What happened
On June 2, 2000, at approximately 15:25 UTC, a mid-air proximity incident occurred roughly 20 nautical miles south of Oslo Airport Gardermo and near the boundary of two air traffic control sectors. The incident involved a Cessna C 650, registration LN-NLD, operating an ambulance flight, and an Airbus A 320, registration HS-IPZ, operating a commercial flight.
The Cessna C 650 was flying an arrival procedure (STAR TOR 2F) and maintaining flight level 100. Simultaneously, the Airbus A 320 was executing a departure procedure (SID SKI 2C) and was in the process of climbing from flight level 100 to 190. Due to significant cumulonimbus activity in the area, the crew of the Airbus A 320 had been cleared to deviate from their standard departure track to avoid thunderstorms. During this maneuver, the crew reported a TCAS warning to air traffic control, indicating a lateral separation of only 2 NM between the two aircraft at nearly the same altitude.
The investigation
The investigation examined the procedures governing the Oslo Terminal Control Area (TMA), which is split into East and West sectors managed by separate controllers. Investigators analyzed the specific arrival and departure tracks, noting that the SID SKI 2C includes a noise abatement left turn that brings the departure path within 5 NM of the arrival path.
To maintain safety, a local regulation requires specific altitude limits for north- and southbound traffic to ensure vertical separation. The investigation also reviewed the operational environment at the time, specifically the impact of heavy weather on controller workload and the effectiveness of the coordination protocols between the two sectors.