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rjdaugh

Joined: 30 Aug 2006
Posts: 195

Posted: Thu Jan 25, 2007 8:46 am Post subject: Fuel Flow, continued.

Dave,

I only put one shut off valve in my system - Right tank.  I use this to stop

the transfer between two tanks when parked on uneven ground or in the rare

case when I have full fuel.



I decided NOT to put a shut off valve on each tank because then both tanks

can not be shut off. Inadvertently, absent mindedly, etc.  When I need to

shut of left tank, I use a hose clamp.



I just believe that the simpler system is safer.  - less to go wrong.  I see

no reason for additional fuel pumps.  The system works fine without a pump.

The pump is just something else to go wrong. 



Randy



.           



--

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

akflyer
Guest

Posted: Thu Jan 25, 2007 11:14 am Post subject: Re: Fuel Flow, continued.

I have had a cap come off on a PA-12.  The tank arrangement is virtualy the same as the fox.  I can tell you that I had a helluva spray over my left shoulder.  The left tank went from tip top full to about 1" left in the tank in the 6-8 miles it took me to notice it... thankfully, the right tank remained full.  I was able get my butt back out of the pass and to port alsworth to re-fuel... again... it was a bit embarassing pulling back to the pump 10 minutes after I had just topped off and take another 18 gallons.. I found the cap in about 2' of water right where I had pulled up to shore and re-fuled the first time.

lcfitt(at)sbcglobal.net
Guest

Posted: Thu Jan 25, 2007 1:08 pm Post subject: Fuel Flow, continued.

I must admit that Deke's expereince has given me pause as to my memory.  I 

checked my log book and apparently didn't log the experience of the 

misaligned fuel cam and resultant fuel loss.  As difficult as it is to admit 

this, I seldom look at my fuel gauges as in almost all lengthy cross 

countrys, my fuel needs are superceeded by others with greater burn or 

smaller tanks.  Since it is easier to view the right tank sight gauge at a 

glance I am pretty sure that the right tank was the low one.  And the flyby 

showed no apparent difference in the caps.  However I can't actually recall 

which tank had the poorly fitted cap.  So I will Defer to Deke.



We may actually have two phenomena working here.  The pitot pressure forcing 

fuel out of the misaligned cap and another thing entirely with a cap 

missing.  I remember many times when I was working for a short time for 

United Airlines on the ramp, where a taxing 737 could suck a puddle dry 

through a miniature water spout as the engine passed over it.  Could it be a 

similar phenomenon with an open cap and the airstream over the wing causing 

a vortex in through the tank opening and sucking out the fuel?



Lowell



---

asq(at)roadrunner.com
Guest

Posted: Thu Jan 25, 2007 1:27 pm Post subject: Fuel Flow, continued.

Hmmmmm, I agree. Just like a Cessna 150 and the Kitfox4( unless you put a 

valve in at least one tank).

                        Larry Huntley,4-1200 Soob

[quote]

Lynn Matteson

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

Posted: Thu Jan 25, 2007 1:33 pm Post subject: Fuel Flow, continued.

Deke-

What is/are the "new set of problems"? I've got 'em on my plane, and  

other than one incident when I parked the plane one wing low, full of  

fuel, I have had no (knock on wood) problems.



Lynn

On Jan 25, 2007, at 9:54 AM, Fox5flyer wrote:



 	  Quote: 	
		   



 Valves on the tank lines would help, but they

 create a whole new set of problems.  Overall, the factory setup as  

 designed

 by Dan Denny/Dean Wilson/Skystar is sound and like any other  

 airplane is not

 foolproof when mistakes are made like forgetting to install a fuel  

 cap or

 installing it incorrectly.

 Deke



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

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Float Flyr

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

Posted: Thu Jan 25, 2007 2:02 pm Post subject: Fuel Flow, continued.

Mike:



What you are saying is here is no need for independent fuel shut offs??  



Are they a necessity...maybe not but they will stop cross tank fuel flow so

you can get both tanks completely full without any loss.  They will also

allow you to isolate a  tank in the event of an in flight problem.



