Re: Gascolator and filter
[long posting]
Ladies and Gentlemen,
We have a lot of first time builders and prospective buyers that lurk on this forum looking for guidance.
I would hope this forum can be a place to exchange ideas and opinions. Instead of saying builders should throw one component or another into the weeds, why not list what you think are the advantages of your system of choice? Conversely, you might relate experiences that would steer you away from a particular component or system. I see little value in suggesting a builder should only take to the air in swathed in bubble wrap and wearing a gas mask if they don’t build it just like yours.
Alternate sources and solutions is what experimental aviation is about. We experiment, we learn, and hopefully we share. Some things work… some don’t. I will not fault anyone for trying something different.
As I see it, there are many different ways to plumb the fuel system; as well as where and what type of filter to install.
Here’s my take on two components.
First the gascolator
My publicly stated choice is the gascolator mounted forward of the firewall. I admit, it is a rather traditional choice having been used in aircraft for more than fifty years. A gascolator effectively filters out debris and small amounts of water. The filters screens are available from 10 microns to 140 microns.
The firewall location is not the lowest point in the Kitfox fuel system when the tail dragger sits on the ground, but there is a header tank behind the seat with a quick drain to purge any water during preflight that has settled in the header. In flight, the firewall gascolator is at, or near, the lowest point in the system.
Are gascolators failure proof? No. But the track record is pretty good at preventing more engine failures than causing them. I like them because of the ease of inspection. You can open them to clean the screen, look at any debris to track the source, and they have a large internal area that is unlikely to clog under normal conditions. Water passing though does not cause the screen to swell or create a blockage.
I like the advantage of being able to take a sample of the fuel during preflight for visual inspection. The sampling also flushes the screen a small amount so that a trend of contamination may be noted.
My gascolator uses AN fittings. I have aluminum fuel line from the header to the engine.
Does the gascolator have any disadvantages? Possibly.
During flight I cannot look at the gascolator and tell if there is any impending blockage. The cost at USD $70 is more than an auto filter, but the screens can be cleaned and reused many times. A new screen costs about USD $3.
Next: Automotive inline filters
The big plusses I see of automotive filters are cost and availability. The low cost allows a builder to install multiple units and change them frequently.
The auto filters come in many configurations lending them to ease of installation.
They can be installed with hoses or hard line. Normally a hose and a clamp is all that is needed. With proper maintenance the installation is perfectly adequate.
Many auto filters are transparent, allowing the user to visually inspect the filter.
The internal element is usually a paper or fiber type with very good fuel filtering capability.
The disadvantages for me are:
The paper element can swell when saturated with water, causing the filter to block fuel flow. For automotive applications that is a good thing as it will stop the engine before water can get to the carburetor or injectors. I would rather an aircraft engine continue to run, even if poorly, than quit.
I find looking through the plastic to inspect for debris is less than accurate. A plastic filter can look new and be completely blocked.
Automotive inline filters are typically plastic bodied with hose barb ends. I prefer the metal body of the gascolator with AN fittings.
There is no quick way to sample fuel from an automotive filter during preflight. Installing one low in the system is pointless as there is no way to flush it to drain any water.
Personal Experience
I’m sure different builders have reports of failures from either system. If enough debris or water gets into the fuel system, either an automotive filter or a gascolator will clog and the engine will quit.
I live in an area with high humidity and water in fuel systems is common. I drain lots of water from airplane tanks and sumps in the summer. We can get 90 degrees and 90 percent humidity here in East Texas.
I’ve had too many of my farm vehicles quit when a filter swelled with water. Because of the experience with the farm equipment, I wouldn’t install one in an aircraft. It’s just a chance I don’t want to take and flying with one is outside my comfort zone. Your experience may be just fine in the arid zones of Central California or Arizona.
This posting is merely my personal opinion and a chance to share my thought process as to why I choose the gascolator over automotive inline filters. It is not gospel and I won’t flame anyone for doing it differently. I welcome your experiences.
John Pitkin
Greenville, TX
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Originally Posted by jtpitkin06
