What happened
On November 30, 2001, at approximately 12:23 local time, two Finnair McDonnell Douglas DC-9-51 aircraft, registrations OH-LYP (callsign FIN 395) and OH-LYZ (callsign FIN 655N), experienced a loss of separation within the Helsinki approach area.
FIN 395 was preparing for a scheduled flight to Kuusamo and was assigned departure from runway 33. Due to a delay, the controller suggested runway 33 to minimize taxi time. Simultaneously, FIN 655N was preparing for a flight to Stockholm-Arlanda, departing from runway 04.
As both aircraft climbed, their flight paths intersected near the end of runway 04. The required vertical separation of 1,000 feet was breached at 12:23:15. During the encounter, the minimum vertical distance between the two aircraft dropped to 600 feet. While the crew of FIN 655N received a Traffic Advisory (TA) from the TCAS and adjusted their climb to 2,500 feet, the crew of FIN 395 did not receive a TA, and neither aircraft received a Traffic Advisory Resolution (RA). There were no injuries and no damage to the aircraft.
The investigation
The investigation examined radar data, radio communications, and air traffic control (ATC) procedures. Investigators reviewed the actions of the Helsinki approach controller, who was managing all workstations from a single position, and the trainee controller working under supervision. The investigation also analyzed the use of standard instrument departure (SID) procedures and the accuracy of flight plan information in the radar systems.
Findings
- The primary cause was the approach controller's incorrect assumption regarding the flight path of FIN 395; the controller believed the aircraft would head north, failing to realize the specific SID would lead it into the path of the departing FIN 655N.
- The controller failed to follow the Helsinki ATC operational manual, which requires the use of "standard clearances" and active departure clearance usage, particularly when runway 04 is in use.
- The controller did not issue any departure time restrictions to either aircraft.
- The controller did not explicitly name the SID during the clearance for FIN 345, which could have drawn attention to the actual flight path.
- The trainee controller was unfamiliar with the specific SID routes, and the supervising controller failed to notice the conflict in the active clearances.
Safety action
- When issuing route clearances, controllers should explicitly use the names of the standard instrument departures (SIDs).
- Air traffic controllers and trainees must maintain a thorough knowledge of SID flight paths.