At the present time I don't have individual shut offs on my wing tanks but

they are on my list of priorities.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

torgemor(at)online.no
Guest

Posted: Thu Jan 25, 2007 6:10 pm Post subject: Fuel Flow, continued.

Hi Guy,



You sure put up some good asumptions here..



Well, once more; Is there any difference if I loose (or forgot to put on)  

the left or the right fuel cap?



I.E. will one or the other situation (loosing left or loosing right fuel  

cap) leave more or less fuel for us to use during flight.  Yes or No  ????



The correct answer here is; there is no "significant" differece if you'll  

loose the right or the left fuel cap!!!!



Second, can't you do anything to avoid loosing fuel if this situation  

arise.  You'll know, if the engine quit due to this situ., there is no  

more fuel left... Well, since you only have the main shut off to play with  

there's not very much you can do. Sure if you're aware about the situ. in  

an early state, you could lift that wing etc...



Yes Guy, if you lift the "actual" wing before it's exhausted...if you  

figure out what's going on..  



OK., folks, remember that this is the latest version with both wing tank  

valves removed..



Do not mix the old system into this late version.  The old setup is to be  

discussed later (-don't worry), with all details we know about.



Be sure my friends, the intentions of the latest system is to have a  

system that's serve you the best with minimum effort over time.



Hovewer, over time tings wear and tear, - then how would my setup behave  

then? And, -is there any kind of redundancy in here?



Also, it is possible to loose fuel even there's no fuel transfer between  

fuel tank's!  Keyword here is; backflow, resonant (flute effect in  

venturi) and direct siphons effect.



Now, why is there a "restriction" in the flow entering from the header  

line into the altimeter??



How will this restriction influence when there's a leaky gasket?

Torgeir.



On Wed, 24 Jan 2007 00:55:59 +0100, Guy Buchanan <bnn(at)nethere.com> wrote:



 	  Quote: 	
		  

 I'm not sure what you're asking, Torgier. I did some calcs and the  

 dynamic pressure at 115 MIAS at sea level equates to about 9" of static  

 fuel head. (Assume the static pressure is the same across the open cap  

 and at the vent pitot tip, a reasonable approximation.) This appears to  

 mean that as long as you're going fast you can empty the left tank. When  

 the fuel level in the left tank/line drops to 9" below that in the right  

 tank you'll be at equilibrium. This will leave nearly the entire left  

 fuel line and vent line full, and the right tank full. Both levels will  

 drop simultaneously, all things being equal, with the left level 9"  

 below the right. (This assumes the top of your header is more than 9"  

 below the bottom of your tanks. I'm pretty sure mine is.)



 If you slow down the 9" static fuel head drops as the square of the  

 velocity. (E.g. at 57.5 MIAS the head will be 9/4" or 2.25") If you  

 climb the static fuel head drops linearly with the air density. So if  

 you find you're blowing fuel, slow down, climb high, lift the streaming  

 wing a little, and you should be fine. Indeed you should be able to lift  

 the wing enough to stop the leak.

 Guy Buchanan

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




	


-- 

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

n981ms(at)yahoo.com
Guest

Posted: Fri Jan 26, 2007 5:02 am Post subject: Fuel Flow, continued.

With my experience of the reversed cap:  The right cap was on backwards.  The left tank was empty in appr 40 minutes.  I had just filled the tanks to 11-12 gallons each.

   

  Maxwell S6/IO240/TD



Lowell Fitt <lcfitt(at)sbcglobal.net> wrote:

  [quote]--> Kitfox-List message posted by: "Lowell Fitt" 



I must admit that Deke's expereince has given me pause as to my memory. I 

checked my log book and apparently didn't log the experience of the 

misaligned fuel cam and resultant fuel loss. As difficult as it is to admit 

this, I seldom look at my fuel gauges as in almost all lengthy cross 

countrys, my fuel needs are superceeded by others with greater burn or 

smaller tanks. Since it is easier to view the right tank sight gauge at a 

glance I am pretty sure that the  right tank was the low one. And the flyby 

showed no apparent difference in the caps. However I can't actually recall 

which tank had the poorly fitted cap. So I will Defer to Deke.



