What happened
On May 29, 2015, a Boeing 737-800 operating within the Warsaw Flight Information Region (FIR EPWW) entered the active danger zone EPD 24 (GND-FL495). The incident began when the aircraft, flying at FL370 and heading toward waypoint TOPUR, was cleared by air traffic control to proceed direct to waypoint BOKSU. This clearance directed the aircraft's path toward the restricted area.
At 05:14:00 UTC, a yellow radar alert (ZN) appeared on the controller's display. Approximately ninety-five seconds later, the controller instructed the crew to execute a 25-degree left turn to avoid EPD 24. The aircraft did not immediately alter its course. Following a second instruction to turn "immediately" at 05:15:50 UTC, the crew began the maneuver. However, at 05:16:10 UTC, a red radar alert (ZN) was triggered, indicating the aircraft had penetrated the danger zone. The alert remained active until 05:17:30 UTC, at which point the aircraft was cleared to navigate via its own navigation systems to BOKSU.
The investigation
The investigation examined the actions of the air traffic controller and the crew's response. The controller was found to be fully licensed and up to date with all medical and professional requirements. The investigation noted that the controller was managing a high volume of traffic, with the workload at the upper limits of capacity. It was established that the controller's attention was focused on lower-level traffic, which resulted in a delayed recognition of the yellow radar warning.
Findings
- The controller's automated clearance for the Boeing 737-800 to fly direct to BOKSU inadvertently directed the aircraft into the path of the active EPD 24.
- The controller failed to notice the initial yellow radar alert due to being preoccupied with other traffic in the lower sectors.
- The instruction to perform a 25-degree left turn was insufficient to prevent the penetration of the danger zone.
- The flight crew delayed the execution of the requested turn despite the controller providing information regarding the proximity to the danger area.
- The primary cause of the incident was identified as errors in Air Traffic Management (ATM) operations.