Has anyone actually used a PLB in anger?

We had a rescue incident here in Cape Town a couple of weeks ago where a paddler activated his PLB when he got into trouble on a Miller's Run. The system failed to alert anyone before he'd already virtually rescued himself after swimming for 1.5 hours.

The details of that episode are here

In the aftermath we contacted the PLB agents and the manufacturers and met with our Maritime Rescue authorities and the NSRI to find out what happened and whether PLBs are practical for our use as surfski paddlers.

In my opinion they're not - the reasons are outlined here.

But I was curious to know if anyone has actually successfully called for help by using a PLB and if so what the circumstances were.

Does anyone know if handheld EPIRBs are any better at acquiring the satellite signal than the PLBs are?

Also, was that a typo.....did you mean use a PLB (when) in danger?

A very thought provoking read Rob ... I assume as the 406MHz network is globally common the same statements apply where ever and to what ever brand of PLB ? Concerning and as you say, little understood !!

I have a friend who used his (ACR, same as I have from memory) during an ocean race here in New Zealand and from memory the response was swift. Its unclear if the response was directly from the PLB or the safety craft ... will try and find out.

I think one major difference is that EPIRBs are designed to float upright, whereas not all PLBs float, and if they do have buoyancy they generally don't float upright to ensure signal transmission.

You need to acquire at minimum three different satellites transmissions, ideally four for the onboard computer to calculate your coordinates. Even if the same chipset is used, there may be differences in the antennae etc, that might result in one or the other being better; but as with the many GPS units I've used you may find that completely dependent on where you are one may be better or worse than another at acquiring and calculating your position from a cold start.

I can't speak for all PLBs vs. EPIRBs, but I know the ACR unit I use, the transmitting power of their EPIRB and PLB are both 5W, so I would think once the coordinates are calculated, they should be similar on that front.

Otherwise EPIRB will give you 48hrs of use, whereas the PLB will run out in 24. Compromises of one being designed for personal wear vs. on a boat.

You need to acquire at minimum three different satellites transmissions, ideally four for the onboard computer to calculate your coordinates. Even if the same chipset is used, there may be differences in the antennae etc, that might result in one or the other being better; but as with the many GPS units I've used you may find that completely dependent on where you are one may be better or worse than another at acquiring and calculating your position from a cold start.

That's correct - for the GPS receiver.

The PLB has two different ways of obtaining your location. In the ideal circumstance, the GPS receiver can see and receive signal from a number of GPS satellites (as you say) and works out your location. If it can't for some reason (like the GPS antenna being obscured), the PLB can still estimate your position using the Cospas-Sarsat satellites.

This needs the PLB unit to connect to two of the Cospas-Sarsat Low Earth Orbit (LEO) satellites. This can take up to two hours to happen; there are only five of these satellites in orbit.

The PLB transmits the unit ID (so that the owner of the unit can be identified) and the position (if it has been obtained, either by GPS or estimation from the LEO satellite data) encoded, via Cospas-Sarsat network to shore.

So - there are two different satellite networks involved - the GPS network, which works with the PLB's built-in GPS receiver and the Cospas-Sarsat network which provides a back-up means of calculating your position and also provides the transmission path to get the emergency notification to shore.

In our waters the battery time is probably irrelevant because you'll die of hypothermia long before the battery runs out!

Also, was that a typo.....did you mean use a PLB (when) in danger?

Apologies, I shouldn't have used that phrase - it just means "to use in a real situation".

Robin,
Thanks. Awesome info as always. One small correction though, whereas the GPS is calculated by the EPIRB/PLB, the Doppler effect estimation by the Cospas is actually calculated by a ground terminal and only requires 1 non-geosynchronous satellite to produce the calculation.

When you spoke with the SAR/Cospas guys were they able to give you the relative resolution of the Doppler estimation vs. GPS? I believe with GPS triangulation the ACR unit is only accurate to 100 yards, whereas Doppler estimation from a single satellite is going to be significantly less accurate, maybe 2-5km.

There are 5 LEOSAR satellites, but luckily it seems they fairly recently started implementing SAR systems on the GPS, GLONASS, and Galileo satellites creating the MEOSAR so they can be used for Doppler calculations as well as receiving as in the case of the 6 GEOSAR satellites, so hopefully the coverage should be improving as we speak.

I think given the very real possibility in delayed rescue I wonder if the procedure should be to pop it off at the first sign of significant trouble, rather than wait as an ultimate last resort when all other options have been exhausted/you are exhausted. I feel like a lot of people for fear of "the boy who cried wolf syndrome" or looking like an a-hole might be reluctant; I think the advantage of also carrying the VHF(in areas where both have reception) is you can notify the Coast Guard and let them know your location/situation at the first sign of trouble before it's truly F'ed, that you are going to try self-rescue, but if they don't hear from you confirming everything is okay in X minutes they should come get you. SAR/Coast Guard groups are the utmost professionals so I doubt they will ever react in a "boy called wolf" manner, but given the nature of surfski as a sport it certainly couldn't hurt if we all donate to our local Coast Guard/SAR groups.