We may actually have two phenomena working here. The pitot pressure forcing 

fuel out of the misaligned cap and another thing entirely with a cap 

missing. I remember many times when I was working for a short time for 

United Airlines on the ramp, where a taxing 737 could suck a puddle dry 

through a miniature water spout as the engine passed over it. Could it be a 

similar phenomenon with an open cap and the airstream over the wing causing 

a vortex in through the tank opening and sucking out the fuel?



Lowell



---

Fox5flyer
Guest

Posted: Fri Jan 26, 2007 5:18 am Post subject: Fuel Flow, continued.

That make sense.  The right cap pitot was  sucking and the left cap pitot was pushing.  

 I recall a long time ago where one of our members  told of getting his fuel topped off and the fuel truck guy put the caps on  backward.  This is the main reason I always ask them to allow me to fill my  own.  So far nobody has minded.

 Deke

 do not archive

 [quote]   ---

Fox5flyer
Guest

Posted: Fri Jan 26, 2007 5:21 am Post subject: Fuel Flow, continued.

Personally, I don't use wing-to-header valves, but if a person chooses to

install them, that's there business. I doesn't bother me because we build

our airplanes the way we want them to be and none of us should have to

defend it.  Lynn, in the past, meaning "many years ago", Skystar recommended

fuel shut-offs be removed from the tank-to-header lines or not be installed

at all. I believe it was due to some fuel starvation issues. Seems to me

there was a bulletin of some sort. Cessna probably had the same reasons

because of simplicityand the fact that they were trainers. Some of the

reasons (some are mine) that I recall were

-potential for compromised fuel flow to the header because of the extra

restriction of the valves.

-potential for leakage from the extra fittings.

-difficulty operating them while in flight.

-the considerable chance that a valve could be forgotten. This is where you

can paste in your favorite "dark and stormy night story" where attention is

diverted to other problems and the fact that the valves are behind you in a

difficult to reach place and they get forgotten.

-turned off when the intention was to turn it on. (Again, diverted

attention.)

-wrong valve operated. (Same reason)

-and most of all, the lack of necessity of even having them (my opinion).

I didn't install them in any of my Kitfoxes mostly because of the "less is

better" rule that I try to use. I've never had a problem with unequal flow

in flight. On the ground I ensure that when I park the airplane it's on as

level of a surface that I can find. That hasn't been a problem and rarely

are my tanks completely full in those cases.

Good luck on your trip to Oshkosh Lynn. It'll be a real adventure and I can'

t wait to read the report when you return.

Deke

 	  Quote: 	

 Deke-

 What is/are the "new set of problems"? I've got 'em on my plane, and

 other than one incident when I parked the plane one wing low, full of

 fuel, I have had no (knock on wood) problems.

 Lynn

 On Jan 25, 2007, at 9:54 AM, Fox5flyer wrote:

 > 

 >

 > Valves on the tank lines would help, but they

 > create a whole new set of problems.  Overall, the factory setup as

 > designed

 > by Dan Denny/Dean Wilson/Skystar is sound and like any other

 > airplane is not

 > foolproof when mistakes are made like forgetting to install a fuel

 > cap or

 > installing it incorrectly.

 > Deke

 >

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

 >

 >

 >

rjdaugh

Joined: 30 Aug 2006
Posts: 195

Posted: Fri Jan 26, 2007 8:50 am Post subject: Fuel Flow, continued.

Only one valve is needed to stop the tank to tank transfer.  Only one valve

(instead of two) gets around some of the scenarios that Deke addresses here.



Randy



.           

--

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

GENTRYLL(at)aol.com
Guest

Posted: Fri Jan 26, 2007 9:05 am Post subject: Fuel Flow, continued.

I read somewhere it was because in a long slip, if the valve was hardlined  horizontally to the tank as opposed to along the line somewhere, you could   pull a vacuum and introduce air in the line. 

  [quote][b]

torgemor(at)online.no
Guest

Posted: Fri Jan 26, 2007 3:00 pm Post subject: Fuel Flow, continued.

Hi Randy,



No need for help here, you're absolutely right!!!



