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Braided line inspections/failure

fixnflyguy

Well Known Member
We all trust those SS braided lines and other flex hoses on our aircraft will seldom fail, and and give them all the standard inspections relevant to the yearly health check or when we have access. I, as an RV builder, A&P, and IA, got the wake-up scare this weekend that sheds some different light on the "normal" inspection. Here is the scenario.. I went to Fla to pick up and fly a recently purchased RV-4 home for a friend who is not yet checked out to fly it. The aircraft was recently condition inspected, regularly flown and didn't seemingly pose any threat to a 3 hour flight back to NC. After the more than normal walk-around pre-flight, I mounted up to depart, with the new owner and a friend standing to the side observing. Boost pump on, 3-4 blades and I get signal from them we have something coming out the cowling. Turns out it was fuel..alot of it, right on the exhaust. De-cowl and find the SS flex line from the carb to the fuel pressure indicator is nearly porous, and weeping out all over. It certainly is undetectable without pressure. This could have been a fireball ! I will add too my inspection criteria, all fuel lines will be checked with pressure applied, and periodic pre-flights will get the same with me not in the cockpit. It would never be seen by someone just going out to fly with no bystander...lessons learned every day. We did get it fixed, and the rest of the adventure home was uneventful...check/replace those flex lines!!
 
I once annualed a Champ that had a braided fuel line made out of washing machine hose. Needless to say it got replaced with the right stuff.
 
No heat marks or close proximity to the exhaust. I haven't done forensics on it yet, as its still in the plane. It is possible it was not compatible with fuel or the liner just deteriorated. Since the aircraft has a fuel flow transmitter installed, I capped the port and flew home without this line being pressurized. Its looks to be a well made line, with no obvious damage or deterioration.
 
Had a very similar thing happen to a buddy. When he was shutting down there was someone watching and noticed there was something leaking from the cowl. It was a braided line and I think just about the same location.

It very well could have been a fire.

Fly Safe.
 
Beware of using hoses which don't have a conductive lining in applications where there are high fuel flow rates. Static charge can build up and eventually cause perforations in the liner.

See Tom at TS Flightlines if you want the proper stuff.
 
I'd guess it was a "rubber" liner with a stainless braid. WE know that today's fuels, whether Avgas or Mogas have additives that attack the 'rubber" liner. Whether its neoprene, nitril, EPDM, whatever is in the fuels attacks it. Looks like heat cracks. So when the hose flexes, it leaks through the liner and out of the braid. NOT FUN.
For our purposes, teflon is the best answer---impervious to all the chemicals we see---in most anything. Hot grease, bio-chemicals, aerospace, automotive, etc.
Good catch Bill----
Definitely would have been a bad day.

Tom
 
Importantly, what type of hose (brand etc) and fittings were involved?

We embark on building and maintaining these aircraft; while in many ways they are stone-simple, often it's the simple things that can really bite us.

Thanks for offering up this learning opportunity.
 
I just replaced every fuel line from the fuel valve to the cylinders and all other fluid lines with the new molded internal fire-sleeved hoses from Tom at TS. The braided lines I took off were apparently original (2004). Finally got around today to looking at the old ones. From the open ends you can see cracking and general deterioration. Glad they are out of my 8!
 
The braided lines I took off were apparently original (2004). Finally got around today to looking at the old ones. From the open ends you can see cracking and general deterioration.

Thing is, though, this isn't any help to anyone without knowing WHAT TYPE of hoses they were, which manufacturer, date of *manufacture* (did they sit on a shelf for 10 years?), etc.

It'd be much more useful for people to post more info on the *parts themselves* when they find a failure or potential failure, so we can be better informed.
 
Problem is many of us didn't build them and the documentation we have doesn't show the brand, type, etc.. Sorry but there is no possible way for me to give you the information you are wanting. In my case, I could find NO documentation showing they HAD been replaced so, to be prudent, I changed them out. Peace of mind is worth the cost of some hoses.
 
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Yep, me too. I just ordered all new FWF hoses from Tom at TS for my new to me RV4. Nothing noted in the logbook about replacement and a couple of them looked like it?s been a while since they were new. Only 300 hours total time on the airframe and engine, but the years count. Replace those old hoses.
 
I have recommended Tom to the new owner at the time I found the problem. Doesnt really matter what my forensics may find. I posted this in the interest that everyone pay attention to ANY line no matter its origin, known or unknown. What's behind us is not as important as to what's in front of us.
 
It'd be much more useful for people to post more info on the *parts themselves* when they find a failure or potential failure, so we can be better informed.

You really should read the first post. The OP said he was helping a friend who just purchased the plane. How could he possibly know any details about the hose and it's installatoin.

personally, I appreciate the poster for sharing his experience.

