Under construction


ELT inside R22 cowl

All Helicopters registered in New Zealand must have an emergency locator transmitter (ELT) fitted and serviceable. One of the reasons for this is that there is so much wild and isolated terrain. It might take a long while for a downed Aircraft to be located. Use of an ELT speeds that process up. Even so, many bush areas are hard to penetrate, there may be no roads nearby. SAR frequently use Helicopters which can be guided to the signal source.
The ELT is either activated by shock if switched to the 'Auto' position (which it should be during flight) or may be activated by the Pilot if an emergency landing has been made. It has its own re-chargable power source (although it relies on the aircraft's power source in normal circumstances) and another aerial mast (seen in picture) so that it may be removed from the aircraft and used as a portable transmitter.

The ELT Transmission frequencies are 121.5 and 243 Mhz. A pulsed signal is transmitted on both frequencies simultaneously. The origin or location of the signal is found by stations constantly monitoring those frequencies and employing radio signal triangulation techniques.

ELT test procedures (by convention) are in place. If the ELT is to be tested it must be done in the first five minutes of every hour, preceeded by a telephone call to SAR HQ. If that wasn't done it may cause a 'false alarm'. The test should also be followed up by a telephone call to de-activate any SAR operation that might have been triggered.

As the ELT is always set to 'Auto' during flight there is always the risk that it may be activated in error, eg. in a bumpy practice engine off landing. For this reason the Pilot must select one of the transmission frequencies (normally 121.5 Mhz) on the Aircraft's radio and check this prior to full shutdown. If the ELT has been inadvertantly triggered it must be disabled and removed for re-setting by engineers. A telephone call to the appropriate authorities and/or SAR agencies must be made to de-activate any SAR operations triggered as a result of the transmission.


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