MOB on ARC.

[noelex 77]

The yacht Ocean Breeze, a Volvo Ocean 70, has lost a crew member overboard on Monday, 2 December, at 02:27 UTC.

At the time of posting, he has not been found.

https://afloat.ie/sail/cruising/item...oogle_vignette

[Dockhead]

Awful. Search was called off.


It will be interesting to know if the casualty had a MOB beacon on him -- I would have thought that would be required on boats of that class. And if so, why it didn't work.

[Montanan]

Technology questions:
How accurate is a personal AIS beacon and what distance will it be able to transmit and be received as worn by a MOB in salt water?
Does the personal AIS signal work similar to a vessel transmitting AIS providing position and drift data?
Are personal AIS beacons rugged devices that can take the wear and abuse of being actively worn and do they go on automatically when submerged or do they need to be manually activated?


From press release:

"In a statement, the World Cruising Club rally organisers say they understand that the casualty was wearing an automatically inflatable lifejacket with a personal AIS beacon attached. We do not know the circumstances of the incident, and we will not speculate.

MRCC (Marine Rescue Coordination Centre) Norfolk issued an emergency alert to all shipping for assistance. ARC yacht Leaps & Bounds 2 and motor vessel Project X are now involved in the search. Due to the incident's distance from land, air cover is impossible.

. . .

Ocean Breeze is an Austrian-flagged Volvo 70 yacht participating in the Atlantic Rally for Cruisers (ARC), an annual event that spans Gran Canaria to Saint Lucia.

Ocean Breeze is one of 11 yachts sailing in the IRC racing division of the rally. Yachts in this division must comply with the World Sailing Offshore Special Regulations for Category 1 and the World Cruising Club safety equipment requirements.

In total, 820 people onboard 140 yachts are sailing in ARC 2024. The event departed from Las Palmas de Gran Canaria on Sunday 24 November, heading 2,700NM across the Atlantic to Saint Lucia. 2024 is the 39th edition of this sailing event."


https://afloat.ie/sail/cruising/item...oogle_vignette

[Dockhead]

Originally Posted by Montanan

Technology questions:
How accurate is a personal AIS beacon and what distance will it be able to transmit and be received as worn by a MOB in salt water?

Accuracy will be the same as any modern GPS; a few meters.


Range according to this test: https://www.yachtingworld.com/featur...our-life-69914 is more than 3 1/2 miles in open water.

Originally Posted by Montanan

Does the personal AIS signal work similar to a vessel transmitting AIS providing position and drift data?

Yes. You get near-real time location data overlaid on your chart plotter, so you should be able to just steer right to the casualty.

Originally Posted by Montanan

Are personal AIS beacons rugged devices that can take the wear and abuse of being actively worn and do they go on automatically when submerged or do they need to be manually activated?

They are supposed to be. They are waterproof to a high IP rating and are supposed to be rugged.


Some are activated automatically and some manually. The automatic ones (like mine) are installed inside the life jacket and are activated by the life jacket's inflation.

[Dockhead]

This is a chilling story, if in fact the casualty had a MOB beacon on him, and it failed for some reason.


I have 4 of these on my boat and it is Plan A, Plan B, and Plan C for finding a casualty if God forbid someone goes over. I'll have to rethink this if these devices are not reliable.


I do carry on my person a PLB in addition to a MOB beacon. But I only have one of those on board.

[PippaB]

For the AIS MOB beacon to give position it has to get a GNSS fix. How long that takes can depend on how long it has been since the beacon was tested/powered on, the orientation of antennas, etc. Until the beacon does get a GNSS fix you only get the Msg 14 safety transmission that there is an MOB, but not any position information. If the unit gets tangled up in a lifejacket, or otherwise oriented so that the GNSS cannot get a signal it is entirely possible that the Msg 1 position report will not get transmitted. You may also never even get the AIS transmission if the beacon antenna is fully underwater.

I wear one on my lifejacket, but AIS MOB beacons are not perfect, and it is easy to envision many scenarios where they do not perform their function.

Purely speculation on what might have happened in this particular case.

One thing that might be of benefit would be for the ship's own plotter to record position when the first MOB Msg 14 is received. For own ship this would at least give you a starting point of "this is where we were when the first message was received". Don't know if any plotters do that.

[Montanan]

Thank you.

