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Roger Lee

Rubber hose replacement and why it's needed

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The Rotax 5 year rubber replacement program has good intentions and a solid past of problems of owners who failed to heed this requirement and its warnings to do the right thing and be safe. Can a hose last longer? Sure they can, but you don't know when it will fail and who you might injure when it does. The idea is to give you a safety margin to protect you, your passengers and the people on the ground.

Here is a video of a piece of fuel hose off a Rotax engine. The hose is 6.5 years old and was not altered in any way.

Change your hoses so you don't show up on America's Funniest Video show hanging upside down in a tree yelling for help out your window.

 

 

 

This could be just as easily an oil hose leak. Fry one $20K engine.

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Hi Roger

 

as you said ..'fairly dramatic' was it leaking before removal ?

 

this is a fuel hose right ?

 

was it a original installation on a CT ?

 

thanks

 

and.. happy and healty new year to everyones on this fantatic forum ;)

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Hi Jacques,

 

It was a factory installed fuel hose. That's how it was discovered. The engine was started and fuel ran all over the ground. It was not a CT, but was a Rotax engine. The most likely place for a hose to start to leak is at the end of the fitting it slides over.from vibration and that's exactly where this one started.

I preach don't skimp on safety maint. because your $100K+ plane and your hide or your passenger isn't worth the money.

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I preach don't skimp on safety maint. because your $100K+ plane and your hide or your passenger isn't worth the money.

 

no problem...I changed all the fuel hose with EXACTLY the same product that was installed.

 

it had 5 years of operation and was not firesleeve protected,,the new ones are

 

I fully agree with you,, it a small expense for safety and I find it strange that some people don't bother to do it.

 

Thank's for putting this video,, hope it will wake up some minds

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Thanks Roger!

Great video to show the importance of safety vs trying to safe a few bucks (I know it's more then a few) but compared to the alternative, I'll just throw a buck a week in a jar!

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Did this hose leak when not under pressure? Do other hoses, say one on for 3 years, leak with the same test?

 

This would be a lot more persuasive if Rotax would come out with a study that shows a wide range of tested hoses. I really don't have any confidence that this demonstration represents the conditions on my engine and my hoses.

 

I will continue to be the iconoclast who believes that maintenance on condition is far superior to maintenance on time.

 

 

 

 

 

 

 

 

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Hi Ernie,

 

It is posted in the Rotax Line Maint manual and it has been posted here on the forum. I posted it just a few days ago again when I was ask about the red hose on top of the engine that feeds the carbs fuel. It has been posted here on the forum at least 4 times. It isn't just FD planes involved it is the entire LSA and Rotax engine industry around the world.

The chute repack and the hose change are not optional. If you don't do them you are out of airworthy and out of insurance not to mention the liability if something happens. If these are not done and it gets to the next inspection period and the mechanic signs the regular inspection off without these being done the inspection is null and void and if the FAA finds out his and your licence may be to.

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Did this hose leak when not under pressure? Do other hoses, say one on for 3 years, leak with the same test?

 

This would be a lot more persuasive if Rotax would come out with a study that shows a wide range of tested hoses. I really don't have any confidence that this demonstration represents the conditions on my engine and my hoses.

 

I will continue to be the iconoclast who believes that maintenance on condition is far superior to maintenance on time.

 

Jim, some of the hoses I've taken off, like the one in the wing root, are a little hard to inspect on condition. It is my thought that it is a little hard to inspect the hose on the inside without removing it first, and after going to all that trouble why not just replace it anyway.

I did a flight review with a fellow in a Tri-Pacer one time. Him and his brother had just been out flying to practice some first. I jumped into the airplane, and around 200 feet in the air after take off the engine started to loose power. He had just switched to the fullest tank prior to take off, but it was a tank that they didn't use that often. The problem was a fuel hose that was coming apart on the inside, but it looked good on the outside.

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...... and after going to all that trouble why not just replace it anyway.

