MOB: PLB or AIS Beacon?

Tim Good

Tim Good

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Ok so the long awaited convinced PLB & AIS units haven't come to the market as expected. Lots of hype in 2016 but still nothing.

So.... it's night time and your couple cruising 100 miles off shore. Water is say 20c. No immersion suit but you have a decide Life Jacket. You go overboards and you partner is asleep down below.

If you could only have one or the other would you take a PLB or an AIS Beacon?
 
If she's sleeping the AIS is useless as you need to know to look for it on the plotter. PLB is fail safe and will get a response from any ship in the area once the CG put out the alert.

Both have their place but we have a PLB unit for our situations on the west coast.
 
The whole point of MoB is to stop it, fit a U-bolt in the cockpit and jackstays, use a harness with one long and one short tether, the latter stops you going over the guard rails. We always clipped on in bad weather and at night whatever the weather. Because of those we viewed life jackets as something you put on before getting into a life raft. Thus we had no AIS or PLB just an EPIRB.
 
pcatterall said:
Will there not be a vhf DSC audible warning?
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Only if the beacon has a DSC function.

The AIS beacon will trigger an alert on the AIS receiver, most of them have an audible alarm function. It will also continue to give a location to the receiver to enable the boat to home in on you. However, it will only alert those vessels in the immediate vicinity, whereas a PLB will alert the shorebased SAR people.

At present, we don't have AIS on board, so a PLB is the only option and is what we have. Once we fit AIS, I'll probably buy AIS beacons as well: they're automatic, so will form the first response. The PLB, being manually triggered would be the second line.

If I was starting fresh with no beacons at all and I had an AIS receiver, I'd probably go for an AIS beacon, because it increases the chances of being recovered by the boat you fell off.
 
KellysEye said:
The whole point of MoB is to stop it, fit a U-bolt in the cockpit and jackstays, use a harness with one long and one short tether, the latter stops you going over the guard rails. We always clipped on in bad weather and at night whatever the weather. Because of those we viewed life jackets as something you put on before getting into a life raft. Thus we had no AIS or PLB just an EPIRB.
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Come on Mike. All us offshore sailors have what you advise. That's not the discussion point though. You could easily say there's no need for gps with good charts and a sextant.
 
ctva said:
If she's sleeping the AIS is useless as you need to know to look for it on the plotter.
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If you carry AIS beacons then you'd be daft not to make sure your instruments give a loud alarm when it's activated. If your plotter won't do it, there are standalone boxes that look out for MOB messages in the AIS stream and close a relay to activate whatever strobes and klaxons you choose to fit.

pcatterall said:
Will there not be a vhf DSC audible warning?
Click to expand...

Not from an AIS beacon or a PLB - why would there be? Unless you mean the Coastguard sending a DSC alert after receiving the PLB signal?

I don't carry either because I don't like to be encumbered with lots of kit, and sometimes sail singlehanded and sometimes with crew which complicates matters. But if I was going to carry a beacon, and always sailed with someone else, I would certainly go for AIS. I might not still be alive by the time the PLB position has trickled down to the RNLI (see recent Scottish fishing boat), and in the meantime my partner is still sailing away from me none the wiser. 100 miles offshore they won't receive any VHF call and might not wake up till tomorrow morning. If they are in range, then once they do hopefully get woken up half an hour later by the DSC alert from the Coastguard they have no means of knowing where I am; the PLB position is only updated sporadically and phoned or faxed to the Coastguard, and my partner doesn't have a receiver for the local homing signal. Essentially by choosing a PLB I'm giving up on my boat and crew and putting all my faith in the shorebased SAR coordination system and then the RNLI.

With AIS (including sensible equipment choices on the yacht) my partner is woken within seconds and can come back for me, with my position visible to them in near-realtime. If they're in VHF range there's nothing stopping them raising a DSC distress and a Mayday at the same time, which will get a more immediate response from the Coastguard because of the direct link and more specific information (no need to go via UKMCC and Falmouth, no need to phone contact numbers, no doubts about whether this is a real emergency or not and where it is). Outside VHF range they could set off a PLB or EPIRB on the boat (we can assume they have one if regularly sailing 100 miles offshore and willing to buy personal beacons) and get exactly the same response as a PLB on my lifejacket would have done. Our positions are close enough (because they stopped, came back, and are homing in on me) for the difference not to matter until a lifeboat is in the area, at which point they can use the AIS signal for homing instead of the 121.5.

I think we can eliminate equipment failure from the comparison because it could happen to either. So with AIS, as long as you can trust your crew to wake up when a big hooter goes off, and make a distress call, you get exactly the same response as you would with a PLB, plus the benefit of immediate highly motivated local searching. To me it's a no-brainer if you've decided that you will carry some kind of beacon and you don't sail singlehanded.

Pete
 
If I was starting fresh with no beacons at all and I had an AIS receiver, I'd probably go for an AIS beacon, because it increases the chances of being recovered by the boat you fell off.
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I agree - I've just bought a couple based on that idea. I've also replaced the VHF for one that sends DSC data to the on-board PC when an alert is received.
Not from an AIS beacon or a PLB - why would there be? Unless you mean the Coastguard sending a DSC alert after receiving the PLB signal?
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The Ocean Signal MOB1 provides a DSC alert if it's programmed for UK use. DSC alerts from these devices are not permitted in France, for some inexplicable reason.
 
northcave said:
Ok so the long awaited convinced PLB & AIS units haven't come to the market as expected. Lots of hype in 2016 but still nothing.

So.... it's night time and your couple cruising 100 miles off shore. Water is say 20c. No immersion suit but you have a decide Life Jacket. You go overboards and you partner is asleep down below.

If you could only have one or the other would you take a PLB or an AIS Beacon?
Click to expand...

In a word you will most likely drown or die eventually from exposure, the chances of your partner hearing you are very slim and even if she awakes the chances of her finding you at night are at best she will probably run over you.
I sail single handed and have a PLB and my DSC hand held VHS radio clipped to my life jacket as its the best chance you have.:)
 
Yes, I pointed that out in post #10.

Though some countries, including France, prohibit the DSC alarm function. The device is supposed to be programmed for the area it is used, but can be re-programmed at any time. I can't see the logic of not having DSC as statistically it's likely to be activated away from other boats and is unlikely to generate nuisance alarms..
 
>Come on Mike. All us offshore sailors have what you advise. That's not the discussion point though. You could easily say there's no need for gps with good charts and a sextant.

I would never say that about GPS etc. we did have a handheld and fixed GPS and we did carry charts, a sextant and used Astrocalc for positions. What we didn't have or want was a chart plotter charts are more reliable.
 
I would rather rely on trained personnel to rescue me than hope that my sleeping partner below deak Can figure it out. Hence I will choose the PLB , especially if it is one of those like McMurdo or ocean signal that can be programmed with an MMSI. It sends the alarm via satellite on bandwidth 406 ,121 , not to mention GPS and a strobe light . Here in Denmark the SAR helicopter covers the whole countries sea territory and will deploy within minutes if they get the alarm call. Likewise you will get a nasty fine if it was a false alarm.
 
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