BUSHWALKERS WILDERNESS RESCUE SQUAD

A volunteer group of experienced outdoors people.

Bush Safety - Personal Locator Beacons (PLB)

PLBs - for Bushwalkers

BWRS encourages people bushwalking in areas without mobile phone coverage to carry an PLB. They are available for bushwalkers either at a nominal cost or for free from the following locations:

Distress beacons are available for different environments and the type of beacon designed for use on land is the Personal Locator Beacon or PLB. The aim of a PLB is to be used to transmit a radio distress signal when the owner is in a life threatening situation so that emergency services can quickly locate you. PLBs are a derivative of the beacon systems designed for use by aviators and seamen and are now quite small, compact and lightweight making them very practical for bushwalking.

When a PLB is activated, it transmits a signal on dedicated world-wide frequencies for distress beacons. The signal is received by satellites and processed by ground stations to provide a coarse location of the beacon. The signal may also be picked up by over flying aircraft who recognise the signal by its unique audio tones and who would then report the hearing to Air Traffic Control. All signal hearings in the Australian region, whether through the satellite system or from aircraft, would be passed to RCC Australia, the rescue coordination centre in Canberra operated by the Australian Maritime Safety Authority (AMSA). The RCC will then activate appropriate resources to investigate the signal. For a PLB on land this is likely to be the Police who are the responsible state or territory search and rescue authority. They would activate emergency services as required to locate and rescue the walker in distress.

If a PLB is activated in a remote bushland area in NSW, the Police Rescue Squad and local Police will be advised and a rescue helicopter will probably be sent to investigate. Most NSW rescue helicopters are fitted with radio direction finding equipment which allow the helicopter to home in on the signal as they approach it.

For more information about how the PLB system works have a look at the Australian Maritime Safety Authority PLB website.

What types of Distress Beacons are there?

EPIRB - Emergency Position-Indicating Radiobeacons

EPIRBs are used in ships and boats and are designed to float upright using the water plane as a reflector to more efficiently get the signal to the satellite. For this reason they have ballast built in and need to be a certain minimum size to ensure they float correctly and their size and weight make them impractical for use by bushwalkers.

EPIRBs are commonly confused with PLBs. Whilst they are both distress beacons they are intended for different purposes and EPIRBs are not suitable for bushwalking. AMSA has discussed with BWRS its wish for the correct terminology to be used for beacons, so please try to call the units suitable for bushwalking PLBs.

ELT - Emergency Locator Transmitters

ELTs are designed for aviation and are larger, generally fixed units in aircraft that are automatically activated when an aircraft crashes. Again they are not suitable for bushwalkers as they are too large and heavy.

PLB - Personal Locator Beacon

PLBs for bushwalking use are called Personal Locator Beacons or PLB. These are small, lightweight units suitable for bushwalking use. The remainder of this article will discuss PLBs.

How Do PLBs Work?

Distress beacons commonly found in Australia currently operate on two systems. The older analogue beacons operate on the aviation distress frequencies of 121.5/243.0 MHz. Newer digital beacons specifically designed for use with the Cospas-Sarsat system operate on 406MHz.

121.5MHz/243MHz Analog Distress Beacon System

This is the older of the two systems and has an extensive range of units available. There are a number of units suitable for bushwalking on this system, two common ones are the GME MT310 and the KTI RB3. These units are small enough to fit in your pocket, weigh around 200g and can be purchased for around $200.

These systems work by transmitting a simple pulsed tone on one or both of 121.5MHz and 243MHz which relies on direction finding by the satellites, aircraft and ground stations receiving the signal to determine the position of the beacon. This often requires several satellite passes before a location of useable accuracy is determined - AMSA indicates the average time for an initial alert from a satellite is 90 minutes but could be anywhere from minutes to 5 hours depending on the satellite passes over Australia at the time of activation. This means you may have to wait some time even before the alert is raised in the RCC so bushwalkers should be prepared to survive until they are rescued. Even after the satellite fix is determined it is only accurate to within 20 kms. For PLBs activated in remote areas the usual procedure is to send a rescue helicopter with radio direction finding equipment to home into your exact location. It is common for the helicopter to take some time with direction finding, especially if the beacon is in an area such as a canyon or gorge as the signal may be masked by the high walls and not picked up until the aircraft is almost overhead or the signal could bend and reflect around the local landforms.

