Belly Pods and CO levels

[Dan L]

We get about one day a week this time of year that is flyable. Yesterday was the day and I made another CO test.

When I built my EX I exit Ed the airframe using a bulkhead type fitting. There was a bit of a gap around these fittings and the aluminum V-shaped belly pan. I put some white duct tape around these.

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Originally I made some white kydex coins to go over the aileron penetration holes and glued them in place using Polyfiber glue. I noticed the coin on the left side had pulled lose on the front and was oily. That indicated to me that some exhaust flow was moving past the cable (which was also oily). My breather is on the left side. So I cleaned and re-glued the kydex piece.

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One or both of these fixes lowered the CO numbers but I still have CO present in single digits and in a descent with flaps it still rises into the 20 PPM range.

Better but not cured yet.

[Springloaded]

This afternoon became a very nice winter fly-day. Cold but clear so I made a new test with the Aithre to see if my hole plugging near the tail helped. The short answer is that it did.

Today my readings were in the single digits for climbing and cruise. Acceptable.

Descending they jumped into the 20s and with flaps pulled up to about 30.

Attachment 11333

I have a T3 tail spring system now and just forward of the attach point there is a small opening where there is no fabric. I cut and sliced a piece of foam pipe insulation and pushed into the hole. This sealed it off well. The foam is black but probably visible in this image.

Attachment 11334

When I built my EX I fabricated an aluminum tail clean-out pan. It is removable with three Southco fasteners. Where it joins the first cross tube I put in two seaplane style drains. The blue painters tape is covering these two drains and the joint. This seems to be the main problem area based on my first test with only the foam filling the hole - not much improvement with just that hole plugged.

My theory is that exhaust gas was following the belly and then low pressure inside the tail section was pulling some inside. Lower pressure in the cabin allowed it to migrate forward and become measurable.

The question now is where is it entering when descending and pulling flaps? Flaps are apparently changing the airflow enough that the under-belly flow is finding a different entrance. Once flaps are retracted it takes some time for the readings to go back to “normal”. Like 5 minutes or so.

Using cabin heat or not makes no difference. And today was surely one for heat. Up at 4500-6000’ it was -5 degrees.

Attachment 11335

The uavioncs AV20S calculates density altitude and today the DA was about -3000 feet from actual altitude.

Attachment 11336

I enjoy seeing the elk out on the open areas.

Dan
I have a smoke system on my plane. So I can see the smoke from exhaust coming in when I have my pod on. It just rolls in from under panel and it almost instant so I’m thinking it from up front. I tryed taping gear leg holes up it didn’t help on mine.

[turbopilot]

Dan
I have a smoke system on my plane. So I can see the smoke from exhaust coming in when I have my pod on. It just rolls in from under panel and it almost instant so I’m thinking it from up front. I tryed taping gear leg holes up it didn’t help on mine.

What type of pod?

[Springloaded]

What type of pod?

Carbon concepts

[turbopilot]

Carbon concepts

We need to get these reports organized by pod type. Had a good discussion with Lew at LewAero. He claims no CO reports associated with his pods have been received.

Now that I have the Aithre 2 hardwired to the G3X the engine log files now show CO readings every second. So it is easy to see when the CO level rise during a flight, even if they are not high enough to trigger a CAS alert. So far the highest readings I have seen are 4 ppm during ground operations. CO is rarely above zero in flight.

[mikemacon]

I have talked to a few people with Lewaero pods and have not found any CO complaints. The pilots I’ve talked to all have fuel pods. Mine is a cargo pod and I have had a CO problem since I installed it. I taped all doors, windows, etc. around the cabin with no luck locating the source of entry. I am now assuming it’s coming from the bottom of the fuselage somewhere and I’m going to work on that next. My high readings are short lived, while I’m landing, but I have at least single digits at all times.

[Dan L]

It sounds like Mike and I are having the same experience; single digit readings always and an increase in the landing configuration.

Today I taped around the teardrop shaped cover over the front elevator pulley. But it was not a good day to fly and test. It is worth mentioning that some years ago I looked at this cover as a potential entry point and put some weather seal around the contact edges on the inside of the cover. That was pre-pod.

D60F0166-EDA8-422E-A7F9-11633B7ECAB8.jpg

Springloaded’s comment about smoke entering immediately from somewhere under the panel is intriguing.

per Bob’s request, if I haven’t already mentioned it, my pod is a Carbon Concepts cargo pod.

[Springloaded]

It sounds like Mike and I are having the same experience; single digit readings always and an increase in the landing configuration.

Today I taped around the teardrop shaped cover over the front elevator pulley. But it was not a good day to fly and test. It is worth mentioning that some years ago I looked at this cover as a potential entry point and put some weather seal around the contact edges on the inside of the cover. That was pre-pod.

D60F0166-EDA8-422E-A7F9-11633B7ECAB8.jpg

Springloaded’s comment about smoke entering immediately from somewhere under the panel is intriguing.

per Bob’s request, if I haven’t already mentioned it, my pod is a Carbon Concepts cargo pod.

I don’t know why I didn’t think about that little panel🤷

[mikemacon]

Taped around the teardrop and a couple of holes I drilled for wires to the LEDs I installed on the gear. No joy.

[FionaMackenzie]

It doesn't look very reliable !