For those considering adding the Delorme(now Garmin) Inreach to their kit, I have one as well although I generally leave it out of my kit(just a lot of stuff already)and below are some pros/cons I've found.

Pros:
- Similar to SafeTRX can give your people on shore a map with breadcrumb trail of your path/last location(unlike SafeTRX where in some areas that information interfaces directly with Coast Guard, this map does not, but unlike SafeTRX is not reliant on cellphone reception)
- There is an emergency button that will transmit your coordinates and relayed through Inreach's service to the appropriate SAR. Not sure how long a delay if any there might be on this, though.
- You can send predefined messages or type messages with your location to any email or cellphone address as well as your personal map site. If you use the emergency button you can communicate two-way with rescue services as well.
- Utilizes the Iridium network of 66 satellites with complete global coverage. Much more reliable than SPOT which has large swathes of uncovered areas.
- Will provide confirmation whether signal transmitted or failed(Some of the newer EPIRB/PLB also provide feedback whether transmission was successful)

Cons:
- NOT a substitute for a EPIRB/PLB
- unlike EPIRB/PLB requires subscription fee for service
- Does not have homing frequency used by SAR found in EPIRB/PLB
- Emergency response is relayed through a third party service
- I've experienced spotty/very delayed transmission of messages even with clear 360 degree sky.
- Have to make sure the battery is charged(might be a con/or a pro as compared to EPIRB where you cannot recharge and some older models didn't tell you how much charge is left in the sealed LI EPIRB/PLB battery)

One small correction though, whereas the GPS is calculated by the EPIRB/PLB, the Doppler effect estimation by the Cospas is actually calculated by a ground terminal and only requires 1 non-geosynchronous satellite to produce the calculation.

Thanks for that... I sent the article to McMurdo and to our Maritime Rescue folks and none of them picked that up! I was confused by a sentence in one of the articles that I read when researching this piece - what they actually said was that if there isn't a GEOSAR satellite overhead, then you'd have to wait up to an hour for a LEOSAR satellite to pick up your signal. I've corrected the article. I read it that they needed a second LEOSAR with an orbit at right angles to the first. Not so.

In terms of accuracy of GPS v Doppler:

"Doppler via the LEO satellites provides a location within 2 miles. If the beacon is equipped with GPS or receives a location from onboard navigation equipment, this encoded location is transmitted to the GEO satellite, providing immediate location information accurate to within 100 meters."

When searching for a surfski in conditions where the sea is covered with breaking waves, a 2mi accuracy is almost completely useless.

I think given the very real possibility in delayed rescue I wonder if the procedure should be to pop it off at the first sign of significant trouble

100% Our NSRI folks always ask us to call for help early, rather than late. A more non-judgemental lot of people I have never met. Even when the victim has been blatantly stupid to get into their emergency situation, they never, ever show anything but compassion. Brilliant people.

Yeah, the interesting thing about the LEOSAR satellites is that they are so low that the amount of ground each one covers is relatively small. That means it could take an hour for one to pass over head, get the Doppler readings from the your PLBs steady transmission, and then as I understand it, itcould take another hour for it to pass over a ground based terminal(there is a network of global LUTs) to transmit the information to be calculated. The 2mi accuracy of Doppler estimation is further confounded by the fact that during the two hours you could've drifted a pretty far distance in any direction further increasing the effective search area they need to cover.

Robin,
A bit off topic, but just wanted to relay the information so you can include in one of your informative safety articles. The white skis being completely indistinguishable from whitecaps by SAR is completely true, and even though any ski regardless of color provides a surprisingly small target for SAR, other colors perform better each within different light conditions. Red works best in daylight(surprisingly black is quite effective during the day), but looks completely black at night. Yellow, works best in lowlight conditions, but is the worst during the day when you have sunlight glare. Dayglo/Safety Lime/Orange seem to be the best compromise overall, and surprisingly I think one Coast Guard article cited Robin's Egg Blue; you'd think blue would be a terrible color, but that shade of blue apparently stands out like a sore thumb because it's just not found in nature.

We recently had a PLB detail update campaign here in New Zealand and I tagged on a couple of questions with my response which were answered today by a helpful fellow. Some interesting reading as below ...

My questions:

Can you please advise:
- What is the maximum and average time for a broadcast to be received by a satellite and broadcast to a ground station to be actioned ?
- Are these times the same globally or is NZ better served than other locations in this regard ?