This later system will transfer fuel if one of your cap is gone, or a  

gasket is leaking, -and there is nothing you can do to stop this as there  

is no valves between the two mains that could prevent this to take place.



If you'll remember, some people reported that their "left or right" tank  

always empty first.  The combination of the leak amount vs. head filling  

capability (remember the restriction built in here) will "balance out" and  

resulting in a decreased tank pressure.



Remember that the differential pressure is around 0.3 psi, and that  

approx. 75 percent of this is caused by the low pressure over the wing,  

-so even a "small" gasket leakage can create a differential pressure able  

to transfer fuel from one tank to the other.



Let's say this pressure can rice fuel -say 3 inches in the main tank, I.E.  

this pressure is not capable to "lift" fuel over the filler neck, so we  

would not loose fuel. But end result is that this tank always empty last.   

So this is indeed a ringing bell asking you to check your cap gasket.



Now folks, check your tank gaskets this is one of the most important item  

that's often forgotten. You can pressurize your tank by using the head  

tube in the fuel cap, blank the other side so it is air tight, set main  

fuel selector to off, then carry out a leak check. A warning here: Never  

use more than 0.2 psi pressure for this test. The maximum pressure drop  

allowed might be 5 percent in 5 minute, however, if you can get no leakage  

here is the better..         Ok., the above numbers is the one Iâ€™m  

using, do not know if the factory have some numbers here.

Torgeir.



On Thu, 25 Jan 2007 03:18:14 +0100, Randy  Daughenbaugh  

<rjdaugh(at)rapidnet.com> wrote:



 	  Quote: 	
		   

 <rjdaugh(at)rapidnet.com>



 Both you guys are right.



 But if your tanks can cross feed - via header or otherwise - the tank  

 that

 will empty is the one WITH the cap on.  Yes, the fuel is going out of the

 tank without the good cap seal, but the air going into the system to

 displace the fuel with be going into the other tank - the one with cap on

 correctly.  So it is the OTHER tank (the one with a good cap!) that will

 empty first.



 Torgeir!  Help!



 Randy

Guy Buchanan

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

Posted: Fri Jan 26, 2007 4:02 pm Post subject: Fuel Flow, continued.

At 06:08 PM 1/25/2007, you wrote:

 	  Quote: 	
		  I.E. will one or the other situation (loosing left or loosing right fuel

cap) leave more or less fuel for us to use during flight.  Yes or No  ????



The correct answer here is; there is no "significant" differece if you'll

loose the right or the left fuel cap!!!!



Second, can't you do anything to avoid loosing fuel if this situation

arise.  You'll know, if the engine quit due to this situ., there is no

more fuel left... Well, since you only have the main shut off to play with

there's not very much you can do. Sure if you're aware about the situ. in

an early state, you could lift that wing etc...


	


I agree completely. With a missing cap there appears to be some kind of a 

"blow-out" that will empty that tank regardless of valve and vent design. 

Now if the tanks are connected it follows that both tanks will equilibrate 

and the entire wing tank load of fuel will be eventually, (rapidly?) lost. 

It's unclear whether the header will also be emptied. Preventing cross flow 

will protect at least one tank of fuel for use. (Again, presuming the 

header is not somehow being siphoned.) And in this latter case it would 

appear that if you want to run with a header tank you would want one valve 

for each tank upstream of the header to isolate the tank with the lost cap 

from the system. If you did not run a header you could simply have the left 

/ right / off valve to isolate the lost cap tank.



So. The big question is, what system is optimal? I'm sure I don't know. I 

fly a Cessna 150 with cross linked fuel feed, cross linked vents, no 

header, and a simple on/off valve. I fly a 172 with cross linked fuel feed, 

cross linked vents, no header, and an off/left/right/both valve. I fly a 

Decathlon with cross linked fuel feed, cross linked vents, a header tank, 

and a single on/off valve downstream. I fly a Bonanza F33A with separate 

feeds, separate vents, no header tank, and an off/left/right valve. My 

Kitfox is similar to the Decathlon.



