copper tubing gas line?

[mhorowit]

An acquaintance bought a Tcraft and I went and admired it. Kicked the tires, and opened the cowling. then looked again. nuts on bolts with holes but no cotter pin in several places which I pointed out to him. nuts with fiber inserts got my comment. Also, the gas line was copper tubing. I don't recall any copper tubing moving fuel in my engine compartment. Is copper tubing acceptable? - Mike

[VictorBravo]

Re: copper tubing gas line?

I SUSPECT that copper tubing is not legal for a main fuel line, but I can almost GUARANTEE it is not correct mechanically. The reason is that the engine moves quite a bit with relation to the airframe. That's why we have big rubber mount bushings.

If the engine moves around relative to the airframe, the tubing will bend back and forth very slightly... millions of times.... until it cracks.

Your friend has a bigger problem. The fact that you could see the tubing at all is not good. There should be a tube made of material called "Firesleeve" over the fuel line from the gascolator to the carburetor. It's big and red and ugly and looks wrinkled. Under certain emergency circumstances it will be the prettiest thing you ever saw.

Common sense tells us that having a properly done, crack-proof, fire-proof fuel line is real important inside the engine compartment. Fuel spray or dribble will cause a fire faster than you'd ever dream. Measure the distance between the fuel line and the exhaust. If it is less than six feet ( ) then you cannot take a risk with it.

This is serious, Mike. Have a REAL airplane mechanic look at it before the next flight, no kidding. If I am wrong, then everyone can have a laugh on me. If I am right, the airplane should be fixed before it is flown. Everyone who has owned more thano ne airplane can tell you stories about how some airplanes are put together.

While you are looking around in there, see if it still has a glass bowl gascolator. I think those are taboo now for obvious reason.

The bottom line is that if someone put that airplane together with improper nuts and bolts, Wal-Mart plumbing aisle tubing and fittings, etc, then you REALLY need to have somebody look around in there to see what else is not right. There is a place on Taylorcrafts for copper or brass tubing, and they were certified with many automotive parts. But there are very important places where that stuff is NOT supposed to be.

Bill

[ROllerton]

Re: copper tubing gas line?

Copper was used for repairs for fuel and oil pressure lines here and there on trucks, cars and tractors. In every case I can remember the lines would crack some where along the run, or under a flair after a few years of use, I have read that the vibrations of an engine cause the tube to work harden and become more brittle with age and eventually crack.

Every factory line I have seen was steel.

Also, I think there is a note over on the web site about the fule fittings on the engine and gascolator being automotive flare (degrees) and not AN from the factory. Some planes could still be this way and some could be converted to AN. There was a flex line that the factory used that I think was unique and and a supplier for this was mentioned in the note.

In cases where small diameter tube has been used for oil pressure (1/8?) you might think about changing it every so often.

Just my thoughts, I am not an AP, make your own decisions.

bob,.

[ROllerton]

Re: copper tubing gas line?

Copper was used for repairs for fuel and oil pressure lines here and there on trucks, cars and tractors. In every case I can remember the lines would crack some where along the run, or under a flair after a few years of use, I have read that the vibrations of an engine cause the tube to work harden and become more brittle with age and eventually crack.

Every factory line I have seen was steel.

Also, I think there is a note over on the web site about the fule fittings on the engine and gascolator being automotive flare (degrees) and not AN from the factory. Some planes could still be this way and some could be converted to AN. There was a flex line that the factory used that I think was unique and and a supplier for this was mentioned in the note.

In cases where small diameter copper tube has been used for oil pressure (1/8?) you might think about changing it every so often before it cracks in flight and makes a mess of your new white bucks. I see a lot of trucks with oil sprayed all over under the dash and floor.

The caution on the glass jar was that a rock might be tossed up from the prop or wheel and strike the glass and crack it causing loss of fule and maybe a little bit of fire. I dont think this was specific to Taylorcraft but the fleet in general. Someone else might pitch in here and add to this, or better yet correct me.


Just my thoughts, I am not an AP, make your own decisions.

bob,.

[VictorBravo]

Re: copper tubing gas line?

Any "hard line" whether it be aluminum copper brass or steel would be subject to the same vibration and cracking. It's gotta go.

