Belly Pods and CO levels

[Dan L]

I would have thought these tail openings would be insignificant compared to the huge holes provided for trim movement of horizontal stab.

Isn't the likely solution to get the exhaust gas flow away from the fuselage? It's a while since I towed with Pawnees but I think there was an exhaust pipe extension that was intended to reduce cockpit CO levels. How does the exhaust outlet position compare between different CC models?

Your snow pictures are making me wonder what I'm missing. Only 1 landing and 2 takeoffs on skis and no reason to buy them living in Arizona.

I think the exhaust flow is pretty much confined to the under side. I have a Vetterman exhaust system, not the original CC style that has the breather plumbed into it. So I get some oil residue from the breather and it is all on the bottom. And the pod is probably changing the flow also. I wondering if the back side of the pod creates a little low pressure area and the two inspection covers there are some of my trouble? I had those taped this morning and removed that tape after my first stop.

When I take the skis off for the season I may remove the pod for a while and see what that changes.

Skis are the most fun you can have in a Cub IMO.

[Dan L]

A little more experimenting this week. Today in cruise I was seeing 4-5 PPM with just the seam between the boot cowl and the triangle belly cover taped. Landing saw mid teens. After some snowshoeing I removed the tape. In cruise flight I was now seeing a steady 10 PPM. Landing configuration was in the 20s.

That joint was allowing about 5-10 PPM in the cabin. I suspect the teardrop elevator cover would have been too but it was already sealed on the inside from a few years ago. My guess is the face of the pod is creating some turbulence here.

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In contrast, yesterday I flew the Cessna an hour to another airport and I never saw anything but zero PPM until I was setup for landing. At that point it crept up to 4 PPM. The return flight was exactly the same.

[JohnnyR.]

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

[turbopilot]

A cool morning in Palm Springs (unusual). Taxied out with windows and overhead vents shut. Heat was off. Belly pod was on. Got a CAS alert on the G3X as CO monitor detected 15 ppm while taxiing and doing run up. Once I took off CO fell to 4 ppm. After opening overhead vent CO drifted down to 0 ppm in flight.

[Dan L]

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

No I don’t think it is a big issue. But the pod will change airflow patterns in this area a lot.

The high quality detectors available now have made me much more aware of the issue. If someone is still using the little cards with the dot that can change color with exposure; I think you’re fooling yourself into thinking everything is fine. Small changes in flight configuration, like flaps deployed, or a small opening near the tail spring can make a big difference in immediate amounts of carbon monoxide entering the cabin. Without a sophisticated detector that responds almost as quickly, you’d never know.

[Dan L]

Recently I’ve been seeing zero readings in cruise after 15 minutes or so. It seems to take a while to get “new” air into the cabin. It’s still been too cold to open the vents.

[Dan L]

In a previous post I said that I was going to remove the pod and see if that made a difference in readings. I returned from an antelope hunt in the Cub and took the pod off and flew the EX today sans pod. That made all the difference. Almost of of the flight and on the ground I saw a consistent zero reading. I was flying a cattle grazing lease for a rancher friend looking for some strays and that involved quite a bit of slow flight and maneuvering. At one point I saw a reading of 3 and later a 2 but they both went back to zero quickly. With the pod I would always see the readings climb up to 20 or so in a descent. And usually a lower number in a climb. Cruise would be in the single digits but almost always a presence.

So, now what? I’m thinking longer extensions may help. I’m going to give them a try.

As a side note I also noticed that the normally hot cylinder #4 ran about 30 degrees cooler. It would seem that the pod hindered the cooling downdraft air to some extent.

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The cows can be hard to find out here. Harder on the ground though and over the years we have a pretty good idea where we’ll find them. None today though.

[mikemacon]

In a previous post I said that I was going to remove the pod and see if that made a difference in readings. I returned from an antelope hunt in the Cub and took the pod off and flew the EX today sans pod. That made all the difference. Almost of of the flight and on the ground I saw a consistent zero reading. I was flying a cattle grazing lease for a rancher friend looking for some strays and that involved quite a bit of slow flight and maneuvering. At one point I saw a reading of 3 and later a 2 but they both went back to zero quickly. With the pod I would always see the readings climb up to 20 or so in a descent. And usually a lower number in a climb. Cruise would be in the single digits but almost always a presence.

So, now what? I’m thinking longer extensions may help. I’m going to give them a try.

As a side note I also noticed that the normally hot cylinder #4 ran about 30 degrees cooler. It would seem that the pod hindered the cooling downdraft air to some extent.
6
7E2FEF97-C8B1-4706-AB92-BA5E83C4D87C.jpg

The cows can be hard to find out here. Harder on the ground though and over the years we have a pretty good idea where we’ll find them. None today though.

Interesting. Thanks for continuing to update. I knew the pod was causing my CO issue and was living with it but I never would have thought the pod would be causing my high cylinder temp problem. In my case it was cylinder #3 that jumped 30 degrees. I had replaced all my cylinders for some burnt intake valve issues and assumed my jump in temp was something that occurred during that process. Time to remove the pod and see what happens.

[turbopilot]

Update on my experience with 2020 CC SS with LewAero belly tank. I have continuous CO monitoring through the G3X with annunciation. There is no difference in CO measurements tank on or off. Some CO up to 15ppm in ground operations depending on wind.

[hawgdrvr]

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.