What happened
On April 22, 1999, a serious air traffic safety incident occurred near Kittilä, Finland. A military BAe Hawk MK 51, registration K-31, was preparing for departure from Kittilä Airport. Prior to takeoff, the pilot communicated with the Kittilä air traffic informer to modify the flight plan, requesting to remain within the Kittilä advisory area at a flight level of "1000 plus." The pilot also indicated that if heavy traffic required it, the aircraft would climb to approximately 8,000 meters to utilize the Rovaniemi training area.
Simultaneously, an Aerospatiale Italiano ATR-72, registration OH-KRD, operating as FIN-451, was approaching Kittilä on runway centerline W1. As the BAe Hawk MK 51 took off and began a climb, it entered controlled airspace without proper clearance. The Rovaniemi approach controller observed an unidentified aircraft climbing through 100 feet in close proximity to the ATR-72, with the distance between the two aircraft narrowing to approximately 10 miles. Upon realizing the conflict, the controller instructed the K-31 crew to immediately descend out of controlled airspace. The military aircraft, which was already at approximately 6,000 meters, complied and descended back into the advisory area.
The investigation
The investigation examined the communications between the Kittilä air traffic informer, the Rovaniemi approach controller, and the K-31 crew. It established that while the pilot had coordinated the flight plan change with Rovaniemi approach, the updated information was not relayed to the Kittilä informer. Furthermore, the investigation looked into the technical capabilities of the radar systems used by Rovaniemi approach versus the area control center, noting that the approach controller's specific equipment allowed for the detection of lower-altitude traffic that was not visible on the area controller's primary system.
Findings
- The primary cause was that the Kittilä air traffic informer assumed the BAe Hawk MK 51 would remain within the local advisory area and therefore failed to request the necessary clearance from Rovaniemi area control for the aircraft to enter controlled airspace.
- The use of the phrase "1000 plus" created significant ambiguity; the pilot intended for the aircraft to fly at 1,000 meters and above without an upper limit, whereas the informer understood the aircraft would remain between 1,000 meters and the flight level ceiling of 65.
- The Kittilä informer failed to notify Rovaniemi area control regarding the modified flight plan.
- The pilot of the K-30 did not request the appropriate clearance required to enter controlled airspace.