Belly Pods and CO levels

[Andy]

Nothing to do with fuel level in a flight attitude. You fill the tank with the tail down, normally. Everyone would have the same tank capacity if you filled the tank in normal flight attitude with the tail up.

So the fuel fill port is sealed and may be lower than the level flight fuel level? Is that correct? if so, how is the tank vented?

[turbopilot]

So the fuel fill port is sealed and may be lower than the level flight fuel level? Is that correct? if so, how is the tank vented?

The fuel cap is slightly higher than the bottom of the tank in level flight. The tank is vented through the cap. So when you fill the tank tail down it will trap air above the level of where the filler neck enters the tank. The amount of air trapped depends on how high the nose. How high the nose depends on the size of the main gear tires. So the fuel cap will always be higher than the fuel level except in a very steep dive.

I doubt I will ever carry more fuel than can be gauged by fuel probe (around 17 gallons).

As you may recall from an earlier thread I made the choice to go with the 24 gallon main tanks and avoid the 42 lb dead weight penalty (tankage weight plus unusable fuel) associated with the two 10 gallon tanks added to achieve the 44 gallon wing tank capacity. The belly tank weighs 19lbs and has reported unusable fuel less than 1/2 gallon. So by going with belly tank I saved around 20 lbs while having the option to carry up 28 gallons, with no cruise speed penalty.

The 44 gallon tanks are an option on the SS with a price of $4,190. The Lewaero Belly tank option costs $5,780.

[Andy]

The fuel cap is slightly higher than the bottom of the tank in level flight. The tank is vented through the cap. So when you fill the tank tail down it will trap air above the level of where the filler neck enters the tank. The amount of air trapped depends on how high the nose. How high the nose depends on the size of the main gear tires. So the fuel cap will always be higher than the fuel level except in a very steep dive.

Ok, thanks for the explanation. Seems strange that they didn't vent the tank at the highest point then tire size wouldn't matter.

[Schwbo]

Today I completed the wiring mating the Aithre EX2 to Garmin GEA24. It was not as difficult as I thought. I found pin 27 of the P243 connector to be a good aircraft ground, so everything was by the install manual.

First challenge and the hardest part was getting the P243 free of the wiring and hanging down far enough that I did not have to stand on my head to complete the pin insertions. Here is the P243 free and hanging.



Next remove the cover and insert the four female pins as described in other posts above. Here is the P243 with the cover off and red arrows pointing the four pins needed 26,27,28 and 29.



Here is the pin out diagram I made up to make sure I was getting the pins in the right spots.



I then mounted the Athrie 2X under the transponder with some double sided tape.




Then I put everything all back together and went through the setup required on the Engine Information System Configuration page as detailed in the manual.

After a reboot this is the first screen you see. For about a minute during startup the CO reading is maxed out.



Then after a minute or two the CO PPM drops down to the current measured level.



So once you have all the parts the install was reasonably easy. The "QTY GAL" indication with the red X through is the new belly tank quantity sensor. I have not calibrated the tank yet. The Lewaero tanks holds in gallons your roughly your tire size plus 2. So I have 26" tires and I am told I should have 28 gallons of capacity. The Lewaero tank with the G3X fuel sensor will on read the last 17.5 gallons in the take, so at 17.5 gallons the fuel indicator will be reading full. Lewaero tank has about a 6 oz unusable fuel quantity in the flight attitude.

Did you end up connecting 3 or 4 pins? Which did you connect? If 4, did you split the ground?

I’m at CC for my 2nd build week on Apr 12-13th. Was wondering if to bring it with me.


Sent from my iPhone using Tapatalk

[turbopilot]

Did you end up connecting 3 or 4 pins? Which did you connect? If 4, did you split the ground?

I’m at CC for my 2nd build week on Apr 12-13th. Was wondering if to bring it with me.

I did it just per the documentation. After confirming good ground on pin 27, I connected 27 and 28 to black on the EX2.

[Chip]

The fuel cap is slightly higher than the bottom of the tank in level flight. The tank is vented through the cap. So when you fill the tank tail down it will trap air above the level of where the filler neck enters the tank. The amount of air trapped depends on how high the nose. How high the nose depends on the size of the main gear tires. So the fuel cap will always be higher than the fuel level except in a very steep dive.

I doubt I will ever carry more fuel than can be gauged by fuel probe (around 17 gallons).

As you may recall from an earlier thread I made the choice to go with the 24 gallon main tanks and avoid the 42 lb dead weight penalty (tankage weight plus unusable fuel) associated with the two 10 gallon tanks added to achieve the 44 gallon wing tank capacity. The belly tank weighs 19lbs and has reported unusable fuel less than 1/2 gallon. So by going with belly tank I saved around 20 lbs while having the option to carry up 28 gallons, with no cruise speed penalty.

The 44 gallon tanks are an option on the SS with a price of $4,190. The Lewaero Belly tank option costs $5,780.

Lesson learned with fuel cap and filler neck. I put a set of Summit skis on my EX and the Lewaero filler neck/cap interfered with the front spring. I chose to shorten the filler tube so the cap was out of the way, but still maintained “slope” for gas to drain into the tank. Started getting occasional gas smell in the cabin. Searched for the cause and saw blue stain on fuselage behind the filler cap. Spoke with Eric Lewis and he confirmed that repositioning the cap to a position lower in relation to the tank opening, in certain attitudes (I read descending) the fuel in the tank will slosh up to the cap and vent out.
Am now designing a workaround that clears the ski spring and sits at least as high as the original.

Chip

[Dan L]

It turned out that my original portable had a Bluetooth connection issue. Jim was very good about it and promptly replaced the unit. I mounted the slide-on attachment mount plate on the right side wing root. I was able to get in one flight with it and it was an eye opener for me. The readings are read on the phone app and it updates every 12 seconds (as I remember now). When I’m in cruise I get readings around 10. But climbing and descending make a big change. The ppm can go into the 50s quickly. Pulling flaps make it worse.

I identified a couple of openings on the bottom of the fuselage near the tail spring that I’ve taped off with blue painters tape that I suspect are drawing it in and then low pressure in the cabin pulls it forward. Waiting for better weather to fly again.

I’m impressed with Aithre 4.0 portable, the app and their customer service. This is a device designed by pilots for pilots. And for $130 the price is comfortable too. It comes with two mounts so I put the other in the Cessna.

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[turbopilot]

The ppm can go into the 50s quickly. Pulling flaps make it worse.

Is this with the belly tank on? My last flight with the Aithre hardwired to the G3X I saw 2 to 4 ppm on the ground and 0 ppm flying with the Lewaero tank. Mine is set up to trigger a CAS alert on the G3X above 30 since the CO ribbon is buried on the engine page and not always in view.

[Dan L]

Is this with the belly tank on? My last flight with the Aithre hardwired to the G3X I saw 2 to 4 ppm on the ground and 0 ppm flying with the Lewaero tank. Mine is set up to trigger a CAS alert on the G3X above 30 since the CO ribbon is buried on the engine page and not always in view.

With the belly pod in place. Mine is not a tank.

The app lets you put in threshold limits and it will talk to you when they’re exceeded through the headset and also every 12 seconds the A on the face flashes a color. Blue is safe then yellow I think followed by amber. (Might have those last two switched).

This is a much better more sophisticated unit than I was using. Glad I bought the Aithre.

[Dan L]

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.

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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.

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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.

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

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I enjoy seeing the elk out on the open areas.