What aircraft was involved and where did it happen?

The accident on 1998-10-09 involved a aircraft, at FI.

What was the probable cause of the accident?

The near collision was caused by the crew of the Boeing 727 failing to adhere to their assigned flight route following a recent change in airway designations, leading to a conflict with an aircraft on an intersecting path.

Near Collision of Two Airliners Near Vihri VOR

A Boeing 727 and a DC-9 narrowly avoided a mid-air collision near the Vihri VOR after the cargo flight failed to follow a newly updated flight route.

What happened

On the night of October 9, 1998, a serious loss of separation occurred between two commercial aircraft approximately 50 nautical miles west of Helsinki. The first aircraft, a Boeing 727-223F (registration OO-DHW) operating as European Air Transport flight BCS 6514, was on a cargo flight from Helsinki to Gatwick. The second aircraft, a DC-9-81 (registration OY-KHR) operating as SAS 714, was on a scheduled passenger flight from Copenhagen to Helsinki.

At the time of the incident, the flight routes for the area had been updated only two days prior. While the cargo flight was cleared for a new route via the UP606 airway, the crew of OO-DHW instead turned toward the SUNNA VOR, following their original flight plan. Simultaneously, SAS 714 was descending through flight level 150. The two aircraft crossed paths at an altitude of approximately 6,250 meters, passing within roughly one kilometer horizontally and only 400 feet vertically of each other.

The investigation

The investigation examined radio and telephone communications between Helsinki ground control, Helsinki approach, and Tampere Area Control. Investigators also reviewed radar video recordings and flight plan documentation. The inquiry focused on the recent changes to the airway names and the clarity of the instructions provided to the crews. The investigation established that while the route change had been updated in the aeronautical information publication, the cargo crew had initially misread their clearance and subsequently failed to follow the corrected instructions.

Findings

The primary cause of the near collision was that the crew of OO-DHW did not follow their assigned and acknowledged flight route.
The flight crew of the cargo aircraft followed their original flight plan rather than the updated RNAV route.
Air traffic controllers at Tampere Area Control identified the conflict and issued immediate commands to both aircraft to stop their climb and descent, respectively.
The pilots of both aircraft responded by activating their landing lights and visually identifying the other aircraft.
The controller could have improved clarity by using the term "rerouted" when providing the new clearance, or by specifically mentioning the KOSKA waypoint to confirm the departure route.
All involved flight and air traffic control personnel held valid licenses and qualifications.