What is an EPIRB?

An EPIRB (Emergency Position Indicating Radio Beacon) is a battery powered radio transmitter, which on activation sends a distress signal alerting the Search And Rescue (SAR) services who then co-ordinate your rescue.

When should an EPIRB be used?

In a DISTRESS situation; one in which there is grave and imminent danger to vessel and persons who require immediate assistance.

How does a 406 EPIRB work?

Modern EPIRBs operate in the 406MHz frequency band and incorporate a homing beacon which operates on 121.5MHz. On activation the EPIRB transmission (a 15-digit identity number ‘HEX’ and position if GPS equipped) is relayed via the COSPAS-SARSAT satellite network. This comprises of two separate satellite arrays; first The Low Earth Orbit Search and Rescue (LEOSAR) satellites which are between 850-1000km altitudes. These satellites cover the whole earth and cross over an area, on average every 45 minutes. The satellite receives the EPIRB distress signal and calculates its position by ‘taking a fix’ using the Doppler shift. This is usually within 2 passes, with a possible delay of 90 minuets and to within 5km accuracy. The message is passed to an earth ground station, a LUT (Local User Terminal). If the LUT is not immediately in the area of satellite coverage (within the footprint), the message is stored and rebroadcast at the first opportunity as the satellite moves on, passing a LUT. The distress alert is then passed on to the nearest Maritime Rescue Co-ordination Centre (MRCC) who then plan and co-ordinate the recovery of the survivors. The 121.5MHz frequency is used to aid the SAR services locate you in the final few miles.

The second satellite array is the Geostationary Search and Rescue (GEOSAR). These satellites appear to be stationary about the earth at approximately 36000km altitude. The satellites can constantly ‘see’ the earth between 75 deg N and 75 deg S of the equator, and therefore detection of a 406MHz is immediate. This is great if you have GPS equipped EPIRBs as the MRCC will know your location within 5 minuets, and the position is updated every 20 minutes. As the GEOSAR is effectively stationary a non GPS EPIRBs transmission will be picked up, but the location will remain unknown as there is no Doppler shift to ‘fix’ the transmitter. The LEOSAR array must pass over in order to locate the distress position as above.

The Polar Regions are reliant upon the LEOSAR array for detection.

For more detailed information on how the COSPAS-SARSAT system works visit:
http://www.cospas-sarsat.org

What do I need to know before purchasing an EPIRB?

All 406MHz beacons must be type approved and compatible with the International Maritime Organisation (IMO) performance requirements. For European standards the EPIRB will have the new ‘wheelmark’ approval showing that it is in accordance with the Marine Equipment Directive. Many EPIRBs will be accepted worldwide as they generally meet or exceed the various specifications.

There are two different types of 406 EPIRB;

Category I EPIRBs are automatically activated and designed to float-free via a Hydrostatic Release Unit (HRU) should a vessel sink. Cat I EPIRBs are supplied with a float free case or a wall bracket which is attached to the outside of the vessel, to ensure the beacon is released clear of the vessel and transmits once on the surface.

Category II EPIRBs are manually activated beacons. They can be ordered with a mounting bracket or kept in a grab bag.

Note that some Cat II EPIRBs incorporate a seawater switch which will activate once in contact with the water, even if the unit has not physically been turned on. This will only happen when the beacon has been removed from its bracket, as a magnet prevents the sea switch from operating. It is always recommended that a bracket is used, even if stowed in a grab bag just in case it gets wet.

Both types will normally have a 5 year battery life from the date of manufacture, and operate for 48 hours in normal conditions.

Temperature operation: Class 2 beacon -20degC to +55degC; Class 1 beacon for arctic areas -40degC to +55degC. Class 2 will normally suit most people’s requirements.

Note HRUs are disposable and are to be replaced every 2 years.

Most EPIRBs also include a flashing strobe light and a second low-power (homing) radio transmitter (121.5MHz) to assist in final location of the survivors by the Search And Rescue (SAR) personnel.

All 406 EPIRBs have a self test facility.

Consult individual manufacturers/operators manual for their model performance specification and operation.

Do I need an EPIRB?

