What happened
On June 2, 1999, at approximately 14:00 local time, a serious air traffic safety incident occurred in the Lappeenranta airport approach area. An ATR 72-201, registration OH-KRH, operated by Finnair, was conducting type training flights involving landing practice. Simultaneously, a private Cessna 172 (registration OH-CLT) was performing a forest fire surveillance flight on a pre-planned route.
The two aircraft passed each other in opposite directions at an altitude between 1,500 and 2,000 feet MSL. During the encounter, the Traffic Collision Avoidance System (TCAS) on the OH-KRH issued both a Traffic Advisory (TA) and a Resolution Advisory (RA). In response to the RA, the pilot of the ATR 72-201 initiated a descent of approximately 1,000 feet, though the actual vertical separation achieved was only about 300 to 400 feet. The pilot of the OH-CLT also performed an evasive maneuver by increasing altitude. At the moment of closest approach, the lateral separation between the two aircraft was approximately 100 meters.
The investigation
The investigation examined radio communications, radar recordings, and flight documentation. Investigators reviewed the flight plans for both aircraft, noting that the ATR 72-201 was operating under IFR (Instrument Flight Rules) for training, while the Cessna 172 was operating under VFR (Visual Flight Rules) for surveillance. The investigation also analyzed the sequence of instructions provided by Lappeenranta Tower and the coordination between the aircraft and the approach control services.
Findings
- The crew of the ATR 72-201 was primarily scanning to the left to monitor a Saab 340 aircraft that had been identified as significant traffic. Because the controller had not provided a specific traffic information alert for the Cessna 172, the crew did not consider the smaller aircraft to be a threat.
- The Cessna 172 was flying at 1,900 feet, and while the pilot had informed the tower of their route and altitude, the controller had not issued a specific traffic alert regarding the ATR 72-201 to the Cessna crew.
- The failure to provide specific traffic information regarding the approaching Cessna to the ATR crew was the primary factor leading to the near-collision.
- The TCAS on the OH-KRH functioned correctly, providing the necessary warnings to prevent a collision.