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Emergency Locator Transmitter

Emergency Locator Transmitter, II

Basically there are three types of emergency locator beacons in use today to transmit distress signals: the maritime EPIRBs - Emergency Position Indicator Radio Beacon. The aviation community uses ELTs - Emergency Locator Transmitters, the PLBs - Personal Locator Beacons are used for land-based applications. Although Cat II EPIRBs and PLBs can be used by the pilot of an aircraft as these are manually activated beacons whereas the CAT I EPIRBs are housed in a special bracket, aviation ELTs are automatically activated and manually tested.

To make sure that the ELT is operating it will need to be tested operationally and maintained according to regulations.

ELT Testing

Test should be conducted only in the first five (5) minutes of any hour and then only for a maximum of three audio sweeps of the transmitter. A VHF receiver tuned to 121.5 MHz should be used to monitor the test. The 406 MHz data message will be transmitted after fifty (50) seconds of the ELT being activated.

The ELT system should be tested in accordance with the manufacturer's instructions for a new installation. This testing is to include verifying the code and will usually require the use of a system tester. The remote control should be switched through each mode of operation according to instructions to determine that the equipment is operating correctly.

Configuration module

Some installations are fitted with a Configuration Module that automatically loads configuration data (coding, etc) into the ELT when it is installed. It is important that the Configuration Module data is correct for the aircraft it is installed on. When it is installed or updated, verify and / or update the Configuration Module data in accordance with the manufacturer's instructions.

With the aircraft engine(s) shutdown and the ELT transmitting, the aural monitor, if fitted, should be heard. If a visual monitor is provided it should be visible from the pilot's normal seated position.

To ensure that the ELT is not susceptible to inadvertent activation by conducted or radiated interference, tests should be done with all avionics powered by the aircraft electrical system operating. The test should be carried out with the ELT armed and monitored on both 121,5 MHz and and the remote indicator panel and include the following steps:

  • Individually operate each and every item of the electrical equipment and system, except HF/VHF/UHF communications transmitters, and evaluate all reasonable combinations of control settings and operating modes common to your operation
  • Individually operate the installed HF/VHF/UHF transmitters on various frequencies in their operating range
  • Repeat the second step with all electronic equipment operating collectively, evaluating reasonable combinations of control settings and operating modes common to your operation

Maintenance requirements

Aviation rules require an operational check of the ELT in accordance with Maintenance Part 43 at intervals not exceeding 12 months or 100 flight hours, whichever comes first. Some transport aircraft are exempt from that rule.

The inspection of the aircraft prior to the release to service should include the following inspections:

  • ELT, antenna, antenna cable and remote switch installation for condition, security and being free of corrosion
  • Placards for legibility
  • System self test carried out in accordance with the manufacturer's instructions

Usually, routine maintenance will not render an ELT unserviceable.


Emergency Locator Transmitter Battery

The rules also require an inspection of the battery condition and its expiry date. This must be recorded in the aircraft maintenance logbook. If the remote control/indicator has a battery fitted, the expiration data of this battery must also be recorded in the maintenance logbook.

Batteries are required to be changed:

  • On or before the expiry date; or
  • When the transmitter has been in use for more than an cumulative hour, test cycles inclusive

If the battery is replaced, the ELT must be tested for serviceability according to the manufacturers instructions.

Temporarily removal

Sometimes an aircraft can be allowed to operate with an inoperative ELT or without one fitted. This will allow an aircraft to be ferried to a place where repairs to, or installation of, an ELT can be carried out. The flight is deemed to be an ferry flight and usually no passengers may be carried.

In case of such a ferry flight under the above provision the ELT, or a suitable cockpit location, is to be placarded inoperative and the appropriate entries to be made in the aircraft logbook or other technical log in accordance with the rules.

Written by EAI.

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