My opinion: old fibre-glass fuel tanks are a real hazard

[Kiriako]

In case this is useful to any Kitfox pilots out there:
Flying my recently purchased 18 year-old Kitfox III I experierienced sudden loss of RPMs (a thousand at a time) with the 582 engine actually spluttering as if it would stop; fortunately it did not and I was able to land safely quite a while later. I dismantled the carburetors and found both jet assemblies full of fibres that were clearly partially obstructing fuel-flow. I had a couple of eventless flights after that but on another flight just recently it happened again and once more the jets were found to be full of fibres! I have now put in an additional BMW fuel-filter in the fuel circuit above the gascolator (the paper-like membrane type) which should finally take care of these horrible fibre-shedding old tanks. I have had a long flight after this latest repair and the engine ran as smooth as silk, I hope the problem has now been definitively laid to rest. Have any of you faced similar problems?
All the best,
Kiriako

[szicree]

It has always been my understanding that paper element filters are a very bad idea on aircraft. Water in the fuel can quickly swell the paper shut and you know what happens next.

[Kiriako]

That is a very interesting point you are making Szicree and I am very grateful for it; I have been told that the paper membrane is folded in 'concertina' fashion in the filter-drum, so if I understand you right what you are saying is that with water the concertina-folds in the membrane swell-up and start binding together, am I right? If this is the case surely there must be some surface area on the membrane that remains unfolded and without overlap so that some fuel can go through (perhaps at the two ends of the 'concertina? Or am I being unrealistically optimistic?

[Kiriako]

I think you are right about the only definitive fix being to acquire some new tanks. Meanwhile I will attempt to flush the exisitng ones as you suggest. The fuel filters I use are the ones used by Rotax for the 912 engine (I replaced the original flimsy disk filters used normally for the 582 model. ) I also thought that the BMW paper membrane filters were also a good high quality solution and would definitely stop the fibers from getting through but the comment by Szicree as to the possibility of any water making them swell-up and obstruct the fuel flow has put the dampers on that idea...
In any case I am very grateful for the advise.
Thank you,
Kiriako

[szicree]

It is my understanding that the paper fibers swell and block the tiny holes in the paper. At this point it is no longer porous and that is not good!

[Kiriako]

Steve, thank you for the clarification .
Kiriako

[Av8r_Sed]

The problem with paper filters is water. If you get water soaked into the paper it will block fuel flow. There are filters with fine stainless steel screens that should solve your immediate problem without causing another. I purchased some from LEAF at Oshkosh last summer.

-- Paul S

[rogerh12]

Yes, these take appart filters are not without there own problems. I had one on my bike and it unscrewed itself and leaked fuel all over (with the vibration and all). Take a look at the link in the previous post, what really holds it together? What if the glass cracks? Perhaps a metal throw away version of this type filter would be best. Also, I suggest a fule pressure guage to monitor fuel flow heath, even on gravity feed systems.

Roger

[Av8r_Sed]

I'm planning to use disposable fuel filters with stainless mesh in each line from the wing tank to the header. These are manufactured by ITW-Fastex.
Here's a link to their datasheets: http://www.itw-fastex-cva.com/content/view/32/33/

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-- Paul S

[moosepileit]

Autozone, $9.99 seems to be the same part as A/C Spruce and Rotax Parts.

Spectre Clearview Part Number 2369. Includes ends for 3/8, 5/16 and 1/4 inch.

Have to see one to make sure it's able to be disassembled for cleaning.