What happened
On 10 May 2010, a near-collision occurred over New Plymouth Aerodrome involving two aircraft engaged in dual pilot training. The incident involved a light helicopter and a light aeroplane operating under Visual Flight Rules (VFR).
The aeroplane was executing a standard overhead joining procedure for a left-hand circuit for runway 14. During its descent, the aircraft passed through the downwind leg of a right-hand circuit being flown by the helicopter, which was operating at an altitude above the standard circuit level. While both pilots were following their respective Air Traffic Control (ATC) clearances, the intersecting flight paths brought the two training aircraft into close proximity.
The investigation
The investigation examined the actions of the air traffic controller, the adherence to flight procedures, and the regulatory framework governing the airspace. Investigators found that while the controller's instructions were legally valid for Class D airspace, the controller failed to manage the heightened risk of a collision caused by the aeroplane descending into an opposing circuit.
Crucially, although the controller identified a potential conflict, traffic information was only communicated to the pilots of the aeroplane, leaving the helicopter crew unaware of the approaching aircraft. The investigation also scrutinized the clarity of the Civil Aviation Rules and the Aeronative Information Publication (AIP), noting that the procedures for overhead joining could be subject to misinterpretation during non-standard traffic situations.
Findings
- The air traffic controller failed to provide mutual traffic information to both parties involved in the potential conflict.
- The risk was exacerbated by the fact that the aeroplane pilots did not stop their descent once they lost visual contact with the helicopter.
- The incident could have been mitigated if the aeroplane pilots had immediately broadcast their loss of visual contact to other aircraft.
- There is a lack of a unified approach among regulators, aerodrome operators, and airway providers to mitigate the risks of simultaneous opposed circuits.
- Ambiguities in Civil Aviation Rule 91.223 and published joining procedures can lead to the misapplication of traffic patterns in non-standard scenarios.
- Some VFR pilots incorrectly operate under the assumption that ATC provides traffic separation in Class C and D airspace.
Safety action
The Commission identified several safety issues requiring intervention by the Director of Civil Aviation. Key recommendations focus on the need for a consistent industry-wide strategy to reduce collision risks from opposing circuits. There is a specific need to address the ambiguity in published joining procedures and to ensure that pilots are explicitly required to notify ATC when they lose sight of traffic. Additionally, the investigation highlighted the importance of strengthening aerodrome user groups to better manage operational risks.