Crew members onboard a shark spotting aircraft in South Australia were forced to urgently open windows and switch off heating after the condition of all three onboard began to rapidly deteriorate.
In a report just released by the Australian Transport Safety Bureau (ATSB), crew members experienced loss of feeling in their legs, chest pains and a tingling sensation in their hands, as well as confusion and light-headedness.
The crew of the Cessna 172 were conducting their second aerial shark patrol above Sellicks Beach in December, 2019 when the incident happened.
About two hours into the flight, the communications officer and the pilot became sick. They initially dismissed their symptoms, thinking they were due to turbulence. The pilot then noticed the aircraft's disposable carbon monoxide chemical spot detector had picked up traces.
The crew immediately opened the aircraft's windows, however the pilot's condition worsened and the crew reported periods of amnesia, loss of feeling in their legs, chest pains and a tingling sensation in their hands.
With support from air traffic control, the pilot was able to return the aircraft to and land safely at near-by Parafield Airport. The landing took place despite the crew experiencing increased light-headedness and ongoing confusion.
On landing, the crew were then taken to hospital, where blood tests confirmed they had mildly elevated carboxyhemoglobin levels.
The ATSB investigation found those onboard experienced symptoms associated with carbon monoxide exposure.
"The crew's physical symptoms and cognitive effects likely resulted from exposure to elevated CO levels in the aircraft cabin," the ATSB acting Director of Transport Safety Kerri Hughes, said.
The investigation was unable to find the source of the carbon monoxide saying there were "no indications of a potential exhaust leak prior to the flight and the post-flight testing found no fault with the aircraft".