Fuel Line Failure (sensor line)

[jimbryan]

I am completing my annual inspection. I am reassembling my RV-4 and I pressurized the fuel system. I was floored to see the (size four) fuel sender line, from the engine driven fuel pump to the sensor manifold, leaking profusely. On disassembly I found that the fittings are secure but when I stripped off the stainless braid I found the hose is similar to a soaker hose. When pressurized the hose has pinhole leaks over its entire length. I used the same hose for the main fuel lines (size six) and the oil lines (size eight). Naturally I am going to strip out the fuel lines but I suspect the oil lines should be OK. All of the hose is the Earl?s Perform-O-Flex Hose which is rated for fuel, oil, pressure and vacuum. Perhaps there is an incompatibility with aviation fuel?

I can only wonder why the hose chose to fail at exactly the best time. It has taken me some time to complete the inspection and this line has probably been dry for two to three weeks. Perhaps that brought on the final failure. I have only used 100 Low Lead and the hose had been in service for two years and 90 hours.

Since I need to build up new hoses, is anyone aware of any problems with the Aeroquip hoses stocked by Van?s?

[osxuser]

Engine hoses (anything FWF) should only be Aviation grade (Aeroquip work) and should be checked VERY carefully for condition about the time they turn 4 years old. I pretty much replace at 7 or 8 years old regardless of condition. I'd personally never use automotive hoses, regardless of their quality, because there is no guarenty that they are compatable with aviation fluids. You are correct that some automotive hoses aren't compatable with Avgas, and even less compatible with Mil H 5606A.

[robertahegy]

Another thing to consider is the shelf life of hoses. The compounds in hoses can break down and be useless and dangerous even sitting and waiting to be used. I think there may be an interval for recommending replacement for all hoses used in aircraft. Anyone have any info on this?

Roberta

[az_gila]

Originally Posted by robertahegy

Another thing to consider is the shelf life of hoses. The compounds in hoses can break down and be useless and dangerous even sitting and waiting to be used. I think there may be an interval for recommending replacement for all hoses used in aircraft. Anyone have any info on this?

Roberta

Roberta.... some good info and references here at Sacramento Sky Ranch...

http://www.sacskyranch.com/h_life.htm

[jimbryan]

Thanks for the input. I really learned a lesson this week. I am considering scheduling full replacement of the flex fuel lines about every four years. Considering the down side of failure, it is cheap insurance.

[s_tones]

I just replaced all flex lines with teflon/stainless steel (archer).
Why use rubber of any kind in an airplane?

Steve

[hgerhardt]

Originally Posted by s_tones

Why use rubber of any kind in an airplane?

Steve

Exactly. Steel-braided Teflon doesn't cost much more, but it lasts forever and seems to be impervious to any liquid we'd ever consider using in our birds, including ethanol-laced mogas.

Just follow the standards for minimum bend radius of the hose. Teflon is more sensitive to kinking than rubber.

Heinrich Gerhardt
RV-6, flying

[frankh]

My hoses are (mostly) supplied by the local hydraulics shoppe and are teflon...

I did'nt knoe there were any rubber hoses in Van's kits..

Frank