ATSB explores hypoxia theory in fatal bushfire plane crash

An ATSB report has shed new light on a plane crash that killed three people in northwest Queensland while mapping bushfires.

A lack of oxygen has emerged as the possible cause of a devastating plane crash that killed the pilot and two passengers during a bushfire mapping mission in northwest Queensland.

The Gulfstream 695A, operated by Victorian company Agair, was flying from Toowoomba to Mount Isa to photograph fire zones on November 4, 2023, when the aircraft went down near Cloncurry, about 120km from the destination.

The Australian Transport Safety Bureau’s preliminary report on the crash revealed both engines and both propellers of the Gulfstream were operating when the aircraft nosedived into the ground in flat, open bushland.

During the flight, it was noted the pilot’s speech changed, becoming slower and lower in exchanges with air traffic control.

Flight data indicated that about 20 minutes after the pilot’s last radio transmission, the Gulfstream’s groundspeed decreased, before it began to descend rapidly.

Two witnesses told the ATSB they heard a “whirring noise” and saw the aircraft coming down in a nose-first clockwise corkscrew motion.

“The witnesses recalled the aircraft’s motion momentarily abated parkway down, before it re-entered the nose-down corkscrew descent,” the report said.

The subsequent crash killed the three occupants, and the aircraft was destroyed by the impact and a fuel-fed fire.

The Gulfstream 695A that crashed in northwest Queensland, killing three people. Picture: Supplied

ATSB chief commissioner Angus Mitchell said earlier in the flight, the aircraft had descended from 28,000ft to about 15,000ft and stayed there for six minutes before returning to 28,000ft.

A short time later, air traffic control requested the pilot change radio frequency, which was acknowledged.

“But the controller was then unable to establish two-way communications with them for over an hour,” Mr Mitchell said.

Once communications were re-established, the pilot advised they were to undertake work in the area near Mt Gordon, the report said.

After being provided with clearance, the pilot sounded uncertain and repeated the clearance four times in four minutes.

“As the investigation proceeds, it will include further analysis of the pilot’s speech during radio communications, including an examination of hypoxia indicators,” Mr Mitchell said.

“During their on-site examinations, investigators were able to account for all major aircraft components, and determined that both engines and propellers had indications that the engines were running at impact. However, it was not possible to determine the operability of the aircraft’s pressurisation and oxygen systems.”

As well as a formal voice analysis, investigators would analyse weather information, maintenance records, operational procedures, flight data, and pilot and crew training and medical records, Mr Mitchell said.

The report revealed the pilot, who has not been named, only joined Agair in September 2023 and had about, 4800-hours total aeronautical experience.

A camera operator who held a commercial pilot licence was also on board, along with young US engineer Will Jennings, who had started with Agair the previous month.

The ATSB’s final report was expected by the end of the year.

Originally published as ATSB explores hypoxia theory in fatal bushfire plane crash