PLB Response Time

[Rivers & creeks]

Real world functionality of the EPIRB may differ little but, particularly in cold UK waters, that 90 min time delay could make the difference between rescue or recovery if you're in the water. Go for GPS version.

I think you've misread the post, in most cases there will be no delay between the two, the point I was making was the value of having either is about the same and if it came to a choice between two non-GPS PLBs or one GPS unit I'd go for the pair, that way the grab bag and the helm can have one. As modern sailors the psychologists working for manufacturers and marketeers have us pretty well sussed - the idea of going for a 'premium' unit because it has a bit of extra functionality that costs them pennies but has a wow factor, has seduced us into all sorts of extra £'s of purchases, me included.

 

[prv]

>>It depends how far you are from a lifeboat station or helicopter.
>Clearly the answer to KAM's question does not depend on this.

What the OP said was 'Does anyone have any idea of the likely response time to get a position from MRCC.'.

Yes, and you ignored this and answered a different question. You answered the question "how long to get rescued". Which the OP didn't ask.

The OP calls the local MMRCC for the area in (say) ten seconds on VHF16, giving boat name and MOB position.

And if he asks them "where is the PLB?", will they be able to answer? After only ten seconds, I'm sure they won't. If he asks them again in ten minutes? Maybe - I don't know. Neither does the OP. That's why he asked.

You can lead a horse to water, but apparently you can't make him read.

Pete

 

[EastYachty]

>>It depends how far you are from a lifeboat station or helicopter.
>Clearly the answer to KAM's question does not depend on this.

What the OP said was 'Does anyone have any idea of the likely response time to get a position from MRCC. I assume MRCC automatically send this data to the local coastguard'.

The OP calls the local MMRCC for the area in (say) ten seconds on VHF16, giving boat name and MOB position, the MRCC immediately informs the local coastguard which immediately informs the lifeboat/helicopter base. Hence I said 'It depends how far you are from a lifeboat station (a time delay for the crew to arrive) or helicopter (on a fast standby) to arrive. If you've ever watched a programme about the MRCCs and Coastguard stations, lifeboats/helicopters you will have see what I mean - it's very fast for obvious reasons.

There's slightly less of a dogleg the MRCC coordinates so will callout the relevant resources ie local coastguard team as well as helicopter/lifeboat.

 

[Daydream believer]

Ok- so I am going off thread a bit ( before PLV calls me an illiterate horse!!)but something puzzles me

When an EPIRB goes off, do all the operating DSC enabled VHF radios within range get an MMSI mayday call
& if the EPIRB has a GPS do they automatically get the position

If it did ,would not a PLB with GPS send a message to my VHF

 

[Daydream believer]

Sounds like you may need to register the number for your mistress as well

dangerous!!!
Programmed to say I am working overtime

 

[FishyInverness]

Ok- so I am going off thread a bit ( before PLV calls me an illiterate horse!!)but something puzzles me

When an EPIRB goes off, do all the operating DSC enabled VHF radios within range get an MMSI mayday call
& if the EPIRB has a GPS do they automatically get the position

If it did ,would not a PLB with GPS send a message to my VHF

Nope, it doesn't broadcast a VHF signal, in the same way that an AIS does, and AIS doesn't broadcast to the VHF radio, it broadcasts on the AIS frequency - it's an interesting point though, I wonder if it could be something that could be incorporated to either piece of kit as an additional notification...an automated distress DSC broadcast on 70.

KAM - To go back to the original question. I actually asked McMurdo this question on their SAR Ecosystem Webinar last month. It can't easily be answered, depends on a number of factors and they said they cannot give a definitive answer to the question - However, the accepted generality is that, on average, it takes 5 minutes from the PLB being activated, to a signal being relayed by the GEOSAR satellites.

