Nose tank sometimes feeds the wing tank

[avenger1949]

sometimes when I am flying and I open the valve at the wing root to refill the nose tank... the gas goes the wrong way and goes into the wing tank causing it to dump fuel on the wing. Is there anyway the nose tank has a vent that get pressure from the air when I fly? I have the wire nose gauge and a vented cap on the right wing. Looking to fly up to Iowa over labor day and really need the wing gas. Sometimes it works right and sometimes not.

[M Towsley]

Re: Nose tank sometimes feeds the wing tank

Is the wing tank vented with the curved tube facing forward, rather than backward?

[astjp2]

Re: Nose tank sometimes feeds the wing tank

Also, what size vent tube in the cap? Tim

[Hank Jarrett]

Re: Nose tank sometimes feeds the wing tank

The area of the boot cowl in front of the windshield can be a high pressure area and if the vent cap tube on the wing tank is facing with the open hole aft you could get even lower than normal pressure on top of the wing (remember that the top of the wing is LOWER than atmospheric pressure already). I have never heard of the pressure between the main cap and wing cap being large enough to pull the fuel up hill but I guess it is possible. Be sure the open hole of the wing tank vent tube is facing FORWARD, not aft.
Hank

[Mark Julicher]

Re: Nose tank sometimes feeds the wing tank

If the wing fuel cap has a bad gasket, the low pressure on top of the wing can trump the pressure rise from the itty bitty forward facing vent tube and set up a siphon.

[avenger1949]

Re: Nose tank sometimes feeds the wing tank

If the wing fuel cap has a bad gasket, the low pressure on top of the wing can trump the pressure rise from the itty bitty forward facing vent tube and set up a siphon.

The curve is forward and the vent size is about 3/16ths I would think since it used to be a nose cap. Now as I think about it I don't remember a gasket being on the cap so will look at that tomorrow. I suppose Orielly's has a cap gasket if mine is in fact gone or hard. Thanks guys will see if that helps. Seemed strange I could get enough pressure to empty the nose tank into the wing tank but that was what is happening

[astjp2]

Re: Nose tank sometimes feeds the wing tank

Get an airplane gasket from univair, the have them that will not disolve in autofuel. Oriellys wont have them because that style of cap hasn't been used since the 60's. Tim

The curve is forward and the vent size is about 3/16ths I would think since it used to be a nose cap. Now as I think about it I don't remember a gasket being on the cap so will look at that tomorrow. I suppose Orielly's has a cap gasket if mine is in fact gone or hard. Thanks guys will see if that helps. Seemed strange I could get enough pressure to empty the nose tank into the wing tank but that was what is happening

[M Towsley]

Re: Nose tank sometimes feeds the wing tank

Let me know if you cannot find one. The original cap company that provided Taylorcraft the caps is still in business and can provide cork or rubber, (not necessarily rubber but I cannot remember what they called it). Chief also has the correct size to fit that will also work with 100ll and auto fuel.

[otrcman]

Re: Nose tank sometimes feeds the wing tank

You can think of your fuel feed situation as the same thing as sucking water up a straw to take a drink. Is it any surprise that the water travels from the glass to your mouth even though it's uphill ?

As Hank said, the air pressure in the area just in front of the windshield is higher than ambient. And we all know that the air pressure on top of the wing is much lower than ambient; that's what causes lift. Combine the increased pressure at the main tank vent with the reduced pressure at the wing tank vent, and it's no surprise that the liquid flows uphill.

The gas caps are placed in a location where the local pressure is perhaps lower than any other place on the airplane. If we put the tank vent in the cap for convenience, then it's necessary to make up for the low "static" pressure by providing "ram pressure". Thus the pitot style gas caps.

Marty, could you post the contact information for the company that made the gas caps ? I've got another project from that era that needs caps.

