Background
On 28 August 2023 at about 0945 NZST, an Air New Zealand Q-300 (registration ZK-NES, call sign ANZ221L) was preparing to depart Whangārei for Auckland under Instrument Flight Rules (IFR). Simultaneously, a Beech 76 Duchess (registration ZK-JED) was tracking north at 7000 ft towards Whangārei from Ardmore, also under IFR. Both aircraft were following standard flight routes in reciprocal directions along route segment Q520.
Narrative
The air traffic controller managed the clearances so that the two aircraft would pass each other in uncontrolled airspace, a common practice at the unit. Once outside controlled airspace, the flight crews relied on traffic information from air traffic services and radio communication to maintain situational awareness. The Q-300 was equipped with an Airborne Collision Avoidance System (ACAS).
At 0942, the Q-300 contacted the Flight Information Officer (FIO) for clearance to climb into controlled airspace. The FIO provided pre-departure clearance for STAR APABO-3C at 12,000 ft but advised that the clearance was not yet validated. At 0953, the Beech contacted the controller near APABO. The controller confirmed the Beech's intentions to hold at SPRINGFIELD and then conduct an RNAV-C approach.
At 0955, the Q-300 advised taxiing and was told to stand by. The FIO then phoned the controller, who confirmed the clearance with a 6000 ft altitude restriction, meaning the Q-300 had to remain outside controlled airspace. At 0957, the controller advised the Beech of the Q-300's departure and climb to 6000 ft.
At 0959, the Q-300 took off from Whangārei. At 1001, the controller cleared the Beech to descend and updated traffic information regarding the Q-300. At 1002, the Q-300 contacted the controller, who withheld clearance to enter controlled airspace and advised them to remain at 6000 ft.
During the encounter, the aircraft passed in close proximity while in cloud. The Q-300's ACAS detected a traffic alert condition. The air traffic control system also raised a Short-Term Conflict Alert. No damage or injuries occurred.
Findings
The Transport Accident Investigation Commission (TAIC) determined that the incident occurred because the two flight crews did not have sufficient, up-to-date traffic information about the immediacy of the potential conflict in time to coordinate their own avoidance actions. The Commission also found that it was common practice for the air traffic control unit to direct IFR traffic south of Whangārei to pass in uncontrolled airspace.
Additionally, the airspace around Whangārei had not been reviewed since 2014, despite a required review period of at least every five years. Multiple safety concerns about the airspace had been identified by pilots, air traffic controllers, and the aerodrome operator but remained unresolved. The Commission made two safety recommendations: one to the Civil Aviation Authority (CAA) to conduct a comprehensive airspace review for the Whangārei area, and one to the Ministry of Transport to address gaps in the Civil Aviation Rules relating to airspace reviews.