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Fuel Flw

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rv73hl(at)comcast.net
Guest

Posted: Fri Dec 29, 2006 7:16 am Post subject: Fuel Flw

My Model IV 1200, has been feeding fuel from the right  tank with gas in the left also.  I finally deceided to run to see if the  gas would transfer.  Luckly for me, it stopped on final at our  airport.  The left tank had gas in it.  It would not start, we added  gas to the right tank, and after a few minutes on choke, it  started.

  

 Question...what would cause the tanks not to flow  evenly.  We had check the lines, and they all flowed.  I would think  the tanks would level up when sitting on the ground, but they do not seem to  cross flow.

  

 Suggestions please.

  

 Howard

   [quote][b]

kerrjohna(at)comcast.net
Guest

Posted: Fri Dec 29, 2006 9:25 am Post subject: Fuel Flw

a similar experience was found to be caused by an undiscovered kink in the left hose when the wing was swung forward into flight position.  we did not make it back to the airport but landed in a nearby hayfield

  

 [quote]-------------- Original message -------------- 

From: "howard" <rv73hl(at)comcast.net> 

    My Model IV 1200, has been feeding fuel from the right tank with gas in the left also.  I finally deceided to run to see if the gas would transfer.  Luckly for me, it stopped on final at our airport.  The left tank had gas in it.  It would not start, we added gas to the right tank, and after a few minutes on choke, it started.

  

 Question...what would cause the tanks not to flow evenly.  We had check the lines, and they all flowed.  I would think the tanks would level up when sitting on the ground, but they do not seem to cross flow.

  

 Suggestions please.

  

 Howard

 	  Quote: 	
		  

	
[b]

torgemor(at)online.no
Guest

Posted: Fri Dec 29, 2006 6:57 pm Post subject: Fuel Flw

Hi Howard,



this is an interesting situation, I've been thinking a little about this  

one. I'll say this is the first issue after the mandatory main tank "fuel  

shutoff valve" removal.



Well, the removal of these two valves was a big mistake that Skystar did,  

IMO. Do you have those installed??



There is three good reasons (at last) to keep this valves installed.



Lets first talk about your "possible" problem.



By some reason the pressure is higher in the right tank vs. the left side.  

This explain the fuel transfere, it also explain your engine stoppage,  

well how.



I'm assuming that you have the feeder went line connected to the left hand  

main tank, right?



As we assume that the head pressure is lower in left tank, the transfere  

take place -and fuel will be transferred by both the left feeder line and  

the vent line. As the feeder is "pressurized" fuel transfere will use both  

lines, that's why this go so fast.



As the left tank go dry, air start entering the feeder, the remaining fuel  

is trapped in the left tank by the air pressure, the engine is using the  

remaining fuel that’s below both feeding lines inside the feeder. Soon  

your engine loose power.



Ok., it's right that some fuel will leak into the feeder from the left  

tank due to gravity, when feeder fuel level go below the feeder pipe  

outlet. However, this leakage will be far to low for your engine demand.

Then to the cause of the low pressure in the left tank, the traditional is  

an old leaky gasket at the main filler, but your plane is not that old so..



Next, could it be a leaky head tube? Or could it be a leaky left fuel tank  

at some high spot? All of these three is hard to spot/verify without a  

tank shut off valve.

So number one reason for having main fuel tank shut off valves, is to  

avoid unwanted fuel tranfere and loss of endurance.



In your case fuel would still be able to tranfere even if you had the shut  

off valve installed. This time via the vent line.



I've many times talked about a cross vent line, such arrangement would  

prevent transfere, but will lower the total head pressure if one of the  

tank is leaking.

Number two is a safety issue, well both tank outlet enter cockpit via a  

rubber housing - if one of those rubber housing start leaking, to stop  

such a leakage you'll need to shut both tank valves, but you'll still have  

the header for landing..

Number three.  When I'm parking, even for long term, one of the main is  

open the other is closed.  For maintenance this valve is a must.



OK.



The last thing you've mentioned, is the lack of transfere from left to  

right via the feeder when on ground.



This is hard to explain, unless you have a rubber flap valve somewhere(one  

way valve), mentioned in one of the old the Rotax Service Information  

Letter, that prevent fuel to go toward the right tank.

Well lets see what happen now..

There is still something to ask, how much fuel was left in the left tank?   

Was the fuel level above the venline tube where it is entering the left  

tank?



Good Luck

Torgeir.

