What happened
On November 30, 2000, during the final stages of the 'Lepakko' night flying exercise, two Finnish Air Force F-18C Hornet fighters, registrations HN-408 and HD-428, experienced a serious loss of separation near Kuopio Airport. The aircraft were returning to their home base at Rissala following operations in the Pohjanmaa region.
As the aircraft approached the terminal area, the radar controller (APP) was managing multiple incoming pairs of military aircraft and a civilian Piper Chieftain. During the sequencing of the aircraft, the pilot of HN-428 (callsign S-26) was instructed to perform a left turn to a heading of 360 degrees and climb to 1,000 meters. However, the pilot executed a much steeper turn through the commanded heading, which directed the aircraft toward another approaching pair of Hornets (T-21/22).
At the moment of closest approach, HN-428 and the lead aircraft of the following pair passed within approximately 1.5 km of each other, with a vertical separation of only 240 meters. This significantly breached the required horizontal separation minimum of 5.6 km (3 nm) and the vertical minimum of 300 meters. The pilots of the involved aircraft did not visually observe one another during the encounter.
The investigation
The Finnish Safety Investigation Authority (OTKES) examined radar data from Kuopio Approach, radio communications, and flight data recorder (FDR) and Head-Up Display (HUD) recordings from both HN-408 and HN-428. The investigation also reviewed the organizational coordination between Kuopio Airport air traffic services and the Finnish Air Force.
Findings
- The primary cause of the separation breach was that the pilot of HN-428 failed to follow the air traffic control instruction, turning through the commanded 360-degree heading.
- Communication deficiencies contributed to the event; the pilot of HN-428 did not read back the critical heading instruction, and the controller did not insist on a formal read-back.
- The controller's workload increased significantly due to a high volume of traffic arriving in a very short window, and the station was manned by only one controller.
- Discrepancies existed between the special airfield regulations and Air Force training programs regarding speed restrictions, as the Hornets were flying faster than prescribed.
- There was a lack of formal written procedures governing the coordination between the airport's air traffic services and the Air Force regarding the level of service required for night operations.