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Near miss with fuel line.

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Posted

I have three Avids, all with Rotax 582s. I have been using the blue flexible tubing sold for fuel line. I went out to fly today, and I don't know why I did it, but as part of the pre-flight I took the cowlings off. I do not normally do that every time, but today I did. Anyhow, in the process of checking the engine over, I noticed a place on the one fuel line between the fuel pump and the carburetor that  appeared to be chafed. When I lifted it to inspect it more closely, the line broke off at the fuel pump. When I flexed it further, it broke off at the carb end. The second line did the same thing. Both lines appeared to have become embrittled where they fit over the brass barb fitting. The ends of the tubing had lost all flexibility, and in fact shattered when disturbed. The remainder of the line remained flexible. I promptly replaced all plastic lines with reinforced automotive tubing. I will do so on the other two planes as well.

With the position of the leaks being on the downstream side of the fuel pump, I could well have had an in- flight fire. Not a pleasant proposition.

 

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Posted

I have been using the barricade fuel hose sold by LEAF. It is a tad more heat tolerant than standard auto fuel hose. But it doesn't really matter if you change it every couple years. I had that happen on my challenger using the blue fuel line. I suspected it was due to being exposed to sunlight, but evidently just due to age. Maybe due to this crappy stuff they sell us as fuel. I am more concerned with the crappy fuel additives more than I am with ethanol. In 10 years of flying 2 strokes, I have never had any issues with 10% ethanol. A friend of mine who is a name brand dist. said that 91-93 OCT doesn't have ethanol added but they are required to label the tank or pump 10% due to tank and tanker contamination. Since I run 91-93 OCT, that may be why I've not had any issues. Who knows?

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Posted

Several years ago, I bought some of the yellow tygon fuel line from a local Farm and Fleet type of store.  In a year or less, it had hardened up, and shrunk in length.  Never caused problems, but I changed it out when I saw what it had done.  What caught my eye was I have the fuel line running under the door in a 1/2" aluminum tube that curves up in front of the door.  I had left a good loop there at the top of the line where it turns and goes under the panel to the fuel valve.  I noticed the loop was gone, and the line was in a more or less straight line from the aluminum tube to it's first tie off point.  Glad I saw it.  Never had trouble with the blue line I've bought from Leading Edge, but also had problems with blue fuel line I got from a local snowmobile shop.  Here is a link to the post I made when I had the bad tygon tubing.  JImChuk

avidfoxflyers.com/index.php?/topic/5277-bad-fuel-line-warning/#comment-46527
 

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Posted (edited)

I am trying out a new (to me) Tygon LP1100 low permeability fuel tubing. It is clear but has a liner. The outer part seems to be urethane like regular UL fuel tubing, but the liner is supposed to be impervious to highly aromatic(sp) stuff in fuel and meets all the California rules for fuel line. Haven’t installed it yet, so don’t know how it will actually work in practice. But if it works like I hope it should have a much longer life and not get brittle and crack. I think I bought it from US plastics if anyone is interested in having a look. 

Edited by ChrisBolkan

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Posted

I have been using the barricade fuel hose sold by LEAF. It is a tad more heat tolerant than standard auto fuel hose. But it doesn't really matter if you change it every couple years. I had that happen on my challenger using the blue fuel line. I suspected it was due to being exposed to sunlight, but evidently just due to age. Maybe due to this crappy stuff they sell us as fuel. I am more concerned with the crappy fuel additives more than I am with ethanol. In 10 years of flying 2 strokes, I have never had any issues with 10% ethanol. A friend of mine who is a name brand dist. said that 91-93 OCT doesn't have ethanol added but they are required to label the tank or pump 10% due to tank and tanker contamination. Since I run 91-93 OCT, that may be why I've not had any issues. Who knows?

To be clear Allen, it's your understanding that it's only 87oct that has ethanol added; not the mid or high?