 

[FishyInverness]

The time taken usually to get a position fix good enough for an SAR operation is about 45 minutes, with two hours being the maximum providing no transmission issues. In practice that means that the PLB with or without GPS alerts the CG at the same time and SAR is activated at almost exactly the same time. The actual finding is done by the homing signal identical on both units; the addition of GPS therefore adds very little to a PLB's real world functionality, costs pennies to add on but enables a £70 price difference - I still bought one with GPS though, you just do don't you

I would disagree here Kip.

While the GEOSAR satellites are the near immediate alert which identifies that someone, somewhere with a PLB/EPIRB is in trouble, so indeed GPS/Non-GPS doesn't matter a hill of beans as far as first alert is concerned; without GPS, you are relying on the LEOSAR satellites to then calculate your position using Doppler. This takes between 45-90 minutes and provides a typical 5km radius.

With GPS your position is calculated within a 62 metre radius, with updates every 20 minutes. As a result, is is estimated that a SAR operation, on average, is launched within 30 minutes of a PLB/EPIRB WITH GPS being activated, as oppose to 1-2 hours for a non-GPS (depending on location in the globe and satellite coverage at time of activation)

I know which i'd rather have, and be happy to pay a bit more for it!

 

[ianj99]

Slightly off topic again, but what is needed is a fluorescent / illuminated 50cm Helium balloon on a few metres of cord which automatically deploys to make spotting the mob much easier.

 

[FishyInverness]

Slightly off topic again, but what is needed is a fluorescent / illuminated 50cm Helium balloon on a few metres of cord which automatically deploys to make spotting the mob much easier.

http://www.illoomballoon.com/ ?

 

[lw395]

....... the addition of GPS therefore adds very little to a PLB's real world functionality, costs pennies to add on but enables a £70 price difference - I still bought one with GPS though, you just do don't you

The GPS antenna and receiver are actually easily the most expensive components in a PLB.
I tend to think they are worth paying for though, unless you are sailing on a boat with its own 121.5MHz homing gear.

 

[ianj99]

http://www.illoomballoon.com/ ?

Just the job and why not if it helps locate the mob! Perhaps they'll make a larger one to lift the mobo clear of the water for easy recovery?

 

[lpdsn]

That's one of the reasons for giving the MMSI as part of the Mayday message as it ties in the beacon registration.

Although it won't necessarily tie in for a PLB which can be used on multiple vessels, or indeed nowadays quite legally on land in the UK.

 

[FishyInverness]

Just the job and why not if it helps locate the mob! Perhaps they'll make a larger one to lift the mobo clear of the water for easy recovery?

It is the same guy that invented the Water-Buoy, so you never know.

 

[MrB]

For the "around the world race teams" etc, would it not be worth having one of these on board?

http://www.oceanmedix.com/?_siteid=oceanmedix&_sessid=b1def5da22ec0c744bf8181cb4049978&action=sku&sku=dOM-HAM_kit01

Quite cheap really if you can find your MOB quickly.

 

[Rivers & creeks]

I would disagree here Kip.

While the GEOSAR satellites are the near immediate alert which identifies that someone, somewhere with a PLB/EPIRB is in trouble, so indeed GPS/Non-GPS doesn't matter a hill of beans as far as first alert is concerned; without GPS, you are relying on the LEOSAR satellites to then calculate your position using Doppler. This takes between 45-90 minutes and provides a typical 5km radius.

With GPS your position is calculated within a 62 metre radius, with updates every 20 minutes. As a result, is is estimated that a SAR operation, on average, is launched within 30 minutes of a PLB/EPIRB WITH GPS being activated, as oppose to 1-2 hours for a non-GPS (depending on location in the globe and satellite coverage at time of activation)

I know which i'd rather have, and be happy to pay a bit more for it!

That's sort of correct, the two key issues though are that the final few miles are homed on using the 121.5MHz gear on the lifeboat and helo, which means they will find you just as accurately no matter which; the second issue about launch of SAR is a bit misleading, CG spend about 40 minutes establishing it isn't a false alarm, so at best the launch of SAR is identical whether you have GPS or not and at very worst is an hour later.

