Radar or VHF Assisted Collisions

[Uricanejack]

Not really.
I might have done much the same. Except I probably wouldn’t have bothered with the radio call.
Avoiding a squall is a perfectly reasonable reason to alter course, particularly for a small sailing vessel.
1st if you do nothing there is no close quarters.
2nd read rule 11 application. Stand on give way only applies when vessels are in sight.
If both vessels are obscured by the rain squall. Rule 19 applies, until the other vessel is sighted.
3rd If the circumstances admit An alteration of course to Port should be avoided, not forbidden, not recommend but?
4th requirement to stand on is not so rigid to require a vessel to run into a potentially hazardous situation.
eg sailing vessels can adjust for the wind and still be considered as standing on and maintining course and speed.
even tacking can be considered in some circumstances to be standing on and maintaining course and speed.
5th rule 2 provides for common sense.

The important parts.
Make the decision early
Make the alteration large enough to be readily apparent to the observer on the other vessel.

hopefully the fish was tasty

 

[Uricanejack]

SpiderMoobs, correct me if I'm wrong, but it's worth remembering that in the situation you describe, no-one is "the stand on vessel" and no-one "the give way vessel" either. Rule 19 applies: Conduct of vessels in restricted visibility. Rules 11 to 18 - with their stand-on and give-way vessels - are for vessels "in sight of one another".

Correct by strict application of the rules. until vessels are close enough to be sighted through the rain.
From which point on rule 11 to 18 apply.
Rule 19. Altering to Port for a vessel other than a vessel being over taken, is rarely a good idea,
My opinion avoiding squall is possibly one of those rare occasions,
The other vessel was still relatively far away, and passing relatively clear.

 

[Refueler]

My explanation in "Essential Boat Radar":

Radar assisted collisions. Despite the widespread use of radar, vessels continue to collide, and there have been tragic
instances where two vessels equipped with radar have managed to engineer a collision which
would never have happened without it. A typical scenario is as follows:

Ship A, heading due north, observes a target fine on the starboard bow, at relatively long
range. Because of the range, the bearing changes very slowly, so the skipper decides that the
other ship is heading south and will pass down his starboard side, but rather too close. He alters
course 5 degrees to port, and instantly the radar picture becomes much more encouraging,
because the target is a lot further away from the ship’s heading line.

Ship B, the target vessel, is in fact heading slightly west of south, and therefore observes
Ship A fine on his port bow. For similar reasons to Ship A, his instinct is to ‘turn away’ from the
target and he alters course to starboard.

Gradually, both skippers notice the target vessel getting closer to their heading line again,
so they each repeat their previous course alteration. This process continues until they collide!

Having personally made a similar mistake, but fortunately with a happier ending (I was unable
to catch up with the ship to collide with it), I am very aware of how confusing this kind of
situation can be. Your own course alterations make it far harder to work out what is going on.
The answer is to observe the other vessel for longer without making any course alterations,
and not make assumptions about what it is doing, particularly at long range when you simply
don’t have enough information.

The book goes on to explain how to avoid such situations by systematic target plotting: and not to "make assumptions on the basis of scanty information especially scanty radar information" (quote from Colreg Rule 7 (c)).

Excellent book, available in all good bookshops and online (Fernhurst Books or Amazon).

Two errors ... so we can put aside all the rest ...

1. Not starting a plot
2. Making silly alterations

There is NO REASON to make those small alterations .... a suitable plot would have answered it well without fuss.

The other factor as I mentioned before is the use of Relative Motion or True Motion on the radar --- makes a big difference.

On one ship - we had a 3/O who liked TM mode and I was caught out by it more than once ... as 2/O I'd relieve him of watch at midnight ... and radar on 24nm ... things looking OK ...
Most OOW in those days used Relative Motion as the plot is simple and direct relation to CPA .....
I'd find out when starting to plot that I'd assumed RM but he'd left it on TM ...

Luckily it never led to consequences.