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Posted (edited)

We are talking about name brand gas like Sunoco, Shell, etc. What one gets from El-Cheapo station is still questionable even calling it gasoline. I was referring to Sunoco gas but according to him, most name brands do the same. 87 OCT still has 10% snapper juice added since it is probably 90% of what is used. This only applies to the United States and not California. Most newly rebuilt engines, 2 stroke, four stroke, are equipped with seals good for 10%. Marine gas as you get at a boat dock is mostly ethanol free, also. Rotax also approves their newer engines (mid 90's) and up okay for 10%. If they ever dump 85% on us, we're pretty much screwed. The ethanol issues still apply to certain tank material found in older tanks. So one still has to pay attention to what they put thru the tanks. The other additives in any gas is probably more dangerous to aircraft tanks and engines than 10% ethanol. 100LL isn't good for smaller aircraft engines, either. In 2 strokes it is almost as bad as carbon buildup.

Edited by Allen Sutphin
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Posted

I did some not purely scientific but informative (to me) testing of various chemicals on Avid fiberglass tank pieces with various tank sealant materials painted in spots on the fiberglass. I put the pieces in Ball canning jars with whatever the chemical was. The sealants were buna “n”, proseal, epoxy resin, and some others. Av gas had no effect on the glass or any sealant. Ethanol free auto gas was good too. The worst was ethanol 10%. It softened the fiberglass and delaminated the buna n, swelled the proseal slightly and did not seem to affect the epoxy. Interestingly, pure ethanol (195 proof everclear) did not have near the bad effects of the 10% ethanol gas, although it did effect on the buna n and a very slight softening of the fiberglass.

While the surface of the fiberglass was softened slightly it did not loose structural integrity over the two weeks, but from my experiment I will not use any fuel with ethanol in my tanks.

i posted a lot more detail on another thread a long time ago on this site somewhere.

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Posted

Kind of shows by the pure ethanol not having the same effects as 10% ethanol, that the additional additives in gas have a bad effect also. But we aren't told what they are or the effects they have.  Alum tanks are the only additive proof tank material but they can have other issues also.Plastic tanks are said to be ethanol proof but what about the other additives? Makes one wonder and be cautious. Just because John Doe flew his fiberglass tanks with ethanol fuel for years doesn't help much, too many variables.

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Posted

I have a question regarding fuel lines.  Why do we use aluminum tubing between the header tank and the firewall?

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Posted

Probably because of big feet squashing flexible line. No reason one can't use flexible line. The aluminum tubing is more durable where there is a chance of big clumsy feet but no major reason that flexible line can't be used if properly secured and protected.

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Posted

It has always been regarded as a safety practice not to have fuel carrying hoses in the cockpit where the people are.  Now on the kitfox and avids, there really isn't a way around it with the folding wings, but if you look at the routing on production airplanes you will see aluminum lines from the tanks all the way to the firewall and hoses from there to the engine.  One reason for this is that all hoses have some permeability, meaning that whats inside gets out to an extent. In the old day it was worse than today and hoses today have such low permeability that it isn't a concern. Another is inspecability. In the case of a production airplane those fuel lines in the cockpit run in places that you would be hard pressed to inspect every inch.  Even on a Kitfox with a hose running from the header to the firewall, it can be run where it isn't easily inspected.  a hose really needs to be able to be nspected along the full length. Finally I'd say replacement. An aluminum line needs to be replaced only when something happens to it.  Hoses should be periodically replaced no matter how good they look on the inside. 

I got a damaged Kitfox IV project that I'm going to be starting on this summer and when it goes back together it will be getting aluminum fuel lines everywhere except for short sections of hose for wing fold and forward of the firewall.

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Posted

Thanks 109jb.  Aluminum for me then.  Now where can I borrow a flaring tool? 

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Posted

My pacer, cubs and 180 had hoses in the fuel system....