On Fri, 29 Dec 2006 16:15:36 +0100, howard <rv73hl(at)comcast.net> wrote:



 	  Quote: 	
		   My Model IV 1200, has been feeding fuel from the right tank with gas in  

 the left also.  I finally deceided to run to see if the gas would  

 transfer.  Luckly for me, it stopped on final at our airport.  The left  

 tank had gas in it.  It would not start, we added gas to the right tank,  

 and after a few minutes on choke, it started.



 Question...what would cause the tanks not to flow evenly.  We had check  

 the lines, and they all flowed.  I would think the tanks would level up  

 when sitting on the ground, but they do not seem to cross flow.



 Suggestions please.



 Howard


	


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

Float Flyr

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

Posted: Sat Dec 30, 2006 6:20 am Post subject: Fuel Flw

Torgeir:



I followed your post with some interest.  I do have a question... How do you

calculate the right tank to have a higher head of fuel than the right tank?

They are both at the same distance over the header tank.



My plane has forward facing vent tubes (on the caps) on both tanks.  The

only way I can see a difference in the head of fuel from each tank is when

both tanks are at different pressures because of differences in the cap

vents.



There may be a little difference in the level of the plane in flight as the

rounded cowl distorts to some extent a persons ability to tell straight and

level.  In a case like that the upper tank will empty first.



As to having separate shut offs on each wing tank I heartily agree with you.

I check the rubber tube connections on the fuel system quite often because I

don't want a gas shower at 3000' !  Shutting off one tank will also allow

you to get a good top off for max fuel in both tanks.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Guy Buchanan

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

Posted: Sat Dec 30, 2006 7:47 am Post subject: Fuel Flw

At 07:15 AM 12/29/2006, you wrote:

 	  Quote: 	
		  Question...what would cause the tanks not to flow evenly.  We had 

check the lines, and they all flowed.  I would think the tanks would 

level up when sitting on the ground, but they do not seem to cross flow.



Suggestions please.


	


Howard,

         We need more information. How much fuel was in your left 

tank? (%) Do you have a header tank? Better yet, what does your 

entire fuel system look like, with sizes and locations of tanks and tubes.

Guy Buchanan

K-IV/1200 w/ 582 C-box & Warp 3 blade

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

lcfitt(at)sbcglobal.net
Guest

Posted: Sat Dec 30, 2006 9:42 am Post subject: Fuel Flw

Noel,



I know this was directed to Torgeir, but I have some thoughts on this. 

Because of the round shape of the top of the instrument panel / cowl, the 

Kitfox doesn't have the typical flat reference to the horizon that a Cessna 

has.  The forward carry through shoud be flat with the horizon, but is a 

distance visually from the horizon in our aiprlanes.  In the group I fly 

with we once had a guy streaming fuel from his fuel cap area and a close fly 

by confirmed he still had his cap on.  When he leveled his wings the fuel 

stream stopped.  He was our highest hour pilot, but when on a long X country 

we tend to settle in and watch the scenery letting the airplane find it's 

confort zone.  This especially if we are un-trimmed i.e., needing a little 

bit of right rudder when in cruise.  When watching Kitfoxes in flight, it is 

not uncommon to see guys flying with a wing low.



I think this is a major part of the uneven fuel flow, as in this 

configuration, you will have a higher head in the high tank.  It is 

interesting also that the high tank will indicate a higher level of fuel in 

the sight gauge, giving the impression that the low wing has less fuel in 

it's tank.  For those that have the tank valves, the common response would 

be to close the valve on the lower tank which would result in full flow from 

only the higher wing tank which might already have less fuel than the other 

tank.



When rigged properly, the system works and this is where I disagree with 

Torgeirs comment regarding Skystar's elimination of the tank valves.  I know 

some that still have them, but, and someone else will have to remind me of 

the exact reason, I believe Skystar eliminated them because of issues that 

developed after the addition of the header tank vent to the system.  As I 

unserstand it, the early fuel system with the panel tank didn't vent the 

panel tank independently from the fuel lines from the wing tanks.



This latter is from my understanding and am always welcome to comments from 

those that were closer to the issues mentioned.

Lowell  N96KL  Mod IV-1200

---

Float Flyr

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

Posted: Sat Dec 30, 2006 11:55 am Post subject: Fuel Flw

Great!  I'm not alone.  After a flight of a couple of hours last year I

found myself happily cruising along left wing low.  I would have put it down

to my weight except I was carrying an additional 70 lb or so in the right

float.  Funny how just before touchdown the plane seems to level itself

out..I have yet to land on one float although I've taken off on one float

may times.