The line from the Gascolator to the carburetor should be at least 5/16" inside diameter, and a flexible hose assembly with firesleeve. In my humble opinion, you should be looking at an Aeroquip AE 466 hose assembly with integral firesleeve, dash-6 size, as shown on Page 122 of the new Aircraft Spruce catalog. Or, you should be using the dash-6 Aeroquip 601 Stainless hose with the Aeroquip Firesleeve added. One of those choices (although probably not cheap) would be your safest and most fire resistant hose. See whether your IA agrees, and take his opinion over mine if he doesn't.

The 5/16" ID is required for the 85 horse upgrade and it indeed makes sense. It would be cheap insurance on a 65 powered airplane, since it seems you have to replace the copper line with something as it is now.

Any IA worth his ticket would demand that you replace a solid copper fuel line to sign off the annual. A safety conscious IA might even red tag an airplane between annuals if he saw a fire hazard like that.

Have someone take a look-see under that cowl Mike. Sorry to be the bearer of bad news.

[mhorowit]

Re: copper tubing gas line?

Have someone take a look-see under that cowl Mike. Sorry to be the bearer of bad news.

Not bad for me!
But I think I will have to push my friend to get to a real A&P - Mike

[Robert Lees]

Re: copper tubing gas line?

glass bowl gascolator

...and what's wrong with these?

[M Jones]

Re: copper tubing gas line?

All good discussion again.

So, it's been a topic more than once, but what is the correct material and size for a line from a wing tank to the header tank? I'm still unclear about that one...

[gilligansae]

Re: copper tubing gas line?

My ship has an Aeroquip main fuel line as well as a fireproof steel-braid reinforced oil pressure line. However I have a copper primer line from the primer plunger to the intake spider that has some strain relief along its length (large radius bends, a couple of coils before it is restrained) and an aluminum primer line from the gascolator to the primer plunger. My IA told me these were acceptable for primer lines only. Is this true?

Jeff
N43294

[ROllerton]

Re: copper tubing gas line?

(I am not an AP/IA, and I dont really know what I am talking about)

While copper might have once been acceptable; Steel and Alum alloys are typically used from tanks, to valves thru firewall to gas strainer. From the ridged firewall/strainer across the flexible engine mounts to the shaking engine a flex line is used. I think originally this was a automotive type cotton reinforced rubber-ish hose. NAPA or Pep Boys? My Taylor A is this way.

Of course now days you would want something better that a rubber hose as Bill points out; a modern aeroquip or equiv hose, with an upgrade to a firesleeve. Any Aircraft hose shop can make this up to order. Watch those fittings, AN versus automotive.

I made a fast glance at the "acceptable Methods, Techniques and Practices" i have here (1988) and there is not much on this except to say to replace lines with what was there before....

Copper line from the primer pump to the carb sounds ok to me cause its only carrying fuel when you are on the ground pumping the primer. On the other hand the line that feeds the pumper should be looked at even though its under slight gravity pressure from the tank.



Hey Eric, what do you think?

[birdlegs]

Re: copper tubing gas line?w/ glass bowl gascolator

Tribe; my last AP/IA was a crusty, cranky, pragmatic old fart. And he never said a word about the glass bowl gascolator on my bird. However some of the plumbing I've encountered "will" be brought to the better standard. There's better products out now than back in '46. NO COPPER PLEASE

[VictorBravo]

Re: copper tubing gas line?

I would suggest a dash 5 or dash 6 rigid aluminum line with flared AN fittings from the wing to the main tank. I don't think is MUST be a dash 6, but if you're making one it sure wouldn't hurt to have the large size. I believe that it is mandatory to have a 3/8 OD and 5/16 ID from the main tank to the gascolator and to the engine for the 85 HP airplane. It sure makes sense even for a 65, but again I BELIEVE it is not necessary.

I would use the "versatube" from Aircraft Spruce because it is soft and easy to work with your hands. It is very low pressure tube (3003 Aluminum I think), but there is almost no pressure in this line at all. 'Spruce also carries a slightly higher pressure line material but it is harder aluminum. I think this big deal is that you can work the versatube by hand without needing a bender tool.

Either way I'd suggest the real AN 37 degree flare fittings.

As someone posted already, it was the fear of cracking that made the FAA shy away from glass gascolators. It's probably rare that they ever cracked, but it is conceivable.

[Len Petterson]

Re: copper tubing gas line?

