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rdmac(at)swbell.net
Guest

Posted: Fri Sep 01, 2006 2:13 pm Post subject: Fuel feed problem

I’m trying to understand if I have a problem or not. The fuel from the left wing tank is being emptied before the fuel in the right tank even starts to go down in my Model 7.  Last week end after putting 5 gallons in each tank; I notice that almost all the fuel had some how migrated over to the right tank and only about two gallon was showing in the left. I made a couple of steep turns to the left to try to get the fuel to run back over to the left wing but nothing seems to happen. I’m really not too concerned about it I just can’t figure out why the fuel seem to migrate over to the right wing. Even after the plane sits on level ground for several days the fuel still will not equalize in each tank. Is it possible that the vent line from the header tank to the right wing tank is pinched and only allowing fuel flow from the left tank first? Will the fuel begin to flow from the right tank after the left tank is completely empty? Opinions please.  

   

Roger Mac  

        [quote][b]

torgemor(at)online.no
Guest

Posted: Fri Sep 01, 2006 4:17 pm Post subject: Fuel feed problem

Hi Roger,



Very interesting report.



Over the years, the fuel system have been some modified. The latter was to  

remove the wing valves. IMHO. -a wrong decision..

Well, the fact is that the "pitot" pressure from each wing tank might  

"differ" some.  Realizing this, it's easy to see that fuel might be  

transported from "high" pressure side to "lo" pressure side.  I.E. the  

differential pressure will transferee fuel (via the header tank) to the  

other tank.



OK., how could the pressure differ?  The fact is -  the wing profile might  

be "slightly" different in the position where the "cap pitot" is located.  

Second, the "cap pitot" might be slightly higher, a little bit more aft,  

or a little bit forward of the "other" side -and this will make different  

tank pressure.



Also -a well blocked tube "can" create such symptom, but seldom like this,  

it's more like "not possible" to get fuel from that side situation.



If this problem is due to differential pressure, a ?cross vented? system  

will solve the problem, -also the reinstallation of the wing tank valves  

will cure such a problem!!   Besides, if you park in a slope (the aircraft  

is banked some), fuel will transfer and drain out via the lo wing side.   

If you fly in rough airfield you?ll know....



Well, check your tank vents (tank pitot), also try to find that they are  

in same relative position..



The best method to use is to measure the wing tank pressure, -I'm sure  

they are different.



Well, first check your "pitot vent" and the cap gasket (very important as  

this "outside" area of wing has lo pressure).



Ok., good luck.

Torgeir.



On Sat, 02 Sep 2006 00:09:27 +0200, Roger McConnell <rdmac(at)swbell.net>  

wrote:



 	  Quote: 	
		   I'm trying to understand if I have a problem or not. The fuel from the  

 left

 wing tank is being emptied before the fuel in the right tank even starts  

 to

 go down in my Model 7.  Last week end after putting 5 gallons in each  

 tank;

 I notice that almost all the fuel had some how migrated over to the right

 tank and only about two gallon was showing in the left. I made a couple  

 of

 steep turns to the left to try to get the fuel to run back over to the  

 left

 wing but nothing seems to happen. I'm really not too concerned about it I

 just can't figure out why the fuel seem to migrate over to the right  

 wing.

 Even after the plane sits on level ground for several days the fuel still

 will not equalize in each tank. Is it possible that the vent line from  

 the

 header tank to the right wing tank is pinched and only allowing fuel flow

 from the left tank first? Will the fuel begin to flow from the right tank

 after the left tank is completely empty? Opinions please.

 Roger Mac




	


-- 

Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Fri Sep 01, 2006 5:52 pm Post subject: Fuel feed problem

At 05:16 PM 9/1/2006, you wrote:

 	  Quote: 	
		  Realizing this, it's easy to see that fuel might be

transported from "high" pressure side to "lo" pressure side.  I.E. the

differential pressure will transferee fuel (via the header tank) to the

other tank.


	


I ran some numbers. If there's a 4 inch difference in surface height 

between the two tanks, that corresponds to about 0.1 psi pressure head. 

