If you wish to contribute or participate in the discussions about articles you are invited to join SKYbrary as a registered user
Controller Pilot Data Link Communications (CPDLC)
Controller Pilot Data Link Communications (CPDLC) is a means of communication between controller and pilot, using data link for ATC communications. (ICAO Doc 4444: PANS-ATM)
CPDLC is a two-way data-link system by which controllers can transmit non urgent 'strategic messages to an aircraft as an alternative to voice communications. The message is displayed on a flight deck visual display.
Messages from an aircraft to ATC may follow a standard format or may be free-text. Messages from a controller normally follow a standard format. Response is required to most messages.
Communication procedures are detailed in ICAO Annex 10 Volume III Part 1 Chapter 3. The CPDLC message set is contained in ICAO Doc 4444: PANS-ATM, Annex 5.