Belly pod, fuel bladder, transfer pump

[KeithO]

I am doing a lot of work on a certified PA-18 and the plane is currently "apart".
I have an Airglas LC18XL on the way and I plan to use it to carry fuel on long trips. Current plan is to use 5 gal metal cans.

I'd like to be able to use a transfer pump with a removable fuel bladder in the pod. The pump and plumbing would be similar to the setup Airglas has for their LTC18 combo fuel/cargo pod.

Has anyone done something like this? I'm trying to determine the feasibility of getting field approval to install an underseat fuel pump and associated plumbing to connect to a removable bladder in the pod.

 

[farm_boy252]

Maybe a used 32g belly pod would be easier. Could switch back/forth with cargo version as needed?

 

[bda]

Metal cans??

 

[KeithO]

Metal cans??

That's the way I am doing it right now. I burn ethanol-free mogas, so on long cross country flights, I carry several metal jerry cans. Not looking forward to the day I have to use the fuel step. I could make a portable transfer pump, but I'm asking about a bladder setup to see if it's practical to do that to get ready for the day I have to carry a lot of fuel.

 

[aktango58]

approved? If you want to get approval, buy the Airglass fuel system and put it in, then the only part the FAA will have issue with is the fuel tank

 

[bda]

https://www.skycowboysupplyco.com/product-page/liquid-containment-bag

Try one of these with their light-weight valve/ spout, you will never go back to metal cans. Safer to throw up on the wing/ safer in the baggage area.

 

[DENNY]

If you do a search some of this has been covered before. Airless makes a combo pod with this you would already have a STC system in place then just add fuel to the pod on a piss break. Bushwheel bags with a ball valve spout makes filling a wing fuel/fuel pod pretty easy, Bushwheel bags unlike cans get small when empty leaving lots of room to get meat/fish back home. While the plane is apart put in a good extended baggage so you have lots of space for the light stiff. Also consider Dodge or Dakota tanks only have to move the fuel once, My last trip I carried 6 bags in the back and used them all so I understand that fuel step issue. Make sure you get that 2,000 lb wing upgrade done while you are working on the plane. It is real easy to build a 1,000 lb or bigger load when you start on trips with 8 hours or more fuel..
DENNY

 

[KeithO]

If you do a search some of this has been covered before. Airless makes a combo pod with this you would already have a STC system in place then just add fuel to the pod on a piss break. Bushwheel bags with a ball valve spout makes filling a wing fuel/fuel pod pretty easy, Bushwheel bags unlike cans get small when empty leaving lots of room to get meat/fish back home. While the plane is apart put in a good extended baggage so you have lots of space for the light stiff. Also consider Dodge or Dakota tanks only have to move the fuel once, My last trip I carried 6 bags in the back and used them all so I understand that fuel step issue. Make sure you get that 2,000 lb wing upgrade done while you are working on the plane. It is real easy to build a 1,000 lb or bigger load when you start on trips with 8 hours or more fuel..
DENNY

Plane already has the baggage and 2000 GWI. Would love the DC 24 gal tanks but that will have to wait until a ground up rebuild. I have the Airglas straight pod so bags would work fine. Just looking for less of a workout since I'm not getting any younger. I can hoist the jerry cans just fine on a ladder but maybe I would use a portable transfer pump for times when there is no ladder available. New panel going in so I am trying to decide on whether to include a hole and label for a transfer pump switch. Seems like using the airglas approved data and going for a filed approval may be the way tot go.

 

[DENNY]

OK now we are down to the good stuff!! Sounds like as myself you have a limited number of flying days left. So don't worry about building a pretty boy Yuppy cub. Build the panel with lots of extra space for gauges and switches. Put a checklist in the gauge hole and just don't label the switch until you hook it up!! A 30 gal fuel bladder can move all the fuel to the wing if you just out stuff in top of it. Think outside the box! Send me a PM with your phone number I got a lot of ways to spend your money and som of them are even good. I can cover 3 weeks of posts in 10 min, well might be a bit longer because I do tend to talk a bit!
DENNY

 

[KeithO]

OK now we are down to the good stuff!! Sounds like as myself you have a limited number of flying days left. So don't worry about building a pretty boy Yuppy cub. Build the panel with lots of extra space for gauges and switches. Put a checklist in the gauge hole and just don't label the switch until you hook it up!! A 30 gal fuel bladder can move all the fuel to the wing if you just out stuff in top of it. Think outside the box! Send me a PM with your phone number I got a lot of ways to spend your money and som of them are even good. I can cover 3 weeks of posts in 10 min, well might be a bit longer because I do tend to talk a bit!
DENNY

Thanks Denny! I'll reach out as soon as I get a chance.

 

[KeithO]

I found an approved 337 with the setup I want - fuel bag and facet pump in a float compartment. That 337 has the fuel line tied in near the fuel selector (with fueling instructions on a placard). I'll try for an approval based on that 337 with a tie in at the upper sight gauge and a fuel bag in the pod or float compartment.

 

[Olivier]

Dear KeithO, I'm attempting the same kind of project with a Sorenson tank. On a Cubby 160hp on amphib.
Could you provide picture of your installation, and the 337 ?

Thank
Olivier

 

[TR Dunn]

I found an approved 337 with the setup I want - fuel bag and facet pump in a float compartment. That 337 has the fuel line tied in near the fuel selector (with fueling instructions on a placard). I'll try for an approval based on that 337 with a tie in at the upper sight gauge and a fuel bag in the pod or float compartment.

