What happened
On 12 March 2019, a potential mid-air collision occurred during the landing sequence for Runway 34 at Wellington International Airport. Three aircraft were scheduled to land: an Airbus A320 followed by two Bombardier DHC-8-311 aircraft operated by Air Nelson.
Both Dash-8 aircraft had transitioned from instrument flight rules to a visual approach. While the first Dash-8, callsign LINK235, successfully positioned itself behind the Airbus, the second Dash-8, callsign LINK285, experienced a critical error. The flight crew of LINK285 mistakenly identified the Airbus A320 as the preceding Dash-8. This error led the crew to turn toward the runway prematurely, placing their flight path on a direct collision course with LINK235.
As the two aircraft converged, air traffic control radar triggered a short-term conflict alert. Although the approach controller attempted to intervene, the LINK285 crew was not monitoring the approach frequency at that moment. The situation was resolved only when the onboard Traffic Collision Avoidance Systems (TCAS) issued Resolution Advisories, instructing one crew to climb and the other to descend. Both crews performed evasive maneuvers, and the aircraft maintained a minimum horizontal separation of 0.8 nm and a vertical separation of 475 feet. All aircraft landed safely.
The investigation
The Transport Accident Investigation Commission (TAIC) examined the flight paths, air traffic control communications, and the technical performance of the aircraft systems. The investigation focused on why the flight crew of LINK285 misidentified the aircraft and why the air traffic controller was unable to establish contact with the crew during the critical phase of the conflict. The investigation also looked into the loss of cockpit voice recorder (CVR) data, as the recordings from both aircraft were overwritten before they could be secured.
Findings
- The crew of LINK2285 mistakenly identified the Airbus A320 as the preceding Dash-8, leading to an incorrect flight path.
- The flight crew lacked sufficient situational awareness regarding their position in the traffic pattern before assuming responsibility for visual separation.
- Poor lighting and visual conditions hindered the crew's ability to accurately identify the preceding aircraft.
- The crew failed to use available secondary means to verify their visual identification.
- Air traffic control procedures allowed for a gap in communication where a controller could be unable to contact a flight crew while still responsible for monitoring them.
- Critical evidence from the aircraft CVRs was lost because the operator did not immediately ground the aircraft or protect the data following the incident.
Safety action
Following the incident, the operator and Airways implemented several measures to address identified safety issues, including:
- Reviewing procedures for visual approaches and the information passed to crews during these transitions.
- Updating phraseology for 'essential traffic' and reviewing controller training for managing loss of separation.
- Revising the conditions for changing radio frequencies during the approach phase.
- Improving internal practices for securing flight data following serious incidents.