 

[Refueler]

Probably just my peculiar Luddite personality traits. The first thing I teach a new hawse piper or cadet. Is to use the wing repeater. When not fitted, a trip to the monkey with the azimuth ring.
Gets the cover off and airs it out, between the swings.
Always have in my hockey puck in my jacket when out in the boat.
And a seastrel In a nice wooden box.

Go on many ships today and you lift the wing gyro repeater cover ... NOTHING !! No azimuth ring ...

I gave up asking guys ... Hey wheres the azimuth ring ? Don't you ever do compass error or bearings anymore ??

The blank looks says it all ....

No wonder I have a job !!

 

[Refueler]

Correct by strict application of the rules. until vessels are close enough to be sighted through the rain.
From which point on rule 11 to 18 apply.
Rule 19. Altering to Port for a vessel other than a vessel being over taken, is rarely a good idea,
My opinion avoiding squall is possibly one of those rare occasions,
The other vessel was still relatively far away, and passing relatively clear.

Do not ignore that fact that the large vessel did not know of his being there until the VHF call ..... which probably prompted him to scroll his AIS screen ... but yot knew he was there

That for me makes me consider NOT doing the alteration to port ....

Sighted or not ... consideration of the consequences of action must be taken ...

 

[Deleted member 478]

Do not ignore that fact that the large vessel did not know of his being there until the VHF call ..... which probably prompted him to scroll his AIS screen ... but yot knew he was there

That for me makes me consider NOT doing the alteration to port ....

Sighted or not ... consideration of the consequences of action must be taken ...

Agreed. I'll need to go back to re-read what I said, but I thought I had covered the alternatives.

The bottom line is that the last several replies have highlighted the fact that I definitely need to hit the COLREGS books again and brush up.

Thank you to all for your insightful replies.

 

[Graham376]

Strange that most folks seem worried about large ships, I've found they rarely suddenly alter course so are predictable. OTOH, fishing boats can dive all over the place regardless of who's around. I may be sailing so theoretically stand on but, if visibility is poor in heavy rain blanking radar and I know there are other vessels around, I will sometimes have engine ticking over just in case.

 

[Kukri]

A recent radar assisted collision involving a yacht:

https://assets.publishing.service.g...d4c100000bb/nedlloyd_vespucci_and_wahkuna.pdf

 

[Refueler]

Strange that most folks seem worried about large ships, I've found they rarely suddenly alter course so are predictable. OTOH, fishing boats can dive all over the place regardless of who's around. I may be sailing so theoretically stand on but, if visibility is poor in heavy rain blanking radar and I know there are other vessels around, I will sometimes have engine ticking over just in case.

Wish you luck trying to argue rights with a fishing boat !!

If in conditions that mean reduced viz etc ... numerous other vessels around - for me - its prudent to have engine on even if not in gear.

 

[Kukri]

I recommend this.

 

[capnsensible]

Very interesting, thanks. Took some thought to figure out how the yacht crew saw the bow of the ship on their port side and were struck by the vessels starboard bow.

As a result of the report has there been a noticeable change to vessel speed in fog? On the other side of the incident there has probably been no improvement in understanding of the use of small vessel radar..

 

[Refueler]

I still have my old Shell Radar Observers manual !!

There's a funny story from Shell ......

Way back when radar was only just starting to be fitted to Merchant Ships .... Shell is supposed to have fitted to its T3 later builds ... while the old jobs still plugged on without. Many of these older were out in the far east where Shell literally reigned supreme.

Picture Singapore anchorage ... a new T3 is slowly making its way into anchorage before its berthing at Pulau Bukom ..... There are a number of older smaller Shell boats at anchor .....
While the T3 is anchoring ... a grubby old Shell job chugs past with radar scanner turning above its wheelhouse .....

WHAT ????

Turns out the old boat had a 'broom handle and piece fitted at end poked up and guy inside turning it to mimic a scanner'!!

Story goes that the Master of the T3 had only just been fitted with his and he took serious 'umbrage' at this !!

 

[RobbieW]

...The other factor as I mentioned before is the use of Relative Motion or True Motion on the radar --- makes a big difference....

