ACARS (Aircraft Communications Addressing and Reporting System)

ACARS (Aircraft Communications Addressing and Reporting System) is a digital datalink system that transmits short messages between aircraft and ground stations. It operates over VHF radio, HF radio, or satellite links and has largely replaced voice communications for routine operational messages in commercial aviation.

What ACARS Transmits

• Departure and arrival times (OUT, OFF, ON, IN — the “OOOI” times)
• Weather requests and ATIS data delivery
• Flight plan uplinks and clearance delivery
• Engine performance and maintenance data (on ACARS-equipped turbine aircraft)
• Air traffic control pre-departure clearances (PDC)
• Fuel load confirmations and weight and balance data

How It Works

ACARS uses a ground network of VHF stations (in North America, primarily operated by ARINC and SITA) to relay messages between the aircraft and airline operations centres. Messages are formatted using standardized labels and queued automatically, reducing crew workload on voice frequencies.

On the TC Written Exam

ACARS appears primarily in CPL and ATPL study material in the context of datalink communications and modern cockpit systems. PPL candidates are unlikely to see it tested directly. Understanding that it is a digital communication system for commercial aircraft is sufficient at that level.