This system has a major problem in that the overwhelming number of PLB activations are false alarms - AMSA indicates about 97% of activations are false alarms. However, when an PLB is detected there is no way of knowing whether it is a genuine emergency or not so they must assume it is genuine and send in resources to track it down. This makes it a very inefficient and expensive system. This problem is one of the major reasons the satellite tracking of 121.5MHz will cease in February 2009.

406MHz Digital Distress Beacon System

This is the newer system which has a number of upgrades over the older system. The 121.5/243MHz system was a simple analog system, but the 406MHz system is digital and therefore allows more information to be sent when a beacon is activated. All digital PLBs on 406MHz transmit a unique identifying number and can be correlated to a database of registered owners of beacons. This means if you get a 406MHz PLB you should register it with AMSA straight away! The advantages of this identifying signal are:

• Authorities know straight away whether the signal is received from a boat, aircraft or a bushwalker and can deploy resources appropriate to the incident more quickly.
• Many false alarms can be eliminated easily as the registered owner of the beacon can be contacted;
• It has a stronger signal strength so is more likely to be received from marginal areas such as gorges and under a tree canopy.

Although the 406MHz system relies on the same Polar orbiting satellites used by the 121.5MHz beacons, there are also satellites in geo-stationary orbit over the Equator that can receive signals from 406MHz beacons. This is one of the major differences that make the 406MHz system far superior to the analogue 121.5MHz system as the Geo-Satellite detections are displayed in the RCC within minutes of activating a beacon. Users must be aware that that a beacon must have line of sight to the Geo-Satellite that will be low on the northern horizon for users in the southern states of Australia. Signals will be blocked by outcrops and heavy foliaged canopies. Beacon users should also be aware that the basic 406MHz beacon will not generate a position when its signal is received over a Geo-Satellite but an alert will nonetheless be received at the RCC and the search and rescue (SAR) officers will have important contact details from the registration database allowing search activity to begin even without a position. Obviously a lot less can be done with this initial alert if the beacon is not registered. This is where registering your beacon becomes very important and a must-do.

Other advantages of the new 406MHz system include:

• The 406MHz system provides alerts far more quickly with alerts being received within minutes from the satellites in Geo-stationary orbit over the Equator.
• The 406MHz beacons are fixed by the Polar orbiting satellites to within 5 kms, so the rescuers are closer to you before they need to start direction finding.

The digital beacons also transmit on 121.5MHz to ensure that aircraft can continue to easily locate the beacon by using homing techniques.

Because 406MHz beacons are digital there is the capability to transmit additional information in the alert. Some beacons have a GPS capability where when the beacon is activated a GPS engine onboard locates the beacon from the GPS satellite system and the far more accurate (<120 metres) that is then transmitted across the Cospas-Sarsat system to the RCC. The use of a GPS capable 406MHz PLB results in a very accurate position being received via the geo-satellite within minutes of the beacon being activated. Not only is the alert received quickly but for bushwalkers in remote and rugged country, the accurate position means that searchers will locate them far more quickly.

Up until recently 406MHz beacons were considerably heavier and bulkier than 121.5/243MHz systems, but that disadvantage has disappeared with new PLB models released by several manufacturers. Good examples are the KTI Mini-Sat, the GME MT410, the ACR TerraFix or MicroFix, or the McMurdo FastFind ranges. Each of these units weighs under 250g and can fit in your pocket and are therefore ideal for bushwalking. They all have the GPS beacon as an option.

Prices are for the new digital units significantly higher then the old analog units and some the model mentioned above are very new at the time of writing this (Nov 2007) so not all units are available at retailers. OzPilot supplies has the McMurdo Fastfind with a list price of $1395, and Bias Boating has the GME MT410G (GPS PLB) with a list price of $589. You can be sure that as the 406MHz PLBs become the standard unit with the phasing-out of the old analog system these prices will fall further, but at this stage some careful shopping around is required to get a 406MHz PLB for a good price.