This is not quite off topic but do not archive anyway. 



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

torgemor(at)online.no
Guest

Posted: Sat Dec 30, 2006 12:17 pm Post subject: Fuel Flw

Noel,



Let's take the questions one by one.

On Sat, 30 Dec 2006 15:20:17 +0100, Noel Loveys <noelloveys(at)yahoo.ca>  

wrote:



 	  Quote: 	
		   



 Torgeir:



 I followed your post with some interest.  I do have a question... How do  

 you

 calculate the right tank to have a higher head of fuel than the right  

 tank?

 They are both at the same distance over the header tank.


	


Sure, the head pressure is the same if; the height of the vent tube (or  

more correct "head pressure tube" installed on the fuel cap), the airfoil  

shape (the wing where the cap is located), and the relative "position  

cordline vs.pitot tip" is equal.



The thing is, when we pre compress our main fuel tanks in this way, the  

air pressure inside the tank will be equal to the head pressure. Equal  

pressure in both main tanks is the normal condition during our flight.



The pressure can't (normally) be higher in the right tank, but if the  

pressure is decreasing (going low) in the left tank, we can say that the  

pressure is higher in the right as this must be the situation in this  

case. You'll that an uncoordinated/banked attitude can be the factor to  

transfer fuel, but our tube size limit this some, so such a transfer cant  

go as fast as Howard experienced.



Lets see some possibilities for development of "reduced" "head pressure",  

see- when this pressure is reduced a little we cant name it "head  

pressure" any more..



Remember, the top of the wing hold the static low pressure that's created  

at the same location as our "head pressure". "The product of static and  

dynamic pressure is always constant". This is one of the most important  

thing to remember about fluid mechanics.  



Well, the thing is that the "filler cap" gasket not only need to hold the  

head pressure it will also need to hold for the differential pressure over  

the wing, the static pressure.



Now folks, you'll see this gasket is very important for our kind of fuel  

setup. This become more clear when we know there is restricted a flow in  

the "header tube", the tube that's attached to the fuel cap, try to blow  

through it and you should feel the resistance (this is valid -at least for  

the older model Kitfox).



This limitation is in some matter very good, but in our case very, very,  

bad. Cause such a limited flow can be "overtaken" by a broken "fuel cap  

gasket", I.E. our supposed "head pressure" can drop below our "true"  

static pressure. In this situation fuel is sucked from the feeder tank due  

to the low pressure in the left tank, on the other side fuel is pressed  

into the header tank from the normally pressurized right tank.



We can also have air leakage in the upper outer part of the tank, in this  

case not that much flow as it is just the header pressure that do the  

transfer.



The latter one is indeed more dangerous..



 	  Quote: 	
		  

 My plane has forward facing vent tubes (on the caps) on both tanks.  The

 only way I can see a difference in the head of fuel from each tank is  

 when

 both tanks are at different pressures because of differences in the cap

 vents.


	


This might be true if the limitation is to hi, It should be easy to blow  

through the "cap vent" and both should be equal.



I use to check my main for leakage in this way; close main valves for both  

tank, then install a tygon housing or anything similar that can fit the  

"vent line". The fuel cap should be installed as normal, then blow into  

the housing and see if the pressure will hold without leaking - should be  

no leakage here..

 	  Quote: 	
		  

 There may be a little difference in the level of the plane in flight as  

 the

 rounded cowl distorts to some extent a persons ability to tell straight  

 and

 level.  In a case like that the upper tank will empty first.


	


Agree with you here, but it seems like Howard’s transfer go much faster  

than possible in the above example.



 	  Quote: 	
		  

 As to having separate shut offs on each wing tank I heartily agree with  

 you.

 I check the rubber tube connections on the fuel system quite often  

 because I

 don't want a gas shower at 3000' !  Shutting off one tank will also allow

 you to get a good top off for max fuel in both tanks.




	


Thank you Noel.



Torgeir.

[quote] Noel



> --

torgemor(at)online.no
Guest

Posted: Sat Dec 30, 2006 4:22 pm Post subject: Fuel Flw

Hi Lowell, my respected Kitfox friend,



I'll agree in all what you say, except the thing about Skystars  

elimination of the main tank valves.



This need an explanation, and this is hard to explain as well -fully  

understand cause of the complexity.



Well, before I'll start, maybe the latter posting has enlighten my  

concern?? Or maybe cleared up a little more the "real" (?) problem -or?



