Civil Aviation Authority UK reports: emergency transmitters change location frequency

The UK’s Civil Aviation Authority (CAA) has issued a reminder to pilots and aircraft operators to ensure that their emergency locator transmitters (ELT) are operating on the new location frequency of 406MHz by February 2009.  ELTs, also known as beacons, have been locating pilots in distress and directing search and rescue operations since their inception in the 1970s. However, from 1 February 2009 ELTs tuned only to the analogue frequencies of 121.5/243MHz will no longer be picked up by the international satellite system that guides search and rescue teams.  Transmissions will only be recognised from digital beacons transmitting on 406MHz.  The new frequency will transmit an encoded message that includes a unique identifier and may include location data if the unit is connected to a global positioning system (GNSS).

The United Nations bodies that mandate safety requirements for aircraft and maritime vessels globally - the International Civil Aviation Organisation and the International Maritime Organisation - have initiated the changeover because of the superior capabilities of the 406MHz alerting system.

Owners of 121.5/243MHz only beacons are advised to replace their systems with 406MHz capable versions with GNSS as soon as possible.  The inclusion of GNSS information ensures that very accurate location of an incident is possible, thereby facilitating rescue.  New ELTs should still transmit on 121.5/243 MHz as these frequencies will continue to be used in the final homing stages of a rescue.

Robb Metcalfe, Head of the General Aviation Inspectorate at the CAA’s Safety Regulation Group, said: “Owners of ELTs need to check that their transmitters can broadcast on the new frequency, as 406MHz beacons are superior to their analogue predecessors and with GNSS input provide far more accurate information to rescue teams, thereby bringing help to pilots in distress much faster than was possible with the old system.”

Further information

ELTs were originally designed as homing devices to alert air traffic control and other aircraft monitoring that frequency. The new generation of ELTs, however, use digital technology to transmit accurate and instantaneous signals, providing search and rescue teams with specific information about the pilot and aircraft.

With a 121.5/243 MHz beacon, only one alert out of every 50 alerts is a genuine distress situation. This has a significant effect on the resources of search and rescue services. With 406 MHz beacons, false alerts have been considerably reduced (about one alert in 17 is genuine) and when properly registered can normally be resolved with a telephone call to the beacon owner using the encoded beacon identification. Consequently, real alerts can receive the attention they deserve.

Devices that operate at 121.5MHz and do not rely on satellite detection will not be affected by the phase-out of satellite processing at 121.5MHz.

The CAA is the UK’s specialist aviation regulator. Its activities include: making sure that the aviation industry meets the highest technical and operational safety standards; preventing holidaymakers from being stranded abroad or losing money because of tour operator insolvency; planning and regulating all UK airspace; and regulating airports, air traffic services and airlines and providing advice on aviation policy from an economic standpoint.


Source: Civil Aviation Authority UK
For further information about Civil Aviation Authority UK, click here

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