That pressure head corresponds to about 75 mph differential velocity 

between the two pitot vents. In my case that would mean one pitot was 

blocked completely! (Which we know would be a problem.) I'd guess you'd 

never get more than 10% velocity variation between the two pitot. 

(Remember, any variation would have to be extremely local, else you'd get a 

lift variation between the two wings and subsequent roll.)



Since the tanks are about 60" apart, center to center, it takes about 1 

degree of roll to generate 1" of pressure head. (That's about 7" difference 

in wing-tip height.) You'd therefore have to fly around with 4 degrees of 

roll, (28" at the tip,) to empty one tank. That's pretty extreme.



What does it all mean? I HAVE NO IDEA! (My tanks don't equalize either so 

I'm trying to figure it out - for purely academic purposes, you understand.)

Guy Buchanan

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

rdmac(at)swbell.net
Guest

Posted: Fri Sep 01, 2006 6:22 pm Post subject: Fuel feed problem

Torgeir,

	Thanks for your comments. I will check the cap pitot/vents for

blockage and also for a bad cap gasket, but other than that I don't see how

I could have a pressure differential. They are identical and are located in

identical locations on each wing. If the problem persists, I may try folding

the right wing and checking the fitting where the vent tube from the header

tank attaches to the right tank. That fitting is straight and the tube has

to make a pretty sharp 90 degree bend and it maybe pinched going into that

fitting. I do have valves on each tank but they stay OPEN. I use a master

valve on the consol to shut off the fuel supply.....thanks again

	Roger



--

barry(at)pgtc.com
Guest

Posted: Sat Sep 02, 2006 4:56 am Post subject: Fuel feed problem

Roger, it sounds like your right side fuel vent is  blocked.  It prevents air entry and so retards fuel flow but at some  point fuel does flow some and this creates a vacuum that sucks the  fuel from the other side.

  

 Barry 

 [quote]   ---

pwmac(at)sisna.com
Guest

Posted: Sat Sep 02, 2006 5:20 am Post subject: Fuel feed problem

Roger,

Maybe I missed it but did you tell us what kind of fuel lines you are 

using. (Vent and fuel feeds). I think If it was my plane here is what 

I would do:

Replace all the lines, the cap gasket as well as confirm that the cap 

vent is truly open & the same on both caps. Examine the fittings at 

the tank for obstructions when replacing the lines. Clean the finger 

strainer and examine them both for similarity.

I would also look inside the tank for bad stuff. The fittings are 

visible from the fuel filler opening. Use a mirror for close exam.

Regards, Paul

pwmac(at)sisna.com
Guest

Posted: Sat Sep 02, 2006 5:23 am Post subject: Fuel feed problem

Good point. It sounds like he used a straight fitting instead of the 

preferred 90 degree fitting at the vent to tank connection.

  Paul

==================

At 06:57 AM 9/2/2006, you wrote:

 	  Quote: 	
		  Roger, it sounds like your right side fuel vent is blocked.  It 

prevents air entry and so retards fuel flow but at some point fuel 

does flow some and this creates a vacuum that sucks the fuel from 

the other side.



Barry

rdmac(at)swbell.net
Guest

Posted: Sat Sep 02, 2006 6:57 am Post subject: Fuel feed problem

Paul,

	The lines are what was supplied from Skystar back in '02, automotive

grade is my guess. The vent tube is clear tygon, either 1/4 or 3/8. I'm

thinking that I do have a blocked vent tube. I'll try to check that in the

next day or two. I probable need to go with a 90 degree fitting at the tank.

 Thanks for your help.

Roger

--

pwmac(at)sisna.com
Guest

Posted: Sat Sep 02, 2006 7:38 am Post subject: Fuel feed problem

If you have trouble finding a swivel fitting try the local farm store 

that sells hydraulic fittings. The hose supplied by Skystar in that 

time frame was Mil 6000 hose - bad stuff for most locals when using 

auto gas. The hose will be properly labeled whether auto hose or Mil 

hose. My recommendation - Replace all hose with SAE R-7 or R-9, 

including the vent. Some R-9 is much stiffer than others. Check 

several auto supply places.



