Header tank cleaning
Though I'd share this in case it is of interest to others. With this year's annual condition inspection I removed the header tank (I have the aluminum header tank) and did a rinse/flush/cleaning and filtered the rinsate to see what the heck a person might find in the bottom of the header tank.
Given that a certain amount of grief with aircraft seems to have to do with the fuel system, I have been extremely careful and dilligent along the way. During construction I thoroughy inspected and flushed tanks, hoses, components before assembling - then did flush throughs of the entire system before starting the engine the first time. The fuel cap pitot tubes have covers which are in place whenever the plane is not flying. The filter is changed regularly and cut open for examination.....never have found any gunk in the filter. 95% of my fueling is done in front of my hangar and I always use a tractor funnel with a chamois to catch any water or particles.
The material in the attached photo had settled out on the bottom of the header tank and stayed there till now. The accumulation represents about 250 hours of flying. The attached photo is a close up where there really is no size reference. The particles you see on the paper are smaller than pepper grains and most are almost like dust. Total quantity recovered once the rinse ran clear is barely what a person could pinch between two fingers...so it really is not a lot.
Now....what was it????? Doing some microscope work I found that most of the stuff, particularily the tan colored material, was plant material...very small particles of what resembles grain dust and also some stuff that looks like small fragments of grass blades. The second largest component was finely divided insect parts. So the vast majority of this little pinch of stuff was organic in nature.....now, the inorganic stuff included a couple small flecks of aluminum and a very, very few spindles of glass fiber. Then there is a little material that looks like plain old dirt or soil.
Now onto rampant speculation......I'd guess most of this stuff probably entered through the gas cap pitot during landing, takeoff, and flying; and, is representative of the agricultural environment around the airports and on grass strips. The limited amount of inorganic stuff, like the glass spindles probably from the wing tanks and the aluminum fleck might be from the header tank itself.
All in all, I am quite happy that the actual accumulation of gunk was rather insignificant; and, I will stick to the fuel system maintenance that has apparently worked OK so far.
Sincerely,
Dave S
KF7 Trigear
912ULS Warp Drive
St Paul, MN
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