Aviation safety investigations & reports

Partial crew incapacitation involving Cessna 172, VH-YXZ 44 km south of Adelaide Airport, South Australia, 22 December 2019

Investigation number:
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase


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Safety summary

What happened

On 22 December 2019, the crew of a Cessna 172R aircraft, registered VH-YXZ and operated by Hartwig Air, was conducting aerial shark patrols. The aircraft departed Parafield, South Australia for the second flight of the day and flew along the coast to Goolwa Murray Mouth, returning along the same route.

About 2 hours into the flight, the crew started to experience symptoms typically associated with carbon monoxide (CO) poisoning, and subsequently observed a localised discolouration on the disposable CO chemical spot detector. The pilot notified air traffic control, who offered the pilot to land at Adelaide Airport. The pilot initially agreed, but as their symptoms resulted in confusion about the runways at Adelaide Airport, they subsequently decided to fly to Parafield, due to their familiarity with that airport.

The aircraft was landed safely and the three crew were taken to hospital for assessment. Blood tests confirmed all crew had mildly elevated carboxyhaemoglobin levels.

What the ATSB found

The ATSB found that, 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. The CO source within the aircraft could not be established. Further, the discrepancy between the low carboxyhaemoglobin levels and severity of experienced effects could not be resolved.

Safety message

Carbon monoxide is a colourless and odourless gas, and its presence may not be detected until the physical symptoms and cognitive effects are more developed. Therefore, operators and owners of piston‑engine aircraft are strongly encouraged to install a CO detector with an active warning to alert pilots to the presence of elevated levels of CO in the cabin. Should any smell or sensation of illness develop, pilots should check their CO detector, ensure cabin heat has been turned off, open all fresh air vents and windows, make prompt decisions to land as soon as possible, and use all available resources for assistance. Further information on CO poisoning and detectors can be found at the following:

Are you protected from carbon monoxide poisoning?

Carbon Monoxide: A Deadly Menace

Download Final report
[Download  PDF: 246KB]
Alternate: [Download  DOCX: 2MB]

The investigation

General details
Date: 22 December 2019   Investigation status: Completed  
Time: 15:45 CSuT   Investigation level: Short - click for an explanation of investigation levels  
Location   (show map): 44 km south Adelaide Airport (Sellicks Beach)   Investigation phase: Final report: Dissemination  
State: South Australia   Occurrence type: Flight crew incapacitation  
Release date: 25 March 2021   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Cessna Aircraft Company  
Aircraft model 172R  
Aircraft registration VH-YXZ  
Serial number 17280885  
Operator Bruce Hartwig Flying School  
Type of operation Aerial Work  
Sector Piston  
Damage to aircraft Nil  
Departure point Parafield, South Australia  
Destination Parafield, South Australia  
Last update 06 April 2021