In aviation, datalink communications are messages between an aircraft and systems on the ground or from one aircraft to another plane. Datalink communications are facilitated through one of two methods: the Aeronautical Telecommunications Network (ATN) and the Aircraft Communication Addressing and Reporting System (ACARS). Both systems provide clear and concise out-of-sight radio communication between aircraft and controllers on the ground or from one aircraft to another.
Text messages reduce misunderstandings
Using data link systems, pilots and air traffic controllers can exchange non-urgent messages and Air Traffic Control (ATC) information by text rather than by voice. Text-based messages help reduce the margin for error and misunderstanding of voice-based instructions. They also allow more airspace on often congested VHF channels for urgent voice communications.
What is the purpose of data link communications?
The reason aircraft use data link communications is to link the aircraft to air traffic controllers on the ground while simultaneously relaying the aircraft’s exact position and altitude. The system is essential when flying over oceans as it allows air traffic controllers to know precisely where the plane is, communicate with it, and relay flight level clearances.
With the aid of ACARS, communications systems can track the following:
- All events from the gate at the departure point to the gate at the arrival airport. The data link system can track the flight and access the aircraft’s fuel status.
- Weather information is sent from the ground to the aircraft in real-time using a Flight Management System (FMS). This information allows the pilots to evaluate their flight plans and make changes when required. For example, divert to another airport should the arrival destination be closed due to fog.
- Data link communications allow controllers on the ground to know the health of the aircraft. The data sent from the plane provides real-time information about the aircraft’s avionics and flight systems.
- Ground controllers can trigger satellites to ping the aircraft every hour to determine its position and see that it is still active. It is like an electronic “are you still there?” To which the aircraft “replies yes, I am.”
- The data link system also tracks and records when the flight crew sends or receives messages between the aircraft and the ground.
Before 1978, all communications between aircraft and controllers on the ground were done using VHF or HF voice radios. Because of the need for a human to record and relay the messages, the information was not as accurate as it would be using an automated system.
Data link messages and cockpit voice recorders
When activated, a cockpit voice recorder captures conversations and data link messages. Cockpit voice recorders only record two hours of discussions and data before overwriting themselves. In the recorded data link readout, airlines would receive a report detailing what messages were sent.
Given today’s technology, you would think that cockpit voice recorders would now be obsolete, given that it is possible to stream real-time data from the aircraft to the ground. The problem is that thousands of aircraft are often in the sky simultaneously. The answer is to introduce new solid-state CVRs with a separate power supply that can record the entire flight and not just two hours. Honeywell has developed the Honeywell Connected Recorder-25, which can record 25 hours of cockpit voice communications and data.