 apply to vessels in sight of one another.

Okay, that's a good start ... in sight, not just a radar/AIS target many miles away.

[Pelagic]

Originally Posted by Dockhead

In my experience, most ships will have maneuvered already by 8 miles. I tend to give them until about 5 to be really sure.

As the captain you are always training and reinforcing proper watchkeeper skills, so when in busy and congested waters
we are working as a team to constantly identify and prioritize targets.

I try to teach and discourage very early long range course changes unless there is an obvious reason to do so.

Our ARPAS do Trial maneuvers..... so between 8 and 6nm, I find it a good teaching opportunity to test their solution for a given CPA.

I also help them scale down and monitor a safe passing on manual gain and interference settings

Also I note that a common weakness of new watchkeepers is that they tend to focus strictly on range and forget to consider TCPA in their decision making.

Radar is the greatest tool, but it requires constant practice and confirmation that you have not made a dangerous assumption.

[Richard_W]

Originally Posted by Dockhead

You start applying these procedures when (a) vessels are in sight of one another; and (b) a risk of collision exists.

...

In my experience, most ships will have maneuvered already by 8 miles. I tend to give them until about 5 to be really sure.

If you want to take really early action, before any risk of collision exists, I would suggest doing it earlier -- more than 10 miles. Of course it's really good seamanship to avoid a Colregs situation from ever arising in the first place -- when you can detect the situation early enough.

...

Avoiding the Colregs situation is what I was after from the get-go.
Looks like we are getting more onto a common ground ...

[Jammer Six]

As long as the idea that a freighter can't or won't alter course for a sailboat is there, or that tonnage has anything to do with it, you and I don't have any common ground.

I sail in very congested waters, with constant commercial traffic and first contact happening at two to five nautical miles, and I've seen commercial traffic of virtually all types (ferries, container ships, cruise ships, tugs and fishing boats) alter course and speed for sailboats. I've heard tugs and cruise ships talk to cruisers on channel 13. The cruise ship captain was polite, the tug captain had quite an imagination and an admirable ability to swear without using a single profane word.

Washington State Ferries can run rings around a sailboat.

I used to agree with your points of view.

Then I read some of Dockhead's posts, some posts by others, then I went back out on the water and watched the commercial traffic, and realized that these guys understood some things that I didn't.

Now I read the COLREGS, watch the posts here, draw pictures, then read the COLREGS again, and try to keep understanding what I'm reading.

It is not simple, it is not intuitive, but I've come to believe that it's important.

[nigel1]

Maybe the really good thing about these threads is that it does get people to start looking at the Colregs, and hopefully from a different perspective.

A few of us on this forum get to see the picture from both sides, and I am still of the opinion that we should all follow the Colregs, in that there is a stand on vessel and a vessel required to give way (when risk of collision exists).

If some want to bail out very early (say more than 10 miles apart), that's all well and good, risk of collision is not really deemed to exist at that point).
This works well in a two vessel situation, but what if there is more than 2 vessels?

In busy waters, you may be obligated to keep clear due to being in a narrow channel, or a TSS, depending on your direction of travel, but in other busy area's, an unpredicted alteration can mess up everyone's plan.

Most commercial traffic will have a far better overview of the situation than any sailboat could. In busy waters, there is most likely 2 to 3 persons on the bridge, with a couple of good radars and two large screen ECDIS. This allows for a full assessment of the situation, and course alteration decisions are dependent on the ships following the Colregs.

So, if I have say a 3 vessel situation, and one of them is a sailboat, I'll be relying on that sailboat to stand on. If the sailboat decides to alter course it may well be into the path of my give way course.

And some of you are correct, there are bad watch keepers out there, maybe playing video games, but hopefully not too many of them (one less this year as I sacked him). But that is where Rule 2 and Rule 17 come into play.

My best advise is use a AIS transponder, it increases your situational awareness, and makes your more "visible" and allows you to positively ID ships causing you concern, and allow you to make proper VHF contact.

[Dockhead]

Originally Posted by Richard_W

I have followed your link at look at some available pages at Amazon ... have not seen specific guideline, but some charts for recommended course changes seem to refer to 6 to 4 miles, and 3 miles and below. I am seriously considering buying the book just to learn a bit of practical application of collision avoidance rules.

I am not trying to be difficult, I am really curious ... and have no problem with Dockhead's explanations and examples that are based on the correct and puristic interpretation of Colregs but the practical application is what I would like to understand better.

So far, there is one Colregs rule that helps me to set context for the rules discussed here ... Rule 11, which sets a practical limitation to the following collision avoidance rules:

Rule 11 - Application
Rules 11-18 apply to vessels in sight of one another.

Okay, that's a good start ... in sight, not just a radar/AIS target many miles away.

Yes, correct and important.

I think I mentioned it myself somewhere above.

If you're not in sight of one another, then collision avoidance procedures don't kick in yet.

How far that is depends on the height of the superstructure of the ship, and obviously on conditions, and also on your own eye height, but for my boat in good conditions and good size ships that's usually 12 miles or so.