I recall MOB exercises during Sea Scout voyages where we would try to find a life preserver ring that the skipper would discretely throw overboard and then let the young scouts take command and attempt to locate. It was hard for ten or twenty scouts to return course and spot the floating ring from more than about 100 yards away and totally impossible in the dark or foggy conditions. This was back in the day before electronics. What the exercises taught us was to not fall off the boat as discovery was far from certain, but the Sea Scout vessel was a veery capable and powerful 63 feet former WWII sea rescue boat leased from the US Navy for $1 per year, not a high performance sailed-boat that would be bucking about and make for a very poor visibility platform.

[Dockhead]

Originally Posted by Montanan

Thank you.

I recall MOB exercises during Sea Scout voyages where we would try to find a life preserver ring that the skipper would discretely throw overboard and then let the young scouts take command and attempt to locate. It was hard for ten or twenty scouts to return course and spot the floating ring from more than about 100 yards away and totally impossible in the dark or foggy conditions. This was back in the day before electronics. What the exercises taught us was to not fall off the boat as discovery was far from certain, but the Sea Scout vessel was a veery capable and powerful 63 feet former WWII sea rescue boat leased from the US Navy for $1 per year, not a high performance sailed-boat that would be bucking about and make for a very poor visibility platform.

Indeed. I always thought falling overboard is simply a death sentence in anything other than the most benign conditions, conditions which never exist where I sail above 60N. Needle in a haystack. I always considered these AIS beacons to be revolutionary, completely changing the odds.


I hope I wasn't wrong about that.

[thinwater]

They may never find the beacon to test it.


We want to know if was a hardware failure (less likely I would think) or a function failure (more likely I would think).


By function failure, I have always wondered how they are affected by repeated dunking under waves. I don't think it takes more than 6-12" to substantially degrade the signal. I know GPS does not like intermittent signals and tends to lose its fix. For example, if it was mounted lower than shoulder height it can fail.


I've always liked tethers. They have their downsides too, so I understand the conflict inshore. Racing around the cans maybe it's safer to just fall in. But offshore the recovery stats are discouraging for crewed boats and worse for short handed boats.

[davil]

Originally Posted by Dockhead

Indeed. I always considered these AIS beacons to be revolutionary, completely changing the odds.


I hope I wasn't wrong about that.

===============================
got me thinking also!

always have a personal AIS on life jacket who ever is on watch alone with the belief will transmit and trigger an alarm on my Vesper .

Not sure now

Review of prior posts seem to indicate in general the personal beacon is reliable?
the human component will be a person responding to the alarm on the AIS unit on board.

[davil]

Originally Posted by PippaB

One thing that might be of benefit would be for the ship's own plotter to record position when the first MOB Msg 14 is received. For own ship this would at least give you a starting point of "this is where we were when the first message was received". Don't know if any plotters do that.

============================
My Garmin plotter has a trigger on screen to mark position

[Shrew]

Originally Posted by davil

[/B]

===============================
got me thinking also!

always have a personal AIS on life jacket who ever is on watch alone with the belief will transmit and trigger an alarm on my Vesper .

Is that a question? {I} always have a personal AIS on life jacket....

Or is that a statement? {You should} always have a personal AIS on life jacket....


and........what's a Vesper?

[PippaB]

Originally Posted by Shrew

....and........what's a Vesper?

Vesper is a manufacturer of AIS units, now owned by Garmin, and would thus be the recipient of an AIS MOB transmission.

[barnakiel]

VOR boats are accident prone. Booms injuring crews and crews washed overboard.


AIS or not, why was the seaman not leashed. I did not ask any questions.


Too bad.



b.

[barnakiel]

BTW dear sailors and cruisers, not all AIS units get triggered by AIS MOB, but all up to date VHF do get triggered by DSC VHF MOB.


A side comment re a comment at the other forum (which I do not recommend, but it does have a good discussion of the accident) - normally, we do not look for a crew lost overboard, we look for the perch thrown into the water (hopefully) right after the MOB event. The MOB victim swims to the perch, and the boat navigates back to the perch (sure, not when AIS guides us right to the person).


MOB visibility at 5-10 knots of boat speed : 3 minutes by day, 1 minute by night.
Perch visibility ... : 20 minutes by day, 5+ minutes by day.


It is a commercial operator so we will get some lessons once the relevant authority does their job and publishes their statement.


I think no AIS no problem, no leash a problem.



b.