Eliminating the Header Tanks

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Eliminating the Header Tanks

Postby EchoWhiskey » Tue Jun 30, 2020 4:09 pm

Has anyone done this?

I admittedly am not a fan of flying with fuel. I understand the need for a header is connected to having only a rear wing tank outlet that may not flow during nose down and low fuel scenarios. Only the rear outlet is used so wings can be folded.

I am planning on installing jiffytite quick connects at the tank which would allow me to completely remove the wing as well as to plumb hard lines to the tank. It occured to me that I could add one to the front tank outlet and eliminate the header tanks.

I know this has been discussed before. Is this a ridiculously stupid idea? Wouldnt be the first. https://www.jegs.com/v/Jiffy-tite/517
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Re: Eliminating the Header Tanks

Postby danerazz » Tue Jun 30, 2020 7:37 pm

I have put a considerable amount of thought into this.

The header tank performs a few functions:

1. Acts as a sump for contaminant separation
2. Is your fuel reserve when the rear pickups are un-ported
3. It SHOULD be vented to allow air to escape (fuel and air should get their own dedicated pathways)

If I were to build a new one, or if I replaced the wings or wing tanks, I would do this:

1. Remove header, replace with small (one quart, maybe less) collector tank to a point under the seats/floor
2. Add front fuel ports to the tanks; run the rear lines BEHIND THE DOORS, front lines IN FRONT OF THE DOORS. They would all end up at the collector tank
3. Add a sump drain to collector, accessible under fuselage
4. Quick disconnects with shut offs on front pickups if folding is expected
5. Vent line from top of collector to one of the wing tanks
Fuel system from collector to carb would be unchanged

This would give positive fuel flow regardless of attitude, a true low-point sump, and the vent allows any air that might be trapped to escape, so the collector is always full and air bubbles eliminated.

Some have added front pickups then ran the lines back (or even “T” them into the rear pickups). This will do nothing, and could possibly make things worse. You have to run the lines down immediately after leaving the tank.

Fuel system issues are oe of the top reasons for E/AB power failures/accidents. I think the fuel system could be greatly improved on the Highlander, and “if I did it again...”

Good find on the jiffy-tite fittings, exactly the type of fitting I was looking for!
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Re: Eliminating the Header Tanks

Postby EchoWhiskey » Wed Jul 01, 2020 5:52 pm

I have tried replying to this 3 times now from my phone and it is getting absorbed into the interweb.

Anyway,

Dane, thanks so much for the detailed reply. Your feedback is appreciated. As I understand it, the rub if you will, is having a sump to act as the missing wing tank sumps which most planes have. A gascolator on the firewall may or may not grab water passing through depending on amount and flow etc. To your point, it may not make it there if not there is a low point and fuel flow is slow enough. Necessitating the need for a small pass through container to act as a water separator

The other reasoning for headers I have heard was to pick up debris. But I suspect this is much less of a concern with aluminum tanks......

As I have only run lines from the headers to fuel switch, I am going to look into possible small 1 quart sump solution.

Question: would it be acceptable to place sump after fuel switch such that only one would be required? One drawback would be if substantial water overloaded the chamber, you wouldn't be able to switch out of it compared to a scenario where there would be one for each tank and you could switch out.......

I was watching an AVWEB video about the very topic of power loss on climb out due to water in fuel.

This just occurred to me:

Has anyone added a sump port on their aluminum tanks? That actually might be the best and easiest solution. Tig an AN bung to the aft inboard side of each tank? Is there a good reason to NOT do that? Maybe that's the ticket.....
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Re: Eliminating the Header Tanks

Postby SheepdogRD » Wed Jul 01, 2020 6:13 pm

I like the idea of sumping the wing tanks. But I can think of two possible concerns with fuel bungs on the bottom of the tanks:

(1) the door may bump into them;

(2) any gas that drops from them onto the doors will damage the Lexan.
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Re: Eliminating the Header Tanks

Postby danerazz » Wed Jul 01, 2020 8:49 pm

I have composite tanks, and I added fuel sumps. 2 per tank. Inboard aft corner next to pickups, and in the little “triangle” outboard of the diagonal wing brace (this is a low point that will never empty without significant sloshing, slowly building up water and debris until a big slug makes its way out).

I agree that it could cause issue with my lean, but sump drains never leak :roll:

As for the low-point sump, you need a drain at the lowest physical point in the system. I think tank drains are a must. The wing pickups are slightly above the bottoms, so a sump in the bottom gets anything out before it gets into the rest of the system. A small collector is a last-chance (notwithstanding a gascolator) to get anything else out, or if so much water gets in it does overflow the pickups. The collector acts as a vapor trap, allowing any air or other vapor to escape through a vent guaranteeing only liquid fuel moves beyond. It will give a place for any debris out of the tank to settle out and hopefully be drained preflight.

I believe a fuel valve should be a shutoff, unless you really need a left-right for some reason (a return from the engine to one tank might necessitate that). If the collector is physically lower than the valve, then that should be the only sump you need after the tanks, unless you have a dip in the line or some other reason water or debris may collect in another spot as well.

