Conductive Teflon hose retrofit kit for the Rotax 912 engine.

[WmInce]

Has anybody seen this yet?

[sandpiper]

I read about this but didn't know it was available yet. If this is Rotax approved, I assume FD will also approve. Or, given that FD says follow Rotax, maybe they don't need to give approval.

 

I wonder what the cost is??

[sandpiper]

OOPS! Didn't see the price is $599.95. Seems worth it given all the post hose change stories on this forum. But, first, I would want to see some history in the fleet.

[Anticept]

It says it is for experimental aircraft, and specifically names the RV-12 in the document. Rotax does not have an approved teflon kit, and US distributors have been putting heavy pressure on them to do it. I don't know why they don't, teflon is vastly superior to rubber.

[WmInce]

As far as I'm concerned, with the documented rubber debris problems of the Rotax 912, this type of mod is way overdue.

I agree with sandpiper though, before it can be blessed by the masses, it needs to have some history behind it.

 

So . . . who's gonna' go first?

 

I hope to hear a comment or two from our resident mechanics here.

[Anticept]

Teflon hoses do have a history. They are used in big birds, GA, and military aircraft alike. The reliability is outstanding, because teflon is extremely chemically stable (only extraordinarily corrosive chemicals can break it down, and even then, it needs to be at an elevated temperature), does not oxidize, has a much higher operating range of temps and pressure, and extremely resistant to UV radiation.

 

Here's a chart of chemical compatibility between PTFE (trade name teflon) and other chemicals: http://www.zeusinc.com/technicalservices/technicalbulletins/chemicalresistanceofpolymers/chemicalresistancechartptfe.aspx

 

I am not 100% sure, but I think CT brake lines are teflon.

 

There is one drawback to teflon though, it does become stiff after being exposed to high temperature.

[FlyingMonkey]

There is one drawback to teflon though, it does become stiff after being exposed to high temperature.

 

What is "high" temperature? Is it a permanent change, or temporary?

[Anticept]

It is permanent, but not dangerous. Basically, once a teflon hose holds it's form on its own in a bend, you are not to try and straighten it back out, or you will damage it. Picture heating pvc pipe so you can bend it, and then it re-hardens when it cools. PTFE hardens when it is heated, but it is not compromised.

 

As for the temperature: I am not certain when the hardening begins.

[FredG]

Are the teflon hoses for fuel delivery or for oil curculation as well? Can't tell from the photo. I have looked but have never found teflon lined hose the size of the oil lines on the 912.

[FlyingMonkey]

It is permanent, but not dangerous. Basically, once a teflon hose holds it's form on its own in a bend, you are not to try and straighten it back out, or you will damage it. Picture heating pvc pipe so you can bend it, and then it re-hardens when it cools. PTFE hardens when it is heated, but it is not compromised.

 

As for the temperature: I am not certain when the hardening begins.

 

That actually might be an advantage for running lines where they need to go neatly.

[Anticept]

Here is what teflon hose looks like:

 

 

It is called braided teflon hose, most commonly the braided jacket is stainless to protect the hose, the intermediate layer is nylon for it's strength against bursting (not required for our low pressure applications, this stuff is rated to 4 digit PSI) and as a sacrificial layer against abrasion, and the core is teflon.

 

It is also used in high performance cars.

[Jim]

Teflon hoses do have a history. They are used in big birds, GA, and military aircraft alike. The reliability is outstanding, because teflon is extremely chemically stable (only extraordinarily corrosive chemicals can break it down, and even then, it needs to be at an elevated temperature), does not oxidize, has a much higher operating range of temps and pressure, and extremely resistant to UV radiation.

 

Here's a chart of chemical compatibility between PTFE (trade name teflon) and other chemicals: http://www.zeusinc.c...echartptfe.aspx

 

I am not 100% sure, but I think CT brake lines are teflon.

 

There is one drawback to teflon though, it does become stiff after being exposed to high temperature.

 

 

If there's fuel flowing through it, I don't think the temp would get high enough to make a change.

[Anticept]

If there's fuel flowing through it, I don't think the temp would get high enough to make a change.

 

I don't think it would be a problem in aircraft at all. I just put that out there that it stiffens up when heated.

[FredG]

I have fabricated teflon lined brake hose for racing bikes and for sports cars. The stuff is great. But, does anyone make it in oil hose size? I have never found any of sufficient diameter for oil lines.

[Heinz]

Here is what teflon hose looks like:

 

 

It is called braided teflon hose, most commonly the braided jacket is stainless to protect the hose, the intermediate layer is nylon for it's strength against bursting and as a sacrificial layer against abrasion, and the core is teflon.

 

It is also used in high performance cars.

[Anticept]

For cars: http://www.goodvibes..._Steel_Hose.htm

 

When looking for hose size, you need an AN# . AN numbers are measured in 1/16 steps, inside diameter. For example, AN4 is 4/16th, or 1/4th inch diameter, inside. As you can see, they have AN20, which is 1 and 1/4 inch!

