EPIRB versus AIS PLB

[Daverw]

PLB's need the casualty to hold the flexible aerial up out of the water with one hand, which seems unachievable in many situations or for very long. You might need that hand for something else, and it would be numb soon anyway?
How long would that be needed to be 100% sure your distress had gone up?

I suspect the same is needed for AIS unit, as radio waves don’t like being under water and line of sight

 

[ShinyShoe]

I suspect the same is needed for AIS unit, as radio waves don’t like being under water and line of sight

The AiS is only transmitting a "few" metres not to the moon. And will be transmitting pretty constant so the odd dropped message is no issue. Sat sends messages less frequently so a missed message could be more important

 

[lw395]

... However a PLB (it stands for Personal Location Beacon with only implied and historical modus operandi in reference to 406) with AIS would offer ....

When you say AIS, do you mean AIS as the rest of the world means 'the AIS system', or do you mean some other 'automatic identification system' such as the one built into your EPIRB, PLB or mobile phone?
Is there any such thing as a PLB with no identification system?

Maybe an O flag on a stick would avoid the need to deal with the jargon?

 

[Iliade]

'All' PLBs also transmit on 121.5. We used to have a thing like a portable TV antenna to DF them with an airband radio. Trouble is that, like the old RDF, you can be 180 degrees out...

 

[Uricanejack]

I am not an expert on modern gadgets.

Even so. I believe an EPIRB is for a boat sinking. While a PLB is for a person falling off a boat. Which are two rather different functions.
Even though a PLB may activate a satellite signal. Which might get attention. It’s still just saying somebody fell in the water.

Which would suggest to me,
Prioritize an EPIRB for the boat fit for the purpose. JIK you have reason to call for distress of any kind.
Then contemplate as budget permits a PLB of a type fit for purpose and your sailing.

AIS is not as far as I know a routinely monitored for distress messages although they do have the functionality, which would lead me to assume.
A PLB which would activate external response via satellite, GMDSS or Would be a better choice.

 

[William_H]

Around here you must carry an EPIRB a PLB is not acceptable due I think to shorter battery life. However a rescue last week involved capsize and sinking of a ali open run about I imagine about 14ft which found the occupants suddenly in the water with no boat. Fortunately they did get the EPIRB and fired it up resulting in a rescue. This kind of boat loss has become a bit more common such that if you were in a tiny boat liable to sudden loss that PLB would be abetter option. Or an additional safe guard. ol'will

 

[ShinyShoe]

I am not an expert on modern gadgets.

Even so. I believe an EPIRB is for a boat sinking. While a PLB is for a person falling off a boat. Which are two rather different functions.
Even though a PLB may activate a satellite signal. Which might get attention. It’s still just saying somebody fell in the water.

A PLB doesn't mean "I fell in the water" it means "*I* am in distress". An EPIRB means "My boat is in distress". Activating either would be fine for a yacht 100 miles offshore, dismasted, with gear tangled in the prop. But the boat hasn't sunk and no-one is in the water.

An EPIRB has some specific extra requirements. It auto activates when wet (hence you associate it with sinking). It transmits at least 48 rather than 24 hrs (that's a battery size thing... PLB needs to be compact to be personal). It floats and should transmit by itself floating (no need to orientate the antenna).

My personal view is on a yacht, where life jacket worn all the time, a PLB on the lifejacket offers almost all the advantage of the EPIRB provided the wearer is able to manually activate it (and if they aren't then no rescue will ever be quick enough to matter).

Which would suggest to me,
Prioritize an EPIRB for the boat fit for the purpose. JIK you have reason to call for distress of any kind.
Then contemplate as budget permits a PLB of a type fit for purpose and your sailing.

PLB or EPIRB will get identical SAR response AFAIK.

AIS is not as far as I know a routinely monitored for distress messages although they do have the functionality, which would lead me to assume.
A PLB which would activate external response via satellite, GMDSS or Would be a better choice.

Agreed. But 100miles offshore, your best chance of rescue (and survival) is your mothership. So giving them a "homing signal" is what is needed..

