EUROCONTROL would like to raise awareness among pilots to keep VHF channels (136.500 -137.000 MHz) reserved for datalink free from voice communication to ensure most efficient communication between air traffic control (ATC) and pilots. Datalink is a key enabler to increase aviation safety and capacity as well as support automation, efficiency and scalability for airspace operations.
While monitoring flights over Europe, EUROCONTROL discovered that the dedicated radio frequencies supporting the air-ground datalink service (CPDLC) used for digital clearances have been misused for voice communication causing a failure of datalink exchange between air traffic control and aircraft. Pilots may have thought these channels are not in use because there is nothing audible, but the channels are effectively in use. On these occasions the provision of efficient air traffic services have been delayed causing unnecessary workload for pilots and controllers during these flights.
In addition, such difficulties undermine the trust in datalink and in future solutions involving this technology. As a means of passing instructions between air traffic controllers and pilots using text messages, datalink has the advantage of reducing the margin of error and misunderstandings in situations of poor voice connection, and liberating space on the congested VHF channels for critical voice communications. While datalink frequencies are selected automatically by the avionics, voice frequencies are dialled in manually, hence the need to raise awareness among airspace users to carefully check the VHF radio configuration.