Background
On June 22, 2015, at approximately 08:46 UTC, a Bombardier DHC-8-Q400 operating a scheduled flight from Rzeszów to Warsaw was descending to FL140 when its Traffic Alert and Collision Avoidance System (TCAS) issued a Traffic Advisory (TA). Simultaneously, an Italian Air Force M346 jet was climbing from Dęblin airbase toward FL370. The two aircraft came within 5 nautical miles lateral and 400 feet vertical separation, triggering alerts and controller interventions.
Sequence of Events
The M346 departed EPDE (Dęblin) after receiving a clearance from the tower that included unrestricted climb to FL370. The pilot requested maximum vertical speed, achieving approximately 8,000 ft/min. The aircraft transitioned through several air traffic services: from Dęblin Tower to FIS Warsaw, then to ACC GAT sector "R". During the climb, the DHC-8-Q400 was descending toward Warsaw, cleared to FL140.
At 08:45:45, the ACC GAT radar displayed a Medium Term Conflict Detection (MTCD) alert for the two aircraft. At 08:46:10, the route of the M346 appeared on the controller's screen conflicting with the DHC-8's descent path. Despite the M346 crossing FL100 and later FL145, FIS Warsaw did not restrict its climb or coordinate with ACC before transfer. At 08:47:00, the M346 contacted ACC GAT sector "R", reporting level FL160. The controller immediately instructed the M346 to stop climb and turn right, and the DHC-8 to stop descent and turn north. A Short Term Conflict Alert (STCA) activated, first yellow then red. The DHC-8 crew reported a TCAS TA (later clarified as TA, not RA). After the evasive maneuvers, the minimum separation was 5 NM laterally and 400 ft vertically.
Investigation Findings
The investigation revealed several operational and coordination issues:
- The M346 received an unrestricted climb clearance from Dęblin Tower, with no altitude restriction before contacting FIS.
- FIS Warsaw did not stop the M346's climb when it entered controlled airspace without proper coordination.
- The ACC GAT coordinator, aware of the DHC-8, issued a clearance for the M346 via planned route without restricting its climb.
- The high climb rate of the M346 (over 8,000 ft/min) limited the effectiveness of the ACAS system.
- Filters in the radar system prevented adjacent units from seeing traffic, increasing reliance on coordination.
- The handover of the M346 involved multiple agencies (military ATC, FIS, ACC) with no standardized procedure documented.
The controller on duty had a valid license and recent refresher training (March 2013). The sector configuration was appropriate for average traffic levels, but the FIS informant was observed struggling with radar tracking and high workload.
Conclusion and Cause
The investigation concluded that the direct cause of the loss of separation was the issuance of an inconsistent air traffic control clearance for the M346 flight by the area control center (ACC). The lack of altitude restriction in the clearance allowed the M346 to climb into conflict with the descending DHC-8. No safety recommendations were issued, but the investigating body forwarded the report to military ATS and FIS training units for preventive action.