This Explains CO Reading….

[Bob Y]

As a control test, you might want to uncover the hole and see if the readings go up again. I’d want to cover it anyway, but your source may have been somewhere else.

 

[SkyDweller]

And the original purpose of that rather large hole was..............? Curious minds want to know........

I’m not sure since it was there when I bought it and I’m not the builder. It looks identical to the mounting point on the back of the rudder for the tail strobe, so maybe there was originally a strobe mounted underneath?

 

[SkyDweller]

As a control test, you might want to uncover the hole and see if the readings go up again. I’d want to cover it anyway, but your source may have been somewhere else.

Nothing else changed since my last modifications and subsequent test flights which had actually increased the readings suggesting the previous modifications limited air in, but not contaminated air. Definitely a good recommendation though, and will give it a test. Always good practice to verify! Thanks

 

[Roadjunkie1]

I’m not sure since it was there when I bought it and I’m not the builder. It looks identical to the mounting point on the back of the rudder for the tail strobe, so maybe there was originally a strobe mounted underneath?

Maybe one of those funky belly-mounted VOR antennae.....? Yeah: time to cover that sucker up! One thing for sure: no water is going to collect in your fuselage with THAT size hole!!