header tank versus gas colator

[syphon]

Hi what's the difference and what are the pros and cons of each..

thanks
Simon

[bobthebuilder]

Maybe Boet or the Duck could better explain, but my take is as follows:

A header tank is just that .... a tank, which is fed by other tanks. A gascolator is a glorified filter.
Gascolators have a metal screen which, although can plug up with too much dirt, are not succectible to being blocked by water. They also have a bowl at the bottom and a drain cock.

[syphon]

thanks bob

[justin.schoeman]

A gascolator is also always the lowest point in the fuel system, so that water settles out into its drain bowl, while a header tank is usually higher up, so that it can gravity feed to the carb if there is a pump failure.

[Dobbs]

Certainly in my Bushbaby, the bottom of the header tank is at the lowest point in the fuel system.

Sampling the contents of the header tank on the first flight of the day is part of my pre flight, and although I change my fuel filter every 100 hours, I have NEVER found any conatminants in the filter. I would definately recommend a header tank if your plane can accommodate

ps - I have no experience with a gascolator.

[Mogas]

Certainly in my Bushbaby, the bottom of the header tank is at the lowest point in the fuel system.

Sampling the contents of the header tank on the first flight of the day is part of my pre flight, and although I change my fuel filter every 100 hours, I have NEVER found any conatminants in the filter. I would definately recommend a header tank if your plane can accommodate

ps - I have no experience with a gascolator.

+1000 on what Dobbs says.
You could consider the header tank in a KFA plane to be a big gascolator.
* It traps the water and anything else heavier than fuel like dust.
* It provides an emergency 5lts of reserve fuel, even if you have forgotten to open the wing tank fuel valves, but not for long!
* Most importantly, it ensures that the engine driven fuel pump is always primed. When you are on a long gentle descent and your wing fuel load is lower than about 10lt a side, it is possible to expose to fuel tank outlet to air until the nose is raised again. There were a couple early Kitfoxes which crashed due to fuel starvation after this happend, header tanks were the fix, we learned from them
About the only improvement on this system is to vent the top of the header back to the tank or higher out on the wing. The way it is now when standard, I sometimes see an airspace on the fuel in the header if I have let the wing tanks run a little low. No big deal, I just bleed the top of the header when required.
This thing has been debated many times and is well covered in the manual, it is part of the build standard accepted by CAA.
If you decide not to fit the header you must apply for modification approval, good luck with that.
There is nothing that says you can not fit a gascolator on the firewall in addition to the header but there is no point.
I use the header on all builds, a large inline fuel filter forward of the firewall and then another smaller one between the EDP and carb.
I filter my fuel coming out of the drum when refueling, do a daily water check below the header and change the fuel filters with my oil every 50 hours. I have never had any water in my fuel nor have I had a dirty fuel filter.

[bobthebuilder]

Thanks for your interesting post Mogas. Do you perhaps have a schematic from a manual of sorts illustrating this for us non Bushbaby / explorer owners?

[Mogas]

No problem.
There is a drawing in the manual, free download on the SAPlanes website, technical section.

[avgas]

Most gasculators only have a 100ml capacity.
The bottom part of the header tank would be about 300ml.
I think that alone is good enough motivation except for Mogases answer regarding long descends with low fuel.(underwear soiling experience ) Have been there and after that I would not recommend you leave out the header tank.