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Carbon monoxide

I have been noticing an exhaust smell in the cockpit of my -7A. I borrowed an electronic CO detector with a digital readout and put it various places around the cockpit. The CO levels were well below the 35-50 ppm range considered the maximum acceptable by various agencies, e.g. 10-20 ppm on the right seat, 12 ppm on the floor, and 18-27 in the baggage area. With the cabin heat on and the detector near the cockpit floor, the reading decreased, so that is not the issue. Since the levels were highest in the baggage area, I suspect the CO is getting in through the flap actuator penetration. Levels rise a bit at slower airspeed/RPM, but not a lot.

The -7A (at least mine) has a negative pressure inside the cockpit relative to the outside, which was evident during Phase 1 when we had a sizable oil leak that got sucked from the belly of the plane into the fuselage (plane is unpainted). So I think that's why the CO is getting in.

Ideas/suggestions on fixing this? The plane's been flying over two years, and i think the reason it's just become noticeable (other than my sensitive smeller) is that I reduced some outside air leaks that were probably diluting the CO that was always there.

And yes, I do have my own electronic CO detector in the cockpit but it doesn't have a digital readout.
 
How long are your exhaust pipes? If they are too short the exhaust can make its way into the airplane that way. If I remember correctly someone told me that it can get in near the tail of the airplane.
 
I did this exercise a few weeks ago in my Cherokee 180. Nothing at all with the heater and defroster on. If I opened the front vents, which intake at the front edge of the wing root, I got a temporary spike of 30-35 while I was in a climb attitude. Not much in level cruise. Also seemed to have more on the ground than I did in the air. Did you check different flight attitudes?

Google came back with this.

The OSHA PEL for CO is 50 parts per million (ppm). OSHA standards prohibit worker exposure to more than 50 parts of CO gas per million parts of air averaged during an 8-hour time period. The 8-hour PEL for CO in maritime operations is also 50 ppm.
 
Google came back with this.

The OSHA PEL for CO is 50 parts per million (ppm). OSHA standards prohibit worker exposure to more than 50 parts of CO gas per million parts of air averaged during an 8-hour time period. The 8-hour PEL for CO in maritime operations is also 50 ppm.

Keep in mind that those numbers probably do not take altitude into consideration. CO + altitude is a formula for hypoxia.
 
The highest I ever see in the air is 6-8PPM, and with proper leaning it is much lower. Any is too much, but that is the best I can get it.
 
How long are your exhaust pipes? If they are too short the exhaust can make its way into the airplane that way. If I remember correctly someone told me that it can get in near the tail of the airplane.
Readings are significantly higher in the baggage area, so I suspect it's getting in mainly through the flap actuator penetrations.
 
How long are your exhaust pipes? If they are too short the exhaust can make its way into the airplane that way. If I remember correctly someone told me that it can get in near the tail of the airplane.
I talked to builder support, and he said this is not unusual, that every plane is different. He also said that because of bulge of the slider canopy, air pressure inside the cabin is less than outside, and air/gas won't come in if it doesn't have a way to get out. He floated pieces of down in the cabin of a -10 to see which way the airflow was going. So the fix is apparently to plug wherever air is leaving the cabin. It'll be a project.
 
I have been noticing an exhaust smell in the cockpit of my -7A. I borrowed an electronic CO detector with a digital readout and put it various places around the cockpit. The CO levels were well below the 35-50 ppm range considered the maximum acceptable by various agencies, e.g. 10-20 ppm on the right seat, 12 ppm on the floor, and 18-27 in the baggage area. With the cabin heat on and the detector near the cockpit floor, the reading decreased, so that is not the issue. Since the levels were highest in the baggage area, I suspect the CO is getting in through the flap actuator penetration. Levels rise a bit at slower airspeed/RPM, but not a lot.

The -7A (at least mine) has a negative pressure inside the cockpit relative to the outside, which was evident during Phase 1 when we had a sizable oil leak that got sucked from the belly of the plane into the fuselage (plane is unpainted). So I think that's why the CO is getting in.

Ideas/suggestions on fixing this? The plane's been flying over two years, and i think the reason it's just become noticeable (other than my sensitive smeller) is that I reduced some outside air leaks that were probably diluting the CO that was always there.

And yes, I do have my own electronic CO detector in the cockpit but it doesn't have a digital readout.

Those numbers are way high. I installed the Aithre shield and connected it to my Skyview. I normally see 0 ppm in flight, maybe, on a bad day in SoCal, 4-6 ppm (which matches perfectly with the data from the air quality folks), and into the low teens in a line of planes waiting to taxi. I've only ever seen values > 30 (using a portable CO detector) in the giant line of planes taxiing out at Oshkosh.

What kind of detector do you have? Are you sure it's accurate?
 
Zero is good

Those numbers are way high. I installed the Aithre shield and connected it to my Skyview. I normally see 0 ppm in flight, maybe, on a bad day in SoCal, 4-6 ppm (which matches perfectly with the data from the air quality folks), and into the low teens in a line of planes waiting to taxi. I've only ever seen values > 30 (using a portable CO detector) in the giant line of planes taxiing out at Oshkosh.

What kind of detector do you have? Are you sure it's accurate?
Zero is good. I've got a battery powered CO detector that has only picked up low single digits when doing a ground run with the wind at my back, and only for a few seconds. In flight, always zero. I think any CO will negatively affect your performance, and if you can find a way to get rid of it, that would be a good investment of your time.
 
You can try rubber boot coverings over your flap actuator arms. My buddy’s RV6 had the same issue. That’s where the exhaust was coming in at. Probably why your baggage area has higher numbers. He also made the exhaust pipes longer. The combination of the two really helped. We also spot lighted the firewall to fill up any holes from the engine compartment with sealant. Remember even low numbers of carbon monoxide at altitude can make a big difference with how your body handles it. It’s a lot different than being down on the ground. Good luck.
 
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