The delay in satellite is probably 30mins+, then the phone shore contacts, launch assets. Typically it will be an hour after you activate it before assets are mobile to you. If that is a help, 100miles out. Depending where you are. They might rescue you an hour later. Maybe 2. Unless you are dressed for immersion your survival will not be great. Sail single handed - it's your only hope (and there have been successful rescues). Sail a well crewed boat using AIS... You could be sipping hot cocoa before the satellite system has even kicked in.

The ultimate device:

AIS - water activated
DSC - water activated (possibly with some form of delay/manual activation before being a full DSC alert)
Satellite - perhaps not water activated (let's avoid mid Atlantic asset deployment due to false alarms where boats can't be contacted)
Odeo type hand flare for positioning
Waterproof
Floating
Floats upright
Teathered to LJ.
USB port to plugin and read diagnostics on own PC
? Rechargeable if not replaceable battery

 

[Kelpie]

Around here you must carry an EPIRB a PLB is not acceptable due I think to shorter battery life. However a rescue last week involved capsize and sinking of a ali open run about I imagine about 14ft which found the occupants suddenly in the water with no boat. Fortunately they did get the EPIRB and fired it up resulting in a rescue. This kind of boat loss has become a bit more common such that if you were in a tiny boat liable to sudden loss that PLB would be abetter option. Or an additional safe guard. ol'will

Why did they have to set it off manually?

 

[Capt Popeye]

Oh deary me; as this subject appears to be a Hot One, might I venture to state that I have a 'Fast Find' , GPS, personal Locator Beacon; thats what it states on the 'TIN' anyway - so can I please ask; is it any good if I go overboard whilst on my own ?
Will I get assistance from ???

Cripes do I have to start over again ?

Any and All replies welcomed (sorry if I have Thread Drifted a tad ?)

 

[bedouin]

A couple of questions about AIS MOB devices.

a) How long after activation would you expect to receive the first position from the MOB?
b) What is the effective range of these when transmitting from a MOB to a typical boat in say a 2m sea?

 

[bedouin]

Oh deary me; as this subject appears to be a Hot One, might I venture to state that I have a 'Fast Find' , GPS, personal Locator Beacon; thats what it states on the 'TIN' anyway - so can I please ask; is it any good if I go overboard whilst on my own ?
Will I get assistance from ???

Cripes do I have to start over again ?

Any and All replies welcomed (sorry if I have Thread Drifted a tad ?)

If you are single handed then it is the best single option. If you go overboard and are conscious to activate it then help will come to you but you have to allow a few hours for it to arrive. So make sure you are dressed to survive that long in the water - in summer oilies etc are probably okay, in winter it may be marginal. I think if I were sailing regularly in winter I would consider wearing a survival suit as a matter of course.

 

[ShinyShoe]

I have a 'Fast Find' , GPS, personal Locator Beacon;
Will I get assistance from ???

FastFind is Satellite PLB for single handing it's the only sensible option as contacting your own boat is pointless. Help will be slow. But will come. Make sure your shore contacts are sensible and will be able to say roughly where you are and that a PLB activation without response on VHF almost certainly means you need help.
Where do you sail? HH VHF could bring quicker help.

A couple of questions about AIS MOB devices.

a) How long after activation would you expect to receive the first position from the MOB?

Probably <3 minutes but could be longer if it's never had a GPS fix.

b) What is the effective range of these when transmitting from a MOB to a typical boat in say a 2m sea?

Will depend where the AIS antenna on the boat is. But likely ~ 2-3miles

 

[ShinyShoe]

Why did they have to set it off manually?

Capsize doesn't usually result in instant sinking. Float free requires submersion to certain depth. But I'd guess an EPIRB on an open Ali hull is not mounted in a float free container. Or floated free into upturned hull which would be a perfect signal blocker...

 

[requiem]

Even so. I believe an EPIRB is for a boat sinking. While a PLB is for a person falling off a boat. Which are two rather different functions.
Even though a PLB may activate a satellite signal. Which might get attention. It’s still just saying somebody fell in the water.

As the other guy mentioned, both are part of GMDSS. In the string of bits that are transmitted it is true that a couple are set aside to indicate things like EPIRB vs. ELT vs. PLB and whether it also sends a 121.5 MHz signal as well. But, what a PLB must do, what an EPIRB must do, etc. are defined by the appropriate standards bodies, which is why "PLB" shouldn't be used as a generic term for things like avalanche beacons, inReach devices, AIS SARTs, etc.