Should I go through a complete risk analysis? If I do this email will get 

awfully long. I did not do so for my Kitfox, because it was factory 

standard, similar to the Decathlon, and showed no obvious flaws. Now I 

suppose draining the tank when you leave a cap off is an obvious flaw. It 

certainly isn't single failure tolerant, whereas having a valve for each 

tank is. And I can't think of any significant failure modes with the three 

valve system, (similar to the 172 with the off/left/right/both valve,) so I 

guess a cursory risk analysis says you should have three valves, 

left/right/header. Yes you can turn off the fuel, but you can turn it back 

on too. Yes a valve can fail, but I've never heard of it happening, and I 

cycle my valves every time I fly, and I would fly with them all open since 

I watch my fuel and would notice a significant fuel loss fairly quickly. I 

guess I could also fly it like the Bonanza, with it's off/left/right, 

switching tanks every 1/2 hour and watching the fuel levels in between. A 

leak would be noticeable sooner, since only one tank would be draining.



OK Torgeir, you have, for the time being, convinced me. I'm not going to 

change over tomorrow, bit I'll look into it a bit to see how difficult it 

will be. (I fold my wings a lot and need a certain fuel line geometry to 

make that happen.)

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.

Float Flyr

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

Posted: Fri Jan 26, 2007 5:09 pm Post subject: Fuel Flow, continued.

I guess if you wanted to you could put a one way valve in each wing tank

line and vent the header outside and above the trailing edge of the wing ...

But that seems to me to only increase the complexity of the system.  I like

the idea of a valve similar to the C172 feeding the header and a separate

main shut off.



I agree with double checking the fuel caps before take off...  I have it

written into my check list three times.  Once after fuelling, once on walk

around and again before getting in the plane.  Main shut off only is

operated for maintenance but that gets checked on the pre flight and pre

start sheets.  Only when I was training did I find fuel selector valves in

the wrong positions.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

torgemor(at)online.no
Guest

Posted: Fri Jan 26, 2007 5:27 pm Post subject: Fuel Flow, continued.

Hi Deke and others,



Good and interesting report.



I've some questions, this because of this "old" model II was (or)  

originally fitted with (let's say) "Denney" fuel system with unvented  

header tank.



Was this fuel system modified according to the Skystar SB.(Service  

Bulletin)? (Removal of both main valves plus header tank vented to the  

right main tank.)



Well, one thing I'm quite sure about; If this AC had the old Denney setup,  

you was having both main valves open, right?  Then to the question about  

what will happen after left tank unporting; the engine will continue to  

run and using the remaining fuel in the header -then the engine stop!!!   

Yes, -and your right main tank is full of fuel...

Remember the old setup do not have the vent line, so air will flow from  

left via the header and uphill the feed line from the right tank. The  

steady and massive air flow will prevent "effective" fuel flow from right  

tank into the header tank.



Now to the scenario if this system is modified according to Skystar SB.  

(like the drawing I made).



Well, remember in my first posting, due to the vent line the header tank  

is filled by gravity only. This is an important note and play a key role  

for understanding of this fuel system.  For flow through pressurization  

will help, for filling no.



Ok., if we look at the situation where the left tank output "unport"  

(inside the header tank), air start flowing from the left tank -this time  

the air will take the vent line path toward the right main. As there's no  

airflow up through the right tank feeder line fuel will flow cause of the  

gravity and the small diff pressure between header and right tank.  So  

this time fuel will stay at the unported level inside the header tank. A  

booster pump just beside or near the header will definitely keep enough  

fuel for the engine, however I'll think the normal engine pump also can do  

that, as it "normally" can bring the inlet pressure down to around 10 psi  

absolute pressure, sure some brands can do better than this.



Well, it's still lot more here, can you figure.  The modified (SB) can  

have fuel starvation and engine stoppage. Go figure..  



The old system can be managed different without engine stoppage.



We're not finished yet.

Torgeir.





On Thu, 25 Jan 2007 13:35:43 +0100, Fox5flyer <fox5flyer(at)i-star.com> wrote:



[quote] 



 As I recall the NTSB archives are full of incidents related to fuel

 starvation and it's probably the number one cause of engine failure, so  

 IMO

 this is a good topic and may save some people the pain of a broken  

 airplane,

 or worse.

