Why did this fuel line produce debris?

[Ed Cesnalis]

The problematic hose has been Gates Barricade Fuel Injection hose. This hose has 5 layers:

1. Tube
   
2. GREENSHIELD® BARRIER
   
3. ADHESION LAYER
   
4. REINFORCEMENT
   
5. COVER
   

 

This line produced debris because it does not have a smooth inner wall. In the photo you can see the reinforcement layer when you look at the inner wall of the tube. The cross hatching isn't visible through 3 layers what shows is a rough texture. The opening is not a circle but instead a circle with a bunch of steps created by the strands in the mesh layer. When this bumpy inner walled fuel line is inserted over a barbed fittings the bumps are shaved off resulting in rubber debris contamination.

 

 

The hose below had been in service for 11 months and removed to check its condition. Smooth inner wall hose like this does not have the reinforcement / mesh layer showing through the inner wall and a barbed fitting isn't likely to shave it smooth.

[Doug G.]

Thank you for this, Ed. It is surprising how much it often takes to have people and companies do the right thing.

[Ed Cesnalis]

Hi Ed,

 

I don't think the fuel injected hose you got from CPS was Gates fuel injected Barricade hose. I think it was another type. If I remember right that some of the hose that old CPS had was made in the US and China.

 

Here's a photo of the hose I got from CPS. It has "Gates Fuel Injection ... Barricade" printed right on the hose.

 

[Doug G.]

If I understand what you are saying, Roger, is that you believe CPS changed hose types without input from Gates, Rotax, FD, or anyone else that knew the hose was unsuitable. They just did it!

[Ed Cesnalis]

I asked gates about the rough texture on the inside of their hose, because when that texture is apparent it is very easy to cause damage with a barbed fitting.

 

 

Ed,

As you mentioned, our fuel line hose is designed with a spiral textile reinforcement to help provide resistance against internal pressures. The visible amount of “texture” may vary between hose types, ID’s, and manufacturing runs, but still be within specification and not affect the performance.

 

Regarding ROTAX, please see the attached Alert Service Bulletin dated May 31, 2012. Since Gates does not support aviation applications, I would suggest that any Barricade hose be replaced. BRP/ROTAX should provide any further direction.

 

Hope this information helps.

 

Regards,

Mark

 

If visible texture results in likely damage but does not result in the hose being out of spec then it would explain the hose getting a clean bill of health while it still causes us grief. Variance between manufacturing runs could explain intermittent results.

 

Look at the reason for the Service Bulletin:

 

1.3) Reason: Due to variations in manufacturing of the fuel hose, rubber particles may become detatched.

 

Read that reason carefully, Rotax came to the same conclusion that I did.

[Ed Cesnalis]

...the hose that Rotax had all the problems with in the new corona pump (ASB-912-061) was Gates Barricade greenshield! It was a batch problem though, the hose is good...

 

That is the whole point, the hose is good, but there is/are batch problems/variances [texture] that results in rubber particles becoming detached [shaved off]

[Ed Cesnalis]

Hi Ed,

 

Bottom line is nothing we can do about it, but use due diligence as an owner and mechanic. It can be any hose on the market that any body supply's. Nobody is immune. It isn't this answer that many want to hear, but it is all we have to work with in reality That's why it does pay at times to shop for parts and even more important at time the mechanics knowledge of that particular subject.

 

I could not disagree more Roger. Virtually every one of us received a new CT free of rubber debris in our fuel systems. A demonstration that the contamination is unnecessary. Tom Baker uses OEM hose and no problem there (one small exception at the fuel pump, and admittedly a small sample)

 

Lockwood has gone to Tecnam's OEM hose, it has a smooth substantial inner-wall. This change completely eliminated the rubber debris issue that they experienced when they used Gates hose. I just skimmed these threads again and there is a truly alarming number of incidents reported, the common factor being gates hose, barricade and not, fuel injected and not. Gates hose from CPS or from NAPA both result in damage if I insert a barbed stem. Gates admits there is variance in their inner wall (the part that gets damaged.)

 

Roger there are 2 things we can do about it.

1. Use OEM or other proven fuel lines - Stop using, marketing and selling Gates hose for CT fuel line replacement, it isn't OEM, it isn't equivalent, its inner wall varies.
    
