I need some opinions on this. I'm Planning a stock fuel injected 540 (at the moment). I don't have the baffle on my tanks yet and I'm wondering if I should put return line fittings in now while it's easy -should I someday need a return line. If yes, do I use the same fittings as the vent line and where should it be located on that end rib? Thanks....
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Fuel Return Line
- Thread starter danboy
- Start date
rocketman1988
Well Known Member
Return Lines
Why not just put a 1/4" NPT Tank Bung in the root rib? A couple dollars cost, a couple of ounces weight, a half hour of time, and you are set, tank wise, for the future. Who knows, EFI may become the status quo at some point...
If you do decide to run a return line in the future, though, remember that you will need to install a return line valve or better yet, a duplex valve to handle the switching of supply and rerun lines...
Why not just put a 1/4" NPT Tank Bung in the root rib? A couple dollars cost, a couple of ounces weight, a half hour of time, and you are set, tank wise, for the future. Who knows, EFI may become the status quo at some point...
If you do decide to run a return line in the future, though, remember that you will need to install a return line valve or better yet, a duplex valve to handle the switching of supply and rerun lines...
Jesse
Well Known Member
I would tend to agree that it doesn't hurt to put in a return fitting and cap it off. I would put it just aft of the forward support "spar" while remaining clear of where the aileron bellcrank will be. Put it high. You can either rivet in a bung or out in a bulkhead fitting. I would recommend an AN-6 size fitting. You can buy a cap that will screw on and it will never be a problem (as long as the fitting is well sealed in the tank). Better to have it and not need it than need it and not have it.
mikeyj350
Well Known Member
Although I tend to agree with folks concerning "sticking to the plans", "keep it simple", and "anything you do outside of the plans takes you 10x longer" ...they are correct about the latter for sure... this is one area I personally decided to install a return fitting on mine. Of course we can't see into the future, but to me it seems likely that full-flow-return EFI systems will become more commonplace in the not-so-distant future. Especially in the E-AB category.
Installing it now adds minimal weight and cost (although a duplex fuel valve is indeed quite pricey if you get one now). Plus, it doesn't affect your standard one-way fuel systems either, so to me there was little/no downside other than some extra time and forethought. Yes, more holes equals more opportunities for leaks, but there's enough "opportunities" for leaks out there already. A leaky fitting is a lot easier to remedy than, say, an under-gooped tank rib.
As for the return location, I put my AN832-6D (full flow) about 1/3 of the way up the side baffle, at about the 4 o'clock position (L tank) from the fuel sender. No extension line, fuel will just dump out the open end of the fitting and back into the tank. Wherever you decide to put it, beware of the top corner next to the vent line, where it looks like a great spot to install the fitting... it will be in the way of the spar bolts. There was a post about this a few months ago. BTW- a million thanks to them (and this forum) for helping prevent me from almost surely making the same mistake!
People may argue to put the fitting higher than I did, but personally I don't see a need for that, and this is an excellent place for accessibility. As long as it's higher than the send fitting, you should be good to go. Also some folks may argue about running a line further outboard so the "hot" fuel doesn't dump out near the send fitting. While this wouldn't hurt anything to do so, it's my opinion that that is also unnecessary and it increases in-tank complexity. The returned fuel will mix very quickly with whatever is in the tank. I took my cue from automotive fuel tanks/senders: I've worked on several, and all just dump fuel right back into the tank, directly above the intake screen. I guess I've convinced myself there is no way my setup will draw worse/hotter/bubblier fuel than those configurations.
There are some photos of the tanks in my blog if you're interested, or feel free to send a PM and I can email you some. Good luck with your decision!
Installing it now adds minimal weight and cost (although a duplex fuel valve is indeed quite pricey if you get one now). Plus, it doesn't affect your standard one-way fuel systems either, so to me there was little/no downside other than some extra time and forethought. Yes, more holes equals more opportunities for leaks, but there's enough "opportunities" for leaks out there already. A leaky fitting is a lot easier to remedy than, say, an under-gooped tank rib.
As for the return location, I put my AN832-6D (full flow) about 1/3 of the way up the side baffle, at about the 4 o'clock position (L tank) from the fuel sender. No extension line, fuel will just dump out the open end of the fitting and back into the tank. Wherever you decide to put it, beware of the top corner next to the vent line, where it looks like a great spot to install the fitting... it will be in the way of the spar bolts. There was a post about this a few months ago. BTW- a million thanks to them (and this forum) for helping prevent me from almost surely making the same mistake!
People may argue to put the fitting higher than I did, but personally I don't see a need for that, and this is an excellent place for accessibility. As long as it's higher than the send fitting, you should be good to go. Also some folks may argue about running a line further outboard so the "hot" fuel doesn't dump out near the send fitting. While this wouldn't hurt anything to do so, it's my opinion that that is also unnecessary and it increases in-tank complexity. The returned fuel will mix very quickly with whatever is in the tank. I took my cue from automotive fuel tanks/senders: I've worked on several, and all just dump fuel right back into the tank, directly above the intake screen. I guess I've convinced myself there is no way my setup will draw worse/hotter/bubblier fuel than those configurations.
There are some photos of the tanks in my blog if you're interested, or feel free to send a PM and I can email you some. Good luck with your decision!
rocketman1988
Well Known Member
location
You do not need to run it further into the tank, root rib is fine.
It seems like the "stick to the plans" comment is coming up a lot, lately. Though I agree that any mods DRAMATICALLY increase the build time, I agree with the previous post...build what you want.
If everyone built exactly to the plans, then no progress would be made. Think about it...if Van was happy and satisfied about the designs available at the time, the wonderful RV series of aircraft would never have been conceived.
Is making huge deviations from the plans for everyone? NO.
Is adding two small fitting or bungs in the fuel tank to prepare for the future a huge deviation? NO.
Do your research and build what you want! This is EXPERIMENTAL aviation.
I would spend the 30 minutes and install return bungs in the tanks. Yes, I did it on mine, and yes, it took about 30 minutes...
You do not need to run it further into the tank, root rib is fine.
It seems like the "stick to the plans" comment is coming up a lot, lately. Though I agree that any mods DRAMATICALLY increase the build time, I agree with the previous post...build what you want.
If everyone built exactly to the plans, then no progress would be made. Think about it...if Van was happy and satisfied about the designs available at the time, the wonderful RV series of aircraft would never have been conceived.
Is making huge deviations from the plans for everyone? NO.
Is adding two small fitting or bungs in the fuel tank to prepare for the future a huge deviation? NO.
Do your research and build what you want! This is EXPERIMENTAL aviation.
I would spend the 30 minutes and install return bungs in the tanks. Yes, I did it on mine, and yes, it took about 30 minutes...
