What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

DIY Braided fuel lines?

I appreciate the vote of confidence.

The link is to pre-made hoses constructed of Earl?s Speed-Seal braided hose with aluminum fittings, both crimped and pressure tested - to the same pressures I believe you stated. Perfectly adequate for the installation.

And if you?re saying that only steel or stainless steel fittings can be used, then Beechcraft needs to have their type certificates pulled as nearly every fitting on my Baron is a ?D? fitting (aluminum). The only steel ones in the IPC called for are on the lower brake hose that connect to the caliper.

This thread is a perfect example of how easy it is to get confused about all the different options out there. Hoses may look very similar on the outside, but there can be huge differences on the inside. There is no reason for anyone to be defensive about their choices. There is nothing wrong with building your own hoses......lots of people do. It is, however, very important to distinguish fact from fiction so informed decisions can be made.

1. Speed Flex hose and Speed Seal Reusable fittings are high quality and come in Aluminum, Steel and Stainless. Certified hose manufacturers typically use SS or CRES for -8 and smaller size hose.

On our pre made assemblies we choose to utilize stainless on our -8 and smaller assemblies for quality and longevity even though it is more expensive than aluminum. For -10 and larger size fittings we utilize Aluminum hose ends. This creates a pricing structure that is very similar to the cost of a high quality do it yourself hose.

2. There is nothing wrong with Beech utilizing aluminum fittings. Every manufacturer has the leeway to specify what their engineers feel is adequate for the job. The Baron is a great plane. We utilize aluminum fittings also in our larger size hoses because it is the most appropriate material for the application.

3. Pressure testing to 150PSI is a good leak check. It is not a good "proof" test. There is a difference. With that said, mechanics have assembled 303 hoses for years with the only leak check being a functional check once it is installed on the aircraft.

4. Like many manufacturers, Earls has a variety of different products at differing qualities for different applications. The link provided for pre-made hoses is not the same quality of components as some other products that Earls offers. It is a low cost option. As such, the components are manufactured differently.
 
I have always enjoyed assembling 303 hoses, new or replacements, using the official assembly mandrels and proper assembly lube. Then followed by the old compressed air blow through test to check for a rubber "flapper" blockage. Never pressure tested.

I had a staInless braided fuel line on my Nanchang leak like a soaker hose just like the video linked to in previous post here. But worse. Ugly. The previous owner had assembled his own hose from hotrod supplies. The hose looked great on visual inspection but was a pasta collander pouring out fuel the full length. A contributing factor was the aircraft used metric fittings with non-standard flare angles which gravitated one towards the hotrod and industrial hose side. This fuel leak was scary stuff and I decided then and there that I wouldn't use any of the stainless braided fuel hose or shiny faux AN fittings from automotive suppliers. The fittings may be the proper dimensions and flare angles to match AN sizes but some appear to be cast prior to cleanup and anodizing. And there is no mention of alloys used.

I still make my own 303 hoses if I am reusing end fittings, but have switched over to TS Flightlines for new assemblies. I just did the firewall forward on my RV-8 and mailed the old hoses to Tim and company for replacement. I am very satisfied with the quality and fit. A side benefit is they are asethically pleasing to look at. If I were doing a pre-purchase inspection on an RV with these hoses in my opinion I would expect it to enhance the resale.

I do have a bit of pause based on the Teflon taking a set over time and the potential for an unitiated owner and/or mechanic to flex or crack the Teflon lining if inspecting the hose the same way they have traditionally done with rubber.

Jim
 
Jim---need metric hose ends for your Nanchang? Well this isnt RV related, except the fact that Vans uses a Rotax in the RV12s, and it does in some cases use metric fittings. SO maybe the moderators will give me alittle leeway here.
One of my pet projects was to design hose ends for both teflon and H8794 (303/111 common hose) in aviation metric. Believe it or not, its NOT the same as the industrial versions we see on a regular basis. YEP---minor differences in the ball head, but its enough to have a potential issue.
Because of our work with Rotax and a few European Warbirds, Steve and I decided to work on a metric set of hose ends to fill the void. Long story short, lots of research and samples back and forth from Germany, pictures and specifications from the Smithsonian, and some OE metric hose ends from Rotax, we have designed metric DIN hose ends for teflon hose. Have a few prototype samples under lock and key with an armed guard. Dont have them all other than drawings done, but we started with -8, (18mm) because it was common to Rotax and their European oil tank. WE 'may' produce these in volume, IF we can justify the expense by sales volume.
OH----the other thing I was going to do--is produce the hose ends in a reusable version for modern H8794 hose thats common around the world. With everything going on-I put that away for a while.

OH---if someone has a 'special' situation (dont know why) and needs a 'creative hose end' solution, let us know.

Tom
 
I disagree with you. ASME B31.1 is a consensus standard to test pressure systems, and as I said previously, the recommended test pressure is to 150% of the system operating pressure.

Dude, you're in defensive mode rather than in learning mode. For starters, ASME B31.1 is a standard for industrial piping....it has absolutely no relevance whatsoever to flexible aviation hoses.

This is what Tom Swearengen of TS Flightlines has to say on the topic: "Pressure testing....slightly more involved than just a leak check at 120psi under water. You want to take it to the rated working pressure OF THE HOSE, then a safety margin."

