Operations resources


Class G communications


Aerodrome Frequency Response Unit AIP GEN 3.4

To assist pilots’ awareness of inadvertent selection of an incorrect VHF frequency when operating into non-controlled aerodromes, a device known as an aerodrome frequency response unit (AFRU) may be installed. An AFRU will provide an automatic response when pilots transmit on the CTAF for the aerodrome at which it is installed.

The features of the AFRU are as follows:

  • When the aerodrome traffic frequency has not been used for the previous five minutes, the next transmission over two seconds long will cause a voice identification to be transmitted in response, for example: ‘Goulburn CTAF’.
  • When the aerodrome traffic frequency has been used within the previous five minutes, a 300 millisecond tone will be generated after each transmission over two seconds long.

A series of three microphone clicks within a period of five seconds will also cause the AFRU to transmit a voice identification for the particular aerodrome.

If the transmitter in the AFRU is jammed for a period of more than one minute, the unit will automatically shut down.

The AFRU improves safety by confirming the operation of the aircraft’s transmitter and receiver, the volume setting, and that the pilot has selected the correct frequency for use at that aerodrome.

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