Time to respond to an EPIRB

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Daydream believer

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In another thread i have said that i would chuck the epirb in the water asap to mark a MOB
However, does anyone know how long it takes to respond to it once the signal has been received by CG.
Do they alert services immediately or do they go through the rigmarole of ringing up Falmouth ( for uk) first to check on details?
How long is it before the signal gets a satellite fix & sends a signal?
I ask that because whilst my on board garmin picks up satellites in seconds but my magellan hand held can take 10-12 minutes
If in range of a receiving station a vhf dsc signal takes seconds but an epirb could be ages before anyone responds
Does anyone know?
 
Daydream believer said:
In another thread i have said that i would chuck the epirb in the water asap to mark a MOB
However, does anyone know how long it takes to respond to it once the signal has been received by CG.
Do they alert services immediately or do they go through the rigmarole of ringing up Falmouth ( for uk) first to check on details?
How long is it before the signal gets a satellite fix & sends a signal?
I ask that because whilst my on board garmin picks up satellites in seconds but my magellan hand held can take 10-12 minutes
If in range of a receiving station a vhf dsc signal takes seconds but an epirb could be ages before anyone responds
Does anyone know?
Click to expand...

OK, basically it works like this.

Your beacon goes off. It will be picked up on the next pass of the relevant satelite - could be immediate, might be an hour or so.
That satelite will either (a) download the signal immediately to the nearest LES (land earth station) or it it will retain it until it can find an LES to download to.
It will pass two positions - each with a probability %age, due to being based on a doppler system.
The receiving LES will pass the details to the state of registry of the beacon, or to the MRCC if within it's own search and rescue region.
The receiving MRCC will check the details, and most like wait for a second pass - we have to, because the positions on the first pass will be wide. At the same time, the MRCC will be checking beacon registry details, shore contacts, anything else that might help us rule out a false alert.
On the second pass, with what is called a "resolved position" (e.g. 90% on one position) if everything else has drawn a blank, we'd start acting.
In reality, offshore, that action would be an EGC (inmarsat distress) relay, and possibly an MF broadcast.
If your EPIRB has an embedded GPS position, we won't need the second pass, but will most likely want one due to the high number of false alerts.
 
All I can tell you is that mine fired off a real signal when I ran the test procedure. I got a call on my mobile from Falmouth CG about 40 minutes later.

p.s. no point using it for a MOB unless it's a GPS type - not accurate enough.
 
Don't forget that the EPIRB also includes a short-range "homing" signal as well as the satelite notification.

Any SAR resources will have the ability to locate it from a range of a couple of miles away.

So relying on the satelite function for MOB is pointless, might as well use VHF, but it can still be a useful thing to do
 
bedouin said:
Don't forget that the EPIRB also includes a short-range "homing" signal as well as the satelite notification.

Any SAR resources will have the ability to locate it from a range of a couple of miles away.

So relying on the satelite function for MOB is pointless, might as well use VHF, but it can still be a useful thing to do
Click to expand...

Yes, but you're relying on the thing coming to you being a SAR asset, able to pickup the 121 homing signal.

Narrows it down a bit ;)
 
snowleopard said:
All I can tell you is that mine fired off a real signal when I ran the test procedure. I got a call on my mobile from Falmouth CG about 40 minutes later.

p.s. no point using it for a MOB unless it's a GPS type - not accurate enough.
Click to expand...

But it has to be accurate enough to get to a liferaft in the atlantic so must have some accuracy -- but how much?
 
chanelyacht said:
OK, basically it works like this.

Your beacon goes off. It will be picked up on the next pass of the relevant satelite - could be immediate, might be an hour or so.
That satelite will either (a) download the signal immediately to the nearest LES (land earth station) or it it will retain it until it can find an LES to download to.
It will pass two positions - each with a probability %age, due to being based on a doppler system.
The receiving LES will pass the details to the state of registry of the beacon, or to the MRCC if within it's own search and rescue region.
The receiving MRCC will check the details, and most like wait for a second pass - we have to, because the positions on the first pass will be wide. At the same time, the MRCC will be checking beacon registry details, shore contacts, anything else that might help us rule out a false alert.
On the second pass, with what is called a "resolved position" (e.g. 90% on one position) if everything else has drawn a blank, we'd start acting.
In reality, offshore, that action would be an EGC (inmarsat distress) relay, and possibly an MF broadcast.
If your EPIRB has an embedded GPS position, we won't need the second pass, but will most likely want one due to the high number of false alerts.
Click to expand...