This is dependent upon the type of sailing/boating that you do. If you have good communications on board and are within VHF radio coastal range (line of sight) then possibly not. If you make passages ‘over the horizon’ then you can not rely upon your VHF radio and DSC set (digital selective calling) then you may like to improve your chances of rescue with an EPIRB. If you are in more remote areas poorly covered by the Coastguard or mid ocean, then the EPIRB will be your best chance of a rescue if you have lost your vessel. Once turned on within minutes the SAR authorities will know that there is a distress in progress, and will be able to locate you very quickly. Over 1200 lives have already been saved using 406MHZ technology.

What about a false alert?

If you suspect that you might have accidentally switched on the EPIRB, even for a very short period, you should leave it turned on and immediately contact the local Coast Guard and let them know. Just switching the EPIRB off and stowing it away will not stop the SAR authorities from starting a potential rescue scenario, even if the transmission stops.
EPIRBs must never be activated at any time other than for a distress situation, as this could waste SAR resources, time and money which maybe required for a ‘real’ distress situation else where. Let the nearest Coastguard have the 15-digit HEX identity number that should be marked on the EPIRB. In the UK you will register this number with H.M. Coastguard Falmouth on purchase.

How do the SAR organisations know who owns the EPIRB?

The EPIRB is programmed with a 15 digit identification number/code on issued. This number will identify (you and) your vessel via the EPIRB when activated, so long as the completed EPIRB Registration Card has been sent to the EPIRB Registry. It is essential that this done as soon as possible. If you purchase a second hand EPIRB ensure that you re-register your own vessel and personal details. Failure to register your EPIRB could result in your distress causing confusion, how long could you hold on for!

Contact: www.mcga.gov.uk or Linda Goulding, EPIRB Registry, MRCC Falmouth, Castle Drive, Pendennis Point, Falmouth, Cornwall, TR11 4 WZ – tel 01326 211569

What about 121.5MHz EPIRBs?

121.MHz EPIRBs may still be available and cost a lot less than the 406MHz, but they are the ‘old’ system and are due to be made redundant in 2009. This is due to the number of false alerts on this low frequency, so save your money! You will notice that this is now the homing frequency in the 406MHz EPIRBS, and used when the rescuers are close by to locate your final position.

The 121.5MHz beacon transmits only a signal and no identification or position unlike the 406MHz. Originally designed to be located by over flying aircraft, the SAR authorities still have to task an aircraft to confirm the transmission. This can be a very costly business hence the change to the stronger and more reliable 406MHz frequency.

If you have a 121.5MHz EPIRB the system will work although possibly taking a little longer compared to the 406MHz EPIRB. The 121.5MHz signal will be received by the LUT at Kinloss, it is suppressed on the first pass of the satellite due to the sheer number of false alerts (98%). They then wait to see if the signal is ongoing probably for the third pass to initiate the response, a lot of treading water! This will continue up to 2009, when the satellite processing 121.5MHZ alert will be turned off.

What about a SART (Search And Rescue Radar Transponder)

Unlike an EPIRB a SART does not transmit an identity code or position and therefore cannot raise the alarm globally. A SART is designed to be used as a location aid for the SAR authorities or a passing vessel with marine (x band) radar. Once turned on the SART can be ‘dormant’ for 96 hours. It is activated by the radar and returns a series of dots to the interrogating radar screen within a range of about 5 miles. The dots give the operator a range and bearing to the SART and the vessel can complete the rescue.

PLB – Personal Locator Beacon

PLBs tend to operate on the 121.5MHz and are therefore a radio direction finding beacon, and used to give the SAR authorities a bearing to your location once they are in the local area. Ideally the SAR services must know you are in distress in the first place to initiate the search, otherwise the transmission may go un-noticed due to the false alerts and weak signal.

The latest PLBs now incorporate 406MHz technology; in fact the McMurdo Fast Find series has many of the same features as their 406MHz EPIRBs, but is a personal location beacon and not registered to the vessel. The Fast Find PLBs are proving to be very popular and as an endorsement to the product the US Coast Guard is purchasing 1 for each for their (operational) staff.