Leaky Nyla-flow Tubing

What's the best way to test the nylo-flow tubing for the pitot-static system? I suspect I have a leak for the pitot but no clue on how to figure out where the leak may be.

Also, wha't the most flexible of the plastic 1/4 inch tubing for use in pitot/ static system. Parker tubing Van's supplies is really tough to bend.

Jim

Instrument tubing

Hi Jim,
The Wings and Wheels site has a soft and "grippy" kind of tubing that comes in colors and works very well. The site caters to sailplane folks but has lots of stuff RV guys can use too. http://www.wingsandwheels.com/page23.htm

Mitch Garner
RV-4 flying
PL-4 flying

Tubing material...

Mitch757 said:

Hi Jim,
The Wings and Wheels site has a soft and "grippy" kind of tubing that comes in colors and works very well. The site caters to sailplane folks but has lots of stuff RV guys can use too. http://www.wingsandwheels.com/page23.htm

Mitch Garner
RV-4 flying
PL-4 flying

Click to expand...

I've had trouble in the past with PVC tubing in my sailplane in the heat... the tubing suffers from "creep" and can loosen around the fitting barbs.

The link at Wings and Wheels states "premium" PVC, which might be better at hot temperature... just don't use the local hardware stuff.

I think a polyurethane tubing might be better... as an example, this one is rated up -90F to 155F...

http://www.usplastic.com/catalog/pr...=USPlastic&category_name=7512&product_id=8115

...it's also available in colors.

I'm using a similar polyurethane tubing from Clippard Instruments...
Mr Clippard lives on our airpark and the price was right. His Minimatic fitting are also nice....

gil A

Jim,
I used tygon tube. See my post in;
http://www.vansairforce.com/community/showthread.php?t=24933
As Gil suggested, polyurethane tubing (available from ACS) also looks like a good replacement. The polyurethane tube is the recommended tube for the Vari-Eze fuel lines. I used it in my Vari-Eze. Lasted for years even with fuel. I suspect it would last forever as a pitot/static line. Both the tygon and the polyurethane are much more flexible than the Vans tube.

Fin
9A Australia

I used a plastic syringe (designed to deliver glue) and inserted the tip inside the end of the poly tube tight enough to seal. Then draw the syringe back to create a slight vacuum. When you have no leaks in your system the altimeter and asi will show a steady altitude and speed. Hold it for a while to assure the altimeter doesn't creap back to zero. if it does you know you have a leak. I can not take credit for this idea, Tom Skaggs showed me. But I can say it works as I just fixed several leaks in the static system this week end. DOn't use nylon fittings for the 1/8 inch MIP to the instruments. AFter 4 years all 5 of mine had cold flowed and became loose. I replaced the nylon fittings with brass to poly. So far after one day, no leaks.
John Adams

Flashing...

RV7AV8R said:

......DOn't use nylon fittings for the 1/8 inch MIP to the instruments. AFter 4 years all 5 of mine had cold flowed and became loose. I replaced the nylon fittings with brass to poly. So far after one day, no leaks.
John Adams

Click to expand...

This may be dependant on the type (quality?) of nylon fittings used.

Some seem to be molded with a "flashing" excess on the threads, while some are clean (machined?) in the thread area.

If you use the ones with visible flashing in the threads, I think you will definitely have long term problems.
This might be one area where "industrial" quality is better than "commercial" (i.e., Ace hardware) quality....

gil A - seen both types...

Thanks for the replies. Looks like USP had a good selection of tubing that I'll try.

Static tubing

Does anyone know what tubing material you get in the Safeair1 static kit?

Jim P said:

What's the best way to test the nylo-flow tubing for the pitot-static system?

Click to expand...

Build some very small pressure inside (1-2psi is enough) and test all connections with soapy water - it will start bubling where air escapes your system. You can also test lines itself if you want to check if they didn't crack somewhere.

SafeAir1

SafeAir1 kit is SAE J944 compliant air brake tubing, nylon over teflon, no reinforcement braid. Indestructable stuff, just don't kink it. If anybody wants to know how to pre-form it, let me know.

Fittings, tube to tube and t's are also air brake parts, all rated for -40F to 180F continious duty. Cut the tubes square, push them moderately into the fittings, give them a pull to verify barb set. Some people use a little lube on the tube to insert, most anything will be fine, even finger grease. The fittings use an o-ring seal, generally a highly saturated nitrile (HNBR), similar, but not quite as capable as 'Viton'. More than good enough, however. Should all be zero leak. The NPT is where you have relaxation, a good thread compound NOT TEFLON TAPE should be used SPARINGLY.

The parts above last life of a heavy truck, in excess of 20,000 hours and 1M miles, generally.

I work for Bendix, the heavy truck side, so yes, I know this stuff really well.

Rick 90432 wings

Rick 90432