 

 

same for the firesleeve covered hoses...if you have to remove the firesleeve to inspect the hose ...why not also replace the hose in the same time

 

my 2 cents

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I guess my question is why five years and not some other number? If the 6 1/2 years in the video is typical, it seems to me like that's not much leeway over the 5 years. So, why not 3 years or 6 years or some other number of years? When did that hose actually go bad. And, is it bad per a standard condition test for that hose and application?

 

There simply has to be some way to inspect on condition. If you saw a hose at 3 years that was not leaking but you didn't like some aspect of it, how do you inspect it to confirm to yourself that it is satisfactory or not? Just replace it based on an uneasy feeling?

 

Once we find what and how the condition is accurately and acceptably determined, we can see if there is a reasonable time limit on it. The British organizational research team in WWII and U.S. air carriers in the 60's proved to themselves that maintenance on condition is far superior to maintenance on time. The reason is that most unscheduled maintenance occurs after scheduled maintenance. The mechanic, being human, did something wrong. The solution is not to let the mechanic near your aircraft except to inspect it to determine if there is something that is unacceptable, whereupon it is repaired.

 

Whenever I see maintenance based on time I always think of old-fashioned thinking and lawyers, not whether or not the part is actually fit for use.

 

 

 

 

 

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Hi Jim,

 

 

6.5 years isn't typical. The problem is you never know so you should error on 50 years of known hose experience and failures and then fall back on the safe side. You can't pull over to the curb and it won't happen at your convenience. I won't say who this person was, but one of our CT friends had an oil hose go bad before its time limit and the cost was a new engine.

 

What criteria do you use to determine when a hose is going to leak or burst?

 

There is really no way that anyone can look at a hose and tell when it will fail unless it is just trash and in late stage decomp and the only real way to know is to pull the hose and pressure test it.

 

We all have lived long enough to have seen hose failures in engines before. Some go sooner than others. Some may last 10+ years. The issue here is we are flying planes and carry passengers that trust we have made sound decisions and if the hose fails our landing options go down the toilet.

 

We have the same problem with fire hose. We don't know by looking at it if it is good unless it is really trashed. So every year every piece of fire hose on the department must be pressured tested at twice it's operating max pressure.

 

If we all had a fortune teller that could tell us the date of a failure we would be okay, but since we don't we change a little early and be thankful we aren't going to have to replace a $20K or pick our passenger out of the tree because we went too long on the hoses.

 

The reasoning behind any smart MFG's decision is product safety, personal safety and liability for its clients.

 

Why throw the dice when you don't need to?

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Roger,

 

You say that you pressure test fire hose annually. That is a condition test, kind of like an air tank pressure test. Visually inspect and over pressurize to a certain limit.

 

I'm willing to bet there is a way to test the hose in question.

 

You say 6.5 isn't typical, as if you know that it should be longer. Under what conditions did this one fail so quickly? If I encounter those conditions I'll be much more careful. But if I don't encounter those conditions, I'd like to have some way other than just some arbitrary date for replacement. Surely Rotax has a reason for the date. I'd like to know it.

 

I am not willing to conduct maintenance based on scare stories. Maybe you're old enough to remember when Army recruits were shown some very graphic and unpleasant pictures of people with venereal disease, apparently with the idea that the recruits would avoid sex. I hate to tell you this, but it didn't work. Telling me that if I don't change a hose at 5 years when I'm asking how to tell the hose is bad is going to have a similarly unconvincing reaction.

 

This is kind of an interesting discussion. On one hand, those with an SLSA have no choice, so why is the topic beat to death? Is it because some will choose to ignore it? How would they do that, lie on the log entry to make it look like it was accomplished? That would be pretty easy to disprove, I'd think. Those of us with ELSA can legally do what we wish. Maybe we'll be penalized on resale, if we sell, unless our airplanes conform to SLSA standards. Maybe not. But, that is our worry. Surely, if the real question is the condition of the hose, someone would tell us how to tell the condition. As I said before, I'd like to know how to check the hose at 3 years or 250 hours or any other interval if I'd a mind to. That may or may not include pressuring a hose as was done in the video, a practice we still don't know if it is appropriate or just somebody's idea.

