Definition
A CPDLC (Controller-Pilot Data Link Communications) message uplinked by an air traffic controller instructing the flight crew to contact the next ATC facility or sector on a specified voice frequency or to log on to the next data link authority. It hands off communications responsibility from one controlling unit to another via the data link rather than by voice.
Plain English
A text message from ATC, sent through the aircraft's data link system, telling the pilot to switch over to the next controller -- usually by tuning a new radio frequency or connecting to the next ATC station electronically.
Context Anchor
Seen in CPDLC operations when an aircraft is being handed from one ATC area to another using data-link messages instead of, or along with, voice radio.
Derivation
"Transfer of Communication" is plain English -- the act of moving (transferring) the talking responsibility from one controller to another. The qualifier "CPDLC" simply identifies that the transfer instruction arrives as a data link text message rather than over the radio.
Why Pilots Care
Maintains uninterrupted ATC contact, prevents loss of separation, and ensures the pilot receives all required instructions without gaps.
Grounding Statement
A TOC is the CPDLC version of being handed off to the next controller, but for the aircraft’s data-link connection.
Intuition Check
Transfer of Communication does not mean the pilot casually starts talking to someone else. In this CPDLC context, it means a specific ATC data-link message changes which controller or facility is connected to the aircraft.
Example Sentence 1
Crossing into the next oceanic sector, the crew received a CPDLC Transfer of Communication message and logged on to the new ATC facility as instructed.
Example Sentence 2
After acknowledging the transfer of communication, the crew established contact with the new facility via CPDLC.