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Posted

The older systems I've seen did have some hose mainly in very short sections used as connectors. Some used more, but more modern airplanes tend to be all aluminum tube from tank to firewall.   I personally prefer aluminum if possible but have to admit my Sonerai is all hose; however, the total length of hose inside the cockpit  is about 1 foot and it is replaced every 5 years or less. My current flying Kitfox has a lot of hose in the cockpit too. I planned to change the hose in the cockpit out for aluminum  this year but now that probably won't happen because I'll be selling it later this year to fund my new project Kitfox. When I do my new kitfox I'll probably do flared AN connections, but haven't ruled out using short (about 2  inch) pieces of tube as connectors. Do what makes you comfortable but be sure to inspect well as I've seen the aftermath of poor maintenance.

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Posted

The older systems I've seen did have some hose mainly in very short sections used as connectors. Some used more, but more modern airplanes tend to be all aluminum tube from tank to firewall.   I personally prefer aluminum if possible but have to admit my Sonerai is all hose; however, the total length of hose inside the cockpit  is about 1 foot and it is replaced every 5 years or less. My current flying Kitfox has a lot of hose in the cockpit too. I planned to change the hose in the cockpit out for aluminum  this year but now that probably won't happen because I'll be selling it later this year to fund my new project Kitfox. When I do my new kitfox I'll probably do flared AN connections, but haven't ruled out using short (about 2  inch) pieces of tube as connectors. Do what makes you comfortable but be sure to inspect well as I've seen the aftermath of poor maintenance.

I think you hit on the key right there.  Maintenance.  I replaced hoses every year on the Avid.  I probably do more maintenance than most and am constantly fixing little things.  It drives me nuts the people that only fill the gas and check the oil between annuals.  If I see it I fix it right then and there.  I do agree 100% that aluminum lines and good fittings are the way to go for longevity.

:BC:

 

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Posted

When I do my new kitfox I'll probably do flared AN connections, but haven't ruled out using short (about 2  inch) pieces of tube as connectors. Do what makes you comfortable but be sure to inspect well as I've seen the aftermath of poor maintenance.

What is the best way to connect an aluminum line to a tube?

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Posted

When I do my new kitfox I'll probably do flared AN connections, but haven't ruled out using short (about 2  inch) pieces of tube as connectors. Do what makes you comfortable but be sure to inspect well as I've seen the aftermath of poor maintenance.

What is the best way to connect an aluminum line to a tube?

I slip the hose over the tube and use safety wire to clamp it.  Never had a leak yet.  I use a double wrap of safety wire for almost all of my small diameter hose connections.

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Posted

When I do my new kitfox I'll probably do flared AN connections, but haven't ruled out using short (about 2  inch) pieces of tube as connectors. Do what makes you comfortable but be sure to inspect well as I've seen the aftermath of poor maintenance.

What is the best way to connect an aluminum line to a tube?

I slip the hose over the tube and use safety wire to clamp it.  Never had a leak yet.  I use a double wrap of safety wire for almost all of my small diameter hose connections.

I was going to do that and wanted to put a bead on the end of the aluminum line to keep the hose from slipping off.  I couldn't find a beading tool small enough for 1/4 inch line for less than several hundred dollars.

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Posted

When I do my new kitfox I'll probably do flared AN connections, but haven't ruled out using short (about 2  inch) pieces of tube as connectors. Do what makes you comfortable but be sure to inspect well as I've seen the aftermath of poor maintenance.

What is the best way to connect an aluminum line to a tube?

I slip the hose over the tube and use safety wire to clamp it.  Never had a leak yet.  I use a double wrap of safety wire for almost all of my small diameter hose connections.

I was going to do that and wanted to put a bead on the end of the aluminum line to keep the hose from slipping off.  I couldn't find a beading tool small enough for 1/4 inch line for less than several hundred dollars.

I went through the same thing.  I had to heat up the end of the tygon hose to get it to slip over the aluminum tube.  After it has been on for a year you have to cut the tubing off or you will twist and destroy the aluminum tube trying to get it off.  I have yet to have a leak on one of those connections.  These are installed in pretty much a ZERO stress condition and they never see stress.  Vegas would not give you odds on the hose slipping off the tube if you use a safety wire clamp.

:BC:

 

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Posted (edited)

I would guess that a small  partial flare with a flaring tool would help to ease any concerns as well.  JImChuk

Edited by 1avidflyer

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