What happened
On July 29, 1999, at approximately 16:00 local time, a serious air traffic safety incident occurred in the Lappeenranda Terminal Control Area (TMA). A Finnair flight operated by Flying Enterprise, a Saab 340B with registration OH-FAF, was on a visual approach to runway 24. Simultaneously, a SZD-50-3 Puchacz glider, registration OH-772, was operating within the same airspace.
The two aircraft crossed paths with intersecting flight paths at an altitude of approximately 4,000 feet MSL. The pilot of the Saab 340B observed the glider and performed an emergency maneuver, pulling the aircraft into a climb to avoid a collision. The pilot of OH-FAF estimated the separation distance at the time of the near-miss to be approximately 100 meters. The pilot of the glider, OH-772, reported that they did not see the airliner at the moment of the encounter.
The investigation
The investigation examined radio communications between Lappeenranta Tower and several aircraft, including the airliner, the glider, a glider tug (OH-HCF), and other VFR traffic. Investigators reviewed the sequence of clearances provided to the glider and the tug, as well as the arrival information provided to the Finnair flight. The investigation also looked into the coordination between the local tower and the Area Control Centre (ACC) regarding the arrival of the commercial flight.
Findings
- The investigation established that the Saab 340B was on a direct approach from the MILSI VOR/DME, a route slightly south of the standard airway, which contributed to the unexpected encounter.
- The pilot of OH-772 was aware of the approaching Finnair flight due to hearing the controller's briefing but believed the airliner was approaching from the northwest, leading to a lack of visual scanning in the correct direction.
- Inaccurate situational awareness regarding the exact flight path of the airliner and the presence of multiple gliders in the vicinity contributed to the risk.
- There were inconsistencies in radio communications, including instances where pilots read back clearances incorrectly or where the controller used non-standard phrasing, such as "old clearance."