Larry
 
OK----Generally speaking, because in experimentals anything goes ---within reason-- 'rubber' lined assemblies use reusable, field attachable screw on hose ends, verses the crimped collar style more commonly in use for teflon assemblies. YES ---there are teflon assemblies that use reusables--Aeroquip Super Gem series fittings--and a few others out there--Earls Performance, Russell, Goodridge, etc, but most of what you'll see is crimped versions.
The resuable type fittings generally are blue and red anodized aluminum for stainless braid rubber type, and gold or blue collars with black steel and blue aluminum nuts for cotton covered H8794 (Aeroquip 303) type hose. Aftermarket 'race car' hose and fittings can be most any color you want. So suspect 'rubber' when you see them.

The types of reusables that are assembled on the rubber hoses are NOT used on teflon. Various reasons why, but generally the threaded stem and collars are of a different ID and OD to be compatible with teflon. Part of that ID difference is in the hose itself. Take the same ID hose in teflon, Rubber (like 701) and 303, and the difference in construction is obvious. Thicker liner wall to enable a good working pressure, tightly woven stainless braid, and or a nylon and steel braid reinforcement with a cotton cover overbraid. All of that contributes to the working pressure of the hose. Teflon doesnt expand like a rubber hose, so the wall can be alot thinner, and witht the stainless braid the overal OD can be smaller. Similar or greater working pressures for the same sized rubber hoses.

Word of caution. Because we all are dealing in experimentals, what you see isnt necessarily what you get. We've seen some rubber lined hoses with crimped hose ends done by the local hydraulic shop. At the same time, we've seen teflon assemblies that were not using a conductive liner for fuel systems. It all about knowing what is acceptable and what is not. As a general rule, all teflon hoses should be conductive especially those where fuel is used. Brakes may be an exception because you arent moving brake fluid for consumption like fuel. Oils dont pick up a static electrical charge, but its still great practice to use a conductive hose. MOST industrial hose shops dont stock the conductive hose.

If there is any question, you can call us and we'll help you identify the assemblies.
Tom
 
Tom, what you describe is exactly what I removed. Blue and red fittings and rubber inner liner. In the hose I looked at today, after removing the reuseable fittings, it appeared the rubber liner had actually begun to separate from the casing. When I tried to pull on it with some forceps, the liner just kind of crumbled. Thanks again for your incredible help in getting my RV-8 up to today's standard. Your hoses, along with the new AFP boost pump, really make it a great set up AND it's one I can fly with confidence.
 
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Rob----I'm not blasting the 'rubber' lines hose. For guys that want to make their own assemblies, its a pretty easy way to do it. BUt we've seen that guys will build them and leave them on for years---until there is an issue---like Bill's.
At the same time, there are ways for guys to make their own teflon assemblies, using reusable hose ends. Earls has an excellent product, but by the time you buy a bunch of hose ends, hose and firesleeve, it would probably be less expensive both in cost and time to have them made and tested.

But for this thread, the question was identification. If you have a rubber lined hose, that has been installed for 5-6 years, It might be a great idea to really check them. In Bill's case, the plane may not have had many actual hours, and who knows when the last time it flew, but it certainly would have been a bad day if he had gotten airborne and had the issue.

NO easy way to sugar coat it---

Tom
 
Rob----I'm not blasting the 'rubber' lines hose. For guys that want to make their own assemblies, its a pretty easy way to do it. BUt we've seen that guys will build them and leave them on for years---until there is an issue---like Bill's.
At the same time, there are ways for guys to make their own teflon assemblies, using reusable hose ends. Earls has an excellent product, but by the time you buy a bunch of hose ends, hose and firesleeve, it would probably be less expensive both in cost and time to have them made and tested.

But for this thread, the question was identification. If you have a rubber lined hose, that has been installed for 5-6 years, It might be a great idea to really check them. In Bill's case, the plane may not have had many actual hours, and who knows when the last time it flew, but it certainly would have been a bad day if he had gotten airborne and had the issue.

NO easy way to sugar coat it---

Tom

Tom,

I used aeroquip FCA rubber hose and Earls fittings for my fuel lines, as I could not source conductive teflon. What should I expect for usefull life on this hose, assuming 100LL?
 
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Many years ago, while doing an annual on an Aerostar, we found some oil seeping from a hose -out the end of a firesleeve. It mystified us and we investigated.

We cut the clamps and slipped off the firesleeve. The braided hose underneath looked *perfect*. We then plugged the hose and applied shop air at 50psi (as I recall) and submerged it in a tray of solvent in the parts washer (convenient). Air bubbled out *all over* the hose through the pretty stainless braid. Wow!

We determined that all the hoses were about the same age (and I'm not sure we conclusively determined what that was exactly) and the long story short is that we found them all in a similar condition -some a little worse than others. Some started leaking after being flexed. None stood up to the pressure test.

I believe (guessing) it was Aeroquip 601 (?). Been a long time.

None of this stuff lasts forever.
 
