Taking a look at the 406 ELT

by Adam Hunt



Carole Smith

The subject of 406 MHz ELTs has been controversial in Canada for several years. Certainly COPA has made plain their opposition to the devices over the past 10 years, while many people in the government have been quite keen to require aircraft owners to go out and buy them.

Some recent events have brought 406 ELTs to the forefront of aviation discussion again. First, as of Feb. 1, 2009 the old 121.5 and 243.0 MHz ELTs no longer have satellites listening to them. Second, the new Transport Canada CAR dealing with ELT requirements that took so many years to get through the regulatory process was stopped by the Transport Minister.

While it offered the hope of alternatives to 406 ELTs, the regulation itself was written as such that none of the alternatives qualify for use in aircraft.

Against this backdrop COPA Flight 8 invited Carole Smith from the National Search and Rescue Secretariat (NSS) to give her presentation, "The Switch to 406:

Information on 406 MHz ELTs" at the May 27 flight meeting.

Smith has given this presentation across the country to pilots and AMEs as part of the NSS public relations effort to spur 406 adoption from its current lacklustre levels, especially amongst private aircraft owners.

She started off her presentation by explaining that she is personally a private pilot, COPA and CASARA member and part owner of a Cessna 172 that is equipped with a 406 ELT. She works for NSS, which is the organization that is supposed to coordinate SAR in Canada amongst the various organizations involved, including the Canadian Forces, Coast Guard, CASARA, RCMP and many local agencies and volunteer groups. As such, NSS reports to the lead minister for SAR in Canada, the Minister of National Defence.

Smith's presentation gave a history of the COSPAS-SARSAT satellite system that became operational in 1982. The system located its first aircraft crash on Sept. 9, 1982, a Canadian Cessna 182. Today the system consists of packages on five low-earth polar orbit weather satellites as well as on geostationary weather satellites.

The geostationary packages provide almost instant alerting anywhere in the world below 75 degrees north and south.

Currently the system picks up aeronautical ELTs, Marine EPIRBs and PLBs all on 406 MHz only. Smith reported that, worldwide, there were 600,000 registered 406 beacons of all types as of February 2009.

After a run-down on how SAR is organized in Canada, Smith explained how the 406 ELT works. Once activated it puts out a primary digital 5W signal every 48-52 seconds on 406 MHz and also a 0.025-0.1W analog homing signal on 121.5/243.0 MHz.

The 406 ELT has a remote cockpit switch to allow testing and also to allow in-air activation prior to an impact. All 406 ELTs also have an integral buzzer that allows anyone outside the aircraft on the ground to identify which aircraft is transmitting. The digital 406 signal includes a 15 character unique hex code that identifies the specific aircraft.

In the past the 121.5 ELTs used to allow COSPAS-SARSAT to determine a location to a radius of about 20 km, giving a search area of 1,260 sq. km. A 406 ELT gives an accuracy radius of 3 km, for an area of 28 sq. km. With GPS data added to the 406 signal it can give a position to a radius of 100 metres, for an area of 0.031 sq. km.

Smith included some reliability information on the old and new systems. She reports that when a 121.5 signal was received only one in eight came from an ELT. The balance were from bank ATMs, big screen TVs, stadium scoreboards and even pirated satellite TV cards, amongst other spurious sources.

With the 406 signals all are from beacons, although to date only one in 16 have been actual emergencies. She attributes most of these false alarms to installation work being done on 406 ELTs that result in an activation.

In covering installation requirements, Smith emphasized that if the aircraft has a later model 121.5 MHz ELT that the mounting tray and some other hardware may be reusable, thus making the installation quicker and less expensive.

She also mentioned that not only must the new 406 beacon be programmed with the correct 24 bit ICAO address for the individual aircraft, but that the beacon must be registered. Registration can be accomplished at www.canadianbeaconregistry.forces.gc.ca and also by phone, fax or mail-in form. Foreign beacons, such as those purchased from the USA, cannot be used in a Canadian aircraft until they have been recoded with the correct codes for Canada, A78, A79, 278 or 279. Twenty-four bit ICAO addresses are now available on the TC Civil Aircraft Register on the entry for each individual aircraft.


Smith explained that the rules have been changed on 406 ELT installations recently and now an AME can install a 406 ELT in an aircraft. An avionics AMO is only required to do installations of 406 ELTs that have remote connections for GPS.

Testing the 406 ELTs is done in a similar manner to the old ELTs, during the first five minutes of the UTC hour for a maximum of five seconds. The aircraft radio will receive the 121.5 homing signal and the buzzer should be audible as well, proving the set works.

It is important to report false alarms to the Joint Rescue Coordination Centre in your area or to the Canadian Mission Control Centre in Trenton, as, with the geostationary satellites on watch, even a brief false alarm will identify your aircraft and start a communications search to ensure that there is no distress situation.

One of the most controversial aspects of the 406 ELT issue has been the time line involved. Smith mentioned that the 40 nation COSPAS-SARSAT organization made the decision in 2000 to change to using 406 MHz exclusively on Feb 1, 2009. They thought that almost nine year's notice would give ample time for governments and individuals to act, although, in the case of Canada, the rules are far from completed or in place.

Smith went over the advantages of 406 ELTs, including better accuracy, that the digital 406 signals can be stored by the satellites and retransmitted to the ground station when in sight and that the land and marine users of beacons have already switched to 406 MHz. She did admit that 406 ELTs are not inexpensive and that the installation requirements are rigorous and take more labour to complete.

One of the concerns NSS has is, even though the old 121.5 beacons are no longer monitored by satellites and only listened out for by ATC, FSS and other aircraft when in range, very few aircraft have installed 406 ELTs so far. Smith reports that while 57 per cent of state-owned aircraft have been equipped, only 38 per cent of commercial aircraft and seven per cent of private aircraft have done so.

Smith discussed why owners have been reluctant to install 406 ELTs, including concerns about reliability, lack of model choice, interest in alternatives, the fact that there is no regulation in place requiring 406 ELTs and, of course, cost.

In addressing these concerns she indicated that reliability has been quite good so far, 74 per cent of 121.5 ELT-equipped aircraft that crashed between 2003-2007 transmitted a signal that located the aircraft. 406 ELT success data is too sparse to be conclusive so far, but is expected to be better than 74 per cent.

The model choice is improving along with the prices, with models now available in the US $1,100 range. As far as alternative devices are concerned the requirements are stringent and include automatic activation. This is, of course, the issue that caused the Minister of Transport to send the regulation back to TC to be rewritten.

Smith admitted that it wasn't clear what the next regulatory steps would be, whether the rules will go back to CARAC for consultation or when a new proposed rule would be forthcoming.

Flight 8 would like to thank Carole Smith for coming to talk to us about 406 ELTs. It isn't easy to convince a group of pilots that they should spend a large amount of money on a device that they will probably never need, but she did a good job of answering the questions that the flight members posed and it was interesting to hear the NSS perspective on the controversy.