FANS 1/A is a later standard that was developed to the AFN (ATC Facilities Notification) protocol, and it has two components: CPDLC and ADS-C. Commercial airlines have used FANS 1/A for more than four decades for oceanic surveillance and text-based communications between pilots and ATC.
• CPDLC (Controller Pilot Data Link Communication) is the text-messaging component of FANS 1/A, and it allows two-way, digital communication between ATC and pilots when the aircraft is out of range of the analog-based VHF (very high frequency) or HF (high frequency) voice radio communications.
• ADS-C (Automatic Dependent Surveillance-Contract) sends information (aircraft position, altitude, speed, and meteorological data) automatically to ATC from the aircraft when ATC has requested it. Pilots do not interact with ADS-C at all, nor can they disable the reporting function. If the flight crew sends a Mayday message, ADS-C automatically triggers a report with time, position information, altitude, and airspeed that goes to ATC.
What Equipment Do I Need for Data Comm/FANS? The equipment you need varies, depending on the current configuration of avionics in your cockpit. At minimum, you need a FMS (flight management system), a datalink unit, and Satcom.