What happened
On July 19, 2015, an air traffic control incident occurred in the Warsaw FIR, southwest of the KOTEK waypoint. An ACC GAT controller, acting in an instructor capacity (OJTI), took over the "J" sector and intentionally disabled the Medium Term Conflict Detection (MTCD) warning system to conduct training under specific workload conditions.
Shortly after, a Boeing 737 (callsign SAS7442) flying the LENOV – MOTAD route reported weather avoidance maneuvers at FL360 and requested direct routing to KOLOB. Five minutes later, a Boeing 772 (callsign AUA52) on the GORAT – TUSIN route entered the sector at the same altitude. Following a course change by the first aircraft, the controller's radar triggered a Short Term Conflict Alert (STCA) yellow alert. The controller instructed the Boeing 772 to descend immediately to FL350.
As the aircraft maneuvered, the STCA escalated to a red alert. The crew of the Boeing 772 reported visual contact with the Boeing 737 and noted they were crossing FL355 while descending. The minimum separation achieved between the two aircraft was 5 nautical miles and 600 feet, failing to meet the required separation standards of 7 NM horizontally or 1000 feet vertically.
The investigation
The investigation examined the controller's operational decisions, the status of the radar warning systems, and the environmental factors affecting the sector. The inquiry focused on why the controller failed to identify the converging flight paths and the impact of disabling the MTCD system during a training session.
Findings
- The controller failed to notice the converging flight paths of the two aircraft while simultaneously managing the passage of two other aircraft (AZA493 and THY1YL).
- The controller did not issue a climbing instruction for the Boeing 737 in conjunction with the descent instruction for the Boeing 772.
- The intentional disabling of the MTCD warning system for training purposes significantly reduced the controller's ability to detect the conflict.
- Contributing factors included high sector workload near maximum capacity and potential controller fatigue, as the individual was performing their fourth consecutive shift following a three-day break.