Laser310
Well-known member
so.., ask the manufacturer if they think your idea of turning it on an off is good one...
I am pretty sure they will say: "no.., leave it on.., even in the middle of the ocean"
S&R mission finds the wrong liferaft
- Thread starter Stingo
- Start date
so.., ask the manufacturer if they think your idea of turning it on an off is good one...
I am pretty sure they will say: "no.., leave it on.., even in the middle of the ocean"
Adios
...
This was in their reply I posted up the thread.
As long as the beacon conforms to the above then there would be enough power in the unit to turn on for up to an hour a day for 24 days use.
The frequency of the emergency transmission, for a COSPAS/SARTSAT beacon is once every 50 seconds until the unit is switched off.
Assuming that the PLB1 has a clear view of the sky, it should obtain a position fix within 40 seconds
Kind Regards
Technical Customer Support
Ocean Signal Ltd.
RunAgroundHard
Well-known member
The Cheeki Rafiki events brought home to me the unreliability of PLBs. Unless the antenna is held up and clear it fails to transmit. IIRC the intermittent received positions and timings formed a trend that was comparable to a person floating in the water, which was stated by USA CG.
It does suggest that using a PLB on and off does work to indicate distress and that it it does not have to be on all the time. Hence, in a liferaft, periodically switching it on and holding the device in the optimal position may not be a daft idea on the face of it. It also suggests that a PLB as a poor mans primary EPIRB is a crap idea.
It does suggest that using a PLB on and off does work to indicate distress and that it it does not have to be on all the time. Hence, in a liferaft, periodically switching it on and holding the device in the optimal position may not be a daft idea on the face of it. It also suggests that a PLB as a poor mans primary EPIRB is a crap idea.
Adios
...
This is more what I'd expect. Other posters seem to believe the CG thinking is purely binary and dull witted. If its on "full response", if it goes off "stick the kettle on". They surely know there is more to contemplate. They have info on which model of device to consider, they have contact numbers of the registered keeper to ring for more info. The reason I said 10 minutes on and then 10 again an hour later, rather than just an hour a day, was that it would be more likely the events would be connected by the same people on the same shift and already after an hour there is a trend.
Sandydog2
Well-known member
I read in the comments on his Facebook page that he bought the plb secondhand and the battery was old and dodgy.
Adios
...
Ocean Signal have pointed me here for more info:
International Cospas-Sarsat Programme - International COSPAS-SARSAT
On the time taken for signals to be transmitted and received by rescuers, example given here https://www.cospas-sarsat.int/images/stories/SystemDocs/Current/IB-29-EN-all-pages.pdf
In summery, from beacon activation, for the initial signal to reach multiple satellites, to be transmitted to a receiving station in France, its position calculated initially without GPS, and all the info relayed to the national responders in the relevant area in Norway took 23 seconds.
50 seconds later a second message was sent that allowed location to be calculated within 500m accurate. Another 50 seconds and by this point the GPS had a lock and this was added to the message.
On the issue of conserving battery life I found this relevant though its in a part relating to what to do if you have multiple beacons and assumes you have an EPIRB as well. Guidance on Multiple Beacon Activation - International COSPAS-SARSAT Still the example clarifies that intermittent on/off use to conserve battery is recommended in certain circumstances and gives a recommended on time of 3 hours.
The yachtsman has an EPIRB with a 48 hour battery life and a PLB with a 24 hour battery. Both beacons should be activated. Early detection allows the Search and Rescue authorities to immediately begin search and rescue operations and request the nearest vessels for assistance.
As this remote rescue operation may take more than 48 hours, one beacon should be deactivated after three hours to conserve the battery. If possible, a GNSS-enabled beacon should remain activated. The yachtsman should reactivate the deactivated beacon again for a period of three hours every six hours.
Even mid pacific 3 days is probably enough isn't it with ships to divert but I'd assume they'd recommend adjusting the times further according to the circumstances.
International Cospas-Sarsat Programme - International COSPAS-SARSAT
On the time taken for signals to be transmitted and received by rescuers, example given here https://www.cospas-sarsat.int/images/stories/SystemDocs/Current/IB-29-EN-all-pages.pdf
In summery, from beacon activation, for the initial signal to reach multiple satellites, to be transmitted to a receiving station in France, its position calculated initially without GPS, and all the info relayed to the national responders in the relevant area in Norway took 23 seconds.
