Warning on carbon monoxide poisoning


CASA has issued an Airworthiness Bulletin on preventing carbon monoxide poisoning in piston-engine aircraft.

This follows indications that the pilot of a float plane that crashed near Sydney in late 2017 may have been affected by carbon monoxide poisoning.

The CASA alert says crew and passengers in piston-engine aircraft have the potential for carbon monoxide (CO) poisoning from cracked exhaust units and unserviceable heat exchange assemblies.

‘This situation can be further exacerbated by unsealed penetration through [the] firewall and can go unnoticed through the fitment of inadequate or inappropriate CO detection units,’ it says.

The bulletin follows an update issued today by the Australian Transport Safety Bureau (ATSB) on its ongoing investigation into the collision with water of a DHC-2 Beaver float plane at Jerusalem Bay, on the Hawkesbury River north of Sydney, on 31 December 2017, in which the pilot and five passengers died.

‘The Australian Transport Safety Bureau is advising owners, operators, pilots and maintainers of piston-engine aircraft to take measures to detect the presence of, and prevent the entry of, carbon monoxide in aircraft cabins,’ the report says.

‘During the draft review process for the investigation’s final report, the aviation medical specialist engaged by the ATSB recommended that carbon monoxide toxicology testing be undertaken on blood samples of the aircraft occupants,’ ATSB Chief Commissioner Greg Hood said.

The results of that testing, provided to the ATSB in March 2020, indicated the pilot and two of the passengers, whose post-mortem examinations established received fatal injuries sustained as a result of the impact sequence, had elevated levels of carbon monoxide.

The ATSB then re-examined the accident aircraft and undertook testing on an exemplar Beaver aircraft to replicate the potential source of carbon monoxide and ingress into the aircraft cabin.

‘Having discounted other potential sources of carbon monoxide exposure, the ATSB considers it likely that the pilot and passengers were exposed to carbon monoxide inside the aircraft cabin,’ Mr Hood said.

‘The ATSB found pre‑existing cracking of the engine exhaust collector ring, which could lead to exhaust leakage into the engine bay. Further, the ATSB found a breach in the firewall from missing bolts used to secure magneto access panels in the firewall under the instrument panel in the cabin. Any breach in the firewall can allow the ingress of gases from the engine bay into the cabin.’





  1. Battery pocket sized carbon monoxide detectors with audible alarms are ready available online for under $40-
    I have one in my aircraft as backup. You don’t always check the small colour changing tablet detectors.

  2. I installed a hard-wired detector in the panel of my aircraft and it alarmed on the first takeoff after installation. My first reaction was to doubt the accuracy of the new detector as there was no detectable exhaust odour present. Subsequent investigation with a digital gas detector showed that CO was entering the cabin via a badly fitting door seal when the aircraft was at a high angle of attack.

    I strongly recommend against relying on the disposable stick-on cards.

  3. A recent Flight Australia story (about a stick-on CO detector card that gave a false positive) recommended installing two cards as a double-check. However, as noted in the article, these cards do have a shelf life, and can be affected by sunlight and cleaning chemicals.

  4. I carry a battery-powered CO detector on my Cirrus, and check it as part of my preflight checklist. But I still worry – loud though it is – whether I would hear it in-flight through noise-cancelling headphones…….

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