 I've been watching this debate with interest because it happened to me  

 with

 my old Model II.  I took off with full tanks for a breakfast run and  

 before

 I'd gotten ten miles I noticed that my left tank was at the half way mark

 while the right tank was full.  I watched it for another minute or so and

 saw that the left tank level was still dropping rapidly so I did a 180  

 and

 headed home, landing just about the time the left tank was nearly empty.

 What I determined was that two things had happened.  One, the right tank

 fuel with the cap not completely secured (on by only one tab) was being

 sucked out, and two, the left tank being pressurized by the secure  

 cap/pitot

 was pushing the fuel from the left tank down through the header and out  

 the

 right tank.

 My conclusion was that the loss of fuel was a combination of both the

 pressurized left tank and the leaking from the right tank.  I don't know

 whether or not the engine would have quit had the left tank run  

 completely

 dry, but I suspect it would not have so long as there was still fuel in  

 the

 right tank, but that's definitely debatable.

 Now, this is different from a tank that has the cap completely missing.

 That's a big hole, especially in turbulence where you can lose a lot of  

 fuel

 very fast, BUT considering the internal baffling, as the fuel level goes

 down the rate of loss will slow, right?  No, because it's still being  

 pushed

 out by the pressurized left tank (which is going down) and the right tank

 level will stay up until the left tank unports.  Right?  What I'm not  

 sure

 about here is what would happen when the left tank empties.

 Personally, I'd really like to see the results of a controlled test in

 flying conditions to see just what would happen if this was allowed to go

 all the way.  It would take the loss of a few gallons of gas and of  

 course

 at altitude above an airport with a long runway, but it shouldn't be  

 hard to

 make the test.  Probably best with two people so the pilot only flies the

 airplane.  Then again, it would depend on the configuration and  

 integrity of

 the fuel system because no two are exactly alike.  I have no idea how a  

 test

 could be made while on the ground.

 Basically I agree with Randy.



 Deke Morisse

 S5 Outback

 NE Michigan and 14F, breezy



 ---

torgemor(at)online.no
Guest

Posted: Fri Jan 26, 2007 6:03 pm Post subject: Fuel Flow, continued.

Hi Dave,



I'll think your system is Ok., easy to handle and secure..



If you loose one cap, you sure only loose fuel from that tank -in worst  

case 3/4 may go due to backflow and "resonant escape". (When backflow  

occur flute effect may create low frequent resonance creating waves in the  

fuel surface throwing droplets of fuel thatâ€™s escape with the backflow.)



I've been thinking of installing two small mirrors as far forward as  

possible this in order trying to see the fuel cap's. I've always forgot to  

check if it's possible to see the tanks pitot from this position.



Of all those fuel cap incidents, thereâ€™s almost none of the low wing  

aircraft forgetting the fuel cap, hmm they're easy to spot from the  

cockpit.. 



The old word, seeing is believing..



For sure I know about the checklist.  The point is this thing still happen.



Torgeir.



On Wed, 24 Jan 2007 17:32:27 +0100, dave <dave(at)cfisher.com> wrote:



[quote] 



 I have 2  - 6 gals wing tanks  and each has it's own shut off.

 Each tank is a pitot tube cap .



 They both flow together to a T fitting  then a Clear Fuel filter and I  

 can clearly see the fuel flowing throught that filter.   Rivht in line  

 after the filter is a Facet pump which I have a manual switch for but  

 only use to transfer fuel to Dash tank  (  about 8.5 Gallon  and you can  

 see the level in until about 2 gals left and you have to rock the wings  

 to see the fuel slosh around)     After the Dash Tank the fuel flows  

 into gascolator then to Fuel pump.



 I usually fly off the main dash tank only and I only open the  

 independant fuel valves from each wing tank  to transfer wing tank fuel   

 as needed to the dash tank .



 If I was to loose a cap in flight -what would happen ?  Is this method  

 ok ?

 Dave

 ---

msm_9949(at)yahoo.com
Guest

Posted: Sat Jan 27, 2007 7:41 am Post subject: Fuel Flow, continued.

