Definition
A digital text-message communication system between air traffic controllers and pilots, carried over the Aeronautical Telecommunication Network (ATN) using VHF Data Link Mode 2 (VDL Mode 2) as the radio link. It allows controllers to send instructions, clearances, and information to the flight deck as data messages rather than voice transmissions, with the pilot responding by selecting a reply on the data link display.
Plain English
It is a way for controllers and pilots to talk to each other by sending typed messages back and forth over a special aviation data radio, instead of speaking on the radio.
Context Anchor
Seen in instrument procedure and RNAV discussions where aircraft communication capability affects how clearances, route changes, or departure instructions may be delivered.
Derivation
CPDLC = Controller-Pilot Data Link Communications, meaning the controller and pilot exchange information via a data link. ATN = Aeronautical Telecommunication Network, the global aviation data network that carries the messages. VDL Mode 2 = VHF Data Link Mode 2, the specific VHF radio standard used to move that data between the aircraft and ground stations. Put together: messages (CPDLC) travel across the aviation data network (ATN) using a particular VHF radio channel (VDL Mode 2).
Why Pilots Care
Reduces voice congestion on busy frequencies and allows precise, error-checked route amendments to be sent directly to the flight management system.
Analogy
Think of it like a dedicated aviation text-message path between the cockpit and air traffic control, but with standardized messages and required pilot action. It is not casual texting and it does not replace the pilot’s responsibility to verify the clearance.
Intuition Check
Do not read “Mode 2” as an autopilot mode or a transponder mode. Here it means a specific VHF digital data-link format used to send controller-pilot messages.
Example Sentence 1
After departure, the crew received their en route clearance through CPDLC ATN VDL Mode 2 and acknowledged it on the data link display.
Example Sentence 2
ATC uplinked a direct routing change through CPDLC ATN VDL Mode 2 after the aircraft passed the initial fix.