A preliminary report details factual information established as part of the ATSB’s ongoing investigation into a mid-air collision at Caboolture airfield on the morning of 28 July.
The report does not contain findings but outlines the accident’s sequence of events. It details that a Piper PA-25 glider tug aircraft, with a single pilot on board having just launched a glider, was returning to land from the west on Caboolture’s runway 06, while a Jabiru J430 light aircraft, with a pilot and passenger on board, was preparing to take-off to the south-east from the intersecting runway 11.
A third aircraft, a Cessna 172 was taxiing at the airfield, with a solo student pilot on board, prior to departing on a solo navigation flight.
Caboolture is an ‘aircraft landing area’, which is an airfield that has not been certified by the Civil Aviation Safety Authority. In addition, it is located within class G non-controlled airspace, where pilots make and monitor radio positional broadcasts on a designated common traffic advisory frequency (CTAF) to ensure separation from other aircraft.
Several witnesses monitoring the CTAF recounted hearing the Piper pilot broadcast that they were commencing a final approach to runway 06 and that they would be ‘holding short’, indicating they would not cross the intersection with runway 11/29.
The pilot of the Cessna, meanwhile, reported having turned down the aircraft radio volume to conduct engine run-ups near the intersection of the two runways and had not subsequently restored normal volume. As a result, the pilot did not hear any transmissions from the pilot of the Piper PA-25, and was not aware of the aircraft approaching on runway 06.
Just prior to the Piper touching down, the Cessna taxied across runway 06 ahead of the Piper. The pilot of the Piper initiated a go-around, broadcasting their intention to do so, according to witnesses.
As the Piper began climbing while maintaining the runway 06 heading, the Jabiru lifted off from the intersecting runway 11.
About 5-10 seconds later, while both aircraft were climbing on crossing tracks, the pilot of the Jabiru commenced a left turn, likely in an attempt to avoid a collision.
The two aircraft collided above runway 06, just north-east of the intersection with runway 11, at a height of about 200-300 feet. The Piper PA-25 remained flyable and landed soon afterwards, while the Jabiru J430 collided with the ground near the end of runway 06. Both occupants of the Jabiru aircraft were fatally injured.
“Thanks to CCTV footage, some recorded radio calls, witness accounts, and an examination of the accident site, ATSB investigators have been able to build an understanding of this tragic accident’s sequence of events,” said ATSB Chief Commissioner Angus Mitchell.
“However, I would caution against making any assumptions as to the contributing factors to this accident, and I would note that aviation systems have multiple layers of defence in place to prevent accidents,” he continued.
“Not all radio calls at Caboolture were recorded and our analysis of witnesses recollections of radio calls is continuing, so we are still building our understanding of the nature of the calls made, and giving consideration to a range of other potential factors.”
As the investigation continues, investigators will continue their analysis of aircraft flight paths, with particular attention given to potential visibility restrictions -trees between the intersecting runways partially obscure visibility.
They will also further review aircraft, pilot, aerodrome and operator documentation, analyse procedures at non-controlled aerodromes with intersecting runways, and further examine of aircraft components and other items recovered from the accident site, including two data recording devices from the Jabiru.
A final report, which will include analysis and detail the ATSB’s findings, will be released at the conclusion of the investigation.
“However, should a critical safety issue be identified during the course of the investigation, the ATSB will immediately notify relevant parties so appropriate and timely safety action can be taken,” Mr Mitchell concluded.
