Beware Carbon Monoxide

Most would remember the tragic crash of a de Havilland DHC-2 Beaver seaplane on the Hawksbury River in Sydney on New Year’s Eve 2017. A recent update from the ATSB (who are finalising the report) has linked Carbon Monoxide (CO) poisoning to the crash as it appears there were possible leaks in the exhaust system and also in the firewall that could allow exhaust gases to pass into the cabin. They also noted elevated CO levels in the toxicology of the pilot and two passengers.

From this, the ATSB considers the levels of CO detected were likely to have adversely affected the pilot’s ability to control the aircraft during the flight.

ATSB Investigation AO-2017-118; Update 3 July 2020.

As you may recall from your training, CO is colourless, odourless and thus impossible for a human to detect. CO poisoning is also highly incidious, as it generally leads to a sense of euphoria. Even though you are slowly dying, you ironically don’t have a care in the world. But luckily, just as we have triggers for other forms of hypoxia, we also have a way to detect CO in the cockpit. CO detectors are key to having a trigger that CO is present in the cockpit, if we see these detectors (either the ‘dot’ version or electronic) trigger then it’s important that we take IMMEDIATE and decisive action. Shut down any heater (as in single engine aircraft these derive their heat from around the exhaust system) and select all fresh air vents to fully open to maximise the airflow in the cockpit. Also, divert to the nearest available airport, you don’t want to be a test pilot in this case! Once you are safely on the ground, you can then diagnose the problem.

It’s important to note that the ‘spot’ type detector has a limited lifespan and can be affected by UV exposure (see article below), so must be included in your pre and post-flight checks as well as routine scans during flight.

As part of the 3rd July 2020 update the ATSB released two Safety Advisory Notices. One for engineers about checks of the exhaust system and firewall, the other for pilots about detecting Carbon Monoxide in the cockpit and cabin of light piston powered aircraft. The SAN for pilots and the media release on the update are linked below. Please take the time to read these as a reminder of the dangers of CO.

The following content originally appeared in the Peninsula Aero Club’s “The Tyabb Flyer” on 20th June 2020 and is republished with permission.

Now it has become cold, the cabin heater is used on most flights. This means we should all be aware of the dangers of Carbon Monoxide. Peninsula Aero Club member Lyndon David has provided his recent experience with CO detectors and what he learned about exhaust systems.

“2 weeks ago… The CO (Carbon Monoxide) stickers’ “chemical circle” turned black in my Piper Cherokee… this was installed by Westernport Aviation (WPA) as part of my annual in April 2020. This was a show stopper for me,  I was anxious and a little worried. So begun the investigation phase of how CO in such large quantities could get into the cabin to cause the “Black Spot”.

The CO sticker’s normal indications are by way of black speckle dots, a bit like freckles, not a complete blanket coverage (see detector on right in photo).

These stickers are highly susceptible to UV light- i.e. Direct Sunlight.

WPA dismantled the exhaust system and sent it away to the only CASA approved welder in Moorabbin, to seal any gaps or possible cracks, none were found. The firewall was inspected and deemed to be unequivocally sealed. It seems the CO sticker was FAULTY… As it didn’t return to its fresh air status.

“Schrödinger’s Cat” experiment comes to mind… How would one know if the sticker was faulty or CO actually did engulf the cabin. As we use cabin heat more, the lesson for me was… Get a second sticker! And I did invest in a digital CO detector too.”

Here are the facts for Carbon Monoxide Levels and Their Symptoms:

50PPMNone for healthy adults. According to the Occupational Safety & Health Administration, this is the maximum allowable concentration for continuous exposure for healthy adults in any 8 hour period.
200PPMSlight headache, fatigue, dizziness, and nausea after two to three hours.
400PPMFrontal headaches with one to two hours. Life threatening after three hours.
800PPMDizziness, nausea, and convulsions within 45 minutes. Unconsciousness within two hours. Death within two to three hours.
1600PPM Headache, dizziness and nausea within 20 minutes. Death within one hour.

Thanks again to Peninsula Aero Club for allowing us to share this important information with PCFC members.


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