What happened
On July 21, 2003, at 12:04 UTC, a loss of radar separation occurred approximately 18 nautical miles northeast of Helsinki-Vantaa airport. Two Finnair passenger flights, an A319 (registration OH-LVD) arriving from Rovaniemi and an MD-83 (registration OH-LPH) arriving from Manchester, passed each other with a vertical separation of only 200 feet and a horizontal distance of 2.4 nautical miles.
The incident began when the arrival controller (ARR) issued an incorrect turn direction to another aircraft, SK1706, which disrupted the established approach sequence. As the controllers focused on managing the resulting traffic disorder, the flight paths of OH-LVD and OH-LPH became intersecting. The approach controller (APP) had cleared OH-LPH to descend to 5,000 feet, while the arrival controller, unaware of this descent, cleared OH-LVD to descend to 6,000 feet and later instructed the aircraft to expedite descent to 5,000 feet. Consequently, both aircraft reached the same altitude while on crossing paths.
The investigation
The investigation examined radar recordings, air traffic controller reports, pilot statements, and radio communications. The commission also analyzed the workload of the controllers, noting that both the APP and ARR controllers were heavily preoccupied with managing the displaced traffic from flight SK1706. Additionally, the investigators reviewed the visual clarity of the radar display monitors, noting issues with color contrast and label readability.
Findings
- The primary cause of the loss of separation was insufficient planning and coordination of arriving traffic, combined with a passive working relationship between the APP and ARR controller units.
- A significant contributing factor was the incorrect heading instruction given to flight SK1706, which caused the arrival sequence to become disorganized.
- The use of visual approaches for other aircraft further complicated the arrival sequence.
- Both controllers failed to notice the developing conflict because their attention was focused on resolving the issues caused by the incorrect turn of SK1706.
- The aircraft's TCAS units provided Traffic Advisories (TA) but did not issue Resolution Advisories (RA).