South Africa's Air Traffic and Navigation Services (ATNS) said that its Controller Pilot Data Link Communications (CPDLC), a system through which air traffic controllers transmit text-based messages to pilots as an alternative to voice communications to aircraft, has been fully restored. 

This follows a failure of the CPDLC service that took place on 6 December 2022 over a huge area of airspace over the ocean to the south of Africa and extending all the way to Antarctica. The airspace has been delegated to SA by the International Civil Aviation Organisation (ICAO).

It was restored in the early hours of 7 December 2022. 

"ATNS is working closely with its data link service provider to determine the root cause of this failure. It must be emphasised, however, that this incident is unprecedented, as ATNS has never experienced an occurrence of this nature before," ATNS responded. 

"Various redundancies are embedded within the CPDLC architecture, and as part of the ongoing investigations, such will be reviewed to identify possible improvements and prevent future recurrences."

Contingency plans

According to ATNS, it has a number of operational contingency plans that may be operationalised at any given time, depending on the levels of service disruptions or risks identified. 

"Air traffic volumes are naturally low within the oceanic air space. Therefore, no separation risks were identified during this incident," said ATNS. 

"Safety is our number one priority. We are part of a global collective that has been rated topmost when it comes to aviation safety. The recent ICAO safety audit report is indicative of the South African aviation industry's stance and commitment to safer skies."

DA member of parliament Chris Hunsinger said in a statement that the party will lodge a formal request to Transport Minister Fikile Mbalula to explain the circumstances following the CPDLC failure.

"The collapse of this system also revealed that the backup system, which is a conventional high-frequency voice-communication system, has been broken and not repaired for close to a year. Without both systems, pilots and ground control had no way of communicating with each other," says Hunsinger.

'Breach of international obligation'

"This communication 'blackout' raises serious concerns with regard to air traffic safety and is a serious breach of the international obligation which South Africa and ATNS must uphold for aviation safety in three different flight information zones."

Aviation expert Linden Birns, managing director of Plane Talking, says the communications failure did not just impact South Africa's ability to provide communication for en-route navigation but also compromise the country's maritime search and rescue coverage and coordination.

Birns says through the Airline Association of Southern Africa (AASA), the industry has repeatedly raised its concerns with the relevant SA authorities over the severely diminished capability and capacity of the SA Air Force and SA Navy, which have compromised their ability to provide the required airborne and seaborne maritime search and rescue services that the government has committed to under civil aviation and maritime treaties. 

In his view, it is far from ideal to have air-to-ground data or radio communications system failures like those recently experienced by ATNS. He does, however, point out that there are standard procedures that aircrew must follow as a precaution in the event of such breakdowns.

A seasoned South African pilot, who wants to remain anonymous, said in a case such as the breakdown of the ATNS link and its high-frequency radio system not working, in theory a pilot could log onto the high-frequency CPDLC of another country and ask them to, in turn, make telephonic contact with ATNS in SA.