What happened
On January 11, 2002, a separation loss occurred southeast of Helsinki-Vantaa Airport involving two aircraft: a Finnair Boeing 757 (registration OH-LBU) and an Aviast Joint Stock Ltd Antonov An-12 (registration RA11962).
The Antonov An-12, operating flight VVA9023 from Helsinki to Samara, Russia, departed Helsinki-Vantaa on runway 22. After an initial error in the transponder code, the departure controller instructed the crew to climb to flight level 70. Simultaneously, the Boeing 757, operating flight FIN1942 from Dubai, was on approach to Helsinki-Vantaa and was cleared to descend to flight level 80.
At approximately 15:55 local time, both aircraft reported reaching their assigned altitudes. However, the Antonov An-12 continued to climb above flight level 70. The crew of the Boeing 757 observed the approaching aircraft via TCAS and visual scanning. As the vertical separation decreased to approximately 500 feet, the Boeing 757 crew initiated an upward avoidance maneuver, climbing to flight level 86. The aircraft eventually passed each other at a vertical separation of 700 feet and a horizontal distance of 0.25 nautical miles.
The investigation
The investigation examined radar recordings from Helsinki-Vantaa, radio communications, and the flight data recorder from the Boeing 757. Investigators analyzed the actions of both the approach and departure controllers, as well as the cockpit procedures of both crews. The investigation also looked into the communication between the Antonov An-12 crew and air traffic control, noting that while radio communications were conducted in English, internal crew communication was conducted in Russian.
Findings
- The primary cause of the loss of separation was that the Antonov An-12 continued climbing above its assigned altitude of flight level 70.
- The Boeing 757 crew acted safely by initiating an avoidance maneuver based on a TCAS Traffic Advisory (TA) and visual observations before a Resolution Advisory (RA) was issued.
- The Antonov An-12 crew failed to maintain the assigned altitude, possibly due to inadequate cockpit coordination or a lack of understanding of the English-language instructions.
- The departure controller observed the Antonov An-12 passing flight level 75 and ordered an immediate descent to flight level 70, but the aircraft had already climbed significantly.
- There was a period of approximately 20 seconds where the Antonov An-12's altitude information disappeared from the radar screen during the altitude deviation.
Safety action
A safety recommendation was issued to Aviast Joint Stock Company Ltd to improve cockpit procedures and crew coordination to ensure all crew members have a consistent understanding of air traffic control clearances.