I would suggest pulling the left tank and weld in a bung for a dedicated top fill (see attached photo). Attempting to fill through the sight tube has two problems both caused by the small tube size, time to transfer and back pressure, (unless your pump is sized for that small tube), the latter not being a direction I would go. A dedicated line (-6 min) from your pump to the top fill bung will yield best results. Place an in-line check valve and sight tube so you can see the bubbles indicating you are near empty and sucking air. Installing the bung will also allow you to install a belly tank in the future if so desired. The photo shows the bung I installed for the belly tank feed and the other is the upper sight tube barb which is inappropriate for a fill IMO. TR

 

[Olivier]

Dear KeithO, thank for the infos.
Have you consider sending the fuel from the bladder directly to the engine, without going thru the left tank ?
With a selector that received from either wing tank or from bladder and out to the engine.

Thank
Olivier

 

[skywagon8a]

Dear KeithO, thank for the infos.
Have you consider sending the fuel from the bladder directly to the engine, without going thru the left tank ?
With a selector that received from either wing tank or from bladder and out to the engine.

Thank
Olivier

Altering the fuel system as you describe on a certified airplane requires many FAA hoops to climb through. Be prepared before you start altering.

 

[Steve Pierce]

The fish spotters I know fill the left wing tank through the site glass fitting. goes into the top of the tank and you can see the flow so you know when the belly tank is dry.

 

[skywagon8a]

..... and you can see the flow so you know when the belly tank is dry.

There is another method which is more complicated to determine when the tank is dry. That is to add a sensitive ammeter to the pump electrical feed. When the amperage draw drops, the load on the pump has decreased indicating it is pumping air. This system was in a Widgeon which I used to maintain.

 

[TR Dunn]

The fish spotters I know fill the left wing tank through the site glass fitting. goes into the top of the tank

This works, however, as I stated above, not the best choice IMO for the reasons given. When pushing a fluid through a confined area by any force, (in this case a pump), any restriction, (small tube diameter in this case), results in an increase in pressure within the system with possible damage to the pump if the pump is not sized correctly (oversimplifying the laws of fluid dynamics here).
My Cub was plumbed through the site tube when I purchased, I did not care for it, again, for the reasons stated. Welding in the bung both "cleaned up" the installation and made it more efficient for my mission.
There are many methods to meet the objective of fluid transfer, all may get you there, however, some are better than others as they go with the flow, (pun intended), vice working against the laws of fluid dynamics.

TR

 

[AkPA/18]

Nothing wrong with plumbing into the site gauge. Works great. Been using this method since 87. There have been hundreds of thousands of hours up here in Alaska using this method with no problem. Only problem I have had with the fuel transfer, the last Cub I had someone plumbed in between the fuel tank and the selector valve. With a quarter tank of fuel and an empty belly tank pumping it would unport the tank causing the engine to stumble until you switched tanks or shut off the pump. Whatever you do don't plumb the line anywhere but the tank.
TR I am curious about your install. Do you have a picture of your check valve/site Guage? I have never heard of this nor seen this before.
Thanks,
Mark

 

[TR Dunn]

Mark, here ya go as requested (photo).
For the record, I never stated there is anything “wrong” with using the site tubes. I personally do not like it and I supported my solution with factual reasons that can be mathematically proven. I am just sharing my solution, not the only solution. Others can do what they want with their aircraft. I know from experience that the laws of physics do indeed apply in Alaska as I operated up there for 15 years putting thousands of gallons through the plumbing system in the Cub as depicted as well as my ASC fuel pod on our 180.
As for your claim of “hundreds of thousands of hours up here in Alaska “ transferring fuel through the site tubes, a dedicated line and fill as I have installed would have reduced that number to a more logical tens of thousands by increasing the flow rate.
TR

 

[AkPA/18]

Mark, here ya go as requested (photo).
For the record, I never stated there is anything “wrong” with using the site tubes. I personally do not like it and I supported my solution with factual reasons that can be mathematically proven. I am just sharing my solution, not the only solution. Others can do what they want with their aircraft. I know from experience that the laws of physics do indeed apply in Alaska as I operated up there for 15 years putting thousands of gallons through the plumbing system in the Cub as depicted as well as my ASC fuel pod on our 180.
As for your claim of “hundreds of thousands of hours up here in Alaska “ transferring fuel through the site tubes, a dedicated line and fill as I have installed would have reduced that number to a more logical tens of thousands by increasing the flow rate.
TR

View attachment 109227

Thanks for the picture. That will help folks on your install.

Personal opinion is I like the original sight Guage for looks and location without the restrictive check valve.

For the record you did call the install inappropriate which is another word for wrong.

I never called your install wrong.

You said you "supported my solution with factual reasons that can be mathematically proven." Then you claim your install pumps 10 times faster. I would love to see that math for us dummies.
Thanks,
Mark

 

[TR Dunn]

You said you "supported my solution with factual reasons that can be mathematically proven." Then you claim your install pumps 10 times faster. I would love to see that math for us dummies.
Thanks,
Mark

For this simplistic example it is assumed the velocity of the liquid remain constant.
Flow Rate = Cross Sectional Area of the tube times Fluid Velocity
Site gauge barb: cross sectional area is approximately .0122
-6 supply: cross sectional area is .1104
.1104 is nine times greater than .0122
You got me, I grossly overestimated the difference at 10 times. (that reply to you was actually tongue in cheek, however, turns out to be fairly accurate, even more so if compounding of time differential is taken into consideration over the duration of your claimed "hundreds of thousands of hours").
My only objective of reply to OP was a better method IMO, larger tube equals greater flow rate, this is indisputable.
I pledge to be more accurate in my future calculations, I would ask you be able to validate your numerical assertions as well, as in "hundreds of thousands of hours".
TR

 

[cubdrvr]

This is one on the right hand wing root.
Tied into the top site gauge fuel line with a shut off valve. Fuels from a rear tank with 12 V cigar outlet. You can also watch the site gauge to verify filling. 3.5 minutes per gallon.