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CO during cruise in TB20 GT

I recently had an Aithre eDot installed in my TB20 GT. Its pretty neat and logs to my iPad.

Immediately started getting warnings during the cruise. It hovers around 14ppm.

The level starts dropping on approach and is back to blue by taxi time. I don’t see anything obvious around the exhaust clamps.

Some searching shows reports on climb out, but I get it on cruise and it stays elevated for the entire cruise. Any ideas where to start looking?

United States

It’s quite a low level for a machine that has an exhaust infront of the occupants, and a big fan to help the exhaust find a way into the cabin. (Gut instinct would say it would blow away, but it’s not always the case)
Can you run a little leaner?
It’s possible to be quite far back on the airframe that fumes get in. I’ve read stories of luggage bay doors and gaps in the lower tail section. Seems unlikely but that’s what people have reported.
At 14ppm I’d personally take a general look for an easy fix and if not, I’d not stress about it unless I regularly did 4 hr legs 3 times a week.

United Kingdom

Have you closed the rear vents that are fed from the tail ? Could be that the exhaust fumes are swirling up at certain rpm settings.

I do get non-zero readings during long climbs with full mix, occasionally. But zero in cruise (Draeger, fairly precise).

EDM_, Germany

I have never seen any CO in my TB20GT, other than when landing behind another aircraft. I have a BW Gasalert – wasn’t cheap.

I would check the integrity of the exhaust system and the air pipework in front of the firewall. This could be dangerous.

Shoreham EGKA, United Kingdom

The level you measure is not quite dangerous, but not completely innocuous either. It is considered “unhealthy” y official US EPA standards.

For reference, when flying “ratty” old PA28, C172 and C182 from the local aeroclub, I’m used to significant CO readings on the ground when behind another aircraft and on the runway when an airliner just landed or took off. But I get essentially zero (certainly less than 5 ppm) in cruise. I do tend to fly rather LOP.


I know its not dangerous at these levels but its high enough that an hour may be enough to lower O2 levels that have a small effect on mental performance.

I went out this morning and took a deeper look at it. I’m not sure how I missed it, but I do have leakage I didn’t see from above. I was focused on the clamps that are midway on the exhaust and not down lower here.

Will see what happens when I get these clamps replaced.

Last Edited by MG at 08 Nov 14:51
United States

See this.

Socata will screw you € hundreds for each of these crap-design clamps, which always leak so the band inside always gets eventually eroded. If the band is OK then use the sealing paste only. If the band is gone, then yes fix the clamps. Also check this.

Lots of people have been there before

Shoreham EGKA, United Kingdom
7 Posts
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