Fuel line fittings

[wingnut99]

I'm having trouble finding the appropriate fittings for my fuel line. I've ordered several 90° elbows from Aircraft Spruce and from Amazon with all of them being wrong. The fuel tank has a 3/8" fitting in the bottom which is the same as the gascolator. Unfortunately if I order a 3/8" pipe fitting the flared portion is only 1/4" and if I order a 3/8" flare to accept the 3/8" fuel line then the pipe thread end is 1/2." I can't find a 3/8" pipe to 3/8" flare elbow. I don't really want to use a bunch of reducers or adapters to get everything to work. To many potential leaks. Any ideas?

[racaldwell]

HI WN99,

ACS has AN816 in 6-6D size. The 6 means 3/8 so this one is 3/8 thread and 3/8 tube. The D is aluminum. AN816 is a straight nipple.

Rick Caldwell
Xenos 0057

[wingnut99]

I moved on to engine installation and wiring. I'll be back to the fuel system soon so thanks for the clarification. I'm seriously considering pulling the altitude compensating carb off for simplicity. I can get rid of 2 fuel pumps and a carburetor heat system and the only addition will be a mixture control. I hate pulling brand new parts off and spending another $500 to replace them but I think it's worth it to speed up the process and eliminate complexity.

[Scott Todd]

After building 3 airplanes and working on dozens more, here is some probably controversial advice; NEVER, NEVER, NEVER use 90 NPT fittings for anything! Its always just a pain in the a$$. Use straight NPT ones so you can get them the right torque and then make or have the other lines made with AN 90 fittings on them. Its WAY easier to get them all tightened and lined up correctly.

[sonex1374]

I buy all by AN fittings through Jegs. They have a great selection, quality is good, and the descriptions and pictures help assure you get the right parts.

https://www.jegs.com/i/JEGS/555/100146/10002/-1

Jeff

[Rynoth]

After building 3 airplanes and working on dozens more, here is some probably controversial advice; NEVER, NEVER, NEVER use 90 NPT fittings for anything! Its always just a pain in the a$$. Use straight NPT ones so you can get them the right torque and then make or have the other lines made with AN 90 fittings on them. Its WAY easier to get them all tightened and lined up correctly.

When space is available, I totally agree. All too-often you have to choose between slightly-undertorqued or over-torqued to get the thing to line up correctly.

[Skippydiesel]

I'm having trouble finding the appropriate fittings for my fuel line. I've ordered several 90° elbows from Aircraft Spruce and from Amazon with all of them being wrong. The fuel tank has a 3/8" fitting in the bottom which is the same as the gascolator. Unfortunately if I order a 3/8" pipe fitting the flared portion is only 1/4" and if I order a 3/8" flare to accept the 3/8" fuel line then the pipe thread end is 1/2." I can't find a 3/8" pipe to 3/8" flare elbow. I don't really want to use a bunch of reducers or adapters to get everything to work. To many potential leaks. Any ideas?

Maaaate! Go "rubber" all the way. No elbows. No Flares. No expensive fittings that may leak. One length between applications, no joins. No vibration issues. Way way less cost. Sure you should replace every 5 years as per Rotax recommendations but its easier than it sounds (could do mine in a morning). Purchase quality fuel hose from your Auto shop - I use Gates hoses. You can look up the specifications for Gates, not so for many auto hoses.

If you do go rubber - make sure you use the latest automotive style spigots (push on fittings) not the old stile multi barb fittings AND never overtighten the hose clamps (which should be the fuel injector style). The hose clamp is a security devise NOT a leak preventer. Make sure your hoses ID is compatible with the spigot OD and you will not have leaks.

[karmarepair]

Maaaate! Go "rubber" all the way.

Me, if I were to start all over again, would got with a hard line all the way from the shutoff valve to a SHORT section of flex hose just before the AeroInjector. NO other filters or fittings, and I'd rig up a proper bulkhead grommet for the firewall penetration. Reasoning is that anything that can pass the finger strainer will pass the needle on the AeroJector, and if you keep the fuel tank full all the time, there is literally no way for water to get in the tank, protected as it is from rain by a tight cap AND the fuel door.

I don't like how close to the exhaust my fuel line runs, from the gascolator a previous builder installed to the AeroInjector, and the multiple 90 degree fittings in my installation have all the problems mentioned, plus one AN fitting is on the BACK side of the firewall where it's all but inaccessible.

At least one Sonex I know of is running this way I described successfully.

[Bryan Cotton]

I did a combination of hard line and braided line - all AN fittings. Documented on page 102 of my thread:
viewtopic.php?f=39&t=578&start=1010







It all runs downhill, and there is a filter on the engine side of the firewall.

The original hard plumbing was redone with the angle shim pictured. There are two layers of firesleeve firewall forward, so you can't see the filter or line. I figure it's as much insulation as it is protection.

No rubber hoses for me.

[Skippydiesel]

Maaaate! Go "rubber" all the way.

Me, if I were to start all over again, would got with a hard line all the way from the shutoff valve to a SHORT section of flex hose just before the AeroInjector. NO other filters or fittings, and I'd rig up a proper bulkhead grommet for the firewall penetration. Reasoning is that anything that can pass the finger strainer will pass the needle on the AeroJector, and if you keep the fuel tank full all the time, there is literally no way for water to get in the tank, protected as it is from rain by a tight cap AND the fuel door.

I don't like how close to the exhaust my fuel line runs, from the gascolator a previous builder installed to the AeroInjector, and the multiple 90 degree fittings in my installation have all the problems mentioned, plus one AN fitting is on the BACK side of the firewall where it's all but inaccessible.

At least one Sonex I know of is running this way I described successfully.

Why?

What advantage do metal lines confer in our class of aircraft?

Where not possible to rout fuel lines away from hot components, heat shields can be easily custom made using builders malleable aluminium flashing, exhaust wrap and high temp silicon gasket goo. Cut aluminium to length/width (always allow extra to do a final trim) Cut exhaust wrap into strips appropriate to aluminium sheet (I like to stop wrap just before edges of aluminium by about 5mm). Using liberal amounts of silicon , glue wrap to aluminium. Leave to set overnight. Wrap "sandwich" around hose/pipe & secure with safety wire or hose clamp (extra weight & cost).