when I built my XL, I replaced the "stock" rubber fuel lines with braided stainless steel coated lines that I fabricated.

After reading the Service Letter that Zenair published last February (02/05/2018 Rev. 0)

under item #3 "Fuel Lines in Airframe" I started to wonder if there is a replacement interval for these fuel lines? (I'm in the middle of my Annual Condition inspection)

Obviously the stainless steel mesh precludes a visual inspection of the enclosed rubber fuel lines-but I have not seen any evidence of degradation (no black flecks in the sumps or gascolator)

Calendar-wise these lines are 4 years old

time wise they have about 120 hours on them

I only run AVGAS through them, no MOGAS

Your thoughts?

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A great source for AN fittings and appropriate fuel lines is:

https://www.anplumbing.com

Many choices of different SS wraped fuel lines, including PTFE, and fittings made for them. Good tech videos too, on how to construct your lines .

If you are asking about the fittings the flex lines attach to, you should be able to use them. The fittings that are part of the hose will not work with the Teflon/stainless braid hose, they use dedicated hardware. However, that hardware has standard AN hose fitting attachement points so the new hose should fasten right up to the AN fitting your old hose was attached to. Only the fittings on the hose won't work. If you made up new rubber hoses you could re-use your fittings but for the Teflon ones they are integral to the hose and installed with special equipment.

And the advice about not saying the word "airplane" when talking to an automotive supply place is very good advice. Some have no worries but many are so afraid of aviation liability they will blackball you in a heartbeat. You are buying parts for a homemade race car of a tractor or an airboat, never refer to anything that involves flight.

Bob,

I agree - only those AN fittings connected to a hose will have to be changed-out if one switches from rubber to PTFE. Mating AN fittings not installed on a hose, such as bulkhead fittings, etc., will accept the new hose fitting and will not have to be changed out. 

One correction, although AN fittings can be obtained professionally installed on prefabricated PTFE hoses with special crimping equipment, there are many sources of AN fittings (Earl's, ARP, ANplumbing, Russell, etc.) that can be easily attached to hoses with simple hand tools and no special equipment necessary.  The ANplumbing.com website has excellent tech videos to demonstrate how to install them.

Some like the simplicity and peace-of-mind of having their hoses professionally fabricated and I have done that a time or two.  However, there is an advantage in fabricating your own hoses for the homebuilder (besides saving $ !):  If you have a long run and the hose needs to run through grommeted holes, etc., you can install a fitting on one end of the hose "on the bench," and then run the hose without a fitting on the other end through all your grommeted holes, determine the exact length you need, and then cut the hose and install the other fitting with the hose in its final position in the airplane.  This results in an installation with a precise length hose and avoids larger holes than necessary since you don't have to make the holes large enough for a fitting to pass through.  If you buy a pre-made hose assembly, most vendors crimp the fittings on and you can't take them off to pass the hose through holes.

 

As an example, when I built my STOL 750, I had to pass a hose from the fuel tank through the rear spar.  By not having the fitting installed on one end, I was able to keep the hole within the critical maximum dimension ( I checked with Caleb, the Zenith engineer) and passed the hose through the grommeted hole and then installed the fitting.

John

After taking everything into consideration (and thank everyone for their inputs) I decided to push replacing the fuel lines to the next annual.

All of the lines are easily pliable, I found no evidence of rubber breakdown in the gascolator or carb inlet screen.

Instead I focused on wheels and tires, replacing tubes, tires and relined the brakes.

Thank you, everyone. I've already started researching the PTFE lines for next annual!

Brad Cohen

N969BC

Another annual in the books!

I think I know the answer but have to ask anyway. If one were to use the PTFE braided hose, would the Zenith-supplied barbed fittings work? If not, why not?

Carl, the only fittings that work with the PTFE lines are those proprietary fittings made for them. Different material so a pressure fit with barbed fittings would never work. Best explained in this video. On a previous plane I made all my own hoses according to this method and pressure tested to 1000 lbs. They all worked perfectly.
https://www.anplumbing.com/speed_seal

Thanks, Don. I saw that video a week or so ago when it was posted above. I was just thinking that 2 worm gear clamps should be fine clamping it in a gravity feed situation. 

Im just being lazy. I don’t mind changing the lines when I can get to them, but was thinking it would be a pain to get st them in the channels where they come down from the wings. 

RSS

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