50 seconds later a second message was sent that allowed location to be calculated within 500m accurate. Another 50 seconds and by this point the GPS had a lock and this was added to the message.
On the issue of conserving battery life I found this relevant though its in a part relating to what to do if you have multiple beacons and assumes you have an EPIRB as well. Guidance on Multiple Beacon Activation - International COSPAS-SARSAT Still the example clarifies that intermittent on/off use to conserve battery is recommended in certain circumstances and gives a recommended on time of 3 hours.
Remote yachtsman
A solo yachtsman is in distress and is thousands of kilometres from land. A rescue operation may take more than 48 hours as the yachtsman is in a remote location.The yachtsman has an EPIRB with a 48 hour battery life and a PLB with a 24 hour battery. Both beacons should be activated. Early detection allows the Search and Rescue authorities to immediately begin search and rescue operations and request the nearest vessels for assistance.
As this remote rescue operation may take more than 48 hours, one beacon should be deactivated after three hours to conserve the battery. If possible, a GNSS-enabled beacon should remain activated. The yachtsman should reactivate the deactivated beacon again for a period of three hours every six hours.
Even mid pacific 3 days is probably enough isn't it with ships to divert but I'd assume they'd recommend adjusting the times further according to the circumstances.
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lustyd
Well-known member
Thanks for pursuing that extra info, very interesting. I am interpreting those words a little differently but it does confirm a few things around timings that they deem acceptable which is very good to know.
I'm curious what they say in single beacon scenarios, I think reading the above I'd probably use half the expected life in one hit and then do the 3 hours every 6. Not that I'd probably be that precise with timings mid pacific!
I'm curious what they say in single beacon scenarios, I think reading the above I'd probably use half the expected life in one hit and then do the 3 hours every 6. Not that I'd probably be that precise with timings mid pacific!
ylop
Well-known member
There are 3 different times for a GPS system to give you a fix. The first is how long it takes to give the first fix (TTFF) when it is turned on after being off for a long time (several days), first used, or if it’s moved a long way (say 100 miles) from its last known position. If the system has no other input data (unlike say a cellphone which has aGPS using its data connection to quickly get the upto date almanac and cell tower type information to give it a good starting estimate for location) this will be a cold start and take a standard GPS 12.5 minutes. It’s possible this has been accelerated with Galileo? My experience of turning on new GPS kit for the first time is it still takes a long time - even since gallileo has been live. PLB/EPIRB manufacturers may have done something standard gps people don’t bother with and prioritised TTFF over accuracy if they can use a partial almanac to do that.
The next is how long it takes for the system to get a fix if the system has been turned off for a short period (say a few hours) but is still in the rough area where it was previously. This is usually less than a minute if it has good visibility of the sky (a warm fix) - it still needs to listen for data coming from the satellites so interruptions in the data (waves, not holding it upright etc) will contribute to delays.
The final is how long if it’s just been rebooted but had good position within the last 30 minutes. This is very fast (a second or so) - a hot fix.
It’s how all GPS systems that don’t have a separate data connection (aGPS) work. they need to know where the satellites they can hear actually are in space.
My point was if you want a system to last >24h buy one that’s designed for the job (which will come with other benefits like Automatic activation, automatically pointing “sky up” etc). If you want one that can be attached to a person buy a PLB but accept its 24h limitation.
Someone in this thread has suggested that previously this has been assumed to be a faulty device. That goes against my instinct, but look up the MAIB report on the fishing vessel that sank off Mingulay for an idea of what REALLY happens when the fax (!!!) with the epirb activation details comes through. This isn’t thunderbirds are go territory and that incident was a lot closer to launch help to check out an uncertain signal than the middle of an ocean.
Clearly a key to successful use of a PLB or EPIRB is properly registering it and ensuring your shore contacts are able to confirm that you are at sea, ideally your plans and last known location and any alternative means to contact you - if that all stacks up then your distress should get the action you hope for. Perhaps in those circumstances turning on and off the device (especially if you have made your shore contact aware this is your planned MO will not be quite as crazy as I suggested). Personally if I am >24 h in a life-raft I might want to be dead anyway!
If you were going to take this approach perhaps the newest devices which allow a “we got your message” acknowledgement to be sent back provide you with some reassurance. I notice manufacturers saying this typically takes “about 10 minutes” - I’m not sure if the acknowledgment = distress received or distress received with GPS location?