At the risk of adding fuel to the embers of this string (sorry), how about Andair check valves instead of shut-offs at each wing tank? Wouldn't that solve the problem of cross-fed, total fuel depletion from one missing or loose cap, where single tank isolation is not wanted or needed?

  

Torgeir Mortensen <torgemor(at)online.no> wrote:

   	  Quote: 	
		  --> Kitfox-List message posted by: "Torgeir Mortensen" 



Hi Dave,



I'll think your system is Ok., easy to handle and secure..



If you loose one cap, you sure only loose fuel from that tank -in worst 

case 3/4 may go due to backflow and "resonant escape". (When backflow 

	




Marco Menezes

Model 2 582 N99KX

   Don't pick lemons.

 See all the new 2007 cars at Yahoo! Autos. [quote][b]

torgemor(at)online.no
Guest

Posted: Sat Jan 27, 2007 2:35 pm Post subject: Fuel Flow, continued.

Well folks, this is hopefully an explanation of the problems to be aware  

of in our kind of fuel system.



The header tank is filled by gravity, only - this is an important thing to  

remember!



Let's assume that we are filling our right main tank with 5 gal. Both  

tanks is equipped with a valve that is closed. The main that goes from the  

header to the gasculator is also closed.



Well, -some notes is needed here, the fuel system here is the same as the  

one we started with, the one valid today. I've installed two valves one  

for each wing tank, this is to make it more easy to understand as I'm sure  

you agree that if both valves is open all the time the functionality is  

equal to the one recommended today.



Now we have the right tank filled with 5 gal, both mains is shut, now we  

install a pressure device on both head tubes and pressurize both tanks  

with pressure equal to 100 Mi. Yes, we are on ground, but we are trying to  

simulate flight, both wing tanks AND the header tank is pressurized (via  

the vent line). Now we open the right main valve. Now, will the fuel rush  

down the line? No, the fuel will flow gently down the line by the gravity  

only. This is true as the header also is pressurized with same pressure as  

the two mains. This is the same as we are on ground with no head pressure,  

agree?  The head pressure only make effect against the carburetor float  

camber as this camber is at the "true" static pressure.



Then I've to let the cat out of the basket.



The thing is, if you have a leakage that's causing filling of the right  

wing tank (and maybe some drop of fuel from here), you "should" be able to  

use all the fuel left in the right wing tank, this due to gravity.   

However, if you have a leaky left hand tank gasket, transferring all of  

the fuel to the left side wing tank, -after unporting air will  

continuously flow toward the left tank and avoiding much fuel flow from  

here. Therefore the header soon exhaust and your engine WILL stop, and  

your landing will be with the left wing tank full of fuel!



Go figure. After all this discussion I'll hope that you're able to figure  

this.



The correct solution here is to vent the header to BOTH wing tanks!



This is something I've said MANY times here on the kitfox list, -but after  

Howardâ€™s incident -lately, I could not stop writing this.



Torgeir.

-- 

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smokey_bear_40220(at)yaho
Guest

Posted: Sat Jan 27, 2007 7:46 pm Post subject: Fuel Flow, continued.

I have been looking at the check valves myself.  I

think they need .5 psi to open, so they should be

mounted at the header to ensure enough tank pressure

for flow.



Another consideration is a shutoff only on the left

tank.  That prevents cross flow, no chance of having

both tanks closed, and the shutoff could be mounted

where you see it when closed, but not open, just to

remind you.



With the right tank full, it can still feed thru the

vent line, if the main line is shut off.  After a bit

this no longer applies, but the left tank is

completely controllable thru the only line.



Right now I use a hose clamp on one line or the other

only, and in cruise only.  I am listening to all of

you for better ideas.



Kurt S.  S-5



--- Marco Menezes <msm_9949(at)yahoo.com> wrote:



 	  Quote: 	
		   At the risk of adding fuel to the embers of this

 string (sorry), how about Andair check valves

 instead of shut-offs at each wing tank? Wouldn't

 that solve the problem of cross-fed, total fuel

 depletion from one missing or loose cap, where

 single tank isolation is not wanted or needed?


	




 

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