Datalink

Datalink, or the Aircraft Communications Addressing and Reporting System (ACARS), is a robust two-way data communications system between aircraft and ground systems. A complete datalink communication, which may be generated either manually or automatically, is referred to as a datalink message. Messages from the aircraft to the ground are referred to as downlink messages and messages from the ground to the aircraft are referred to as uplink messages. Services available via datalink include flight plans, weather reports and forecasts, air traffic services, and two-way messaging.

The datalink system can be separated into three parts: datalink avionics, datalink infrastructure, and the datalink service provider.

Datalink Avionics

The GDC provides service to multiple datalink platforms, including:

Request GDC services through a Flight Management System (FMS) interfaced with any of the datalink platforms listed above. All datalink platforms use an internal or external Very High Frequency (VHF) transceiver for VHF datalink communications and may also use a satellite data communications system for Ultra High Frequency (UHF) datalink communications.

Datalink Infrastructure

The datalink platform communicates primarily via the ground-based ACARS VHF network, which includes the Société Internationale de Télécommunications Aéronautiques (SITA) subnetwork, the Aeronautical Radio, Inc. (ARINC) subnetwork, China's Aviation Data Communications Corporation (ADCC) subnetwork, the Aeronautical Radio of Thailand Ltd. (AEROTHAI) subnetwork, the Avicom Japan Co. Ltd. (AVICOM) subnetwork, and Brazil's Departamento de Controle do Espaço ?�ereo (DECE?�) subnetwork. Based on position information provided by the aircraft FMS, the datalink platform automatically tunes the VHF transceiver to the appropriate subnetwork. In areas where VHF coverage is unavailable, the datalink platform may use the Inmarsat Aero-C (datalink only) or Aero-H, Aero-H+, or Aero-I (datalink and voice) networks. The datalink platform switches to and from the satellite UHF network based on the availability of ground-based VHF network coverage. All datalink transmissions require line of sight to a VHF ground station or Inmarsat satellite.

Datalink Service Provider

As a provider of flight support services, the GDC is at the hub of the system. In addition to providing datalink host processing for all supported platforms, the GDC has telephone, fax, and network connections to ATC facilities, FBOs, multiple weather providers, and customer flight departments.