Controller-Pilot Datalink Communications (CPDLC)

Most European Area Control Centres have started to operate controller-pilot datalink communications (CPDLC) over the past years to help mitigate the shortcomings of traditional voice communication.

CPDLC – an air/ground datalink application – offers the benefit of an additional, independent and secure channel, which reduces the strain on busy VHF sector frequencies, transmitting clear messages with no risk of misunderstandings. Use of the system increases capacity and safety; it improves the day-to-day efficiency of communications between controllers and pilots.

For example, currently more than 23% of the traffic crossing the Maastricht Upper Area Control Centre (MUAC) airspace use CPDLC on a daily basis. MUAC uses it as a secondary communications medium, complementing VHF voice communications, which remains the primary means for tactical communication.

As of February 2020, CPDLC will be required to operate above FL285 in Europe.


Using CPDLC with an Area Control Centre (ACC)

To operate CPDLC operators need to have certified future air navigation system (FANS) or preferably state of the art aeronautical telecommunications network (ATN) datalink avionics on-board their aircraft.

The CPDLC log-on address (e.g. EDYY for MUAC or LOVV for Vienna ACC) offers datalink services 24/7 to all aircraft equipped with the appropriate CPDLC avionics in the upper (above FL 245) and often even in the lower airspace.

To promote the regular use of CPDLC, MUAC has come up with a catchy slogan:

“Don’t text while driving. Text while flying!”


Message types

CPDLC operations support the following message types in general:

  • Datalink integration capability (DLIC)
    Log-on is a prerequisite for operational datalink services via the exchange of address information in order to establish flight plan/address associations in the ATC system, ensuring correct message delivery.
  • Air traffic control clearance (ACL)
    ACL enables the air traffic controller to issue climb/descent clearances, direct clearances, turns and headings and SSR instructions, or to reply to aircrew requests. The ACL service also enables the aircrew to make operational requests and to respond to ATC clearances and instructions.
  • Air traffic control communication management (ACM)
    ACM supports automated controller/aircrew communications hand-off, via both R/T and datalink, from one sector/centre to another.
  • Air traffic control microphone check (AMC)
    AMC provides air traffic controllers with the capability to uplink an instruction to check that pilots are not inadvertently blocking a voice frequency/channel with a “stuck microphone switch”.

Click here for further information on CPDLC (link to Wikipedia)

Photo Credit: AviationXpert.com

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