Distress beacon testing

Background

There are a number of reasons to test 121.5/243 or 406 MHz distress beacons. These include:

operational/functional testing to ensure the beacon is transmitting the distress signal correctly;
prototype beacon testing; and
tests for new beacon models.

Distress beacons can also be used for system testing of the satellites, ground receiving stations and control centres. Cospas-Sarsat and national authorities normally conduct these tests.

Any beacon test could have an impact on the search and rescue system. Many tests are undertaken without the need for Cospas-Sarsat support, nevertheless, low earth orbit satellites, geostationary satellites and over-flying aircraft may still receive such transmissions.

Tests that are intercepted by the Cospas-Sarsat system impact on it in terms of system overheads and may result in genuine distress transmissions not being detected. Local User Terminal (LUT) or ground station specifications also have a defined processing capability and live-to-air tests may jeopardise the interception of distress beacons being activated in an emergency situation.

Rescue coordination centres (RCCs) are also affected, as reports will be received from the Cospas-Sarsat system and over-flying aircraft reporting hearing 121.5 MHz sweep transmissions. Again, these may be confused with a genuine distress situation and with increased testing of beacons could lead to aviators being wary of making hearing reports when they are continually advised that it is a 'test' activity.

Given the reasons above, there is a need to ensure that beacon testing is done responsibly.

Summary

EPIRBs and PLBs can be tested at any time using the self-test function without the need to notify RCC Australia;
ELTs (121.5/243 MHz and 406 MHz) in situ in aircraft and in accordance with AIP can be tested operationally for 5 seconds only.
Any 406 MHz beacon tested for longer than 5 seconds must be coded with the TEST protocol and the 121.5/243 MHz homing transmitter disabled;
Any operational test longer than 5 seconds will require two days notice and the information as listed in the maintenance tests section is to be provided;
A test of a 406 MHz beacon for longer than 5 seconds with an OPERATIONALLY coded protocol is not permitted under normal circumstances; and
Any request for tests with an operationally coded beacon will need to be discussed with AMSA's Cospas-Sarsat Adviser during normal business hours.

Relevant regulations and instructions

EPIRB and PLB

International regulations on the carriage of 406 MHz EPIRBs are contained in chapter IV of the International Convention for the Safety of Life at Sea (SOLAS). International instructions for the annual testing and shore-based maintenance of 406 MHz EPIRBs are contained in IMO circulars MSC/Circ 1039 and MSC/Circ 1040 respectively.

Australian State and Northern Territory regulations relate only to carriage requirements for 406 and/or 121.5MHz EPIRBs and do not refer to testing requirements. Commercial users subject to State and Northern Territory regulation and recreational users should note the information contained in international guidelines for annual testing and shore-based maintenance of EPIRBs.

ELT

The carriage of distress beacons in aircraft and life rafts used in aircraft is regulated by the Civil Aviation Safety Authority (CASA).

The Visual Flight Rules (VFR) Flight Guide Section 4 and Aeronautical Information Publication (AIP) GEN 3.6 paragraph 8.4 refer to the testing of ELTs. Although the frequency of the ELT is not stipulated, the instructions refer equally to ELTs operating on 406 MHz and 121.5/243 MHz frequencies.

Beacon testing requirements

Self-test function (EPIRB and PLB)

The most common reason to test a distress beacon is to ensure that the beacon is operating correctly and producing the correct signal for transmission. EPIRBs and PLBs have a self-test switch that is spring loaded so it cannot be left on inadvertently and reduce the life of the battery. There will be an indication, generally a light, indicating that the circuits are operating correctly and the signal is reaching the antenna.

In most cases, when operating a 406 MHz EPIRB or PLB self-test, the beacon is allowed to radiate a single burst that is specially coded so that it is ignored by the Cospas-Sarsat system. The 121.5 MHz homing signal during operation of a 406 MHz EPIRB or PLB self-test is also restricted to one second or less to ensure that the SAR system will not react. The 121.5/243 MHz EPIRB self-test is limited either in power output or duration of transmission to ensure that it is not heard for long enough to cause the SAR system to react.

It is important that the self-test of these beacons is undertaken periodically or prior to undertaking a trip. The self-test function will be designed to meet Australian Standards and will restrict 121.5 MHz transmission to less than one second even if the complete self-test process takes longer (eg 20 seconds). There is no requirement to advise authorities when testing an EPIRB or PLB using the self-test function. The beacon should reset itself when the test has been completed. Should the beacon continue to operate inadvertently, notify RCC Australia either directly on 1800 641 792 or through the police or local search and rescue volunteer organisation.

Operational tests (ELT)

Whilst most 406 MHz ELTs are fitted with a self-test function this may not be used when testing operation of the beacon from the cockpit. Thus when testing the functionality of aviation ELTs, the test often allows for the beacon to transmit live to the system on the 406 MHz and/or 121.5 MHz frequencies. In accordance with AIP, pilots and maintenance crew must not test the beacon for longer than 5 seconds and the preferred procedure is that they be conducted within the first 5 minutes of the hour. Before operational tests for any period are conducted, operators must contact RCC Australia (1800 815 257) so that they can alert other centres to be prepared for any reports of 121.5 MHz alerts from overflying aircraft. Should the beacon continue to operate inadvertently after the test has been completed notify RCC Australia either directly on 1800 641 792 or through Air Traffic Control.

Maintenance tests

Except in the case of operational tests as described in the previous section, distress beacons should not normally be tested by actual operation. Generally, if a 406 MHz distress beacon needs to be tested using the operational system for any length of time longer than 5 seconds it is coded using a test protocol and would have the 121.5 MHz frequency disabled.

In the unusual circumstance that a beacon is to be tested for longer than 5 seconds, a request should be made to RCC Australia in writing via e-mail or facsimile giving at least two days notice of the test and providing the following information:

Applicants name, company and contact details (including mobile telephone number to be used for communications during the test);
The preferred date/time/duration of the test (noting that the actual time of the test maybe dependent on satellite geometry);
The location of the test beacon in latitude and longitude;
The make and type of distress beacon, including the beacon's 15-HexID (bits 25-85);
The objective of the test; and
Intentions regarding he disabling of the 121.5 MHz homing signal.

RCC Australia will then consider the request and provide appropriate advice.

The provision of two days notice is to allow time for the international Cospas-Sarsat system to be warned of the test transmissions.

Any live tests requiring detection and location by the Cospas-Sarsat system will need to be undertaken during a defined window when mutual visibility exists between beacon, satellite and the LUT. These tests should normally be conducted with a test-coded beacon and the use of operationally coded beacons will only be approved in exceptional circumstances. It should be noted that the duration of such tests would normally be 20 minutes to allow for the beacon to warm up to operating temperature. There is also a requirement for the associated low powered 121.5 MHz transmissions for beacon homing to be disabled.

Test equipment

There is test equipment and methods available that limit the effects of beacon testing on the SAR system. These include the use of shielded rooms, dummy loads to absorb 121.5 MHz transmissions and special test rigs. Manufacturers of the distress beacon types being tested should be approached for information on test equipment and methods.