The response:

Good afternoon David and thank you for your queries below. The notification time from beacon activations has been reduced considerably with the introduction of the MEOSAR (Medium Altitude Earth Orbit Search and Rescue) satellite system. This system now has a total of 20 United State GPS satellites and twelve Galileo satellites which are in continuous earth orbits. These satellites, when in view of a transmitting beacon, independently send the beacon identification to ground station antenna. If three or more satellites receive the beacon signal a ground location can be determined. If only the identification of the beacon is provided from one satellite, and it is registered, then a SAR response can be initiated. In New Zealand we have installed a six antenna ground station north of Taupo and in collaboration with Australia we now receive beacon alerts within two to five minutes. Normally a response would be commenced, at least into the planning stage, within ten minutes. The time to have a SAR asset at the location of the distress beacon can vary considerably and can be affected by the availability of a SAR asset and the weather, sea state or terrain.

The earlier LEOSAR (Low Earth Orbit Search and Rescue) satellite system is still functional and in use. This system currently has five satellites in orbit and the rotate around the earth in north/south polar orbits about every 105 minutes. They have an equatorial spacing of approximate 25 degrees between satellite orbits so at times it can be a long as four hours between suitable passes depending on your location within our Search and Rescue Region. With these satellites they determine position using a doppler technique and provide two positions equally spaced either side of the satellite track on each beacon activation. As a consequence we also need two passes to resolve the positional data that is provided. RCC operational response to the first message received is as with the MEOSAR system – if it is registered then it is normally possible to eliminate options and concentrate on one of the first two locations provided and then the planning cycle commences. If not registered, and there is no other indication of a distress situation, then we have to wait for the second satellite pass to confirm which of the two positions is the likely location of the beacons activation before dispatching any SAR resources.

In response to your second question I would like to think that we are better than the rest but in fairness I would say that the response that you would receive here in NZ is similar to what you could expect from most countries that maintain a Joint Rescue Coordination Centre.

Now days it is normally the registration of (or not) of the beacon and the availability of a suitable SAR response asset that determines the time between when we receive the beacon alert to when you are rescued.

Hope this helps.

robin.mousley wrote:
When searching for a surfski in conditions where the sea is covered with breaking waves, a 2mi accuracy is almost completely useless.

When notified the rescuers use the embedded 121.5 signal as an omnidirectional beacon to home in on the exact position within that 2-3 mile space where they began. Otherwise, yes it would be mostly impossible, but the use of that signal allows them to find the beacon. Obviously this works better in a helicopter than from a ship, but it is effective.

One more precaution for those who are redundant safety minded is to take a vial of safety dye/marker with them. I am in helicopters trying to spot relatively small objects frequently. The green/yellow dye makes that job much easier (though it is still surprisingly difficult, even when you know where the object is supposed to be). The yellow/green color is by far the most visible, much more than safety orange or red.

When notified the rescuers use the embedded 121.5 signal as an omnidirectional beacon to hone in on the exact position within that 2-3 mile space where they began

Good point.

But it does depend on whether the rescue craft has an RDF receiver installed. It sounds like the Aussies have all the toys, we're not so lucky here in SA.

I just spoke to one of our guys involved in SAR here in Cape Town and he confirmed that our SAR choppers are not equipped with anything more than the ubiquitous 121.5 receiver. They'll know that someone within 5km has activated a beacon, but they don't have the capability to home in on it.

I'll already established that the NSRI vessels (the volunteer-run SA equivalent of a coast guard) mostly do NOT have RDF receivers either for reasons of cost.

One more precaution for those who are redundant safety minded is to take a vial of safety dye/marker with them. I am in helicopters trying to spot relatively small objects frequently. The green/yellow dye makes that job much easier (though it is still surprisingly difficult, even when you know where the object is supposed to be). The yellow/green color is by far the most visible, much more than safety orange or red.

Yep, this is a big issue (trying to spot white skis on an ocean covered with white horses). In our SR exercise that we did years ago we also found that brightly coloured skis and, surprisingly, pencil flares worked pretty well for the chopper.

Slightly off topic, but does anyone know where people are getting the large bright stickers for their boats?

Slightly off topic, but does anyone know where people are getting the large bright stickers for their boats?

I only have an extremely local answer for that one... Here in Cape Town you can get them from Orka Paddling.

Where do you live?

I'm in US Pacific NW

Most marine and boating stores will will carry similar stickers or reflective tape. Scotchlite makes SOLAS (safetey of life at sea) tape and stickers.

www.westmarine.com/buy/taylor-made--scot...-3309739?recordNum=5
www.westmarine.com/buy/3m--scotchlite-so...-3761871?recordNum=4

It comes in different colors and is highly reflective. You can do a search online for SOLAS tape/stickers for more options.

Something like this should work too.

ORACAL 6510 Fluorescent Orange Cast Vinyl Wrap

Back on topic, I have more info on the availability of RDF receivers in aircraft in South Africa. In general civilian aircraft (like the AMS Rescue chopper in Cape Town) don't have it, but South African Air Force assets do.

Which in effect means, don't count on it.