Dick

[Hank Jarrett]

Re: Nose tank sometimes feeds the wing tank

If you have a Farm Supply or Tractor Supply in your area you might want to check their "Aviation Tractor and Engine" section. A lot of the parts originally used on our era planes came from auto and farm supply stocks.
Hank

[avenger1949]

Re: Nose tank sometimes feeds the wing tank

If you have a Farm Supply or Tractor Supply in your area you might want to check their "Aviation Tractor and Engine" section. A lot of the parts originally used on our era planes came from auto and farm supply stocks.
Hank

Will check my aviation department at tractor supply and thanks guys for the info I just didn't want to discover there was a vent somewhere in the cowl that was pressurizing my nose tank. I guess I could always drill my cap for a larger ram air port. After I posted the message about maybe not having a gasket I realized that the cap fits tight so I must have one there although it might not be sealing. Which might explain why sometimes it works fine and sometimes it doesn't. I could always put a small inline low pressure one way pump on the line as well I suppose. I had one on my MiniMax to move gas from the wing to the nose tank because they were about at the same level. I am betting the rubber gausket is NeoPrem and if you give the address here I will order one as mine is probably original.

[Hank Jarrett]

Re: Nose tank sometimes feeds the wing tank

I saw a great wing tank vent that was just a small line from the filler neck through the wing to the BOTTOM of the wing (wing tank cap was sealed). Looked like it would work great, but of course TOTALLY illegal unless he had paperwork behind it. That is the way the wing tank SHOULD be vented.
Hank

[astjp2]

Re: Nose tank sometimes feeds the wing tank

Hank, is that based on engineering data or personal opinion? Considering most Taylorcrafts have been flying for 70 years with wing tanks vented by the original design, I really dont see it as a problem in the design, just a lack or maint. or availability of correct parts. Tim

I saw a great wing tank vent that was just a small line from the filler neck through the wing to the BOTTOM of the wing (wing tank cap was sealed). Looked like it would work great, but of course TOTALLY illegal unless he had paperwork behind it. That is the way the wing tank SHOULD be vented.
Hank

[Robert Lees]

Re: Nose tank sometimes feeds the wing tank

The wing tank vent should of course point forwards, to pressurise the wing tank.
Last week at Oshkosh I bought spare fuel tank gaskets, part number T308-2 from one of the Flymart vendors; these have always fitted fine for me. $2.50 a piece. These are the same as Cessna oil filler gaskets (I believe).


Just as an aside, and while we're on the subject, the photo below shows two different Taylorcraft wing tank caps (from two different aircraft) both show a tiny hole drilled in the back of the copper tube.

The only logic for this, is in case the tube gets blocked (say by an insect) then air can still flow into the tank, so preventing the tank crushing, under atmospheric pressure as the fuel level drops.

[Hank Jarrett]

Re: Nose tank sometimes feeds the wing tank

I spent some of my career working fuel systems and it is standard practice from the 30s to vent wing tanks like the standard Taylorcraft wing tanks, but most system designers recognized it wasn't the "best" way since you were venting to one of the lowest pressure areas on the aircraft. Most more modern designs try to vent to an area of at least static atmospheric pressure for the altitude of the aircraft. The Taylorcraft system makes up for part of the problem with the forward facing vent tube, but it is not a very elegant solution (cheap and fairly workable, but not elegant). When I saw the small tube coming out of the filler neck and going down through the top covering I knew immediately where it would come out (the bottom skin). Engineers just tend to like elegant solutions and I really liked that one.
That said, I did NOT consider doing it to my plane. What is there already is pretty well proven (with occasional problems) and I like keeping things original. I also don't like to make undocumented configuration changes and like to avoid confrontation with the FAA when making something "better". Lots of times, they don't agree with what I think is "better". ;-)
Hank

Hank, is that based on engineering data or personal opinion? Considering most Taylorcrafts have been flying for 70 years with wing tanks vented by the original design, I really dont see it as a problem in the design, just a lack or maint. or availability of correct parts. Tim