I'm still here

[ppilotmike 24]

Haven't been posting much lately, thought I better let everyone know I am still alive and kicking. The 532 was a total bust. My new greyhead 582 is getting inspected and prepared by a Rotax repair station for duty on the front of 991CD. I have decided to put a new IVO ultralight 3 blade on the front, sold all the props I had to fund it. I consider my model 1 a fat ultralight and will operate it as such, although I realize it truly is an airplane just a very light one. I have been spending every free moment doing research on experimental aviation and the Kitfox in general, quite different from the certified world I come from yet still the same. I bought the flying a Kitfox book as well as the build manual from the nice folks at Kitfox. The book is well written and thorough and I now see how much was missing from the build manual I got with the plane. One of the big bugaboos with my bird is the fuel system. I am uncomfortable with its flow rate, it consists of two 6 gallon aluminum tanks and a 1 1/2 gallon header. I have to force feed the wing tanks to the header to get the flow to start using an outboard motor squeeze bulb for now. Seeing as how I will not be going on any long cross countries I would like to put the original design tank in front of the pilot in it, Is this a bad idea? Should I consider upgrading to a later design? Anyone else run into this? I have become very attached to this little airplane and will do what it takes to make it a safe regular flying bird again. Merry Christmas to all of you and thanks for all the advice you have given me. Joeys little Avid videos is what hooked me on these planes, thanks Joey. For now its back to studying for me. Mike

[1avidflyer 1983]

Where is you headed tank located now?  Also, where does the fuel exit the wing tanks?  Later Avids and Kitfoxes have the header tank behind the seat.  No issues with gravity flow to the header with those planes.  Of course you then use a fuel pump to get the fuel from the header tank to the carbs.   You should also have 1\4"ram air tubes pointing forward on the gas caps to slightly pressure the tanks to help fuel flow.  Aluminum tanks have been known to develope leaks from cracking caused by the wings flexing in flight.  JImChuk

[Richard Smith 32]

I have a aluminium tank which is bespoke made and haven't had any issues with it in the 6 years it's been in. My header tank is behind my seat with a double facet pump system just in case one fails. 

[ppilotmike 24]

Header tank is up front Jim. Mike

[Av8r3400 1179]

That is a bad spot for the header.  Too much looping fuel line relying on gravity flow.

[1avidflyer 1983]

I think I agree with Larry.  Better if it was behind the seat and then pumped forward, although, with my MK IV Avid, I fly with gravity feed with an electric pump for full throttle ops.  Engine is a Jabiru.  Header tank also needs a vent to get all the air out of it and full of fuel.  JImChuk

[ppilotmike 24]

I think I agree with Larry.  Better if it was behind the seat and then pumped forward, although, with my MK IV Avid, I fly with gravity feed with an electric pump for full throttle ops.  Engine is a Jabiru.  Header tank also needs a vent to get all the air out of it and full of fuel.  JImChuk

So what are your thoughts on getting an original front tank, Edmo has one and said he would sell it to me for a very reasonable price. If I don't do that than it seems like moving the header tank behind the seat might be an option. I think I would mount it as High as I could, I remember seeing a Kitfox that used an old keg mounted behind and higher than the seat for a header tank. One of my concerns are low spots that might collect moisture and ruin my day so I am going to re-plumb the system using hard 3/8" lines. My other major concern is not knowing how fuel is in the header tank. Mike

Edited 18 Dec 2017 by ppilotmike

[nlappos 413]

ppilotmike,

I run back to your note that the flow from the wing tanks is low. (" I have to force feed the wing tanks to the header to get the flow to start using an outboard motor squeeze bulb for now.") That is not at all normal, check for debris and blockage at the fittings at the tank bottoms. A small screen might be there and that gets flakes of stuff that blocks it. I had to clean out mine annually.

The wing tank, header tank system works really well, and should be your default configuration, IMHO. It works well.

[1avidflyer 1983]

The Kitfoxes use a vent line from the header tank top going into the upper side of the right wing fuel tank.  Avids use a tube that goes out the top of the right side butt rib.  I have a valve in that line on my Avid, that keeps the fuel from getting sucked out in flight.  Whichever method you use, if you can see through that vent line, you will be able to see air bubbles going up as the header tank fills with fuel.  When the bubble stop, the header tank is full.  As far as fuel line size, I always have used1/4" fuel lines.  When I've done gravity feed fuel flow tests, I've gotten 10 gallons per hr with that 1/4"system.    1 1/2 times what you will ever burn with a 582. I don't think you have mount the header real high, my Avid tank bottom is about 2" above the bottom of  the plane.  The fuel line comes out about 3" above the bottom of the tank, and runs forward under the door.  JImChuk

[ppilotmike 24]

I guess I should have clarified that my header tank is vented.

This is a before photo, the clear line is the vent.

 

The line runs all the way up to the top of the cabin and then back down and exits near the gascolator.

The valve in the center of the instrument panel controls the vent. It is need because with the right tank full it will overflow fuel onto the ground. I like your Idea of going thru the rib with a vent, I think I will try that first. Right now the fuel system is 1/4'' line. My flow rate was 1gallon and a quart in 10 minutes which comes out to 7.5 gallons an hour. I did the test with the tail on the ground, should it be preformed with the tail up in  the level fight position? The flow rate was taken at the  lowest point which is the gascolator. I can see the fuel level in the vent line so that would solve that problem with the valve open. Mike

Edited 18 Dec 2017 by ppilotmike

[FredStork 453]

There are 2 kinds of vents... those that are ALWAYS OPEN and those with valves that are ONLY OPENED WHEN NEEDED...

If you have an always open vent on the header tank you can get 2 things into the tank, fuel (very nice) or air (not nice at all). 
The vent on a header tank (regardless of it is behind the panel or behind the seat) should only be opened to fill up the header tank with fuel (i.e. to get air out of the header tank after running out of fuel in the main tank). Sure, in a perfect world the vent could remain open all the time as fuel would always gravity feed freely and keep the tank full - but here is the bad news: It is not a perfect world...

Don't underestimate the suction power of the small membrane Mikuni fuel pumps most of us have installed just before the carburetors. I once run with the valve between main tank and header tank closed and the round little Mikuni imploded my header tank so the fittings came loose...

In this not perfect world the fuel flow is sometimes low and if it is easier to suck air into the header tank than slow flowing fuel whatever pump you use will go with air - every time... So better use that suction power to drag fuel through the clogged line than fill your header tank with air. 

As long as there is no open vents between the main tank and the engine the gravity flow is only needed to initialize the flow - once you have vented out the air. Always open, forward facing (not to create venturi suction*), vents on the main tank goes without saying  (but it is OK to write it). 

A way to increase the flow from the main tanks is to used both fittings (most of the tanks have one for the fuel line and one for purging the tank). Get a "Y" connection and use both for the fuel line and purge through the header tank. By placing the purge on the header tank low (like behind the seat) it can purge the the entire fuel system (as long as there are no midway vents open...).

(*) If you insist in having an open vent on your header tank make sure your main tank vent is not creating a venturi suction as lowering the air pressure in the main tank will reduce the flow and, as described above, a reduced fuel flow could result in filling the header tank with the free flowing air... I'm sure this has happen more than once and when on the ground (happily or unhappily) the fuel fill up the header tank and the in-air fuel shortage is a mystery... 

Can I get down from my soap box now?

 

Edited 18 Dec 2017 by FredStork

[ppilotmike 24]

Thanks for your comments Fred. Mike

[Bandit 286]

1200 hours on this system. 

[1avidflyer 1983]

Can't get any simpler than that. And often times more complicated means more chances for problems. JImChuk