What happened
On September 6, 2006, an incident occurred in the Prague FIR involving a conflict between a commercial flight and military aircraft. The event began during a coordinated flight plan for a pair of JAS 39 Gripen jets, operating under callsign 2611, traveling from Pardubice (LKPD) to the TRA60 airspace at FL160. To accommodate this military activity, the military air traffic control center (MACC) Prague established active coordination and temporary reserved airspace up to FL240.
During this period, a Boeing 737-500 operated by ČSA, flight CSA024, was climbing through FL140 toward Ostrava (LKMT). While climbing, the crew of CSA024 reported an interruption in their climb due to conflicting traffic appearing to their left and right, approximately 2,000 feet above them. The aircraft's TCAS provided a Traffic Advisory (TA) during the encounter. The conflicting traffic was identified as being approximately 7 NM away.
The investigation
The ÚZPLN investigation examined the actions of the flight crew, the air traffic controllers (ATCOs) at both the military (MACC) and civil (ACC) centers, and the communication protocols used during the coordination of the military flight. The investigation focused on the handover of flight information between the radar controllers of the terrain sector and the North Southeast (NSEL) sector, as well as the accuracy of the clearances issued to the commercial flight.
Findings
Several critical failures in coordination and monitoring were identified:
- The MACC radar controller issued an improperly defined clearance to the NSEL procedural controller, which did not provide sufficient parameters to ensure separation.
- The NSEL procedural controller accepted a clearance for CSA024 before the aircraft had even established radio contact with the NSEL sector.
- The NSEL radar controller issued clearances to CSA024—including a change to fly direct to point HLV—that significantly increased the risk of a separation minima infringement with the military jets.
- Inadequate monitoring of the traffic situation by the NSEL radar controller was a primary contributing factor.
- There was a failure in information transfer, as the NSEL procedural controller did not inform the MACC of the change in the commercial flight's route to point HLV, and the NSEL radar controller failed to relay information regarding significant traffic when the crew reported the climb interruption.
The incident was classified as a significant incident involving a separation minima infringement.