What happened
On August 20, 1996, at 11:57 local time, a military training aircraft, a BAe Hawk Mk 51 with registration U25, departed Oulu Airport on a VFR navigation flight. Following takeoff from runway 30, the pilot climbed directly to 600 meters (QFE) before turning right toward the SANKI waypoint.
Simultaneously, a Finnair McDonnell Douglas DC9-51, operating as FIN3614, was approaching Oulu from the direction of Kemi. The airliner was descending from 5,000 feet to 2,300 feet (QNH). The air traffic controller at Oulu informed the crew of FIN3614 of the departing Hawk, noting it was approximately 3 nautical miles ahead. The crew of FIN3614 acknowledged seeing the military aircraft. However, the pilot of U25 did not see the oncoming airliner. The two aircraft passed each other at a lateral distance of approximately 3 km while flying at nearly the same altitude.
The investigation
The investigation examined the flight clearances provided by Oulu tower, the adherence to established flight procedures, and the specific instructions regarding the "Villisika" training exercise. Investigators reviewed the radar data from the MSSR-radar, which showed the aircraft were at similar altitudes. The investigation also looked into the pilot's understanding of noise-abatement procedures and the clarity of the air traffic controller's instructions regarding traffic separation in Class D airspace.
Findings
- The pilot of U25 failed to comply with the specific flight clearance provided by the controller.
- The pilot of U25 operated under a mistaken belief that noise-abated climbing procedures for the training exercise applied to all flights, whereas the specific instruction for the departure was intended to maintain separation from the descending airliner.
- The noise-abatement instructions for the training exercise were poorly drafted, as they did not explicitly state that standard AIP Finland procedures should be followed for flights outside of the specific training area transit.
- The pilot of U25 had limited experience flying high-performance military aircraft outside of the Kauhava airbase.
- In the Class D airspace, the controller did not have a mandatory responsibility to provide vertical separation between IFR and VFR traffic, though providing traffic advisories to both aircraft would have been safer.
The primary cause of the incident was the failure of the U25 pilot to adhere to the assigned air traffic control clearance.