I have a fully respect for the intention that Skystar had when they made  

the last modification to the fuel system. However, I could not see the  

"basement" of their decision, and they never explained "exactly" the  

problem and why this solution.



Over the years, I've been reading everything that I could find about a  

Kitfox plane, cause I had to justify why I wanted to by a Kitfox!! Well,  

I've not only checked the Kitfox, But I've also checked the Avid...



In 8 to 10 different setup (Kitfox and Avid - maybe you may find even more  

out there), there is one common parts that's sill the same!!!



(I'll know one that's not having this setup, -but only one.)



Yes. this is the way we "boost" the fuel pressure a little!



I’ve spent quite a few hours in order to explain this physics, -but for  

"death ears", maybe my explanation is not good enough -or maybe people  

don't care.



Sometimes I'm just wonderin if it is not best to close my eyes and leave,  

-you know.



The thing is, this part need some scheduled maintenance-, then we'll need  

just more education about the system- and how to handle/operate it  

correctly!



Or- maybe a redesign is in place, if we want a system like Cessna, we need  

to go all the way -not somewhere in between, like Skystar did.



Sorry folks, -sometimes you'll need to go all the way!



Now Folks, I'd like to wish one and everyone



A Happy New Year and all the best



Cheers



Torgeir.





On Sat, 30 Dec 2006 18:41:04 +0100, Lowell Fitt <lcfitt(at)sbcglobal.net>  

wrote:



[quote] 



 Noel,



 I know this was directed to Torgeir, but I have some thoughts on this.  

 Because of the round shape of the top of the instrument panel / cowl,  

 the Kitfox doesn't have the typical flat reference to the horizon that a  

 Cessna has.  The forward carry through shoud be flat with the horizon,  

 but is a distance visually from the horizon in our aiprlanes.  In the  

 group I fly with we once had a guy streaming fuel from his fuel cap area  

 and a close fly by confirmed he still had his cap on.  When he leveled  

 his wings the fuel stream stopped.  He was our highest hour pilot, but  

 when on a long X country we tend to settle in and watch the scenery  

 letting the airplane find it's confort zone.  This especially if we are  

 un-trimmed i.e., needing a little bit of right rudder when in cruise.   

 When watching Kitfoxes in flight, it is not uncommon to see guys flying  

 with a wing low.



 I think this is a major part of the uneven fuel flow, as in this  

 configuration, you will have a higher head in the high tank.  It is  

 interesting also that the high tank will indicate a higher level of fuel  

 in the sight gauge, giving the impression that the low wing has less  

 fuel in it's tank.  For those that have the tank valves, the common  

 response would be to close the valve on the lower tank which would  

 result in full flow from only the higher wing tank which might already  

 have less fuel than the other tank.



 When rigged properly, the system works and this is where I disagree with  

 Torgeirs comment regarding Skystar's elimination of the tank valves.  I  

 know some that still have them, but, and someone else will have to  

 remind me of the exact reason, I believe Skystar eliminated them because  

 of issues that developed after the addition of the header tank vent to  

 the system.  As I unserstand it, the early fuel system with the panel  

 tank didn't vent the panel tank independently from the fuel lines from  

 the wing tanks.



 This latter is from my understanding and am always welcome to comments  

 from those that were closer to the issues mentioned.

 Lowell  N96KL  Mod IV-1200

 ---

Float Flyr

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

Posted: Sat Dec 30, 2006 5:32 pm Post subject: Fuel Flw

I expect the thing to do if any problems are encountered is to install wing

tank shut offs (2) and a crossover line left to right tank. The only time I

did have a problem was with fuel over flowing.  What caused that was only

having one cap with a forward facing vent.  I flew like that for a few hours

while trying to get another cap to fit and there was no doubt about it the

tank with the vented cap emptied long before the other one.



I have been playing with the idea of installing fuel shutoff cocks on my

wing tanks for quite some time now.  I would want ball valves (1/4 turn on

and off) which have less chance of weeping fuel.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Lynn Matteson

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

Posted: Sun Dec 31, 2006 3:37 am Post subject: Fuel Flw

I followed Bill Willyard's idea and installed ball valves in my fuel  

lines right in the cabin area, behind my seat, visible by turning my  

head, and reachable while flying. They are in the Grainger catalog,  

item #6GD45 for the 1/4" NPT size. I haven't had a bit of trouble  

with them, and at about $4 each, they are cheap. I use one on each  

drop from the tanks, and another as my main fuel line shutoff on my  

console. I can turn these off to facilitate changing fuel lines,  

filters, etc.



