- Use finger strainer
- Either ensure it works without a fuel pump or have a back-up pump
- Prevent insects from nesting in the vent
- Pressurize the tank using forward vents
- If you pressurize the tank, make sure the O-ring seals of the fill caps are tight.
- Consider a tank selector with a "both" position
- If you have a taildragger, consider putting the fill caps in front of the spar to gain about 25% more capacity per bay. For a nose wheel configuration, put the fill caps behind the spar.
- When the tanks are completely dry and/or the fuel lines have been drained,
the loop formed by the front tank outlet-tee-rear tank outlet is prone to
trapping air when the tanks are refilled. To cure this problem:
- Put a tee in the front line and run a line from it to a third outlet near the top of the tank to vent the lines while filling the tanks for the first time
- Or, drain at least a quart of fuel out of the gasolator for each tank. The gasolator must be run dry to allow the trapped air to vent out of the lines.
- Or, use at least .50 lines in the front outlet-tee-rear outlet loop and fill the tank slowly to allow the lines time to purge
- Or, if you loop your rear fuel line behind the doorpost, under the door and up to the tee, put a gasolator in the bottom and drain at least a quart of fuel out of it every time you refill after letting the lines go dry
- Or, designate one tank as the take-off/landing tank and never let it go dry.
- Unporting a tank outlet will not necessarily import air into the system. However, if the combination of fuel sloshing, acceleration and other factors combine to unport both a tank outlet and the tee, air can be imported into the system downstream from the tee.
- Lowering the fuel line join (the tee) helps the unporting problem, but make sure the tee doesn't become the lowest point in the system and by design become a water trap.
- Consider cross venting the two fuel tanks (especially with a selector that has a "both" position)
- If you route the rear tank outlet line behind the door post, under the door and up to the tee, put a gasolator or other drain at the low point to prevent the line from becoming a water trap.
- Use larger diameter fuel lines (3/8" to 1/2") fuel lines to allow fuel to flow around bubbles and the bubbles to raise up.
- Consider the "Cessna" concept where each fuel line has it's own vent line, see Lance Schlichter's article. This seems to be a simple yet effective solution.
- The system works well without a header tank and all the air is purged out of the lines. In the past one of the insurers has required a header tank, but apparently this is no longer a requirement. But a header tank with a proper low-fill-state warning gives you several minutes before the engine stops because of fuel starvation. ·
- If using a header tank make sure all the vents in the system interconnect or make sure the vents switch from the header tank to the corresponding feed tank as you switch tanks.
- Having a header tank doesn't stop air from being trapped in the front outlet-tee-rear outlet fuel line loop. Provisions for purging these lines must still be made.
- If using a header tank it must have a warning light for low fill.
- For first flights, fill the header tank separately. Don't rely on filling the wing tanks and assume the fuel will automatically fill the header tank.
- The majority of builders recommend placing the header tank at the firewall at the right side. There are draw-backs placing it behind the back seat that are to be considered.
- For new builds, or anytime you modify your fuel system, do a fuel flow
test for each tank. Each tank should easily flow at least 20 gallons per
hour. 20 gallons per hour is about one and one-half quarts per minute. To
test your system:
- Turn your fuel selector valve to off
- Fill both wing tanks (or all tanks if you have more than wing tanks)
- Remove the end of the fuel line that connects to you injector or carburetor system and put it into a clean 5-gallon bucket or other fuel container.
- Turn your fuel selector valve to the right tank. Time how long it takes to get at least two gallons of fuel through the system. As a minimum, the system should flow two gallons in less than 5-minutes
- Repeat the test for the left tank, and any remaining tanks.
- If you have a header tank, flow at least it's capacity plus two more gallons. Do this for each wing tank.
- Do several high power setting test runs over several minutes on the ground before the first flight. Consider this after you've drained the lines.
- If the fuel lines have been drained, drain at least a quart of fuel out the gasolator for each tank. You may have to blow into the tank fill caps to move air out of the fuel lines.
- Use a sieve during filling to filter out dirt.
- Do not take off with less than ¼ tank of fuel in the takeoff tank. The combination of acceleration and fuel sloshing may unport the tee and put air in the system.