Analysing the Actual Use of Controller–Pilot Data Link Communications

Controller–pilot data link communications (CPDLC) is a digital protocol and part of air navigation systems where Air Traffic Control (ATC) can text an aircraft instead of engaging in voice communications. This research used a CPDLC receiver at the airport of a European capital -EETN and captured all the CPDLC messages for one year. The total number of messages, more than 4.7 million might not be directly relevant since the COVID-19 pandemic affected the number of flights during that period. Still, the classification of the captured messages reveals the usage of this communication channel. Some characterisation analysis of the data traffic shows that only 2% of the 4.7 million messages are Connection-Oriented Transport Protocol (COTP) messages. If we do not consider the messages necessary to connect and establish a connection (e.g., next data authority, release request), there were, in the downlink, from aircraft to ATC, 4626 “wilco” messages, 74 free text messages, and 225 other messages. We found 6357 instruction messages and 9991 free text messages in the uplink. Therefore, only 0.3% of all VDL-2 messages have an operational added value. This enormous overhead, the limited available bandwith and the predicted increase of users of CPDLC, such as unmanned aircraft and recreative flights will saturate this completely this communication channel.