Lynn



Lynn

On Dec 30, 2006, at 8:32 PM, Noel Loveys wrote:



 	  Quote: 	
		   



 I expect the thing to do if any problems are encountered is to  

 install wing

 tank shut offs (2) and a crossover line left to right tank. The  

 only time I

 did have a problem was with fuel over flowing.  What caused that  

 was only

 having one cap with a forward facing vent.  I flew like that for a  

 few hours

 while trying to get another cap to fit and there was no doubt about  

 it the

 tank with the vented cap emptied long before the other one.



 I have been playing with the idea of installing fuel shutoff cocks  

 on my

 wing tanks for quite some time now.  I would want ball valves (1/4  

 turn on

 and off) which have less chance of weeping fuel.



 Noel

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

dchuser2(at)comcast.net
Guest

Posted: Sun Dec 31, 2006 8:06 am Post subject: Fuel Flw

The most likely reason one wing tank flows more or  less than another is that the ball is not centered in the turn-and-bank  indicator.  The Kitfox, with its tapered nose, can easily be flown in a  slight crab without realizing it - especially if you're an old Cessna or Piper  driver having flown with straight sided cowls.  

  

 Dennis-in-Michigan

 [quote]   ---

torgemor(at)online.no
Guest

Posted: Sun Dec 31, 2006 12:15 pm Post subject: Fuel Flw

Hi Lowell and Kitfox flyers/Builders,

Sorry for being a little "hot" here, but this topics do interest me more  

than most.



Thank you Lowel, for triggering me.   I'll know I've to do better, so  

I'm going to draw the whole Kitfox fuel system, but, next year.



So again.



To All and everyone of you.



A Happy New Year.



Torgeir.



On Sun, 31 Dec 2006 01:22:18 +0100, Torgeir Mortensen <torgemor(at)online.no>  

wrote:



 	  Quote: 	
		   

 <torgemor(at)online.no>



 Hi Lowell, my respected Kitfox friend,



 I'll agree in all what you say, except the thing about Skystars  

 elimination of the main tank valves.



 This need an explanation, and this is hard to explain as well -fully  

 understand cause of the complexity.



 Well, before I'll start, maybe the latter posting has enlighten my  

 concern?? Or maybe cleared up a little more the "real" (?) problem -or?



 I have a fully respect for the intention that Skystar had when they made  

 the last modification to the fuel system. However, I could not see the  

 "basement" of their decision, and they never explained "exactly" the  

 problem and why this solution.



 Over the years, I've been reading everything that I could find about a  

 Kitfox plane, cause I had to justify why I wanted to by a Kitfox!! Well,  

 I've not only checked the Kitfox, But I've also checked the Avid...



 In 8 to 10 different setup (Kitfox and Avid - maybe you may find even  

 more out there), there is one common parts that's sill the same!!!



 (I'll know one that's not having this setup, -but only one.)



 Yes. this is the way we "boost" the fuel pressure a little!



 I’ve spent quite a few hours in order to explain this physics, -but for  

 "death ears", maybe my explanation is not good enough -or maybe people  

 don't care.



 Sometimes I'm just wonderin if it is not best to close my eyes and  

 leave, -you know.



 The thing is, this part need some scheduled maintenance-, then we'll  

 need just more education about the system- and how to handle/operate it  

 correctly!



 Or- maybe a redesign is in place, if we want a system like Cessna, we  

 need to go all the way -not somewhere in between, like Skystar did.



 Sorry folks, -sometimes you'll need to go all the way!



 Now Folks, I'd like to wish one and everyone



 A Happy New Year and all the best



 Cheers



 Torgeir.

Float Flyr

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

Posted: Sun Dec 31, 2006 12:42 pm Post subject: Fuel Flw

Almost 6 P.M. here now so it's time to wish every one here a Happy and

Prosperous New Year!!



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

kitfoxmike

Joined: 05 Dec 2006
Posts: 373

Posted: Sun Dec 31, 2006 2:21 pm Post subject: Re: Fuel Flw

Just to let everybody know, I have a very simple system, one vent line from the right tank to the header tank, and one line from each of the tanks to the header.  I have a 1/4 inch ball valve on each wing tank and currently I have the left tank in operation.  I to have a problem with the right tank going into the left tank when both are open, but will stop after a bit, I just watch the levels on the tanks and only open one at a time. Never had a problem doing so.  On airplanes that are low wing you can only operate on one tank at a time so I have no problems doing it with the fox.

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