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Fuel migration

Matronics Email Lists Forum Index -> Kitfox-List

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cschmokel

Joined: 04 Aug 2009
Posts: 23
Location: Pullman, WA

Posted: Wed Jun 02, 2010 7:06 pm Post subject: Fuel migration

Hey guys,



Full disclosure, I'm relatively new to aircraft, so pardon the possibly stupid question.  I've got a Kitfox 5 with 13 gallon tanks.



Yesterday, I had only 2 or 3 gallons in my tanks.  Fuel sight tubes showed no gas.  I put roughly 3 gallons in one tank, and marked the fuel level on the sight tube.  Today, the sight tube for the tank I added the fuel to is down all the way, but the other sight is much higher than yesterday.



Looks like the fuel is migrating .. why?  The wings are level and there should be no pressure differential .. so what's going on here?  Thanks!



Carl

Tom Jones

Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

Posted: Thu Jun 03, 2010 4:49 am Post subject: Re: Fuel migration

Yes, fuel will migrate from one tank to another.  If the level of one tank is higher than the other it is probably just because the wings are not level.  Probably due to the ground it is sitting on is not level.



Have you found the Kitfox aircraft web site and looked at the service bulletins and service letters yet?  http://www.kitfoxaircraft.com/



Here's a direct link to a service letter that explains a proper fuel system.

http://www.kitfoxaircraft.com/support/service_letters/sl45.htm

_________________
Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA

lcfitt(at)sbcglobal.net
Guest

Posted: Thu Jun 03, 2010 4:51 am Post subject: Fuel migration

Carl,



Unless the wing tanks are separated by shut off valves, they are connected 

through the header tank.  The fuel will seek it's level.  Welcome to the 

world of Aircraft.



Lowell

--------------------------------------------------

From: "cschmokel" <cschmokel(at)gmail.com>

Sent: Wednesday, June 02, 2010 8:06 PM

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

Subject: Fuel migration



 	  Quote: 	
		   



 Hey guys,



 Full disclosure, I'm relatively new to aircraft, so pardon the possibly 

 stupid question.  I've got a Kitfox 5 with 13 gallon tanks.



 Yesterday, I had only 2 or 3 gallons in my tanks.  Fuel sight tubes showed 

 no gas.  I put roughly 3 gallons in one tank, and marked the fuel level on 

 the sight tube.  Today, the sight tube for the tank I added the fuel to is 

 down all the way, but the other sight is much higher than yesterday.



 Looks like the fuel is migrating .. why?  The wings are level and there 

 should be no pressure differential .. so what's going on here?  Thanks!



 Carl





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=299808#299808

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Thu Jun 03, 2010 5:15 am Post subject: Fuel migration

Carl,

  If the header tank is full, you can expect the fuel to do that. Fuel will seek its own level and balance out between the 2 tanks. I often put gas in one of my wing tanks knowing that it will balance out over a short time. I am asuming of course you don't have a big leak inside your aircraft.

                               Dick Maddux

                                Milton,Fl

  [quote][b]

rexinator

Joined: 31 Jan 2009
Posts: 33

Posted: Thu Jun 03, 2010 7:44 am Post subject: Fuel migration

This may be obvious to everyone else.

Should the aircraft park on an angle such that this migration might 

exceed the full tank level on the lower tank, would the tank overflow 

and dump fuel on the ground? Seems possible if you don't use fuel shut 

off valves.



Rexinator

Colorado

M2/582



Lowell Fitt wrote:

 	  Quote: 	
		   



 Carl,



 Unless the wing tanks are separated by shut off valves, they are 

 connected through the header tank.  The fuel will seek it's level.  

 Welcome to the world of Aircraft.



 Lowell

 --------------------------------------------------

 From: "cschmokel" <cschmokel(at)gmail.com>

 Sent: Wednesday, June 02, 2010 8:06 PM

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

 Subject: Fuel migration



> 

>

> Hey guys,

>

> Full disclosure, I'm relatively new to aircraft, so pardon the 

> possibly stupid question.  I've got a Kitfox 5 with 13 gallon tanks.

