What is a normal CO reading?

[JJ Campbell]

I have a very nice TOCIN CO monitor Velcroed to my console. Unfortunately, to keep it at zero, I have to keep the vents open which is getting increasingly more uncomfortable as the weather gets colder.

It takes constant management. I let the CO level creep up to 10, open the vents some more (they are never fully closed) until the meter drops to zero. Rinse and repeat.

Do I have a leak that needs to be found and fixed or is this normal? BTW, it seems to make no difference whether or not the heat is on.

Before you ask: 2012 Tecnam P92 Eaglet with a Rotax 912 ULS.

[Type47]

I have been dealing with this in my P92 for 4 tears. The co goes up whenever the vents are closed. Seems the tecnam draws a vacuum through the tailcone and sucks exhaust in through any gap. I installed better weatherstripping on the doors, put gap tape on the wing roots, taped over the gear bolt holes. All made a small difference.
At the last annual, i noticed black sooty buildup inside the left side main gear cover with traces of smoke buildup inside the gear strut box.filled the gap with light foam rubber packing inside black plastic bag stuffed gently around the gear. Then I reinstalled the cover.
The difference was profound. Co runs 3-4 now at worst. I’m going to do the same on the other side. Maybe that will get me to zero.

[JJ Campbell]

I have been dealing with this in my P92 for 4 tears. The co goes up whenever the vents are closed. Seems the tecnam draws a vacuum through the tailcone and sucks exhaust in through any gap. I installed better weatherstripping on the doors, put gap tape on the wing roots, taped over the gear bolt holes. All made a small difference.
At the last annual, i noticed black sooty buildup inside the left side main gear cover with traces of smoke buildup inside the gear strut box.filled the gap with light foam rubber packing inside black plastic bag stuffed gently around the gear. Then I reinstalled the cover.
The difference was profound. Co runs 3-4 now at worst. I’m going to do the same on the other side. Maybe that will get me to zero.

Thanks! I'll look at the plane the next time I'm at the airport. You're talking about where the leaf-spring strut attaches to the airframe?

[Type47]

Yes, where both the wing strut and the gear attach rear of the door bottom.

[Warmi]

Sometimes I will get up to 10 in my Sting when on the ground .. depends on wind and outside conditions... never in flight though- always at 0.

[JJ Campbell]

Yes, where both the wing strut and the gear attach rear of the door bottom.

So you unscrewed the teardrop shaped thing the strut goes through and then the plate that is under that that the leaf-spring goes through? Then stuffed it all with stuff? (Just looking at a photo now.)

[Type47]

Just took the plastic fairing off, nothing else. Lightly packed around, and replaced it.
With a flashlight, it’s obvious how the air can get in.

[Type47]

My first idea was to use great stuff expanding foam, but i think that’s probably a bad idea because it traps moisture and may react with the aluminum not to mention the mess to remove the gear leg in the future.
In cars, it’s common for the manufacturer to insert little spongy things in black plastic inside panels to seal and reduce noise.
You wouldn’t want something that would absorb moisture and corrode, hence the plastic wrap.
There is some talk over on Tecnam Talk boards about extending the tailpipe a few inches to get less exhaust staining on the bottom of the aircraft.
I like the idea of that for getting the exhaust farther away, but i hesitate to add to what I think is an already weak (fragile) muffler support system and amplifying the vibrational forces.

[JJ Campbell]

My first idea was to use great stuff expanding foam, but i think that’s probably a bad idea because it traps moisture and may react with the aluminum not to mention the mess to remove the gear leg in the future.
In cars, it’s common for the manufacturer to insert little spongy things in black plastic inside panels to seal and reduce noise.
You wouldn’t want something that would absorb moisture and corrode, hence the plastic wrap.
There is some talk over on Tecnam Talk boards about extending the tailpipe a few inches to get less exhaust staining on the bottom of the aircraft.
I like the idea of that for getting the exhaust farther away, but i hesitate to add to what I think is an already weak (fragile) muffler support system and amplifying the vibrational forces.

Great suggestions. I'll give it a whirl.

I was flying today and could not get the CO meter below 4 no matter how much or long the vents were open. Then I noticed the bottom of the passenger door had a half inch gap. I had to bank to the right before I could get the door closed all the way and locked properly. After that, I could get the meter to zero.