Incident Overview
On March 20, 2003, between 12:18 and 12:20 UTC, a Czech Air Force MiG-21 operated by the Air Force of the Army of the Czech Republic came within less than 4 nautical miles of a Singapore Airlines Boeing 747 (flight SIA025) at Flight Level 310 near airspace TSA 60. The military aircraft, registration SSR A2451, was part of a pair of MiG-21s tasked with a mission under the NATINEADS alert system within TSA 60 (FL 120 to FL 350). The Boeing 747 was en route from Frankfurt to Singapore (EDDF/WSSS) along airway UL 984.
Sequence of Events
At 12:18 UTC, the two MiG-21s separated: the first turned right to heading 270°, while the second continued south for several seconds then turned right to 270°. During this maneuver, the second MiG-21 descended and exited TSA 60, approaching the Boeing 747 from the north at the same altitude. The civil flight crew reported the situation to Prague ATC; no TCAS alert was issued. Radar data showed the separation minimum was reduced, triggering a Short Term Conflict Alert (STCA). The military aircraft had departed from Čáslav airbase at 11:53 UTC.
Investigation Findings
The joint commission (ÚZPLN and AČR) identified several issues:
- The combat radar controller failed to notice the second aircraft approaching the southern boundary of TSA 60 and did not prevent its exit.
- The controller did not utilize Mode C altitude data from air defense radar during the maneuver.
- When the military pilot queried about traffic, the controller provided information about departing traffic rather than the approaching Boeing 747.
- Phraseology used between the military aircraft and the controller did not conform to the prescribed "Frazeologie pro vedení taktické činnosti letectvem."
Conclusions
Vectoring of the military aircraft occurred without informing the pilots that they were at the southern edge of TSA 60. The combat controller failed to use altitude data from air defense radar. Control elements did not adequately consider the proximity of the international airway and the potential for conflict with civil traffic, compromising aviation safety in the area.
Recommendations
The commission recommended that military and civil aviation authorities pay increased attention to shared airspace usage. The AČR command was to brief all combat controller shift personnel about the incident and implement its own proposed measures within its purview.