What aircraft was involved and where did it happen?

The accident on 1998-09-08 involved a aircraft, registration OH-FAF, at FI.

What was the probable cause of the accident?

The primary cause was the air traffic controller's failure to accurately assess the position of the calibration aircraft and the potential for conflict with the arriving scheduled flight. This was compounded by the **Beech C-90**'s failure to follow separation instructions and the **Saab 340B**'s delayed evasive…

Near Mid-Air Collision at Pori Approach Area

A Saab 340B and a Beech C-90 experienced a loss of separation during simultaneous final approaches at Pori, Finland.

What happened

On September 8, 1998, at approximately 10:45 UTC, a serious loss of separation occurred in the Pori approach area involving two aircraft. The first aircraft, a Beech C-90 (registration OH-BAX), was conducting an ILS calibration flight. The second aircraft, a Finnair Saab 340B (registration OH-FAF), was operating a scheduled flight (FIN 253) from Helsinki to Pori.

At the time of the event, both aircraft were on the final approach for runway 30. The Beech C-90 had performed a missed approach and was climbing to 2,000 feet, intending to re-approach from 2,000 feet. The air traffic controller instructed the OH-BAX to move to the north side of the final approach course to wait for the arriving Saab 340B. However, the Beech C-90 began a turn toward the final approach path.

Simultaneously, the Saab 340B was descending through 3,000 feet at a high speed of approximately 250 knots. As the Saab 340B approached the final approach course, the crew observed the Beech C-90 at a distance of about one mile, positioned slightly below them. The Saab 340B crew observed the Beech C-90 banking to the right and prepared for an evasive maneuver, instructing the other aircraft to turn left. The Saab 340B eventually passed the Beech C-90 at a distance of approximately 7 NM from the DME, with the Beech C-90 positioned about 100 feet below the Saab 340B.

The investigation

The investigation, conducted by the Safety Investigation Authority, was based on radio recordings from Pori, radar data from Tampere Area Control, and interviews with the involved crews and the air traffic controller. The investigation examined the flight paths, the controller's instructions, and the timing of the aircraft movements. Radar analysis confirmed that the Beech C-90 was in a radar shadow, making it difficult to track, while the Saab 340B's descent and speed were verified through radar data.

Findings

The air traffic controller failed to accurately monitor the position of the Beech C-90 or calculate the timing of the aircraft's intersection point.
The Beech C-90 did not immediately comply with the instruction to remain on the north side of the approach course.
The Saab 340B did not initiate an appropriate evasive maneuver early enough, which led to the unexpected proximity of the two aircraft when the Beech C-90 banked toward the path.
The Saab 340B was operating at a high speed, near the maximum allowed for the airspace class.