All 406MHz beacons should be registered. Registration is free and can be done here.

Be aware that some overseas beacons are not compatible with the Australian system. The safest way to avoid this problem is to purchase your PLB from a reputable Australian retailer, but if you wish to purchase internationally you must ensure the unit you are purchasing is compatible with the Australian system. Further information on this issue can be found here.

See the Australian Maritime Services Authority website for a more detailed comparison between 121.5/243MHz and 406MHz beacon systems.

USE of PLBs

Maintenance and Storage

Generally all beacons have a test button to confirm that they are operating correctly. As a minimum, test the beacon at the manufacturer's recommended interval. The batteries have an expiry printed on the unit and you usually need to contact the manufacturer or an agent for replacement. Make sure you keep the PLB battery up to date. An PLB with an expired battery is useless!

When storing the PLB or packing it in your pack, make sure that the cover or case for the PLB is correctly fitted and nothing is bumping the activation switch. You don't want to accidentally become another false alarm! PLBs are waterproof as specified by Australian Standard AS/NZS 4280.2.

Accidental Activation

If your beacon has been activated accidentally then turn it off and phone 1800 641 792 as quickly as possible to let the RCC know that it was a false activation.

In a Bushwalking Emergency - When and how to activate an PLB

The PLB system is to be used as a last resort only. Your initial distress alert should still be made by telephone, radio or other direct communication if possible. Direct communication will result in a faster and more appropriate response as you will be able to explain the situation to the emergency services. If you are near your vehicle you could consider sending somebody to walk out and drive to summon assistance. An PLB should only be used if no method of direct communication is possible and urgent assistance is required.

Before activating an PLB, if possible move to an open area, as high as possible with a clear view of as much of the sky as possible. You want to get your signal out as clearly as possible and give the helicopter when it comes to you plenty of room to see you and get somebody to you. Move away from cliffs, tree cover and steep ground. Have something highly visible ready so you can signal the helicopter and help it find you.

To activate the PLB, follow the instructions on the device. My PLB, a GME MT310, has the following instructions and other devices are likely to be similar:

1. Remove the PLB case or cover.
2. Activate the PLB according to the directions on the device. For the GME 310 this means you push down the yellow button and slide it to the on position. This will break the device safety seal.
3. Check the red light is flashing to ensure it has activated.
4. Fully extend the antenna. The GME MT310 antenna has 4 sections and is 450mm long when extended.
5. Place the PLB in an upright position in an open space so the antenna is clear of surrounding objects. The antenna should not be leaning against anything if possible. Do not touch the antenna with your fingers while it is transmitting as it will reduce the transmittion strength.

Now the PLB is active prepare for a long wait. If you are near a major city a one-to-two hour wait is normal, although the wait may be several hours. If you are well away from major centres the wait is likely to be at least several hours.

Do not turn the PLB off until directed to do so by the emergency services. If you have not been located yet then leave it on until the battery goes flat.

If you have two or more beacons in the party then only have one beacon active at a time. When the first beacon's battery goes flat then turn it off and activate the second one. You will not get a stronger signal by activating two beacons at the same time - the transmittions actually interfere with one another and make it harder to find you.

There are some times when a PLB either will not work or you will have to wait a long time before rescue. They include:

• Deep gorges - A distress signal from a narrow gorge such as a Blue Mountains canyon may not be detected. If it is detected it may be difficult for the rescue helicopter to track.
• Night - The satellites will pick up an PLB signal at night, but a rescue helicopter may choose not to fly immediately and wait until first light the next day.
• Bad weather - Lightning may make the signal difficult to get an accurate position and delay rescue. The rescue helicopter will not fly in weather risky for the aircraft, such as reduced visibility such as fog or in high winds. Either ground crews will be sent in or the helicopter will wait for the weather to improve, either way you will have to wait a long time.

Further Reading

The Australian Martime Safety Authority search and rescue page is an excellent source of more information about distress beacons. It has extensive information about PLBs on its beacons web page.

Information about the global Cospas-Sarsat system can be found here.