Aerodrome Frequency Response Unit (AFRU)

• 3.3.21 An AFRU is a unit that provides confirmation to pilots that they have selected the correct aerodrome frequency, and that their aircraft radio is operating correctly. It may operate as a supplementary device to a ground facility (UNICOM) operating on the aerodrome frequency, or it may be the sole ground communications device.
• 3.3.22 If an aircraft operating within radio range of the AFRU makes a transmission on the aerodrome frequency, the AFRU will detect the transmission and automatically respond on the frequency with either:
  • (a) a pre-recorded voice message, (normally the aerodrome location and frequency) if no aircraft transmissions have been received in the period (typically 5 minutes) preceding the transmission; or
  • (b) a short tone burst if any transmissions have been received in the preceding period.