3003 vs 5052 aluminum tubing

[Big Ed]

Pretty sure my Bellanca fuel lines are 5052 aluminum, which is the more rigid alloy. It comes in straight lengths of 6 or 12 feet. Most of the old school docs I ran across advise 5052 for fuel lines because it is harder.

Just conversed with Chad and he said ACA uses 3003. That is the softer tubing that comes coiled and is straightened before use. He said it was easier to work with. So if I ordered PMA parts from ACA I would get 3003.

I trashed a few of my lines while stripping the frame. Thoughts on which material would be preferable? Seems like I could make a legal case for either.

From a practical perspective, 5052 seems harder to bend and less tolerant of imprecision. OTOH I read somewhere that the softer stuff was actually harder to flare.

 

[Bartman]

I bought the coiled tubing, it was easy to work with and flared nicely. If you look at photos of factory airplanes, the tubing all looks hand bent and working it through the frame in places, it needs to be bent in place.

having said that, when we did the Citabria, I bought lengths of the rigid stuff for a few of the lines from the tanks in the wings but it lent itself better to that application I guess.

 

[Big Ed]

I took a closer look at the old lines today. They are not marked. I assumed they were 5052 but not so sure now. The longer pieces are waavy in between bends, like they were straightened rather than being bent from straight pieces.

You mentioned in an old Facebook comment that the versatube you bought did not seem to match the old lines. Do you still think that?

The main 1/2" line from the manifold to the header tank is 10 feet long. Lengths longer than 6 feet require truck shipment, which I assume is expensive. Aircraft Spruce East is an 8 hour drive from here, but it is on the way to my mom's house, so I could combine the trips.

 

[Bob Turner]

Do a bit more research. With copper (used on older birds) the accepted procedure was to anneal it after a while. Harder materials crack quicker. Not sure why the harder aluminum line would be better in an environment characterized by vibration.
I will try to look it up.

 

[Bob Turner]

This is from "tubingchina dot com" - who knows? But it is a start. "Dash O" is dead-soft.

Most tubing failures on aircraft are caused by fatigue. You are warned that this chart does not compare fatigue strength. Tubing on aircraft vibrates. How well your tubing endures when subjected to load reversals, impulses, and vibration is called "fatigue strength". Of the three tubing types shown in the chart, 5052-0 has the best fatigue strength.

Originally aircraft used soft copper tubing. There is even some of this still around. Although copper was strong enough, it was replaced with aluminum and stainless steel because of the the high fatigue failures of copper. For lower pressure, 5052-0 became the tubing of choice because it has the best fatigue strength of any of the non heat-treat aluminum alloys. Copper tubing on older aircraft should be removed and replaced with 5052-0 before it breaks. There is no warning when copper tubing breaks. One cannot "inspect" it and declare it ok.

Some experimental and light-sport aircraft have hydraulic and fuel lines built with 6061-0 or 3003-0 tubing. Low ultimate tensile strength and low fatigue strength provide a narrow safety margin in dynmic (vibration or impulse) applications. Take extra care in clamping and preventing tube vibration. The aircraft industry's long experience with copper tubing failures proved the importance of fatigue strength. 5052-0 has higher ultimate tensile strength and higher fatigue strength at small price difference. Both 5052-0, 3003 have the same cold work ability Rating of A (easy to work with). 6061-T6 has a far lower rating of C.

 

[Big Ed]

Most of the internet resources I have run across say that 5052-O is the norm for fuel lines on certified aircraft.

However, the current ACA factory spec is 3003-O. Chad says they tried 5052-O and decided it was too hard to work with.

That's why I'm curious about what the old Bellanca and Champion aircraft use. If they also used 3003, then that is a pretty good lifespan without a record of failures. 50+ years vs 30.

 

[Big Ed]

The only issue is the 1/2" line from the manifold to the header. That is 9.5 feet long. Spruce sells 5052 in 12 foot lengths, but requires truck shipment at additional cost. Or I can drive 8 hours to Atlanta and pick it up, and visit family while I am there.

All of the other runs are less than 6 feet, so 5052 and 3003 are equally available. The local parts store has 5052 in 6 foot lengths, and I can order any length of 3003 from Spruce.

 

[Bob Turner]

But can't 5052-0 be coiled? Hard 5052 (say, 5052-T3) cannot be, but I would stay away from hard line. "airparts" says they will roll up 12' lengths for shipping.

Aircraft and Vintage camper building supplies - 5052-0 Fuel And Hydraulic Tubing

5052 is the highest strength alloy of the more common non heat-treatable grades. In this '0' condition, the 5052 is soft and workable, for fuel line, hydralic line, and brake line. The ends are flared and fittings attached to make the type of line that you want. Fatigue strength of 5052 is...

www.airpartsinc.com

 

[Big Ed]

But can't 5052-0 be coiled? Hard 5052 (say, 5052-T3) cannot be, but I would stay away from hard line. "airparts" says they will roll up 12' lengths for shipping.

Aircraft and Vintage camper building supplies - 5052-0 Fuel And Hydraulic Tubing

5052 is the highest strength alloy of the more common non heat-treatable grades. In this '0' condition, the 5052 is soft and workable, for fuel line, hydralic line, and brake line. The ends are flared and fittings attached to make the type of line that you want. Fatigue strength of 5052 is...

www.airpartsinc.com

From what I've read, it "can", but each coiling and uncoiling weakens it. I will look closer at Airparts, however. That might be an option. Since I have the old run, I could measure the exact length and have it fabricated.