I've also seen ground and water stabilised in reference to RADAR, is that the same as Relative/True ? I believe the Wakhuna report uses that terminology (but I've not checked for this thread)

 

[Uricanejack]

Very interesting, thanks. Took some thought to figure out how the yacht crew saw the bow of the ship on their port side and were struck by the vessels starboard bow.

As a result of the report has there been a noticeable change to vessel speed in fog? On the other side of the incident there has probably been no improvement in understanding of the use of small vessel radar..

Personal observation, I doubt it,

 

[Refueler]

I've also seen ground and water stabilised in reference to RADAR, is that the same as Relative/True ? I believe the Wakhuna report uses that terminology (but I've not checked for this thread)

TBH - you lost me there ... ground and water stabilised ???

Relative Motion in effect has you at centre of screen stopped. So all target motion is a composite of their course / speed + your course / speed.
(You can offset your reference position on screen if you wish but most will accept centre).

True Motion has your speed and course input to move you on screen as well as the target ... this means that simple plotting no longer works and vector addition must be used to determine CPA.

I can only assume that mis-naming of the terms may have occurred as you could have Speed / Course over ground input or Speed through water and course steered input to True Motion ... further complicating the issue.

We of course have left out :

Head Up

North UP

Offset

.....................................

 

[Lucky Duck]

No real mention that I can see of MARPA on this thread - is that deliberate?

 

[Deleted member 478]

I recommend this.

View attachment 93722

Damn, can't find it on the shop.rnli.org website.

 

[RobbieW]

TBH - you lost me there ... ground and water stabilised ???

Relative Motion in effect has you at centre of screen stopped. So all target motion is a composite of their course / speed + your course / speed.
(You can offset your reference position on screen if you wish but most will accept centre).

True Motion has your speed and course input to move you on screen as well as the target ... this means that simple plotting no longer works and vector addition must be used to determine CPA.

I can only assume that mis-naming of the terms may have occurred as you could have Speed / Course over ground input or Speed through water and course steered input to True Motion ... further complicating the issue.

We of course have left out :

Head Up

North UP

Offset

.....................................

From the bottom of p24 of the MAIB Wahkuna report...
"The radar information displayed on P&O Nedlloyd Vespucci was ground-based, the incorrect format for anti-collision avoidance. It should have been waterbased, in accordance with IMO guidance. When radar is ground-stabilised, the output of data will relate to their ground track and, although accurate, can be highly misleading when assessing target aspect. "

It does sound like the same thing as True/Relative

 

[Refueler]

Very interesting, thanks. Took some thought to figure out how the yacht crew saw the bow of the ship on their port side and were struck by the vessels starboard bow.

As a result of the report has there been a noticeable change to vessel speed in fog? On the other side of the incident there has probably been no improvement in understanding of the use of small vessel radar..

One of the biggest discussions when the IRPCS changed in the early 70's was the matter of vessels speed in reduced visibility, a vessel equipped with radar - may be interpreted and then vessel maintain a higher speed than one without ..
Rule 6 section b.

There are a number of parts of the IRPCS that led to some interesting discussions those days ...

 

[Refueler]

From the bottom of p24 of the MAIB Wahkuna report...
"The radar information displayed on P&O Nedlloyd Vespucci was ground-based, the incorrect format for anti-collision avoidance. It should have been waterbased, in accordance with IMO guidance. When radar is ground-stabilised, the output of data will relate to their ground track and, although accurate, can be highly misleading when assessing target aspect. "

It does sound like the same thing as True/Relative

The word STABILISED was confusing ..

If you read the last part of my post in answer - I do mention Course / Speed formats ....

True Motion has your speed and course input to move you on screen as well as the target ... this means that simple plotting no longer works and vector addition must be used to determine CPA.

I can only assume that mis-naming of the terms may have occurred as you could have Speed / Course over ground input or Speed through water and course steered input to True Motion ... further complicating the issue.

Many seagoing OOW's especially old geezers of my time would differ on the IMO guidance ... as RELATIVE motion is far easier to assess CPA etc.
IMO guidance there is referring to True Motion ... which I for one never liked.