Copper tubing comes anneled (softend by heating it after it is drawn)
If you have copper tubing attached to anything what vibrates( engines for example) the point were the flare is made will brake, for 2 reasons.
When the flair is made, the streching of the material work hardens the copper, now the vibration work hardens the copper some more and the flair will brake of from the tubing.
I belive if you have coper tubing from the wing tanks to the main, it would not be unsafe and possibly leagal as it may have been there from the factory.
But if your fuel flow is LOW from the wingtank to the main, check for corrosion internaly in the ends of the tubing. Aluminium and copper creates a galvanic element and corrosion of the weaker element will take place.
I can picture a white dot of aluminum oxide in the end of the coper tubing after some years, nicly restricting the fuel flow.
If the oil pressure line (1/8") if it is very old take a torch to it and annile the end of it agin if it is any reason can suspected to have vibrated excesivily.
A 2 turn coils after a attchment pint should make it last almost for ever.
Make shure the turns does NOT tuch leather straping/ties is need to hold them a part if what is the case. The size to material thinkness ratio in the small tubing makes it super strong, not so in larger sizes.
The fuel lines in my plane are aluminum, with all hoses being 3/8", the hoses are coverd with fire sleevs and the gas colector bowl is metal and the bow holing it up is safty wired! Note in Canada fluel lines has to have a minimun of 3/8" outside diameter. This equals a inside diameter of 5/16" +-.
Tubing is mesured od, pipe is id. ? If you change material thicknes you change the id of the tubing ( and the pipe but what is another story)
I reasantly read a story about a aircraft where a broken fuel line was discoverd during a annual, no leaks, the fire sleeve held the fuel! Good (and bad)instalation of the sleeve!
Len Petterson

[ROllerton]

Re: copper tubing gas line?

The main concern (IMHO) is that the tube gets work hardened from the tiny forceful vibrations that travel the length of the machine and over a long time take its toll. Flexing is seperate, but more expedient problem. I was told to not bother with rubber mounts or adel clamps as it would stil happen. I dont know if thats good or bad advice.

I installed a lot of 3/8 copper tube on trucks to run gas to a rear mounted pump engine one summer. Did a real nice job and used real store bought tubing clips and drilled neat bolt holes all in a straight line. I saved the precious bailing wire for my dads pickup repairs. And then replaced it all one truck at a time over the following 5 years.

[ROllerton]

Re: copper tubing gas line? (Glass Gascolators)

Say Glass Gascolator 3 times fast.

First, if glass was good enough for Henry's T and A, and V8, it ought to be good enough for a Taylorcraft!

I asked Mr. knowitall Doug Combs of Luscombe fame about this as it was a big issue over there. He has PMAs for some parts that you all might be interested in for said device. Here is what he said, your Milage may Vary:

There is no AD or blanket regulation which obsoletes the use of glass gascolator bowls or the la tour glass "tube" style gascolator. These are preferred by many pilots who seek to observe any contaminant that the screen/filter is separating from the fuel.

Obviously with the bowl usually located in the low point of the fuel system, it is usually low on the firewall, and can be damaged by rocks from the nose wheel, or churned up by the propeller when the airplane is nose low (like in nose wheel airplanes). Damage and leakage are a function of loose surface materials and a source that drives a rock or other item into a glass bowl at just the right angle to damage it.

Canadian regulations demand/strongly advocate the use of metal gascolator bowls since many strips and roads there are unpaved, they have lots of rocks, and pilots who routinely operate from unimproved strips. That is much less a problem in the lower 48 of the U.S.

I repeat that there has been no service letter or AD, and the issue is one's ability to observe the fuel contaminant, vs. the limited exposure to breakage of the glass gascolator. As you are aware, these old glass bowls are very thick, very damage resistant, and very difficult to damage, or even dislodge. It is likely that one person's opinion about the glass bowls has been er....embellished.

For those seeking a replacement Tillotson gascolator unit (or bowl), or someone seeking a Latour gascolator, and all of the gaskets one should replace at annual time, Classic Aero Support has all of these items in stock and ready for shipment at 480-650-0883. CAS also have Shinn-Firestone linings with rivets, and FAA PMA 3" BALL BEARING cable pulleys available to fit Taylorcraft.

You may reprint this on the Taylorcraft list, or elsewhere that is useful.

Doug Combs, Aviator and Professional Consultant on aeronautical matters.
Full classic support at www.Luscombesilvaire.info
Parts at www.luscombesilvaire.info/inventory.htm