Also, for aluminum tanks, you could add a riveted/pro-sealed FNPT fitting your the tank, you would only need to make sure it is empty and could be done after the plane has been flying. Just make sure drilling the holes doesn’t cause any fires! :shock:

Vans aircraft part number VA-112 is a 1/8” FNPT riveted flange $8.50. Looks like this picture. Drill your holes, pro-seal and then use closed-end self sealing pop rivets to hold in place.
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Re: Eliminating the Header Tanks

Postby EchoWhiskey » Thu Jul 02, 2020 7:58 am

I have decided to give it a shot. Thanks for tip on the Van's part. I am not sure about the sealer approach. Would suck to have that spring a l leak. My rv6a has a small annoying leak on right side that leaves a constant stain but I dread pulling it all apart. It seeps out the fairing.

Anyhow, I will make sure to update my progress here for anyone else that's interested. Thanks again Dane.
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Re: Eliminating the Header Tanks

Postby danerazz » Thu Jul 02, 2020 9:15 am

Vans has a couple sizes of those fittings. The -112 is the 1/8” one. They also have a 1/4” and I think a 3/8”.

If properly sealed between the tank and flange, and sealant on the rivets before they are installed, and use sealed rivets, it should not be a problem. I’d be worried about future cracks or pinholes with welds.

I did exactly this and used riveted aluminum to build an oil tank for my plane. I used the vans fitting for the oil temp probe port. So far no leaks with hot oil (though in all fairness just have had ground runs thus far).

Just think like gasoline and put sealant EVERYWHERE.
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Re: Eliminating the Header Tanks

Postby EchoWhiskey » Thu Jul 02, 2020 5:07 pm

20200702_170326.jpg
This is from a Citabria. Dihedral high wing. No header, no fuel switch, 4 lines from front and back of tanks feeding this block.

NO FUEL PUMP ! Gravity fed.......

The line from back of tanks is 1/2"
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Re: Eliminating the Header Tanks

Postby danerazz » Thu Jul 02, 2020 6:41 pm

You could probably just use a multi-port manifold. May not need a collector. The collector is a bit of a “belt and suspenders” method, and is very similar to many Cessna systems and is a product of my paranoia.

I would still put it at a low point and put a sump drain in it. The vent probably would not be needed in that case either.

The only citabria experience I have is a 7KCAB which has a header on the firewall for inverted flight.
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Re: Eliminating the Header Tanks

Postby R Rinker » Sat Jul 04, 2020 3:31 pm

I'm a fan of a sump drain in aluminum tanks, because where I lived everytime I drained a sample from the tank sump I could always see tiny water droplets filtering down the plastic sample tube, caused by condensation on the bare aluminum above the fuel level inside the tank. With fiberglass tanks or rubber bladders it is totally different. So with aluminum tanks why not eliminate that water before it reaches any filters etc. where it can freeze and cause blockage or ???? However, it really should be an actual sump, which means a depression in the low corner of the tank, as opposed to just threading a drain attachment onto the flat aluminum bottom....
I'm glad to see a good lively discussion on this fuel supply system topic, because it seems to be a weak point in homebuilts.
Same thing is true if using a metal gas can to fuel up with. In Alaska it used to be common to buy fuel in metal cans. I 'always' ran this through a chamois fitted in a big funnel, and 'everytime' had water in the chamois. When the plastic gas cans became common, I didn't get any more water, so don't use the chamois anymore.
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Re: Eliminating the Header Tanks

Postby danerazz » Sat Jul 04, 2020 6:37 pm

The sumps in the fiberglass is to eliminate any rainwater or other, plus to hopefully eliminate (or detect) the sediment that several have noted in the composite tanks.
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Re: Eliminating the Header Tanks

Postby stede52 » Sun Jul 05, 2020 12:02 pm

Just FYI, here is how they run their sump lines for the carboncub and probably most cubs, which could easily be done on the highlander. Of course if you wanted folding wings you would add the disconnects in the forward tank outlets.
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Re: Eliminating the Header Tanks

Postby EchoWhiskey » Fri Jul 10, 2020 7:39 pm

I had 1/8 npt alum bungs welded to tanks on inboard aft corners for drains.

However, I learned that as the Apex is fuel injected, 90% of the sent fuel gets returned. I was not aware of that. The return needs to go to wing or header

So, I either need to run a single header with said return to that or get a duplex valve. I am leaning towards the latter.

I am not sure about the headers.

The cub drawing looks like the Citabria I looked at.
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Re: Eliminating the Header Tanks

Postby danerazz » Sat Jul 11, 2020 9:36 am

One other option is to run a return to one wing tank, and then use a L-R-Off fuel valve. You would have to monitor and switch tanks to manage like older pressure carb aircraft required.

The duplex valve seems like the best option. Just add the two ports. If it is beyond welding due to installation you could use the Vans NPT bungs that rivet in with sealant. Mount them high on the tank if you are concerned about leakage.
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Re: Eliminating the Header Tanks

Postby Tralika » Sat Jul 11, 2020 6:44 pm

As long as your header tank is of reasonable size, two gallons or so, you need not run a return line to your main fuel tanks. You want to have a large enough header tank so the return fuel will cool off before it get circulated through the fuel pumps again.
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