With the advent of the personal locator beacons (PLBs) and personal AIS units rescue operations are now much easier to perform. We take a look at the best PLBs and AIS on the market and explain the difference between them

Not so long ago simply locating a crew member who had fallen overboard in anything other than the most benign of conditions was a massive challenge, thanks to personal locator beacons (PLBs) and personal AIS units this has fundamentally changed.

PLBs are small devices, typically fitted on a lifejacket, that send a distress message, including GPS position, via satellite to a coastguard operations centre. They therefore work in a similar manner to EPIRBs, but require manual activation and have a shorter operational battery life (usually 24 hours).

A newer type of gadget – personal AIS – both triggers an alarm on board your boat (usually via DSC) and transmits an AIS position that can be seen on your chart plotter and on those of other vessels in a 2-4 mile radius if they are equipped with AIS receivers.

In many situations, personal AIS will therefore be a better bet than a personal locator beacon that only transmits a position to a remote location ashore. Some personal AIS units can also be set to activate automatically when a lifejacket inflates. It’s important to understand the fundamental differences between the two types of device.

What’s the difference between a personal locator beacon and a personal AIS unit?

Personal AIS transmits locally and enables the casualty’s position to be displayed on the chartplotter of your own boat and others nearby, including lifeboats once near the scene.

By contrast, personal locator beacons transmit their primary 406MHz signal only to a remote rescue coordination centre. This can be helpful in raising the alarm and in deploying search and rescue assets, but doesn’t help your own boat and others around you to locate a person in the water.

Personal locator beacons transmit a secondary signal on 121.5MHz, which is helpful for lifeboats homing in on a casualty, but other vessels are rarely equipped to receive this signal. In addition, although the units are generally buoyant, all PLBs need the antennal to be held in the air manually and the body of the unit must be supported out of the water for the GPS antenna to work.

For some time there has been talk of combining both these devices into a single product. There’s no technical reason why that shouldn’t happen, however, there are regulatory hurdles that have yet to be overcome, so it’s unlikely a combined device will be available any time soon.

What’s the best option? Ideally both a personal locator beacon and personal AIS for each crew member – that’s what I have when racing offshore or undertaking long passages when cruising. Don’t underestimate the massive step forward this represents – having both devices all but eliminates the search element of a search and rescue mission. Their adoption therefore ought to become widespread.

If forced to choose only one type, providing my boat was equipped with an AIS receiver, I’d likely plump for the personal AIS, particularly if sailing with other people on board and in an area in which there are generally other boats around.

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