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jonbakerok
08-26-2008, 05:29 PM
I've been studying all the stuff about fuel systems on the Matronics forum. There seems to be a consensus that you need a header tank, usually installed behind the seats somehow. But there doesn't seem to be any mention of why.

Anybody know why we need a header tank?

Is it so you can draw from both tanks? I'd just as soon not do that. I like redundancy. Or is it because the wings aren't high enough to provide enough fuel pressure when you're climbing or something?

I'm thinking of just running both fuel lines to a Van's-style fuel valve, with an electric fuel pump ahead of it just like on my RV. Anybody know why that would be a bad idea?

DanB
08-27-2008, 03:38 AM
Jon,
If you are interested in a header tank I have an extra. Will let it go for $25 + shipping.

jonbakerok
09-04-2008, 06:32 AM
Has anybody taken a look at the "Just Plane" fuel system?

Their header tank looks like a much better design. Note that it doesn't need a vent line because the feed lines enter at the top instead of the middle of the tank. Isn't it kinda weird to feed a tank that's supposed to be full all the time from the middle? I wonder why the Kitfox tank is designed that way.

There's an interesting discussion going on in the Matronix email list about fuel systems designs. I had just about decided to use a forward tank fed over the doors because it's a much shorter, direct run with less fuel running around inside the cockpit, and the uphill part is a lot shorter. My kit came with a forward tank and when I fitted it and realized how heavily protected it is by the framework, I wasn't so afraid of having it up there almost in my lap. But then these guys are saying that the short uphill run over the doors is a problem because it's too close to the tank to develop enough head to make it up the hill. So now I'm undecided again. Maybe I'll call Just Aircraft and see if they'll sell me a header tank. Seems dumb to run a little plastic vent line full of fuel right next to an aluminum line to the same tank.

I still think a better fuel system would be one that used a fuel pump instead of a header tank. Seems like the wing tank unporting issue could be solved if the fuel tanks picked up the fuel in the middle of the wing root instead of the rear -- the same way low wing designs solve the problem.

Where is it written that all high wing planes must use a gravity feed fuel system?

jdmcbean
09-09-2008, 07:52 PM
Note that it doesn't need a vent line because the feed lines enter at the top instead of the middle of the tank. Isn't it kinda weird to feed a tank that's supposed to be full all the time from the middle? I wonder why the Kitfox tank is designed that way.

Where is it written that all high wing planes must use a gravity feed fuel system?

The current Kitfox header tank is not designed that way.. and has not been for years.. The main lines come in the top and the vent line exits the top back to the right wing. The vent is needed.. The fuel tanks in flight are actually being pressurized.

jonbakerok
09-10-2008, 06:31 AM
It would be nice to have the simplicity and redundancy of a low-wing style fuel system, but I've come to realize that one of the things that makes a Kitfox so practical is what makes that kind of fuel system impractical -- the wings fold. The folding wings require the pickups to be located toward the rear where they can become unported in a descent, so a header tank is needed.

However, gravity may not quit, but it hardly ever pulls in the direction you want it to -- forward towards the engine. And the Kitfox fuse is too short generate much head purely by gravity. Fortunately, the standard Kitfox engine has a fuel pump, as does the Jab 2200 I'm using. But I think I'll add a Facet, just in case I need to climb on the day my mechanical fuel pump fails.

RandyL
09-11-2008, 11:45 AM
I'm happy to fit a Facet aux pump in my Super Sport, and maybe I will just for peace of mind, but won't the late model Kitfox fuel systems gravity feed if the Rotax engine pump fails? In that sense isn't there already a backup?

As we all know one model Kitfox may very different than another, maybe the design of the early models won't readily gravity feed where the later models will.

barrywest
05-25-2011, 11:32 AM
We have a Kitfox lll with the two wing tanks and a round header tank behind and level with the top of the seats. The header has inlets near the middle, a vent to the right wing at the top and an outlet to the engine at the bottom. The right wing tank wiil not feed to the left tank. If left overnight with a full right tank and an empty left tank none of the fuel will feed to the left tank. The right tank will feed to the header. Anybody have a way to solve this? We don't know if the engine will continue to get fuel in flight if the left tank is empty.

jtpitkin06
05-25-2011, 01:50 PM
Did you check your fuel caps to see if they are venting properly? Try testing the transfer with the fuel caps removed.

JP

cap01
05-25-2011, 03:27 PM
welcome aboard berry . you can always put the tail up on a stand and pinch off the fuel hose from the right tank and check to see how the gas flow is from left tank at the gascolator drain .