So estimate of quickest & longest time for launch of a lifeboat or air support is ---?
& " false alerts" are they making use of epirb in , say, the north sea or channel redundant?
 
nigelmercier said:
An EPIRB? A PLB, surely?
Click to expand...

No - an EPIRB transmits while floating unattended, a PLB will either sink or roll upside down with the aerial shorted out; it needs to be held upright.

Daydream believer said:
As i understand it one needs to look at instruments to find a plb
Click to expand...

No - you're thinking of either an AIS SART or one of the older analogue homing beacons. A PLB does the same as an EPIRB in terms of signalling, the difference is shorter battery life (a "mere" 24 hours) and the inability to auto-trigger, float free, or transmit while floating.

Pete
 
Daydream believer said:
But it has to be accurate enough to get to a liferaft in the atlantic so must have some accuracy -- but how much?
Click to expand...
It only has to be accurate enough to get the SAR resources into the correct general area so they can pick up the short range homing signal (243?) That probably has the range of a few miles
 
Daydream believer said:
So estimate of quickest & longest time for launch of a lifeboat or air support is ---?
& " false alerts" are they making use of epirb in , say, the north sea or channel redundant?
Click to expand...

Every instance is slightly different, but, best case example -

EPIRB hit in UK waters, satelite to LES, LES to MRCC, MRCC checks contacts, contact says "oh yes, he's out sailing" and resolved position - assets tasked in around 30 minutes.

Worst case - unresolved position, unregistered beacon, south atlantic or somewhere with no SAR infrastructure - no assets at all tasked.

The really key thing in all this is make sure your registration details and alternative contacts are up to date on CG66 as well as the EPIRB registry.
 
bedouin said:
the short range homing signal (243?)
Click to expand...

121.5, I believe. A warbling note on that frequency used to be the sole distress beacon transmission, no identification or position. But it's been there for many decades (since WWII?) so that's what all the emergency DF kit is built to use. They stopped responding to tones on 121.5 due to excessive false alarms, but it's still there, unchanged, as the last-mile homing signal.

Pete
 
chanelyacht said:
contact says "oh yes, he's out sailing"
[...]
The really key thing in all this is make sure your registration details and alternative contacts are up to date on CG66 as well as the EPIRB registry.
Click to expand...

I've put my mum as the contact, as the most likely person to know I'm on my way to the Channel Islands or whatever and not be on the boat. But she sails as well, albeit mostly pottering around the Solent, so it's not impossible that she might set off the PLB for which she is her own registered contact!

I might be mistaken, but I don't remember a facility to add more than one contact on the EPIRB registration site or paper form. Since the EPIRB registry update backlog seems to be currently running at a couple of months, we can't exactly change it to reflect who is on board for any given trip!

What happens if you ring a contact and get no answer?

Surely if the signal comes with a GPS position that is at sea, the owner (or at least his boat) is clearly out sailing? OK, it could still be a false alarm (guest fiddling with the funny thing on the bulkhead, someone slipping through the hatch and kicking it off its mount, etc) but the shore contact can't help you with those anyway.

Pete
 
Which all goes to show that you must not expect an immediate response to electronic emergency signals. They are primarily designed for finding ships in distress on the ocean and with an appropriate timescale, not for fishing swimmers out of the Solent before hypothermia sets in.

Methinks there is sometimes too much reliance on "I'll call for help and the rescue services will turn up in minutes like they do on TV". Chances are they won't.

The EPIRB telephone verification system is clearly designed for commercial shipping where a company contact is always available. Relying on your domestic contact being available and by the phone when you fall over the side is dreamland. The system is full of holes and thus cannot be relied upon.
 
prv said:
I've put my mum as the contact, as the most likely person to know I'm on my way to the Channel Islands or whatever and not be on the boat. But she sails as well, albeit mostly pottering around the Solent, so it's not impossible that she might set off the PLB for which she is her own registered contact!

I might be mistaken, but I don't remember a facility to add more than one contact on the EPIRB registration site or paper form. Since the EPIRB registry update backlog seems to be currently running at a couple of months, we can't exactly change it to reflect who is on board for any given trip!

What happens if you ring a contact and get no answer?

Surely if the signal comes with a GPS position that is at sea, the owner (or at least his boat) is clearly out sailing? OK, it could still be a false alarm (guest fiddling with the funny thing on the bulkhead, someone slipping through the hatch and kicking it off its mount, etc) but the shore contact can't help you with those anyway.

Pete
Click to expand...

Alt contacts are on the CG66, which is why we really like both.

If it's at sea we will start to take action, which may well just be passing coordination to the local competent authority (but keeping an eye on progress).

The problem is when the two doppler positions have similar percentages, we have little choice but to wait for the resolved position.
 
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