Basically we agree though, the inclusion of GPS makes us feel better about the purchase, in real world useage it doesn't matter more than 60 minutes for us coastal/channel types, and the inclusion allows the manufacturers to sell it with a lot more profit. A few years ago I sourced some sewing machines for a charity in South Africa, I got the UK's biggest distributor to supply them at their landed cost price and being a charity type I asked for the cheapest model price; the MD asked why I hadn't gone for the almost top of the range because it was waaaaaay better featured, I said because it costs £185 more retail. He said it cost them £5.20 more landed price and how many did I want

 

[prv]

When an EPIRB goes off, do all the operating DSC enabled VHF radios within range get an MMSI mayday call

They may do, if in coastal waters and the Coastguard decides to send a Mayday Relay in response to the distress situation. But not directly from the EPIRB, no - why on earth would they? They're utterly unrelated.

For the record, you also would not receive notification via BBC Radio Two, GSM mobile telephone, or semaphore. Those also are unrelated to the 406MHz EPIRB system.

Pete

 

[prv]

The GPS antenna and receiver are actually easily the most expensive components in a PLB.

That seems surprising. They're cranked out by the bazillions for mobile phones, whereas the 406MHz and 121.5Mhz transmitters and the PLB controller stuff is far lower volume.

Pete

 

[bbg]

If the OP's question is to get a GPS position so he can search for the MOB, and he actually sees the MOB go over, the boat is likely to be able to give data to the CG faster than the CG can give data to the boat.

Most GPS data now is displayed in DD MM.MMM

Since 1 minute is 1 mile, and one mile is 6076 feet, you would need to get accuracy from the GPS device to at least two decimal places (61 feet), assuming no error or discrepancy in either the sending device (PLB) or receiving device (on the boat). If you got data to three decimal places, even better, but you need to know how current that information is. If it is 15 minutes old it won't be as useful as if it is 1 minute old.

There is a MOB button on GPS sets for a reason: that gives a confirmed starting point for a search.

 

[prv]

For the "around the world race teams" etc, would it not be worth having one of these on board?

http://www.oceanmedix.com/?_siteid=oceanmedix&_sessid=b1def5da22ec0c744bf8181cb4049978&action=sku&sku=dOM-HAM_kit01

Maybe they do; that certainly seems to be the intended market.

For the rest of us, investing in 121.5Mhz homing for MOB seems like backing the wrong horse to me though. An AIS SART like the Kannad R10 will do much the same job for far less money, with no bulky receiver to stow, and should be much easier to use for the reduced (and possibly disoriented) remaining crew. It's true that at present you have to decide between AIS SARTs and PLBs, so if the parent vessel is completely unable to help (even by broadcasting a mayday or setting off its own 406 device) then the MOB is on their own - but that seems an acceptable tradeoff to me. In any case I hear rumours of a combined AIS / 406 device showing up in a year or so.

Pete

 

[FishyInverness]

That's sort of correct, the two key issues though are that the final few miles are homed on using the 121.5MHz gear on the lifeboat and helo, which means they will find you just as accurately no matter which; the second issue about launch of SAR is a bit misleading, CG spend about 40 minutes establishing it isn't a false alarm, so at best the launch of SAR is identical whether you have GPS or not and at very worst is an hour later.

Basically we agree though,

With you there, and I agree we do to a point. I completely agree on the final few miles with 121.5 direction finding, but that 28 square miles to start with if not using GPS must be pretty daunting.

However, the 2nd point is taken directly from the Search and Rescue Webinar from McMurdo, which was hosted by various independant experts as well as McMurdo themselves. The reasoning being that SAR cannot be launched until they know where the SAR is happening - IIRC correctly (I may be sketchy on this) a first pass from LEOSAR can take anything up to 45 minutes and may require a 2nd pass to use the doppler system to get a location, hence the 90 minutes. I think the Webinar has been saved as a live recording, if you're interested, I'll find the link to it....