What happened
On September 5, 2007, at approximately 09:10 UTC, a loss of separation occurred within the Helsinki Terminal Control Area (TMA) involving two aircraft on visual approaches to runway 15. The first aircraft, a Finnair A319 (callsign FIN166), was arriving from St. Petersburg, while the second, a SAS MD82 (callsign SAS1712), was arriving from Copenhagen.
To expedite traffic, air traffic controllers cleared both aircraft for visual approaches. The controller at the Helsinki Approach radar workstation assigned FIN166 to the inbound sequence and later transferred it to the local controller. Simultaneously, SAS1712 was vectored toward the runway and cleared for a visual approach. Because the aircraft were operating on different radio frequencies, the crew of SAS1712 was not immediately aware of the position of FIN166.
As the aircraft approached the runway, the separation between them dropped to less than 1.5 NM, significantly below the required 3.0 NM minimum. The vertical separation was also insufficient, with a difference of only approximately 200 feet. The crew of SAS1712 eventually identified FIN166 and performed a left turn and a 360-degree maneuver to restore safe distance, resolving the conflict.
The investigation
The investigation examined the sequence of events, the air traffic control procedures, and the subsequent reporting of the incident. Investigators reviewed radar recordings, which showed that the separation violation was nearly unavoidable due to the timing of the traffic information provided by the controller. The investigation also looked into the communication between the various controller workstations and the adequacy of the aircraft's TCAS, which provided a Traffic Advisory (TA) but no Resolution Advisory (RA).
Furthermore, the investigation scrutinized the reporting process, finding that the incident was not reported to the authorities via the required channels immediately, and there were delays in the flow of information to the Safety Investigation Authority.
Findings
- The primary cause of the serious incident was the air traffic controller providing visual approach clearances to both aircraft without ensuring that minimum separation could be maintained.
- The controller provided traffic information regarding the proximity of the two aircraft too late to prevent the loss of separation.
- The aircraft were operating on different radio frequencies, which prevented the crews from coordinating their relative positions.
- The decision to change the arrival sequence of the aircraft contributed to the conflict.
- The air traffic controller's classification of the event as a standard incident rather than a serious incident led to non-compliance with established reporting procedures.
- There were deficiencies in the reporting forms used by the air traffic service provider, which contributed to delays in notifying the investigation authority.