Carbon monoxide (CO) is a colourless, odourless and poisonous gas produced from partially combusted fuel within piston engines, then expelled through the exhaust valves.
Most piston powered aircraft get their cabin heating by directing fresh (ram) air over the engine muffler (silencer). Engine exhaust may also enter the cabin through inadequately sealed firewalls and wheel wells.
If a piston engine has maintenance deficiencies, such as a crack in the engine exhaust system, it can provide a route for CO to leak out of the engine into the cabin.
If you ingest CO at high levels it can cause:
- headaches, dizziness, nausea
- muscular weakness, incoordination, and impaired judgement
- increased pulse, rapid breathing, chest pain
- unconsciousness, convulsions, and death if not removed from exposure source.
Chronic exposure to CO can occur at comparatively low concentrations and cause:
- prolonged headaches and migraines
- insomnia
- personality disturbances.
People exposed to high levels of carbon monoxide can suffer from carbon monoxide poisoning.
Effects of carbon monoxide poisoning on pilots
Exposure to toxic carbon monoxide gas is a hazard, especially for pilots flying piston engine aircraft.
In Australia, there have been instances where a pilot's exposure to CO has resulted in an accident. If a pilot doesn't detect a CO leak early, they may become incapacitated and unable to fly the aircraft.
How to identify the presence of carbon monoxide in an aircraft
We strongly encourage pilots of piston engine aircraft to carry a portable electronic carbon monoxide detector as a fail-safe way to identify CO leaks.
Portable electronic carbon monoxide detectors are small, inexpensive, and reliable. They can measure the levels of CO present in the atmosphere and will sound an audio alarm if the device detects CO. This can alert the pilot so they can take necessary measures to land the aircraft.
There are several alternate carbon monoxide active detector devices available on the market, such as colour-metric variations. Although, the ATSB have found these have limitations in their accuracy and function, including:
- being damaged by heat and sunlight
- not having an audible alert function
- doesn't show the level of CO present
- requires replacement every 3 to 12 months
- can't revert to their original colour when exposed to fresh air.
It is important to remember you should not use carbon monoxide detectors as the primary method of detecting CO in an aircraft. It is important LAMEs conduct maintenance checks thoroughly and accurately to identify any engine deficiencies early to prevent the chance of a leak later.
For further information see: