Two Dash-8s avoided collision on approach to Wellington Airport (saved by human and automated systems) after one Dash-8 followed the wrong lead aircraft.
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Nobody was hurt and there were no damage. All safety issues are resolved, so there are no new Transport Accident Investigation Commission (TAIC) recommendations.
Three aeroplanes on scheduled passenger flights were sequenced to land at Wellington Airport, approaching in this order:
• A320 (JST-290) approaching from the south-west
• Dash-8 (LINK-235) joining from the north-east
• Dash-8 (LINK-285) also joining from the north-east, 2 minutes behind LINK-235
Two Dash-8s chose visual approach:The crews of the two Dash-8s requested and received permission from the (Christchurch-located) approach controller to make a visual approach to land. The approach controller instructed LINK-235 to follow the A-320 and LINK-285 to follow LINK-235.
Dash-8s on conflicting course: LINK-285 had two planes ahead of it. It misidentified the A320 as the Dash-8, and turned to follow the A-320. This put LINK-285 into a conflicting flight path with LINK-235, too close to LINK-235. An automatic short-term conflict alert warning alerted air traffic controllers that the two Dash-8s might collide.
The Christchurch-based approach controller was unable to reach LINK-285 via radio because LINK-285 had already switched radio channel to Wellington Tower. However, Wellington Tower was under the impression that Approach Control was still responsible for LINK-285 so said nothing to LINK-285.
In quick succession: the approach controller telephoned the Wellington tower; Wellington air traffic control broadcasted a radio warning; the Dash-8s saw each other and took evasive action; and seconds later the onboard traffic-collision-avoidance systems of both Dash-8s called for evasive action.
All three aeroplanes landed without further incident.
LINK-285’s flight crew had not absorbed all available information to correctly identify which aeroplane was ahead of them. Light and other visual conditions made the task harder, and didn’t use other means to double-check their perceptions, the Commission found. ■