What happened
On April 2, 1997, at approximately 13:30 local time, a serious loss of separation occurred within the Kajaani flight information area. A Finnair Beechcraft A36 Bonanza, registration OH-BBK, was performing a VOR/DME approach to runway 25. Simultaneously, a Finnair DC-9-51, registration OH-LYY (operating as flight FIN 385), was approaching the same area from the south on a visual approach.
The two aircraft were flying in instrument meteorological conditions (IMC) and did not see one another. At the point where the aircraft crossed altitudes, they were approximately 9 NM apart. As they continued on nearly parallel tracks, their lateral separation decreased to approximately 5 NM, with a vertical separation of only 500 feet.
As the situation became uncertain, the pilots of both aircraft filed reports to the aviation authorities. The OH-BBK pilot eventually climbed to 4,000 feet to ensure a safe buffer from the DC-9's potential missed approach altitude, which was 2,400 feet.
The investigation
The investigation examined the actions of the Rovaniemi Area Control Center (ACC), the Kajaani Aerodrome Flight Information Service (AFIS), and the flight crews. Investigators analyzed radio communications, weather conditions, and the coordination procedures between the ACC and AFIS. The investigation also looked into the use of the Pommery system for calculating arrival estimates and the impact of the aircraft's flight paths on the timing of traffic information.
Findings
- Late radio contact: The crew of FIN 385 established contact with Kajaani AFIS only 11 miles from the field, leaving insufficient time to utilize the traffic information provided to avoid the other aircraft.
- Inadequate traffic information: The Rovaniemi ACC provided a traffic information message to the DC-9 that did not allow the crew enough time to prepare for the conflict, as the aircraft was already past the point of effective avoidance.
- Lack of radar surveillance: The Area Control Center did not have radar contact with either aircraft at the time they became a conflict.
- Inconsistent coordination: There was a lack of specific instructions in the coordination manual between the ACC and AFIS regarding when the AFIS should provide additional traffic details to the ACC for transmission to arriving aircraft.
- Ambiguous procedures: The use of the phrase "joining the VOR/DME approach following the initial approach route" was found to be imprecise, as it did not clearly indicate whether the aircraft was performing a direct approach or a racetrack pattern, leading to significant discrepancies in estimated arrival times.