Clogged fuel lines

[kitfox5v]

Shane,
Sounds like ethanol my be the culprit to me. just a thought.

[War Eagle]

War Eagle,

Just had a buddy make an emergency landing due to fuel in the cockpit. He had the blue poly hoses. They had literally just disintegrated and allowed fuel to spill all over the cabin. I wouldn't have believed it if I didn't see the plane in person. We use to use that fuel line on snowmobiles because it would remain very flexible in cold temps. The strangest thing is the hose was still flexible right around where they broke.

Either way with any fuel system, I don't believe it's bad practice to go through and replace all the hoses like that every few years. Cheap insurance

That's correct. Polyurethane is just another option for fuel lines but you always need to use do diligence in managing your maintenance and replacement schedules.

[beeryboats]

I removed my poly header tank tonight and even though it was half full, no fuel came out when I removed all the lines. It has been setting for ten years and all the fittings were plugged solid. That made the tank removal very easy, but I was surprised how much the Mil-6000 hoses had degraded and came apart inside. So now after reading this thread, I don't know what hoses to buy as replacements.

[PropellerHead]

Slightly off topic now but it seems to me that, if you intend to run auto fuel then automotive fuel lines would be a good choice. I replaced my Mil-6000 hoses with automotive fuel lines when I started smelling fuel in the cabin about five years ago. I don't believe that my current problem is related to the fuel lines degrading but rather the fuel itself went bad. I'm personaly leaning towards an all metal solution now (except for those parts that need to flex for wing folding of course). I have no experience with metal fuel lines but it seems like it shouldn't be too difficult...

[Dave S]

PropellerHead,

Your idea is precisely what I followed....since autogas was my fuel of choice, hoses, etc seemed the best bet - afterall, cars have been using SAE hoses and autogas for a while - I never installed the milspec hoses.

If you are looking for some guidance on fabricating metal lines.....there is a huge library of on line videos on the EAA website titled "Tips for homebuilders" I believe metal tubing fabrication for fuel lines is out there. Lots of other good stuff too.

The biggest issues with metal fuel lines is bending, including the correct radius; and, most of all, forming the flanges for the 37 degree fittings - takes a bit of practice and a bad one can crack under the fitting. Practice makes perfect.

Sincerely,

Dave S
KF 7 Trigear
912ULS Warp Drive

[Danzer1]

Dave and Luis,

The biggest problem with all metal fuel lines is metal fatigue due to vibration. Do a search on "work hardening". Personally, I wouldn't do it. You really need flex points - particularly before of after bends, hard connections to different parts of the structure, before and after bulkhead through fittings (firewall) and connections to the biggest vibrator of all - the engine. Not to mention the additional fabrication work to make something that will eventually fail over time, if not totally isolated from all vibration.

Good Luck, Greg

[PropellerHead]

Hmm. Sounds like good reason to do the opposite and replace all my lines with automotive fuel line. Especially if it's something that has a high possibility of breaking early because I did it wrong.

[Danzer1]

I suppose you could, but then you need to be careful with attach points and thru bulkhead fittings (firewall) as the vibrations at those points can cause chafing and wear on non-metallic piping. There are good reasons for seeing both used on fuel systems of all machines, not just aircraft.

Greg