The thing to remember if one is using auto gas is that some places 

have very chemically bad stuff. I just read that there are now 50 

formulations of gas used in the US. This may explain why some guys 

get away with using the Mil hose.

Good luck, Paul

===================

At 08:56 AM 9/2/2006, you wrote:

[quote]



Paul,

         The lines are what was supplied from Skystar back in '02, automotive

grade is my guess. The vent tube is clear tygon, either 1/4 or 3/8. I'm

thinking that I do have a blocked vent tube. I'll try to check that in the

next day or two. I probable need to go with a 90 degree fitting at the tank.

  Thanks for your help.

Roger

--

dosmythe(at)cox.net
Guest

Posted: Sat Sep 02, 2006 7:47 am Post subject: Fuel feed problem

Roger,

    Don't know what Skystar provided in 02 but would suspect MIL-6000 black. 

The MIL-6000 will be marked as such on the line.  If so, get rid of that 

stuff anywhere it's used in the plane.  I would recommend either clear 

Polyurethane (from Spruce) or SAE-R7 (automotive line) or SAE-R9 (fuel 

injection automotive line).  The R9 injection line is more expensive but is 

better with ethanol.  I have used the clear Polyurethane line from Spruce 

for several years.  It works great but will discolor over time.  I have read 

a bunch of stuff on fuel lines and came to the conclusion that "clear Tygon" 

is not fuel rated.  Only the yellow Tygon is????

    In my opinion, a blocked vent tube would not cause unequal tank drains

---

clint_bazzill(at)hotmail.
Guest

Posted: Sat Sep 02, 2006 10:07 am Post subject: Fuel feed problem

test

From: "Roger McConnell" <rdmac(at)swbell.net>

Reply-To: kitfox-list(at)matronics.com

To: <kitfox-list(at)matronics.com>

Subject: Fuel feed problem

Date: Fri, 1 Sep 2006 17:09:27 -0500

I'm trying to understand if I have a problem or not. The fuel from the left

wing tank is being emptied before the fuel in the right tank even starts to

go down in my Model 7.  Last week end after putting 5 gallons in each tank;

I notice that almost all the fuel had some how migrated over to the right

tank and only about two gallon was showing in the left. I made a couple of

steep turns to the left to try to get the fuel to run back over to the left

wing but nothing seems to happen. I'm really not too concerned about it I

just can't figure out why the fuel seem to migrate over to the right wing.

Even after the plane sits on level ground for several days the fuel still

will not equalize in each tank. Is it possible that the vent line from the

header tank to the right wing tank is pinched and only allowing fuel flow

from the left tank first? Will the fuel begin to flow from the right tank

after the left tank is completely empty? Opinions please.

Roger Mac

clint_bazzill(at)hotmail.
Guest

Posted: Sat Sep 02, 2006 10:14 am Post subject: Fuel feed problem

My tanks never are equal in fuel usage.  However, the lower my fuel is the 

more evenly they become.  Clint

From: Guy Buchanan <bnn(at)nethere.com>

Reply-To: kitfox-list(at)matronics.com

To: kitfox-list(at)matronics.com

Subject: Re: Fuel feed problem

Date: Fri, 01 Sep 2006 18:49:20 -0700

At 05:16 PM 9/1/2006, you wrote:

 	  Quote: 	
		  Realizing this, it's easy to see that fuel might be

transported from "high" pressure side to "lo" pressure side.  I.E. the

differential pressure will transferee fuel (via the header tank) to the

other tank.

I ran some numbers. If there's a 4 inch difference in surface height between 

the two tanks, that corresponds to about 0.1 psi pressure head. That 

pressure head corresponds to about 75 mph differential velocity between the 

two pitot vents. In my case that would mean one pitot was blocked 

completely! (Which we know would be a problem.) I'd guess you'd never get 

more than 10% velocity variation between the two pitot. (Remember, any 

variation would have to be extremely local, else you'd get a lift variation 

between the two wings and subsequent roll.)