>

> Yesterday, I had only 2 or 3 gallons in my tanks.  Fuel sight tubes 

> showed no gas.  I put roughly 3 gallons in one tank, and marked the 

> fuel level on the sight tube.  Today, the sight tube for the tank I 

> added the fuel to is down all the way, but the other sight is much 

> higher than yesterday.

>

> Looks like the fuel is migrating .. why?  The wings are level and 

> there should be no pressure differential .. so what's going on here?  

> Thanks!

>

> Carl

>

>

> Read this topic online here:

>

> http://forums.matronics.com/viewtopic.php?p=299808#299808

>

>

rdmac(at)swbell.net
Guest

Posted: Thu Jun 03, 2010 5:13 pm Post subject: Fuel migration

Fuel will also migrate from one tank to the other we you work the rudder

when the plane is in level flight. Step on the left rudder, fuel will

transfer to the left tank. And vise versa.



Roger McConnell, Duncan, OK

Model 7 Trigear, Rotax 912uls 

Flying sense Jan. 06



--

cschmokel

Joined: 04 Aug 2009
Posts: 23
Location: Pullman, WA

Posted: Thu Jun 03, 2010 9:21 pm Post subject: Re: Fuel migration

Fair enough .. the tie down pad must be off kilter a bit.  Thanks guys



Carl

Float Flyr

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

Posted: Fri Jun 04, 2010 3:47 am Post subject: Fuel migration

One other time when fuel will migrate from one tank to another is when

either one of the vent tubes are blocked ...  like by flies or spiders.

When this happens evaporating fuel may actually push gas to the other tank

and cause it to overflow.  It's a good part of a pre-flight walk around to

check the fuel vents at the same time you check the caps are properly

locked.



Depending on where your filler cap is in the wing chord it is more than

possible for gas to be siphoned out of both tanks if one cap comes off

either before or in flight.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

N81JG(at)aol.com
Guest

Posted: Sun Jun 06, 2010 4:10 pm Post subject: Fuel migration

If you have flown the plane since the fill, an air leak around one cap  gasket will expose the tank to quite a bit of negative pressure and siphon fuel  from the opposite tank. This happened to my son's Kitfox 7 and was solved by  fresh gaskets. I think he said the gaskets are the same as in a Mercedes  car.

  

 John Greaves

 Redding, CA

  

  In a message dated 6/3/2010 6:14:18 P.M. Pacific Daylight Time,  rdmac(at)swbell.net writes:

 [quote]-->    Kitfox-List message posted by: "Roger McConnell"    <rdmac(at)swbell.net>



Fuel will also migrate from one tank to the    other we you work the rudder

when the plane is in level flight. Step on the    left rudder, fuel will

transfer to the left tank. And vise    versa.



Roger McConnell, Duncan, OK

Model 7 Trigear, Rotax 912uls    

Flying sense Jan. 06



--

FlyboyTR

Joined: 04 Nov 2006
Posts: 215
Location: Mobile, Alabama

Posted: Wed Jun 16, 2010 6:53 am Post subject: Re: Fuel migration

Yes...if the plane is not level (wings), fuel will gravity feed to the low wing's tank (as stated by many folks so far...).  When I park my Vixen, I always turn one wing tank off to prevent flow to the other tank.  Two years ago while on a cross country flight, we stopped for the day, topped off both tanks and moved the plane to the tie down area.  In my rush...I didn't realize how unlevel the plane was.  To make matters worse, I had picked up a screw in the left tire (which was already the low side of the plane) and the tire went flat during the night.  Fuel had ran out the left vent, down, over and under the wing, down the lift strut, fuselage and landing gear.  It took 7 gallons to top the right tank off after the tire was repaired.



That is why I usually always turn one wing tank off when parked!  ...Lesson Learned!

_________________
Travis Rayner
Mobile, AL
Skystar Vixen, N-789DF
Continental IO-240, Prince P-Tip Prop
ADI-II Autopilot
AnyWhereMap Navigation with weather
www.enotam.net (My Flying Info Website)

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