 

On that site, AGAIN FOR CARS, they attest their hoses may be used for any fluid, including explicitly stating oil and coolant!

 

I assume no liability if you install this hose in your plane.

 

EDIT: Sorry the above link is CPE hose in larger sizes. Just google search for braided teflon in the AN size that you need.

[Heinz]

I installed the braided teflon hoses in my CTSW fuel system back in 2007 and they have been no issues ever since, checked them after 5 years, still looked like new and they will stay in for a long time. The hose was purchased from a "hotrod " shop. I also removed the stainless steel lines and installed the teflon hose in its place. Makes life easier. The rules in Canada are not as strict as in the US, so no issues there. This is just to report that it has been done before.

[FredG]

Anticept, on the website you linked to, the Teflon hoses are AN3and AN4 only. Braided steel shrouded hoses are available in larger sizes, but I see no indication that they are Teflon lined.

[Anticept]

Whoops. Just google braided teflon hose, and the AN size that you need. Here's another example: http://shop.parkland...TFE-Hose_c7.htm

 

That one goes up to AN16 (1 inch), and the category says "Stainless Steel, Nylon Braided and PTFE Hose". Scratch that, it's not PTFE lined after AN4. See my next post for some real stuff.

[FredG]

I just looked at the site. The largest PTFE (Teflon) hose is also AN4. The larger sizes are not Teflon.

[Anticept]

Nylon/Braided/PTFE (in order from outer to inner layer) 250 series up to AN12, Braided/PTFE 200 series up to AN16: http://www.aeroflowp...alog/index/hose

 

HAPPY NOW FREDG?

 

In fact, here's some more, various sizes:

https://www.pegasusa...sp?Product=3480

https://www.pegasusa...sp?Product=3490

http://www.flexicraf...ndustrial_Hose/

 

By the way gentlemen, make sure you know what the minimum bend radii is for the teflon tube you are using. You can't just stick a spring in it like rubber.

[FredG]

Awesome! I have looked in the past but never found these larger sizes in Teflon hose. Thanks.

Fred

[Runtoeat]

Anticept, why can't springs be used with teflon hoses? The only reason might be they don't like abraision from the springs?

[Anticept]

Teflon is not as flexible as rubber. If you are using springs, you are bending it too far.

[Aircraft Specialty]

Good afternoon everyone. I just came across this forum and discussion and wanted to weigh in on the Rotax 912 hose retrofit kit. It has been in development and testing for a little bit over 6 months currently.

 

The kit was developed for the RV-12 aircraft because we have such a large population to use as samples. Being experimental, we run into no regulatory issues with testing on them. So far, the kit has performed flawlessly, and we are very excited to be offering this for the 912 engine.

 

Teflon hoses have been around for a long time, but there is a common misconception about teflon. There are basically two types. There is regular teflon and then the conductive teflon type hoses that we use. Rotax, I believe, has a service bulletin out about NOT using teflon hoses because they will leak over time. What happens is that fuel flowing through the hose causes static electricity. It discharges and creates little pinholes in the lining of the hose. However, what Rotax doesn't tell you about is the superiority of the CONDUCTIVE TEFLON hoses. This is a completely different animal. If you look at the hose picture that was posted, you will see the black layer on the inside of the hose. It is a very thin layer of a conductive carbon material. What it does is dissipates the static electricity through the fittings into the airframe. It acts as a conductor and basically makes the hose part of the ground plane of the aircraft.

 

Conductive teflon hoses have NO max service life. We offer a 10 year warranty on all our hoses. Our hoses are flying in hundreds of aircraft and are also being used by a major airshow team in their fleet.

In addition, the rotax 912 kit was designed to eliminate all the rotax proprietary fittings. We have done away with the banjo fittings and the push on rubber fittings. Everything is a standard 37 degree flare fitting which is what most aircraft mechanics are used to. In addition, we have vides of fabrication on our website. If you pay attention to the pressure testing, you will note that these hoses are tested to close to 3,000 psi. The birst pressure is around 10,000 psi.

 

We are working with the experimental market to develop hose packages aircraft by aircraft. If anyone is interested in working with us to get approval from CT for this kit we will be happy to provide any information that they might need. Rotax has not contacted us yet, but if they are interested, we will be happy to produce conductive teflon hose kits for their engines.

 

Please feel free to email us at steve@aircraftspecialty.com and we will also continue to monitor this forum.

 

Have a great weekend,

Steve

 

http://www.aircraftspecialty.com

www.tsflightlines.com

 

P.S. We stock conductive teflon hoses up to 1/2" in diameter, (a typical aircraft oil hose), but we can go larger. Also, we will be developing a coolant hose kit and oil replacement kit over the next year or so.