What happened
On September 9, 2008, a serious air proximity incident occurred in the Oulu Terminal Area (TMA) near Kiiminki. A Finnish Air Force Fokker F.27 transport aircraft, operating a VFR flight from Ivalo to Jyväskylä, was flying at approximately 450 meters. Simultaneously, a formation of four Boeing F-18C Hornet aircraft, participating in the Ruska 2008 military exercise, was approaching Oulu aerodrome.
The Hornet formation was flying in an open formation, spanning roughly three kilometers in width and nine kilometers in length, at an altitude of approximately 300 meters. Upon receiving clearance from the Oulu approach controller to maintain an altitude of 900 meters or higher, the lead aircraft of the Hornet formation (Wisent 11) began a climb. During this ascent, the lead aircraft flew directly through the flight path of the Fokker F.27 without the crew noticing the transport aircraft. While the other three aircraft in the formation spotted the transport plane and maneuvered to avoid it, the lead aircraft's path intersected the transport aircraft's trajectory. The crew of the Fokker F.27 subsequently detected the approaching traffic via TCAS and observed two Hornets passing near their flight path.
The investigation
The investigation examined the coordination between military and civil air traffic services, the accuracy of radar data, and the adequacy of the risk analysis prepared for the Ruska 2008 exercise. Investigators looked into the technical capabilities of the Eurocat radar system and the communication protocols between the Rovaniemi Area Control Center and Oulu approach control.
Findings
The air traffic controller failed to provide timely traffic advisories to the VFR aircraft, attempting instead to separate the aircraft by altitude without verifying their actual flight levels. Several contributing factors were identified:
- The radar data for the lead Hornet (Wisent 11) did not reflect its true altitude. Because the secondary surveillance radar (SSR) was not in C-mode, the controller's screen displayed a default flight level of 95 (9,500 ft) based on the flight plan, rather than the actual altitude.
- Conflicting instructions and regulations regarding noise abatement procedures at Oulu led to a misunderstanding of the military aircraft's intended flight levels.
- The risk analysis for the military exercise was insufficient regarding air traffic services, specifically failing to properly manage flight plan data for exercise-related flights.
- There were technical discrepancies in air traffic communications and a lack of coordination between military and civil air traffic control units.
Safety action
Following the investigation, several improvements were noted, including an updated cooperation agreement between the Finnish Air Force and regional air traffic services. The investigation also prompted recommendations for Finavia to standardize the publication of local instructions and for the Air Force and Finavia to formally approve all military flight procedures at Oulu aerodrome.