And this is what Steve Tschurwald of Aircraft Speciality has to say: "Regarding pressure testing...a 150psi pressure test will give peace of mind, but will not serve as a proof test for the fittings. We could crimp a hose that would hold at 150psi that would fail over time under under normal operating pressures and vibration."

Now maybe these people who are actually making a living out of fabricating aviation hoses might just know a thing or two.

Personally it doesn't worry me one bit if you do not want to utilize aviation best practice in pressure testing your home-made hoses, but it does worry me that you might encourage other builders on VansAirforce to adopt a fundamentally unsafe practice.
 
Personally it doesn't worry me one bit if you do not want to utilize aviation best practice in pressure testing your home-made hoses, but it does worry me that you might encourage other builders on VansAirforce to adopt a fundamentally unsafe practice.

Back in the day, most all of us built our own hoses, and even now, many people still do. I don't remember any failures from improper hose assembly.

I think TS Flightlines and others in the hose business are providing a very useful service and a high quality product, but I (and presumably others) have used them out of convenience, rather than because of demonstrated safety concerns over DIY hoses.
 
I have built all sorts of hoses and have a pressure test setup I fabricated with an old bottle jack and pressure gauge. You'd almost have to be brain dead to misassemble an Aeroquip 303 hose and 491 fittings. The majority of certified aircraft fly with 303 hose so its nice to stock just a few sizes of hose and reuse the fittings. New 303 hoses are very flexible and I believe these hoses transmit the least vibration to the airframe for fuel and oil lines connected to the firewall or engine mount, when compared to stainless braided lines. I have used stainless braided lines on my airplanes but they're heavier and overkill.

A few weeks back I found a truck air brake line lurking under some firesleeve for the fuel line on a Cherokee 6. That got replaced with 303 in a heartbeat.
 
Last edited:
I have built all sorts of hoses and have a pressure test setup I fabricated with an old bottle jack and pressure gauge. You'd almost have to be brain dead to misassemble an Aeroquip 303 hose and 491 fittings. The majority of certified aircraft fly with 303 hose so its nice to stock just a few sizes of hose and reuse the fittings. New 303 hoses are very flexible and I believe these hoses transmit the least vibration to the airframe for fuel and oil lines connected to the firewall or engine mount, when compared to stainless braided lines. I have used stainless braided lines on my airplanes but they're heavier and overkill.

A few weeks back I found a truck air brake line lurking under some firesleeve for the fuel line on a Cherokee 6. That got replaced with 303 in a heartbeat.

Bob,

You're absolutely right that a lot of certified aircraft utilize 303 hose. A lot are starting to migrate to Teflon as the standard on many new installations now also.

https://www.lycoming.com/content/engine-hoses

"Lycoming has phased in Teflon hoses with silicone-coated fire sleeves. These are the only hoses which are available for field replacement, and they will be found on engines shipped from the factory." - Quote from link above.

303 is an ok hose and was the standard for a long time....but it is definitely NOT lighter than stainless braided teflon hose. a -6 303 hose has a weight of .228lbs/foot. Conductive Teflon hose is slightly less than half that weight and a lot less bulky.

The minimum bend radius on 303-6 and the conductive Teflon -6 hose we use is the same at 4".

The OD of the Teflon hose is less than .45" whereas the 303 hose is .672. That is due to the much thicker wall on the 303 hose.

Again, there is nothing wrong with 303 hose, but it is heavier and bulkier than conductive Teflon with a much shorter life.

A truck air brake line huh? I'll add that one to the list of interesting stories we have heard. :) Sadly it's not anywhere near the craziest.
 
Last edited:
Dude, you're in defensive mode rather than in learning mode. For starters, ASME B31.1 is a standard for industrial piping....it has absolutely no relevance whatsoever to flexible aviation hoses.

Personally it doesn't worry me one bit if you do not want to utilize aviation best practice in pressure testing your home-made hoses, but it does worry me that you might encourage other builders on VansAirforce to adopt a fundamentally unsafe practice.

Good engineering practices are applicable regardless of whether the hose is in a pipe rack, buried underground or flying in the air. For the record, a hydraulic hose operating a servo at 8,000-10,000 psi on a 170MW GE 7FA gas turbine turning a 120 ton rotating generation assembly at 3600 rpm has a much more exposure to vibration and higher energy forces than an oil line on an IO-540. BTW, those hydraulic hoses are tested to 150% of operating pressure as well, meaning 15,000 psi. It's not unsafe.

What concerns me is that there are people, based on the statement above, who clearly do not understand the engineering involved and create an environment of fear, uncertainty and doubt within a community where education, knowledge sharing and encouragement should be the hallmark.

I have no issue with being called defensive - I am defensive against misinformation, group thinking and the "it's what we've always done" mentality.

It's apparent that there are many people who prefer not making their own hoses and many who want to do it themselves - with drivers being everything from tooling, skill, money, time, fear, and many more I'm sure... (the basis for my statement previously regarding "never ending debate"). But rather than tell folks NOT to do it themselves and dissuading people, instead, let's pursue the design parameters, performance requirements and processes to let people decide how to proceed without impugning their decisions.
 
Back
Top