Belly Pods and CO levels

[Narwhal747]

I just brought home my FX-3 (27 hours) across the US to Virginia from Hood River with a CarbonConcepts pod on and the integrated CO monitor into the G3X. In flight CO shows around 3, on the ground up to 50 with windows open (verifies it's working). Startup will be go into the caution range then in flight it reduces to 3 once there is airflow.

Interesting. Did CubCrafters install this monitor for you at the factory as part of your build? I'm very interested in getting one too, if so! Glad to hear your CO isn't too high in-flight even with the pod on.

[hawgdrvr]

Interesting. Did CubCrafters install this monitor for you at the factory as part of your build? I'm very interested in getting one too, if so! Glad to hear your CO isn't too high in-flight even with the pod on.

They did install it for me and other items for a fee after AW cert. The guy that does all the avionics (Jamie?) is a super great guy. Impressed with all he did with my plane in the custom wiring requests.

[Narwhal747]

They did install it for me and other items for a fee after AW cert. The guy that does all the avionics (Jamie?) is a super great guy. Impressed with all he did with my plane in the custom wiring requests.

That's fantastic, really glad to hear it!

[Dan L]

I made a few more flights without the pod and my readings were mostly zeros. Occasionally I’d see a single digit for a few minutes but not often. This week I put the pod back on and flew today. My readings were back up into the high teens on takeoff and climb and also on landing. Cruise was mid single digits. There’s no doubt the pod is causing this. It also seemed like cylinder 4 was running hotter again.

I haven’t put longer extensions on yet but that’s next.

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Part of the reason I removed the pod was to paint it. Last winter, while on skis, I ran over a cone that marks our grass strip. It was half covered with snow and and it scuffed up the pod. Just cosmetic but I painted it with Aerothane flattened to match the Polytone on my fabric. 🙃

[Dan L]

Extensions. Clint at Vetterman exhaust systems made 10” extensions for me.

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These have all but completely eliminated the CO problem for my scenario. I flew 4.1 hours today and probably 4 of those hours the reading was zero. And for a few minutes, on takeoffs, I saw 2-5 PPM readings. Descents were zeros where in the past they were the biggest problem.

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This is the goal.

The downside is they’re long and ugly. I may shorten them until I see consistently higher readings and then ask Clint to make another set at the shortest acceptable length.

[KevinB]

Any update on what ended up being the perfect extension length?

[Dan L]

Any update on what ended up being the perfect extension length?

I left mine at the 10”. Everything is fine with CO at that length and decided not to fix what wasn’t broken.

[JohnnyR.]

More data points: our experimental Legend MOAC does the same thing with the XL pod from Alaska Airframes. Non-detectable in taxi, take-off, landing or cruise by our digital meter when pod is removed. When pod is on, 120-130 ppm in climb and 50-70 during landing.

Taping up leading edge of belly cleanout pan at tail plus taping around the twin belly fuel sumps aft of cargo pod resulted in a 50% reduction of detectable CO (from 130 to 66ppm) during takeoff and climb out and a 35% reduction (from 70 to 45ppm) during landing.Removing the pod while still taped up resulted in no alarms (below 35ppm on our digital unit) during 30 minute test flight consisting of 3 takeoffs and landings, performance climb from 400’ to 4,500’, max speed run, and cruise for 10 min at 60% power.

Finished by taping inspection panel on belly under front seat, sealing the metal boot cowl to fabric seam and sealing small 1/2" holes next to gear leg attach points. Results with pod on were no detectable CO gases during all phases of test flight.

Is this a known issue in PA-18’s, as well as other experimental Cub kits?
Not being able to safely utilize a pod would be frustrating for me, as most of our flights are full of gear into remote areas.
J