Question for SAR crew - EPIRBS/PLB's
 

We were wondering if multiple EPIRB's/PLB's at a resuce location cause confusion, or perhaps make it easier for SAR crews tracking in on a 121.5 homer. We have a 406/121.5 EPIRB on the boat but crew members also carry personal locator beacons on the same frequencies and we were wondering if we had three PLB's and an EPIRB going off at the same time if this would be a good idea or not?

One is enough to home to, more than one is a waste of resource.

My answer (ex Mil & ex SAR), if all survivors are co-located, would be to conserve the group's overall battery power / transmit time by using one at once.

I'd agree with ST about only using one at once. Presumably though, you have individual PLBs in case one of you goes overboard. Anything that makes you more "conspicuous" as a MOB has to be worth keeping.

It is always best to have the kit transmit on both 121.5 and 406 as they do different things, of course.

If you really want to turn your system into the best possible, think about fitting a 121.5 direction finder on your boat to search for an MoB with his PLB.

What is currently taught on BOSIET is that one of the Maintain actions in a liferaft is to ensure that only one beacon is operatiing at a time and one should select the most powerful. This normally means seeking evidence of operation of an ELT or EPIRB and switching off all PLB.

Perhaps a pprune member from a wee room in Morayshire will come along and put us right on this one.

You can't 'home' in the classic sense to a 406 beacon as it is a burst transmission every 50 seconds or so but you will have a position to go to once that signal is bounced off the satellite and downlinked to the MRCC.

That in itself is no guarantee that you will be pinpointed immediately as the beacon message is in two parts and sometimes the second part (with the accurate GPS position in it) gets lost or disrupted, leaving only a coarse position (within 10nm or so).

Hence the need for a 121.5 signal (constant transmission) to actually home to.

Multiple beacons in the same location are not too much of a problem as you can home to the 'centre of mass' but if you have a lot of them spread over a larger distance (hundreds of metres say) then, unless you can spot the survivors visually (or thermally) you will have to start at one end and work your way through, switching off the beacons as you recover each casualty.

One other problem with modern 121.5 beacons is that they don't have the same helpful characteristics of the military PLB signal that many will be familiar with - that is a pause between each transmission that allows you to associate the audio with the needle indication and differentiate between multiple signals. The only option with the 'constant beep' beacons is to home to the strongest signal first.

So the answer to the question depends on the scenario - if all the survivors are in one raft then you don't need all the 121.5 beacons going off - if you have multiple people in the water then they should all have them on.

The other issue with multiple beacons in the one location is that some of the newer beacons do not activate if they detect another beacon already going off in the near vicinty. It was a problem with the ETAP ditching a few years back, the pax had 121.5 beacons on their wrists which activated but were a weak signal. The crews beacons didnt transmit on 121.5 as they heard another signal already going on it so the searching aircraft is very bad visibility had difficulty locating the rafts.

Yes, the so-called 'smart' beacons are actually not so smart.

Thanks to you all for the info, a much appreciated insight into the question.

Crab you are not fair ...... the 'smart' ones are only as smart as their human designers make them. Wonder if oil company did a proper risk assessment before introducing them! :rolleyes:

tistisnot - I doubt it - either that or they asked some 'expert' like Jim Ferguson (see other threads) with no specific SAR experience what beacon homing is like in such scenarios.