What happened
On April 28, 2003, at 03:48 UTC, a loss of separation occurred approximately 20 nautical miles northeast of Helsinki-Vantaa airport involving two Finnair passenger flights. The first aircraft, an Airbus 321 (registration OH-LZB), was on a scheduled flight from Oulu, while the second, an MD-11 (registration OH-LGC), was arriving from Bangkok.
The two aircraft passed each other with a vertical separation of only 700 feet and a horizontal distance of 1.9 nautical miles, failing to meet the required separation standards of 1,000 feet vertically or 5 nautical miles horizontally.
The incident began when the approach controller, a trainee on only their tenth operational shift, attempted to manage the arrival sequence. To maintain separation from a preceding ATR72, the controller ordered the Airbus 321 to turn left. During the maneuver, the aircraft's altitude settings were changed from QNH 1003 to standard pressure 1013, causing the aircraft to momentarily climb to 6,300 feet before descending back to the cleared flight level 60. Simultaneously, the MD-11 was cruising at 5,000 feet. The proximity was detected by the TCAS systems of both aircraft, issuing Traffic Advisories (TA).
The investigation
The investigation examined the actions of the approach radar controller, the supervising instructor, and the coordination between arrival and departure radar positions. The investigation reviewed radar recordings, radio communications, and the training status of the personnel involved. It also analyzed the altitude setting procedures used by the flight crews of both aircraft.
Findings
- The primary cause of the loss of separation was inadequate planning and control of approaching traffic combined with the passive working method of the instructor supervising the trainee.
- The trainee controller was managing a relatively heavy volume of arrival traffic, which was high relative to their limited experience.
- The instructor failed to intervene with precise instructions until after both vertical and horizontal separation had already been lost.
- The instructor provided imprecise directional instructions, specifically assuming a turn would occur to the right when it was actually to the left.
- There was a lack of effective coordination between the approach (APP) position and the arrival (ARR) and departure (DEP) radar positions; specifically, the APP controller did not react to warnings from other controllers regarding the loss of separation.
- The flight crews of both the Airbus 321 and the MD-11 operated the aircraft in accordance with the instructions provided by air traffic control.