What happened
On the morning of 23 September 2015, a near-miss occurred within the Gothenburg/Säve control zone during daylight hours. A Eurocopter 120 B, registration SE-JLN, was cleared to cross the runway and depart the control zone to the north under VFR conditions. Simultaneously, a Cessna Citation 525, registration D-IRSB, was established on an ILS approach to runway 19.
As the helicopter proceeded north, it approached the incoming airplane on a collision course. The air traffic controller realized the conflict only when the airplane contacted the tower. To prevent a collision, the controller issued immediate emergency instructions, ordering the helicopter to turn right toward heading 090 and the airplane to turn right toward heading 270. The minimum distance between the two aircraft was recorded at 1.28 NM horizontally and 200 feet in altitude.
The investigation
The Swedish Accident Investigation Authority (SHK) examined radar data, radio communications, and interviews with air traffic controllers, the flight crew of the D-IRSB, and the flight instructor and student in the SE-JLN.
The investigation focused on the coordination between Landvetter terminal control and the Säve tower. It was discovered that the controller in the active position (AD1) had been assisting an off-duty colleague with administrative tasks, specifically preparing training materials. Furthermore, the investigation looked into the use of non-standard phraseology used during aircraft arrival notifications.
Findings
Several factors contributed to the loss of separation:
- The coordination between Landvetter terminal control and Säve tower was abbreviated, failing to follow established procedures.
- A practice of using the phrase "en tjuga" (a twenty) had become common to shorten arrival notifications, which meant the controller did not properly verify the aircraft's callsign.
- Due to the abbreviated communication, the controller failed to correctly place the flight progress strip for the incoming D-IRSB on the Flight Progress Board.
- The controller forgot about the incoming airplane until the aircraft contacted the tower directly.
- The controller's involvement in administrative duties during the shift likely distracted from active traffic monitoring.
Safety action
SHK has recommended that the Swedish Transport Agency ensure air navigation service providers utilize correct and standardized phraseology when performing coordination tasks to prevent future misunderstand and oversight.