Since the tanks are about 60" apart, center to center, it takes about 1 

degree of roll to generate 1" of pressure head. (That's about 7" difference 

in wing-tip height.) You'd therefore have to fly around with 4 degrees of 

roll, (28" at the tip,) to empty one tank. That's pretty extreme.

What does it all mean? I HAVE NO IDEA! (My tanks don't equalize either so 

I'm trying to figure it out - for purely academic purposes, you understand.)

Guy Buchanan

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sat Sep 02, 2006 1:04 pm Post subject: Fuel feed problem

Paul-

In my IV tanks, made in 1994, the vent opening is so close to the top 

flange of the tank that it would be impossible to use a 90° fitting, 

because you would not be able to rotate it. Where did you hear about 

"the preferred 90 degree fitting"?...and what makes it preferable?

Lynn

On Saturday, September 2, 2006, at 09:22  AM, PWilson wrote:

 	  Quote: 	

 Good point. It sounds like he used a straight fitting instead of the 

 preferred 90 degree fitting at the vent to tank connection.

  Paul

 ==================

 At 06:57 AM 9/2/2006, you wrote:

> Roger, it sounds like your right side fuel vent is blocked.  It 

> prevents air entry and so retards fuel flow but at some point fuel 

> does flow some and this creates a vacuum that sucks the fuel from the 

> other side.

>

> Barry

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

pwmac(at)sisna.com
Guest

Posted: Sat Sep 02, 2006 5:53 pm Post subject: Fuel feed problem

Yes the vent is at the top of the tank under the 

flange. One can use a swivel 90 deg fitting. Some 

have female threads so one has to use a close 

union In any event they are available .Check 

hydraulic supply houses. Check the car nut places 

like Earls. Attached is a couple of pics foe an 

even easier way using AN fittings & a straight 

swivel from the hydraulics house + soft Al tubing.

Paul

=============



At 03:04 PM 9/2/2006, you wrote:

 	  Quote: 	
		  



Paul-

In my IV tanks, made in 1994, the vent opening 

is so close to the top flange of the tank that 

it would be impossible to use a 90° fitting, 

because you would not be able to rotate it. 

Where did you hear about "the preferred 90 

degree fitting"?...and what makes it preferable?



Lynn

On Saturday, September 2, 2006, at 09:22  AM, PWilson wrote:



>

>

>Good point. It sounds like he used a straight 

>fitting instead of the preferred 90 degree 

>fitting at the vent to tank connection.

>  Paul

>==================

>At 06:57 AM 9/2/2006, you wrote:

>>Roger, it sounds like your right side fuel 

>>vent is blocked.  It prevents air entry and so 

>>retards fuel flow but at some point fuel does 

>>flow some and this creates a vacuum that sucks the fuel from the other side.

>>

>>Barry

>

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janderson412(at)hotmail.c
Guest

Posted: Sun Sep 03, 2006 12:24 am Post subject: Fuel feed problem

Roger, you can do all the steep turns you wish so long as they are ballanced 

and no fuel will transfer, only slipping wil have the effect





From: "Roger McConnell" <rdmac(at)swbell.net>

Reply-To: kitfox-list(at)matronics.com

To: <kitfox-list(at)matronics.com>

Subject: Fuel feed problem

Date: Fri, 1 Sep 2006 17:09:27 -0500

I’m trying to understand if I have a problem or not. The fuel from the left 

wing tank is being emptied before the fuel in the right tank even starts to 

go down in my Model 7.  Last week end after putting 5 gallons in each tank; 

I notice that almost all the fuel had some how migrated over to the right 

tank and only about two gallon was showing in the left. I made a couple of 

steep turns to the left to try to get the fuel to run back over to the left 

wing but nothing seems to happen. I’m really not too concerned about it I 

just can’t figure out why the fuel seem to migrate over to the right wing. 

