Incident Overview
On 12 March 2019, three aircraft on scheduled passenger flights were sequenced to land on Runway 34 at Wellington International Airport. The first was an Airbus A320 (JST290), followed by two Bombardier DHC-8-311s (Dash-8s) operated by Air Nelson with callsigns LINK235 and LINK285. The two Dash-8s were joining from the northeast via a standard arrival route.
Sequence of Events
LINK235, the first Dash-8, requested and was approved for a visual approach behind the A320. The crew extended downwind and then turned base leg. LINK285, about two minutes behind, also requested a visual approach to follow the Dash-8 ahead. However, LINK285's crew mistakenly identified the A320 as the preceding Dash-8. They turned towards the runway to position behind the A320, placing themselves on a conflicting path with LINK235.
Air traffic controllers received a short-term conflict alert. The approach controller attempted to contact LINK285 but could not reach them. The tower controller then broadcast a message. Simultaneously, the flight crews of both Dash-8s visually acquired each other and took evasive action. Their Traffic Collision Avoidance Systems (TCAS) issued Resolution Advisory messages. All three aircraft landed safely without further incident.
Investigation Findings
The Transport Accident Investigation Commission determined that LINK285's crew misidentified the aircraft they were to follow. They had insufficient situational awareness of their position in the circuit pattern before accepting responsibility for visual separation. Lighting and visual conditions hindered identification, and the crew did not use other available means to validate their visual interpretation.
The Commission also noted that automatic and human defenses in air traffic control and aircraft systems detected the conflict and prevented escalation. Three safety issues were identified: critical information for visual approaches was not required to be passed to flight crews; ATC procedures could prevent controllers from contacting flight crews during monitoring; and post-incident, the operator's practices risked loss of cockpit voice recorder evidence. The Commission considered operator actions adequate and made no safety recommendations.