What Are AIS EPIRBs?

I have already discussed regular EPIRBs in-depth on this website. In the article “How Do EPRIBs Work?”, we looked in detail at how they work, and briefly introduced the concept of AIS EPIRBs.

AIS EPIRBs are set to become a lot more common as they will soon be a standard part of a ship’s GMDSS equipment. So, what are AIS EPIRBs?

AIS EPIRBs are satellite distress beacons (EPIRBs) with an integrated AIS transmitter. In addition to the regular EPIRB distress transmission on 406 MHz, they transmit on AIS so that the distress can also be detected by vessels in their immediate vicinity.

As they transmit on 406 MHz, they work in the same way as all other EPIRBs. The difference comes in the additional integration with AIS. This makes AIS EPIRBs an upgrade over the traditional EPIRB.

If you find yourself in a distress situation, the AIS EPIRB will send a signal on 406 MHz to satellites, which can be detected from anywhere on earth. This signal is routed to your national rescue coordination centre, who dispatch vessels to look for you.

Once those vessels are on scene, they can detect the additional AIS transmission on their own navigational equipment and proceed directly to you.

Example of an electronic chart showing an activated AIS EPRIB

Without the AIS integration, rescue vessels would instead have to rely on a relayed position from the rescue coordination centre, based only on the satellite signal.

You could find yourself in the position where you can see other vessels, yet when you activate your EPIRB they do not know you are in distress because they do not carry equipment that can detect 406 MHz signals.

Using an AIS EPIRB instead means that your distress is detectable by all vessels in your vicinity, as well as national coordination centres via satellites.

The AIS EPRIB is basically two distress beacons, combined within a single unit.

How do AIS EPIRBs work?

AIS EPIRBs primarily work in the same way as other EPIRBs.

Upon activation, they start transmitting their identity on 406 MHz so that the signal can be detected by satellites.

Simultaneously, they start searching for GNSS satellites to calculate their own position. Most will use GPS, but they could use Galileo, GLONASS or any other approved GNSS system.

Once they calculate their own position, they add that to the 406 MHz transmission.

The 406 MHz signals are then actioned in the same way as any other EPIRB transmission. You can read in detail about how EPIRB signals are actioned in this article: How Do EPIRBs Work?

AIS EPIRBs, however, also take the position that they have determined and broadcast it using their integrated AIS transmitter.

The AIS transmission is broadcast over VHF, which is detectable by vessels within the immediate vicinity.

Equipment that detects an AIS transmission interprets the data to draw it onto the navigational equipment of the detecting vessel. It is the same system that they use to plot other vessels that are transmitting on AIS. The only difference is that the distress beacon shows up as a distinctive icon so that it can be readily identified.

The icon for an AIS emergency beacon is easily identifiable on an electronic chart.

Are AIS EPIRBs compulsory?

AIS EPIRBs are not yet compulsory on vessels. They are, however, due to become compulsory from 2022 onwards.

From that date, the Maritime Safety Committee of the International Maritime Organisation has decided that the performance standards of EPIRBs will change to include AIS integration.

This effectively means that GMDSS compatible EPIRBs will all need to be AIS EPIRBs.

In MSC.471 Annex 24, they state that EPIRBs shall:

“…be provided with an Automatic Identification System (AIS) locating signal in accordance with the Recommendation ITU-R M.1371, Technical characteristics for an automatic identification system using time division multiple access in the VHF maritime mobile frequency band.”


While they are not yet compulsory, over the coming years they will be.

What is the difference between an AIS EPIRB and a GNSS EPIRB?

The only difference between a GNSS EPIRB and an AIS EPIRB is the additional AIS integration within the AIS EPIRB.

A GNSS EPRIB is an upgrade over traditional EPIRBs because it includes integration with a Global Navigation Satellite System. Normally, they include a GPS receiver which allows them to transmit their own position with the 406 MHz satellite signal.

In turn, an AIS EPIRB is an upgrade over a GNSS EPRIB. AIS EPIRBs take the data provided by the integrated GNSS receiver and transmit it to vessels in their immediate vicinity using their integrated AIS.


Are AIS EPIRBs better than other EPIRBs?

The primary purpose of an EPIRB is to give you a means of signalling for help in a distress situation.

By its very definition, every EPIRB uses a constellation of satellites to relay their signal to an appropriate authority ashore.

Regular EPIRBs then rely on the shore authorities to relay their position to rescue vessels. The rescue vessels then search on scene until they locate the beacon.

With AIS EPIRBs, they have an additional transmitter which transmits on AIS channels. This means that rescue vessels have a means of electronically locating the beacon without needing the position to be relayed from the shore.

Additionally, AIS EPIRBs have the ability to signal other vessels directly, even before the shore authorities have detected the distress.

In an area with a lot of shipping traffic, it is especially important to be able to transmit to local vessels. Not only does it increase the potential, speed of your rescue, but it also means they will be aware of your distress and less likely to collide with you.

Should you buy an AIS EPIRB?

In my opinion, you should consider buying an AIS EPRIB when you need to replace your current model if you can afford it.

We have already identified that AIS EPIRBs are better than other types of EPIRB because they can potentially increase the speed and ease of any rescue. 

Their main disadvantage, however, is their cost.

Over time, the cost of AIS EPIRBs will reduce as the technology becomes more common. 

At the time of writing this article, however, the AIS version of one brand of EPIRB is approximately 40% more expensive than the non-AIS version.

McMurdo SmartFind G8 EPIRB with AIS Automatic Housing£699.95
McMurdo SmartFind E8 EPIRB Automatic Housing£499.95

Source: www.marinesuperstore.com (accessed 16th February 2021)

If it is not compulsory for you to carry an EPIRB anyway, you may well be put off by the additional cost.

As with any discretionary safety equipment though, it is up to you to decide if the additional cost is worth it for your particular use case.