   
2. Use appropriate beaded stems with flat landings - there is no good reason to apply sharp cutting edges to the inside of our rubber fuel lines.
   

[Jim]

Ed is right. If the fuel line was defective, someone needs to take responsiblilty. If the fuel line was an incorrect application, someone needs to take responsibility. If the fuel line was installed incorrectly, someone needs to take responsibility. If the fuel line replacement procedures were incorrect or nonexistant, someone needs to take responsibility. If there is less risk to do a 5 year condition inspection than a wholesale replacement, that should be changed too. Do you see a pattern here? I'll tell you what it is. Ed didn't do anything wrong. One or more other people did.

 

My opinion is this: First of all, the hose replacement should have been done on a condition inspection. If a condition inspection is good enough for Beech and Cessna, it's good enough for me. The old hoses that were removed from my aircraft were in good shape. Five years from now, on my airplane, it will be a condition inspection. If my A&P won't sign it off, I'll take the airplane to experimental. All of this could have been avoided with a condition inspection.

 

Has anyone addressed Ed's question about whether or not the Gates hose was a proper application? I don't recall seeing an authoritative reply.

 

Now on to the big question in my mind. Is there a replacement procedure for the hose? Specifically, is there clear instructions that the hose must be flushed, blown or otherwise cleaned after the fittings are installed? That this must be done is common knowledge amongst the certified and experimental people. If it were done and it was obvious that the hose was shedding chunks of rubber, it would be a giant red flag.

[S4Flier]

Not touching culpability for Ed's hose issues but Rotax isn't alone in the rubber replacement service.

 

If a condition inspection is good enough for Beech and Cessna, it's good enough for me.

 

If those Beech, Cessna (or anyone else) are powered by a Lycoming then they have a similar replacement service. The latest maintenance manual is a bit more stringent than Rotax:

As airplanes and engines attain age, there appears to be a need to reemphasize the inspection or replacement of engine hoses or lines carrying fuel, oil or hydraulic fluid. The hose manufacturers definitely recommend regular inspection and replacement of all such hoses at engine overhaul even though they look good. Age limit of rubber-steel or fiber-banded hose has generally been established at four years. This limit of four years is generally considered to be “shelf” life.

 

..........

 

 

Lycoming Service Bulletin No. 509 must also be complied with if rubber hose is used to carry low-lead aviation gasoline. Aeroquip, the manufacturer of hose used by Lycoming, has recorded several failures of 601-type rubber hose. Although it is satisfactory for other purposes, this hose appears to be adversely affected by low-lead aviation gasoline. 601-type rubber hose used for low-lead aviation gasoline is to be replaced after no more than two years of use. Aeroquip and Lycoming recommend that rubber hose be replaced with Teflon hose

[Jim]

I'll make my reply nice and simple, Roger. I've owned my own company for 18 years. We design, build and ship electronics. We've made lots of mistakes in those 18 years. The vast majority of those mistakes are fixed long before a faulty product reaches a customer, because our employees are taught from day one that their first duty is to fix problems as soon as they are identified. My standard spiel is that it costs $2 to fix a problem in engineering, $20 dollars to fix it in production and $200 to fix it after the customer receives it. Nobody gets punished for identifying a mistake, whether it's their's or someone else's.

 

If a customer believes we shipped him a faulty product, we investigate immediately and we *fully* disclose what we know to the customer. If it's our fault we make it good. That might involve shipping good product overnight at our expense, giveing them a discount on their next order, or simply saying we're sorry and that we screwed up. Whatever makes it good. And then we make sure that the problem doesn't happen again. That usually involves training or better documentation. And we usually go back and tell the customer what we did to make sure it doesn't happen again.

 

Simple rules. At the very least, Ed, and all the other Rotax owners that are in a similar situation deserve to treated as fairly.

 

Finally, I really have to emphasize that there needs to be a written procedure to clear out any debris after a hose replacement. I wrote an email to John Gilmore two or three months ago advising him of this. He agreed, but I'm not sure there was any follow through. Your comments about researching turning up all kinds of information doesn't do Ed any good. Rotax has been selling 912's and Flight Design has been selling aircrafts for year and should have the common sense and corporate responsibility to give the maintenance people all the info they need to do a job properly.