Had a sneaky one last year

We all trust those SS braided lines and other flex hoses on our aircraft will seldom fail, and and give them all the standard inspections relevant to the yearly health check or when we have access. I, as an RV builder, A&P, and IA, got the wake-up scare this weekend that sheds some different light on the "normal" inspection. Here is the scenario.. I went to Fla to pick up and fly a recently purchased RV-4 home for a friend who is not yet checked out to fly it. The aircraft was recently condition inspected, regularly flown and didn't seemingly pose any threat to a 3 hour flight back to NC. After the more than normal walk-around pre-flight, I mounted up to depart, with the new owner and a friend standing to the side observing. Boost pump on, 3-4 blades and I get signal from them we have something coming out the cowling. Turns out it was fuel..alot of it, right on the exhaust. De-cowl and find the SS flex line from the carb to the fuel pressure indicator is nearly porous, and weeping out all over. It certainly is undetectable without pressure. This could have been a fireball ! I will add too my inspection criteria, all fuel lines will be checked with pressure applied, and periodic pre-flights will get the same with me not in the cockpit. It would never be seen by someone just going out to fly with no bystander...lessons learned every day. We did get it fixed, and the rest of the adventure home was uneventful...check/replace those flex lines!!

Bill,
I had an oil leak that I could not find, despite really looking for it.
It got progressively worse. Finally with the help of some RV'ers at my field discovered the stainless steel line from the prop governor to the prop had been rubbed and was the source of the leak.

Tom build a beautiful fire sleaved replacement.
Solved.

Daddyman
 
Wow

I'm a novice to AC engine work but it looks to me that anyone who doesn't know the 'pedigree' of his/her fuel lines should seriously consider a compete removal of said fuel lines and verify if they pass a thorough and complete inspection. As said above, it's the little things that can get you but in my opinion, this is not a little thing.

Having said that, can anybody tell me what the composition of factory new ROTAX 912 ULS fuel lines is? I have a new 912 ULS. Maybe I should replace the fuel lines before first start? Rotax says to replace the fuel lines in five years. I will pull and check my fuel lines before first engine start. I think that this is one of those things that go with flying - "if you can't afford to do it right then don't do it al all". Sell your AC before you kill somebody.

Tom???
 
...can anybody tell me what the composition of factory new ROTAX 912 ULS fuel lines is? I have a new 912 ULS. Maybe I should replace the fuel lines before first start? Rotax says to replace the fuel lines in five years.

If you have a Rotax with S/N 6781191 or higher, all the fuel lines are Teflon and are not subject to the five year rubber replacement cycle. The Rotax part numbers on these Teflon hoses are 874337 and 874347. For more information refer to SI-912-020 R10 and the heavy MM.

FYI, the VA-213,VA-214 and VA-215 oil lines are Teflon too, as is the VA-216 fuel return line.
 
Ed---Mike got to this before I did. Still----CHECK the hoses. Just because its teflon doesnt mean its conductive. (Email me)
Larry---Aeroquip FCA hose has their 'elastomer' liner. Now understand their 'performance' racing hose isnt Aviation hose. I'm NOT a chemist, so I dont know the additives in the different fuels, but I would carefully check the hoses often, and replace at least at the 5 year mark. Who knows the actual life expectancy of a non tested hose with AVGAS, that wasnt approved for it.

As you found out, not alot of 'race car' parts suppliers carry conductive teflon. Most industrial shops dont either. (And if you ask for it-they should know EXACTLY what you are going to do with it.) Earls has an aviation disclaimer for its Speedflex hose as do most other non-aviation hose suppliers.

Check fuel filters often-it will start as discolored fuel, then little pepper sized bits. You get the idea.

Tom
 
I am curious what the weight difference might be on standard lines verses high quality stainless braided lines. Is it significant?
G
 
George, I think Steve actually did a weight comparsion of a firesleeved teflon hose and a comparible length rubber hose. Dont know the actual details off hand, but I'd bet the teflon assemblies are lighter.

Tom
 
Parker 919B hose ("B" is important) is conductive teflon with stainless overbraid. Compatible field-installable fittings are Parker 90 series; they are typically plated steel in a variety of configurations. Mentioned only for those who are determined to make their own hoses.

I have made many with that stuff, though all for automotive applications. As Tom pointed out, by the time you add firesleeve, and if you value your time greater than zero, you are probably better off buying pre-made hoses from him. Which, having done so, has always been a positive experience. And it pretty much guarantees you won't stab yourself with errant strands of stainless steel wire :rolleyes:
 
Lars---MOST good domestic industrial teflon hose manufacturers have optional conductive liners. Most shops dont carry it, because in industrial applications its rarely needed. Back in my industrial days, we had it because we built fuel hose assemblies for automotive and marine applications. So instead of having both types, we had the conductive liners in -4 through -10.

Yes the 919B/929B are excellent hoses.

Tom
 
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