A midair collision overhead Caboolture airfield highlights the risks of aircraft using multiple runways at non-towered aerodromes, an ATSB investigation report details.
On the morning of 28 July 2023 a Piper Pawnee being used by the local glider club as a tug aircraft was returning to land from the south-west on Caboolture's runway 06, while a Jabiru J430 with a pilot and passenger on board was preparing to depart to the east from the intersecting runway 11.
"Caboolture has two intersecting runways and is a non-controlled aerodrome where pilots rely on making radio calls and visual scans to maintain separation from other aircraft - a principle known as 'alerted see-and-avoid'," explained ATSB Chief Commissioner Angus Mitchell.
Just prior to the Pawnee touching down, a Cessna 172 being taxied by a solo student pilot, who was unaware of an aircraft on approach, crossed runway 06.
In response, the Pawnee pilot initiated a go-around, a routine procedure when an aircraft encounters an issue on approach and landing.
"The Pawnee pilot applied power and initiated a climb, maintaining the runway heading as they made a go-around radio call," Mr Mitchell said.
"At the same time, the Jabiru lifted off from runway 11."
The two aircraft converged, and shortly before impact the Jabiru commenced a left turn, likely in an attempt to avoid the Pawnee.
However, they collided above runway 06, just beyond the runway intersection, at a height of about 130 feet.
The collision separated the Jabiru's right wing-tip and aileron, and it pitched downward and rolled to the right before impacting the ground, fatally injuring both on board and destroying the aircraft.
The Pawnee remained flyable despite damage to its left wing and landed safely with no injuries to the pilot.
"While in the circuit, the Pawnee pilot had made positional radio calls, and a call stating their intention to land and hold short of the runway intersection, but did not hear an entering runway or rolling call from the Jabiru," Mr Mitchell said.
"Based on the Jabiru pilot's apparent unawareness of the Pawnee until just before the collision, and most witnesses not recalling hearing any calls from the Jabiru throughout the event, it is likely that the Jabiru pilot could not transmit or hear radio calls.
"Because of this, and a stand of trees between the intersecting runways that blocked visibility between them, neither pilot was aware of the other aircraft."
While both the Jabiru and Pawnee pilots were familiar with the aerodrome and its line-of-sight limitations, the ATSB found that the aerodrome operator did not effectively manage or inform pilots of the risk of trees and buildings preventing pilots from seeing other aircraft on intersecting runways and approach paths.
"The local gliding club regularly chose to operate on runway 06 when winds and traffic were light, including during periods when other traffic was generally using the intersecting runway."
Since the accident, the aerodrome operator has prohibited simultaneous runway operations, and has mandated take-off radio calls.
"The investigation also found that the regulatory guidance pilots relied on when using non‑controlled aerodromes like Caboolture was not clear in defining what was considered an 'active runway', leaving room for different interpretations," Mr Mitchell noted.
Further, this guidance did not provide practical advice to pilots using a secondary runway, and in some situations, it was contrary to existing regulations.
Following the ATSB investigation, CASA is removing all references to the term 'active runway' to better align guidance with the regulations and avoid confusion, and will also expand the guidance to assist industry understanding of this issue.
"This tragic accident highlights that relying on alerted see-and-avoid principles for separation at non controlled aerodromes is not infallible," Mr Mitchell concluded.
"Pilots can help mitigate this by establishing two-way communication with other traffic, being mindful of the potential for radio communications to be missed or misinterpreted, and never to assume a runway is safe to use simply because no other aircraft are visible."
You can find here the final report: Midair collision involving Jabiru J430, VH-EDJ, and Piper PA-25-235, VH-SPA, Caboolture Airfield, Queensland, on 28 July 2023