 

[requiem]

Oh deary me; as this subject appears to be a Hot One, might I venture to state that I have a 'Fast Find' , GPS, personal Locator Beacon; thats what it states on the 'TIN' anyway - so can I please ask; is it any good if I go overboard whilst on my own ?

How old is the beacon? Since I know people often carry very old kit with them, there are a few changes to be aware of:

• GPS hardware has vastly improved since the turn of the century, and other issues (e.g. GPS week rollover) mean that older hardware can take much longer to acquire a fix, or simply not work.
• Testing of EPIRBS back around '03-'04 found that some had had great difficulty acquiring a GPS fix, and so couldn't transmit their location. (Impetus for testing was that a majority of real-life activations of GPS-enabled EPIRBS didn't include coordinates.)
• Satellites no longer monitor for 121.5 MHz signals.

So, I'd suggest buying a current unit if yours is more than a decade old.

 

[obmij]

Massively confusing thread.

I don't think there is actually a SOLAS definition of a PLB unit nor is it covered under GMDSS. I don't think it is covered by the MED either. If anyone knows differently please post a link.

Practically speaking, there are three types of PLB's commonly in use...as I understand it

1. Those that broadcast on 121.5. Very common commercially. Works well for local SAR. Need a base unit. WILL NOT BE PICKED UP BY SATELLITE. Example Sea Marshall
2. AIS / DSC PLB. Used both commercially and otherwise. Normal VHF range. Example Ocean signal MOB1
3. EPIRB type PLB, transmitting on 406 and possibly 121.5 & AIS also. Will be picked up by satellite & with the above advantages also

 

[obmij]

For what it's worth - if I were single-handing offshore then option 3 would be the obvious choice.

For normal coastal sailing or work I'm happy enough with option 2

Option 1 is of more use in a controlled commercial environment.

 

[bedouin]

Massively confusing thread.

I don't think there is actually a SOLAS definition of a PLB unit nor is it covered under GMDSS. I don't think it is covered by the MED either. If anyone knows differently please post a link.

Even if not explicitly defined there is a general understanding of PLB, which includes transmitting on 121.5 mHz- I don't think you will find any manufacturer referring to an AIS MOB device as a PLB.

It all comes down to who you want to rescue you. If you want your own vessel to then go AIS, if you want CG/RNLI go EPIRB/PLB

 

[Graham_Wright]

Sounds like you sail as a couple. If you have a WmOB AIS may be your best hope. Without being sexist, what if you have a MOB - will she even be able to get you back on board.

That's a completely separate issue and one which can be practised unlike sending out a broadcast alert by whatever means.
At the very least, I'll be able to say my farewells and check she knows where the will is.

There has been a great deal of discussion on recovery on this forum that I have contributed to. Once we reach warm, sheltered waters, we will practise.

 

[maby]

I would be interested to see the results of a real-world range test of an AIS beacon - because I suspect that it is very short. They are using the same frequencies as your VHF handie but with much smaller antennae and operating at an inch above sea level. With moderate wave heights, I would not be surprised to hear that many AIS beacons have a range of a mile or less.

Looking at the original question, PLBs/EPIRBs and AIS beacons are two very different classes of device that address the same problem - they each have advantages and disadvantages relative to the other. The range of an AIS beacon is certainly going to be short - even under ideal conditions it will not be more than a few miles. The range of a PLB/EPIRB is effectively infinite - you press the button anywhere on earth and within a few tens of minutes someone will know that you want help and where you are to an accuracy of a few tens of yards. With that range difference, the AIS beacon is only really useful to help recover an MOB by the boat that he/she fell off - ok, if you fall overboard in the middle of the Solent, you'll have many more potential rescuers, but ten miles off shore you will probably go unheard. Balanced against that is the time that it takes for an EPIRB/PLB alert to be processed.

The ideal solution is to carry both - let's face it, they are not very expensive by the standards of sailing gear! Until combined units become readily available, the problem is really the practicality of carrying both - my lifejacket has a dedicated pocket for a location device, but only one - which do I put in it?