Built by airline pilots. Designed to get you hired.

ADS-C stands for Automatic Dependent Surveillance – Contract.

It is a type of position reporting system used in remote and oceanic airspace where radar and real-time surveillance are not available. Unlike ADS-B, ADS-C transmits data only when requested, based on a contract between the aircraft and the ground station.

How it works

• A contract is established between the aircraft and ATC (typically via CPDLC).
• The aircraft automatically sends position reports based on:
  • Time intervals (periodic contract)
  • Waypoints crossed or other event (event contract)
  • Request from ATC (demand contract)

What data is transmitted

• Current position (latitude, longitude, altitude)
• Time of position report
• Estimated time and position at next waypoint
• Navigation intent information (e.g. route and flight plan data)

Benefits of ADS-C

• Enables ATC surveillance in non-radar areas such as the NAT HLA, Pacific, and Indian Ocean FIRs
• Supports reduced separation minima when combined with RNP-capable systems
• Provides reliable position monitoring in remote environments

Note: ADS-C is a key component of FANS (Future Air Navigation Systems) and works in conjunction with CPDLC to improve communication and surveillance beyond radar coverage.