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Carbon Monoxide in Piston Helicopters


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During the Holidays, I went for a introductory flight in a R22. I have been a fixed-wing pilot for 16 years but helicopters are my real aviation passion. The outside air temperature was -10°C so performance was great and cabin heat was on. As I always do when I fly in a piston aircraft, I carried along a CO detector (sometimes 2).

 

I was surprised to see that during the 30 minutes of the flight, my CO detector recorded on average 28 ppm with a maximum reading of 40 ppm. This was continuous. This level is below the NIOSH Recommended Exposure Limit of 35 ppm ( Nonetheless, I think that the cabin should be free of CO. I routinely recorded levels around 5 to 10 ppm on the ground in a C172 but once airborne, the level would return to 0.

 

Comments, observations ? Thanks.

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During the Holidays, I went for a introductory flight in a R22. I have been a fixed-wing pilot for 16 years but helicopters are my real aviation passion. The outside air temperature was -10°C so performance was great and cabin heat was on. As I always do when I fly in a piston aircraft, I carried along a CO detector (sometimes 2).

 

I was surprised to see that during the 30 minutes of the flight, my CO detector recorded on average 28 ppm with a maximum reading of 40 ppm. This was continuous. This level is below the NIOSH Recommended Exposure Limit of 35 ppm ( Nonetheless, I think that the cabin should be free of CO. I routinely recorded levels around 5 to 10 ppm on the ground in a C172 but once airborne, the level would return to 0.

 

Comments, observations ? Thanks.

 

It’s not surprising given the turbulent flow all, piston and turbine, helicopters operate in while hovering and on the ground with the rotors turning, take a look at the figure below. The fact that the heater was on could also be an issue given any exhaust leaks or exhaust recirculation during prolonged hovering.

 

A few EMS operations have found carbon monoxide levels ranging from 8-76 ppm depending on location of sampling and speed of operation of the engine, especially during hover and on the ground with the rotors turning. Some say this level of carbon monoxide is potentially a problem.

 

However, most have concluded, even though a majority of flight crewmembers are regularly exposed to exhaust fumes during EMS operations, clinical symptoms were rare, and carbon monoxide measurements stayed below toxic levels.

 

They agree, more studies are warranted to specify operational and occupational hazards to both flight crews and transported patients. You can lookup the following research papers for more information:

 

Medical helicopters: carbon monoxide risk

 

Carbon Monoxide Exposure in Norwegian Rescue Helicopters

 

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Edited by iChris
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Interesting article Chris

I still wonder why Schweitzer used that exhaust heat exchanger on the CBi Etc, the early VW beetle heater was a warning, as an aside with all that weight hanging on an all most solid tail boom mount it makes the CBI harsh & if you take it off When balancing TR you will find the IPS much lower, the engine vibe through that mount :ph34r:

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