replace header tank with gascolator

[yellow fox]

can any one explain the purpose of the header tank and can we replace it with a gascolator.do they make a 2 inlet gascolator, and if i put it in the same place as the header tank will it affect the tanks drain flow. would i still need to keep the header tank vent line

[jtpitkin06]

Your question is really multi-part but deals with separate fuel delivery questions.


First the gascolator. A gascolator is not a substitute for a header tank. It is a device that by design separates contaminates from fuel; most often water but it can also remove sediments. It is typically the last item in a fuel system before the carburetor or fuel injector pump.
Its purpose is solely contaminate removal. Usually a quick drain feature is added to the gascolator to facilitate fuel sampling and flushing of the gascolator. A gascolator does not have sufficient fuel volume to take the place of a header tank or sump tank.


Now the header tank.


There were a few known fuel flow issues on earlier Kitfoxes. The small header tank near the firewall was removed and a larger tank installed behind the seat to improve fuel delivery. The lower header tank position, along with a more direct fuel line path ensures an adequate fuel supply.



Even with the new lower header tank, it is possible during skids or prolonged slips to cause the fuel in one wing to reverse flow. By using a header tank with a vent line reverse flow from the header tank is prevented. The vent line breaks the siphon. Fuel will continue to flow into the header tank from the opposite wing tank. This is why it is important to not use individual wing shutoff valves or a left/right selector valve unless you are in level flight.


The header tank vent line also ensures pressure in the fuel line to the engine does not go negative.



Simply put…By using a header tank the engine will have fuel available in steep climbs, steep descents, skids and prolonged slips.


In summary:


Installing a header tank low in the fuselage is a proven system used on many certified aircraft. The vent line is a safety item and should not be eliminated as it prevents reverse flow and fuel starvation. A gascolator is a separate feature and may be installed between the fuel shut-off valve and the carburetor or injector.
Feel free to contact me if you have any fuel system questions or concerns.


John Pitkin
Greenville, TX

[Mnflyer]

Hi John, excellent posting on gascolators and header tank(s).

[dholly]

Many Avid Flyers use what I always considered to be a combination header tank/gascolator. It was a cylindrical affair made from a length of spar tubing with a quick drain in the bottom that exited the under belly fabric. There were two fittings in the top, one used for wing tank(s) inlet and the other a vent outlet. The vent line originally went back up to a tank but many ran it up to a loop, added a 'burp' valve and exited it near the quick drain. That way, since it's rather difficult to see through aluminum, you could confirm a full header during pre-flight. Or, if your low fuel warning indicated air in the header tank in-flight for some reason, you could reach over and purge the air in flight. Not really a good pic, but here's one from my Mk-IV that might give you some idea of shape and location behind the seat pan if you're not familiar with them. I polished mine.