• The ASA carbon dioxide detector turns grey/black in the centre when high CO2 levels are present in a cockpit. (ASA)
    The ASA carbon dioxide detector turns grey/black in the centre when high CO2 levels are present in a cockpit. (ASA)

The Australia Transport Safety Bureau (ATSB) has found that the crew of a shark-spotting Cessna that became partially incapacitated in 2019 were probably effected by carbon monoxide poisoning.

C172 VH-YXZ was on a mission south of Adelaide in December 2019 when the crew of three experienced "nausea, headaches, fatigue and light headedness." The pilot experienced memory loss, confusion, numbness/tingling, chest pains and mildly blurred vision.

The observer reported experiencing chest pains, fatigue and breathlessness, while the communications officer reported vomiting.

After noting the CO detector in the cockpit had changed, the crew opened the windows, but smoke from a nearby bushfire made the situation worse. ATC was notified and the pilot requested a clearance direct to Parafield, but was offered direct to Adelaide International, which they intially accepted. However, the pilot found he was becoming confused over the Adelaide runways due to light headedness, so reverted to Parafield because the runways were familiar.

The aircraft landed safely at Parafield and the crew were taken for medical checks, where slightly elevated levels of carboxyhaemoglobin were found. The aircraft had been fitted with a new engine only 10 days before the incident, but inspections found no faults or leaks in the exhaust system.

“Despite having only mildly elevated carboxyhaemoglobin levels, the crew’s physical symptoms and cognitive effects likely resulted from exposure to elevated CO levels in the aircraft cabin,” said ATSB acting Director Transport Safety Kerri Hughes.

“Owners and operators of piston-engine aircraft are strongly encouraged to install active warning CO detectors to alert pilots to the presence of CO before it adversely affects their ability to control the aircraft or become incapacitated.

“Further, once they experience any smell or sensation of illness pilots should check their CO detector, ensure cabin heat is off, open all fresh air vents and windows, and make a prompt decision to land using all available resources for assistance–such as contacting air traffic control–to do this safely.”

The ATSB was unable to determine the source of the CO and elected to complete a limited-scope investigation only.

The full report is on the ATSB website.

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