Even after the plane sits on level ground for several days the fuel still 

will not equalize in each tank. Is it possible that the vent line from the 

header tank to the right wing tank is pinched and only allowing fuel flow 

from the left tank first? Will the fuel begin to flow from the right tank 

after the left tank is completely empty? Opinions please.



Roger Mac



_________________________________________________________________

Become a fitness fanatic (at)  http://xtramsn.co.nz/health

neflyer48(at)cableone.net
Guest

Posted: Sun Sep 03, 2006 5:36 am Post subject: Fuel feed problem

I believe the only purpose of the fuel vent line is  to insure that the header tank stays full. If the fuel is being used only from  your left tank, then the right tank doesn't have equal pressure. Check your fuel  cap vent on the right tank.

  

 Jerry Kohles  M3-912

  

  

  

 ---

rjdaugh

Joined: 30 Aug 2006
Posts: 195

Posted: Sun Sep 03, 2006 1:22 pm Post subject: Fuel feed problem

This comes up often.  I believe that fuel levels in the two tanks are simply

the BEST indicator that we have of whether or not we are flying in a

coordinated manner.  As John pointed out steep banked turns should have NO

effect if we are coordinated.  But uncoordinated flight does.  Try it an

see.



If Guy's calculations are right (and I suspect that they are - Thanks for

the analysis Guy!) It just points out how sensitive the fuel levels are to

flying with one wing low.  Are there really Fox drivers out there that are

so good that they can tell if one wing tip is 7" higher than the other?

With the plane on a level surface (hangar floor?) this is easy too

determine, but try it out on a sorta level field.  You need a good level to

tell.



When I fly, I just use the ball for an immediate indication of how level I

have the wings.  I use the fuel levels in the tanks to tell me if I am

favoring one side or the other.  It is fairly easy over a time period of 15

to 30 mins to move fuel from one tank to the other while flying.  I very

seldom fly with full tanks, but when I do, I close a valve so that I am

drawing from only one tank, so I don't lose fuel out one vent or the other.



I am not saying that there can't be other explanations, only that a majority

of the time we are simply flying uncoordinated to a small degree.



Put a 3/4" piece of wood under one main wheel and check the levels again in

the morning.



Randy  - straighten up and fly right!



.           



--

_________________
Randy
Kitfox 5/7 912S
Black Hills, South Dakota

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Sep 03, 2006 4:43 pm Post subject: Fuel feed problem

Last summer I lost one of the vented gas caps. (Don't ask) I decided for the

last flight of the summer I would swipe the gas cap off my Bombardier J5

track machine.  This cap will fit but is not vented.  The first thing to

happen was pressure built up in the un-vented tank and caused the vented

tank to over flow.  Then the vented tank emptied before any fuel came out of

the tank with the un-vented cap.  



I went to Canada's what not, come hardware, come tire shop, Canadian Tire,

A.K.A. "Crappy Tire" for another cap. The only one I could find had one of

those one way vent valves in it. No improvement from last summer!  I then

drilled out the one way valve ( plastic) and drilled a 1/4"+ hole in the gas

cap I then soldered about 5" of steel brake line (1/4") into the hole and

bent the line forward into the slip stream.  It is cheap, with a capitol

"C".  And works like the original.  Remember when soldering, heat the work

not the joint.  I also took the rubber sealing gasket out before applying

the heat for the soldering.  Now if they would only make chrome plated brake

line it would match the chrome caps.... Maybe later the fall I may paint

both gas caps.



BTW the home brew vented cap works great!



Noel

Mod III-A  R582 Grey Hd., "B" box, Ivo In flight adj three blade UL.

[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Sep 03, 2006 4:46 pm Post subject: Fuel feed problem

I doubt there is actually a workable definition of exactly what "gas" or

"gasoline" is ... Emptor cravat!



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Sep 03, 2006 5:10 pm Post subject: Fuel feed problem

Mod III-A  has a site tube for the gauge..... I  like your gauges...much

easier to read.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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