History
On 30 June 2015, a serious incident occurred in the Warsaw Flight Information Region (FIR EPWW) involving two aircraft: an Airbus A320 (registration DAIZB) operated by Deutsche Lufthansa AG (flight DLH2564) and an Airbus A321 (registration OYKBE) operated by Scandinavian Airlines System (flight SAS2831). Both aircraft were cruising at flight level (FL) 350. At 10:26:25 UTC, the crew of SAS2831 established radio contact with the air traffic controller (ATCO). At 10:32:20, DLH2564 also contacted the ATCO at FL 350.
At 10:35:07, the Short Term Collision Alert (STCA) system generated a yellow alert. The ATCO then instructed DLH2564 to make an immediate left turn from heading 026 to 355 degrees, and SAS2831 to make an immediate left turn from heading 152 to 130 degrees. Both crews acknowledged. Shortly after, the crews reported that they were following commands from the Airborne Collision Avoidance System (ACAS). DLH2564 climbed to FL 356, and SAS2831 descended to FL 346. The horizontal distance between the aircraft was measured at 2.9 NM, below the required minimum of 7 NM.
At 10:36:43, DLH2564 reported "clear of conflict" and returned to FL 350. Both aircraft were subsequently cleared to continue their flights via own navigation to their respective waypoints.
Causes
The Polish State Commission on Aircraft Accident Investigation (PKBWL) determined that the cause of the serious incident was errors in Air Traffic Management (ATM) work, which led to the dangerous proximity.
Findings
- All crew members and the ATCO held valid licenses and medical certificates.
- Continuous radio communication was maintained throughout the event.
- The ATCO had completed a refresher course in October 2013 and had been on a six-day break prior to the incident.
- The Medium Term Conflict Detection (MTCD) function had been disabled by a previous shift controller; there was no requirement to keep it enabled.
- The ATCO focused on monitoring separation between DLH2564 and another aircraft (AFL2307) outside his sector, inadvertently neglecting the loss of separation in his own sector.
- After the STCA activation, the ATCO issued immediate turn instructions, but did not inform the crews of conflicting traffic.
- Both aircraft followed ACAS resolution advisories.
- No injuries or damage to either aircraft occurred.
Actions Taken
The Polish Air Navigation Services Agency (PAŻP) distributed the report to relevant departments and initiated steps to improve awareness of MTCD status during shift handovers and consider uniform logging standards.