Other than the 9 foot main run of 1/2" tubing which I cut to remove, and one section of 3/8" which a bent, all the rest of the tubing is intact. I figured since I was refurbing the fuselage, it made sense to replace all the lines. 45 years is a lot of vibration. But reusing some or all of the other lines is an option. I could replace the 3 year lines that are difficult to access with the cover on, and reuse the stuff forward of the panel, which can all be easily replaced later.

 

[Sully]

Short of possible leaks there is no reason you could not use a union to "repair" the longer run of tubing.

 

[Big Ed]

Short of possible leaks there is no reason you could not use a union to "repair" the longer run of tubing.

Other than that, Mrs. Lincoln, how was the play?

 

[Sully]

I have never had a repair by union leak but there is always a possibility.

 

[Big Ed]

I have never had a repair by union leak but there is always a possibility.

I considered joining 2 shorter pieces. It actually would make more sense. As currently designed, the long run is captive in the frame by sharp bends at each end. The only way to remove it from the frame is to cut it or bend it straight. A union in the middle would make it easier to service.

However, not sure whether that would conform to the type design or not, since the parts list shows the line as a single part (#6). The less departures my IA feels like he as to explain on the 337, the easier this is going to go and the less it is going to cost me.

 

[Bob Turner]

Check 43-13 for either approved data or indications that such a repair/installation is minor. I suspect a union is truly a minor repair, but if it is not, then surely it is a minor alteration. No 337 needed for the union. Opinion.

 

[Joe]

Opinion. 5052 has slightly better corrosion resistance. Either 3003 or 5052 in a soft -0 condition is likely sold in rolls. I would avoid anything harder than a -0 unless ACA had spelt it out (more difficult to flare without cracking). Your original tube was likely 3003 and lasted 50 years without incident or need to be removed for service.

 

[Big Ed]

Opinion. 5052 has slightly better corrosion resistance. Either 3003 or 5052 in a soft -0 condition is likely sold in rolls. I would avoid anything harder than a -0 unless ACA had spelt it out (more difficult to flare without cracking). Your original tube was likely 3003 and lasted 50 years without incident or need to be removed for service.

Most sources sell 3003 in rolls and 5052 in straight lengths of 6 feet. Spruce sells 12 foot lengths.

Current ACA spec is 3003, but they told me they changed it from 5052 at some point because of ease of working with it and shipment.

I would like to know what my original tube is. The static line is very soft and pliable, while the fuel lines are stiffer and harder. Therefore I am surmising the static line is 3003 while the fuel line is 5052. I am going to buy a length of 5052 type O from the local parts store for comparison.

Bart, how easy is it to bend the 3003 in 3/8" diameter by hand? I can bend my 3/8" tubes but it takes some force and is easy to kink, while the 3/16" static line is like a noodle and can be bent with fingertips.

Interestingly, the line from the manifold to the drain is copper, and recent ACA photos show same. I wonder why the difference?

 

[Hiperbiper]

5052 0 is rigid and I've never seen it sold rolled...
3003 is soft by comparison, easy to roll, bend and shape. Easy to tell the difference side by side...if you can make a 90° bend in 3/8" or larger tubing by hand it ain't 5052.
5052 requires forming tools and benders. 3003 can be formed with your hands, a spring bender or with a tubing bender. Both require flare tools.
5052 is much less tolerant of reshaping and will crack and fatigue if worked too much. 3003, being much more pliable, can be re-shaped to a much greater extent. 5052 is much harder to abraid which is one reason it was used so widely; properly moored and protected from the elements it will outlast any airframe...
The Navion I restored had the original hydraulic, oil and fuel lines in it...since 1946! Though the nomenclature has changed it is/was 5052 tubing.
And yes, repairing a low pressure fuel line using a proper union, nuts and ferrels is perfectly acceptable...higher pressure lines (hydraulic) might be a different story. See your maintenance manual for details...
Chris

 

[Big Ed]

I picked up a 6' length of 3/8" dia 5052 today. Will compare it to the stuff that came out of my plane tomorrow. I suspect the old lines were also 5052.

 

[Eric Brown]

Gentlemen;

Just as a reference, Champion fuel system installation drawing 7-1102G (5-1964) specifies .035" wall thickness 3003-0 tubing for all of the fuel system tubing. The 5052-0 1/2" tubing can be bent into a large loop - enough to put in your car for transport - and then be straightened for your application. I've done it.

 

[Big Ed]

I've hatched a plan. Am headed to Atlanta this weekend to visit family. Will drive by Spruce on Saturday and pick up tubes on will call. Measured my car and I can fit 11 feet straight line if I drop the rear seat. Need 9.5 for the longest run, so that should work without bending.

I know Bellanca beefed up various areas when they designed the Decathlon. Wonder if changing from 3003 to 5052 was part of that?

Most of the lines are well supported by structure. However, the main 1/2" run from the manifold to header tank has a couple of longer spans where it is hanging in space, particularly the section from former #1 to the steel bulkhead at mid cabin.