Bryan,
The slosh and pour you accomplished is recommended by the factory,
but as you noted, it’s impossible to get all the fuel—and any
debris—out. After doing this with my (IV-P) tanks, I mounted the wings to
the airplane and proceeded with fuel tank calibration tests. This required
filling and emptying each of the tanks at least a couple of times. I filled one
tank at a time (measuring the input with a “calibrated” can,
sloshed it around a bit after completing the calibration checks, etc, and then
pumped/drained fuel to the other tank through a filter—again using the
calibrated can to fill the second tank. A large funnel with a chamois skin
stretched across the top makes an excellent filter for this purpose. Like the
slosh and pour, it won’t get out all of the fuel and debris, but a couple
of fill up and empty cycles will get almost all of it. I found a couple of
small particles in the bottom of the gascolator at about 20 hours of the test
period, and nothing in three checks since, so this worked pretty well for me. I
must note that we were absolutely religious about keeping the tanks clean
during construction and closed/sealed afterward until installation on the aircraft.
If you’re tanks have been open to shop dust/other for any time at all,
additional cleaning might be needed…perhaps more “fill and pump?”
I installed two in-line fuel filters in my fuel lines between
the wing tanks and the fuel switching valve in the cockpit. On the advice of
several good friends/experts who looked at my (not so) clever idea, I took them
off and replaced with straight aluminum line. The conventional wisdom is to
never install any type of flow-restricting device (e.g. filter) in the “suction”
side of the fuel system, as even the tiniest leak between the filter and the
engine will draw air into the fuel system—especially big trouble for a
fuel-injected engine. I considered putting the filter in-line between the electric
fuel pump and the engine, but since I expected to fly without the electric pump
on much of the time, this only “shortened” the vulnerable area and
did not eliminate the basic problem. In the end, I gave the filters to a
friend. (BTW, they are available at ACS as a “Flow EZY” filter, part
number 05-28905. They are high quality aluminum with replaceable fine mesh screen
filter elements)
I am now running with a fuel system as specified in the original
Lancair construction manual. I understand that later manuals specified ˝”
aluminum fuel line but I kept the original 3/8” line specified. I have
the Lancair-specified gascolator mounted on the front of the firewall, just
above the right exhaust tunnel. In 200+ hours of flying to date, I have never
had the engine falter or quit while switching tanks—or for any other
reason for that matter—although some have reported this problem.
My recommendations: Install a gascolator—between your electric
pump and the engine. It will separate any water contamination you collect in your
tanks over time. Most also have a filter that will at least strain the large
rocks out of your fuel. <grin> Don’t install an additional filter
in your fuel system. If your tanks are contaminated, flush them (with fuel
only) until you don’t collect any observable debris when you filter the
outflow as described above. Plug the ends of your fuel system at the tank and
at the engine, and run an end-to-end pressure test of the complete system. If
the tanks and fuel are clean and the system is leak free, it works well as designed.
Good luck!
Bob