 

I suspect that if I asked Rotax, they'd not want to tell me about how to tell hose condition and point at the time limit. But, if I get to a venue where Rotax is exhibiting, you can be sure I'll ask the question and I'll post the answer here.

 

 

 

 

 

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We have a ton of time replacement items on the Unmanned Airplanes I fly including hoses. Most of the time change hose times are derived from the hose manufacture recommendations based on how it is being used, ie fuel, heat, coolant, etc. We even have shelf life times on certain hoses that changes based on how they are stored. Other time change items are based on tracking failures of components then determining a safe margin for replacement prior to failure. I would think Rotax engineers thought this thru with recommendations from the hose mfg and decided 5 years would provide a good margin for safety and it's not just an arbitrary number. I certainly understand your interest in learning why 5 years is the magic number, and maybe one day we will find out.

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There is a simple answer to this and it is driven by the legal profession. Without a time limit given for hose replacement on their engines, Rotax leaves itself open for lawsuit by "ambulance chaser" lawyers. In the car industry, we called it "best practices". If one manufacturer came out with a better air bag technology and the other manufacturer's did not incorporate this, any accident that occured with the old tech air bag was open for law suits. Of course, by incorporating the new tech, the manufacturer was leaving himself open to lawsuit on older systems because he was slow to incorporate the new. In the case of equipment on aircraft, lawyers have a field day on systems without a "due dilligence" carried out by the manufacturer for design or replacement. Rotax could have given probably some other number of years for replacement but I suspect "best practice" is 5 year on rubber hose replacement. Follow the herd or get eaten by the lions.

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More pics of a cracked coolant hose and found in the nick of time (during hose change). This hose is from the left side that connects the expansion tank and the radiator.

 

Second pics are of a hose where safety wire is used to secure heat shielding on the coolant hose and it has caused a serious reduction in hose inside diameter. Use wire ties and don't crank them down. Also safety wire is not an acceptable standard ASTM practice for the CT to secure fire sleeve on fuel and oil hoses.

 

 

Hose change at 5 years is there to protect you.

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"Hose change at 5 years is there to protect you."

 

I don't believe this. I think hose change at 5 years is to protect Rotax and FD. From the examples posted above, it looks to me like we should all be educated in what constitutes good hose condition and we should be inspecting for it much early than 5 years. Like at least every 100 hour and annual, if not every pre-flight.

 

Do we have to remove the hose to find the kinds of deterioration shown above? If so, we should be doing it a lot earlier than 5 years.

 

The safety wire issue is good to know. Obviously it is something we should inspect when we look at hoses, but if a hose is abused we can't complain that it barely lasted 5 years. We should gig the mechanic who made a faulty installation. This should have been caught and corrected at the first 100 hour or annual after it occurred.

 

What I am gathering from this discussion is that inspecting on time is better than not inspecting at all, but I maintain that inspecting on condition is safer than inspecting on time. Roger has shown a number of examples that I maintain should have been caught earlier than 5 years. He has not shown any examples of items that were fully functional and may have met standards for considerably more than 5 years.

 

I'm going to continue to try to educate myself on how to determine hose condition so I can use that knowledge in addition to the 5 year requirement.

 

 

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Out side issues are easy to see, but not all areas of the hoses on the engine are visible and we can't see the inside of the hose which can be any issue too. I agree that Rotax has a vested interest here, but it helps us too. The hoses I have shown in bad condition have come from 6 - 6.5 year installs. I find many mechanic mistakes on hose and illegal clamps used too many times. I find A&P's make far more mistakes than RLSM-A's that were trained for the LSA industry which would stand to reason. This is one good reason for our forum. We can educate our A&P's and make sure they do the right thing on our planes.

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