Final Report

Summary

What happened

At 1503 Eastern Standard Time on 27 May 2014, mutual traffic information was not passed to the flight crews of a Department of Defence (Defence) Boeing CH‑47 Chinook helicopter (CH‑47), and a Cessna 172S, registered VH‑PFU (PFU), operating in the circuit area at Townsville Airport, Queensland. At the time, the Defence air traffic controller with jurisdiction over the circuit area (the tower controller), had six other aircraft on frequency. All of the aircraft were operating under visual flight rules in visual meteorological conditions.

The complexity of aircraft operations, and a high level of radio frequency use, resulted in high workload for the tower controller and the tower supervisor.

The flight crew of the CH‑47 had been issued with a clearance limit of a point on the coast north‑east of the airport. At the same time, the flight crew of PFU were tracking on the centreline of runway 07 as instructed by the tower controller. As the flight crew of the CH‑47 turned left to commence an orbit at the clearance limit, they sighted PFU in close proximity. The flight crew reversed the turn, tracking away from PFU.

Seeing that the CH‑47 had commenced a turn away from the track of PFU, the tower controller did not provide traffic on PFU, but instead provided traffic on another aircraft that the CH‑47 was to track behind. Additionally, traffic on the CH‑47 was not passed to the flight crew of PFU. When the flight crew of the CH‑47 first reported sighting PFU, surveillance data indicated that the aircraft were at the same altitude and separated by about 0.5 NM (1 km).

What the ATSB found

The ATSB found that mutual traffic information was not passed to the flight crews of the CH‑47 and PFU prior to them coming into proximity. Then, when the flight crew of the CH‑47 reported PFU in sight, the tower controller did not pass traffic on that aircraft as they believed that the proximity risk had been resolved by the CH‑47 turning away. At the time of the occurrence, compromised separation recovery training deficiencies existed within Defence.

What's been done as a result

Actions by Defence in relation to compromised separation recovery training have adequately addressed the identified training deficiencies. In addition, Defence has reinforced to controllers, via briefings, the importance of workload and traffic management.

Safety message

The impact of workload can be insidious, the affected person(s) not realising an increase until it has reached a high level. The ATSB suggests that consciously self-monitoring and actively monitoring the workload of colleagues can assist a work group to better manage workload. Holding aircraft on the ground or outside the airspace are valuable tools for an air traffic controller. The ATSB also notes that flight crew operating under visual flight rules in Class C airspace should remain aware that the provision of an air traffic service does not negate their responsibility to see and avoid.

The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions