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Fuel flow, summary so far.

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torgemor(at)online.no
Guest

Posted: Wed Jan 31, 2007 3:52 pm Post subject: Fuel flow, summary so far.

Hi Folks,



I've just finished two new sketches of the "failure modes", then the old  

"original" Denney setup and the cross vented main tank setup as I'll like  

to see it.



The first drawing show a leaky gasket in the right tank, in this situation  

we'll be able to use fuel from the right tank until empty. The next  

drawings has some explanation text included in the drawing itself.



This first drawing show the situation with a leaky right hand fuel cap  

gasket, the second drawing is same situation -with left side this time,  

the third drawing is the original Denney fuel system setup as far as I'll  

know, and finally the fuel system of to day but –cross vented as I'll like  

it to be.



Now folks, remember this failure modes can be tested safely on ground for  

everyone to see...   You could also test the benefit of a cross vented  

system..



There is one thing to be said in general, if your system is kept in good  

condition (maintenance well) both system will serve you fine. However, if  

things "worn" over time -no one can assure for correct function..

Next time I'll like to address some other items in the fuel system.



(PS. Will be travelling for some days.)



Torgeir.

-- 

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Jim Shumaker

Joined: 09 Jan 2006
Posts: 106

Posted: Wed Jan 31, 2007 5:52 pm Post subject: Fuel flow, summary so far.

Excellent Torgier

  

 Another keeper for my archives and another change to be made on my plane.

  

 Jim Shumaker



 [quote][b]

_________________
Jim Shumaker

lcfitt(at)sbcglobal.net
Guest

Posted: Wed Jan 31, 2007 6:20 pm Post subject: Fuel flow, summary so far.

Torgeir,



I think I see a problem with your figure (fuel_4).  My water manometer shows 

a column of water 4.5" tall will create the pressure at the pitot tube to 

register 100 mph.  which is a bit more than the avarage Kitfox will fly 

(sorry to the 5 through 8 guys, but average is average and you guys will 

come in later).  A rough estimate gives a column of fuel at say 6 inches at 

that speed.  Conversely an airplane flying at 100 mph will has the ability 

to lift a column of fuel about 6 inches.  What that indicates to me -  if 

the header tank is full and the left tank is full as you show, there will be 

fuel to some level in both the fuel line and the vent line on the right side 

due to head pressure from the full tank.  The level will be somethiing like 

6: below the tank fuel level.  As I measure it I have about 10 inches from 

the level of the fuel tank outlet to the header tank inlet.  There is 

insufficient pressure generated from the "pitot tube" type air vent on the 

non leaking tank to force a breach into the header tank as long is there is 

at least some fuel in the (leaking gasket) tank and the airspeed is no 

higher than, say 115 mph.   Air at .04 psi won't lift a column of fuel 10 

inches.



Further all aircraft sold after about 1994 - the aircraft capable of higher 

speeds have the header tanks low behind the seats with a pressure head of 

more like 18 to 20 inches.  With these airplanes the .04 psi from the intact 

fuel cap won't force air in the fuel line or vent line more than about 

11inches below the fuel level in the system even at VNE.   I doubt there is 

any way to introduce air into the full tank to header tank feed line in our 

airplanes in the scenario you illustrate.



Also the diagram of the header tank reflects the round header tank of 

several models ago consistent with the diagram of  (Fuel_5)  The newer 

header tank has the inlets from both tanks on the top surface as well as the 

vent line.  Provision is made for a quick drain on the bottom and fuel 

outlet about an inch or two above that on the forward facing side.



Lowell

---

Float Flyr

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

Posted: Wed Jan 31, 2007 6:53 pm Post subject: Fuel flow, summary so far.

Torgeir:



On the second diagram you showed the left tank dribbling fuel into the

header tank.   I expect that you won't get a pressurized head of air over

the fuel in the tank but neither will you get a vacuum to hold the fuel up

in the tank. Let alone suck air from the empty tank. Even though the cap

isn't properly fitted the pitot effect should be enough to brake the low

pressure ( hardly a vacuum) on the top of the wing.



Why bother connecting a vent from the header to the cross vent in the last

diagram?  Once you have the cross vent tube installed the air pressure on

top of the fuel should be consistent across both wing tanks regardless of

whether or not one cap is not properly installed..  The header will self

purge because you don't fill both tanks at exactly the same speed to trap

air in the header.... That is assuming of course you ran or drained the

header dry.  One other thing... On my plane the inlets to the header tank

are "almost" at the very top of the header tank....  The vent comes off the

same level as the inlets.



Nice diagrams.  I do like the idea of the cross vent.  Then again I like the

idea of controlling the fuel flow too.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Guy Buchanan

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

Posted: Wed Jan 31, 2007 9:52 pm Post subject: Fuel flow, summary so far.

At 03:52 PM 1/31/2007, you wrote:

 	  Quote: 	
		  The first drawing show a leaky gasket in the right tank, in this situation

we'll be able to use fuel from the right tank until empty. The next

drawings has some explanation text included in the drawing itself.


	


I agree with Lowell. My calc's, (already posted,) show you can't push 

air down to the header tank using dynamic pressure from the pitot 

vent. Therefore, though you can empty one tank, you can't drive air 

into the header and out the other tank, precluding its feed. You 

should therefore have about a 9" difference in fuel levels right to 

left until the lower level hits the header tank. On my aircraft that 

means you get to use one tank of fuel, right or left, since my header 

sits low behind the seat.





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.

Lynn Matteson

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

Posted: Thu Feb 01, 2007 3:23 am Post subject: Fuel flow, summary so far.

Guy-

When you say "you get to use one tank of fuel, right or left", do you  

mean that once that tank of fuel is gone you will run out? The reason  

that I ask is because of what happened to me twice during my recent  

trip back from Oshkosh. I'll tell about that soon.

Lynn

On Feb 1, 2007, at 12:41 AM, Guy Buchanan wrote:

 	  Quote: 	

 At 03:52 PM 1/31/2007, you wrote:

> The first drawing show a leaky gasket in the right tank, in this  

> situation

> we'll be able to use fuel from the right tank until empty. The next

> drawings has some explanation text included in the drawing itself.

 I agree with Lowell. My calc's, (already posted,) show you can't  

 push air down to the header tank using dynamic pressure from the  

 pitot vent. Therefore, though you can empty one tank, you can't  

 drive air into the header and out the other tank, precluding its  

 feed. You should therefore have about a 9" difference in fuel  

 levels right to left until the lower level hits the header tank. On  

 my aircraft that means you get to use one tank of fuel, right or  

 left, since my header sits low behind the seat.

 Guy Buchanan

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

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

alnanarthur(at)sbcglobal.
Guest

Posted: Thu Feb 01, 2007 8:29 am Post subject: Fuel flow, summary so far.

Torgeir etal.



Add a second airspeed indicator to your panel.  Connect it's input to  

the crossover header vent / crossover tube (drawing 4) between tanks.



If during flight, the second ASI shows zero or negative airspeed,  

land and check your gas caps.



Al Arthur

On Jan 31, 2007, at 3:52 PM, Torgeir Mortensen wrote:



 	  Quote: 	
		   Hi Folks,

.........
	




 	  Quote: 	
		   There is one thing to be said in general, if your system is kept in  

 good condition (maintenance well) both system will serve you fine.  

 However, if things "worn" over time -no one can assure for correct  

 function..

 Next time I'll like to address some other items in the fuel system.



 (PS. Will be travelling for some days.)



 Torgeir.

 -- 

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

 <Fuel_3.jpg>

 <Fuel_4.jpg>

 <Fuel_5.jpg>

 <Fuel_6.jpg>

Guy Buchanan

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

Posted: Thu Feb 01, 2007 8:40 am Post subject: Fuel flow, summary so far.

At 03:25 AM 2/1/2007, you wrote:

 	  Quote: 	
		  When you say "you get to use one tank of fuel, right or left", do you

mean that once that tank of fuel is gone you will run out?


	


When you have a cracked cap, (not the cap off,) and the high pressure 

tank pushes the fuel out the cracked cap, it will continue to do so 

until there is about a 9" disparity between the tank levels. At that 

point both levels will drop together until the lower level gets to 

the header tank whereupon vapor will transfer through the header 

tank, possibly preventing additional flow from the higher level tank. 

If your header is more than 9" below the tanks, you will then get 

about all of the fuel from the higher level tank.

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: Thu Feb 01, 2007 7:57 pm Post subject: Fuel flow, summary so far.

Not with a cross feed vent.   Another good reason to install one.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

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

Posted: Thu Feb 01, 2007 8:00 pm Post subject: Fuel flow, summary so far.

Cheaper to check the caps before flying....  Especially with the cost of gas

or whatever else they, oil and government, feist off on us.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

torgemor(at)online.no
Guest

Posted: Fri Feb 02, 2007 6:46 am Post subject: Fuel flow, summary so far.

PS. Yesterday I sent 3 postings, all of the returned, so really don't know what happend.

Hi Lowell,



this is a good and correct observation.



However, you'll know I've never mentioned the height. 



Sure, I've been informed that the new tank is located behind the seat all 

the way down to the floor.



And you're right, the feeder tank I'm describing is the pre. 94 model 

tank, "high" located behind the seat.



Let's do some calculations:



Now; 10.58 millibar (or 0.1534499 PSI) is equal to 92 mph or ~80 Kts.



Another important thing is the influence the low pressure might have here, 

my finding is based on a standard profile at 5 deg AOA gave approx. 14.4 

PSI with 92 Mph.



(This is a little conservative calculation, -but hopefully close to the 

reality, at high angle the pressure can go down to ~14.2 PSI.)



Well, all of my assumptions is worst case, so anything less is better..



I.E. Delta P=((14.7-14.4)+0.153)PSI=0.453 PSI. This is the pressure that 

will try to force the fuel downward the line until there is pressure 

balance. The height between top of fuel surface inside left tank and the 

level of the "downpressed" fuel.



Let's see what height this will be;



14.7 PSI represent 393.7" column of water (equal to 10 meter). The 

following formula is valid for this calculation; 14.7 

PSI/393.7"=0.453PSI/X



Then X=0.453PSI*393.7"/14.7PSI=12.123" column of water. Now, since fuel 

(Mogas) is lighter than water we must recalculate as this:



Column of fuel = Column of water/spec. weight for 

fuel=12.123"/0.71=17.088" (0.43 meter)



The height difference between the main tank output flange and the 

carburetor inlet flange is 0.6 meter or 23.62". The old header in my 

example is in between here, I.E. less than 0.6 meter.



Next thing is that the size of the feeder lines of this old setup 

"originally" is 1/4" of diameter.



With the fuel demand from the engine, and this reduced flow the header 

will decrease in level until the line unport and air start flowing.



Here's another one; the total length of all feeding fuel lines in my plane 

is 5.13 meter equal to 16.6 feet!



And this one, let's say that the left only have say 5 Gallon and the pilot 

make some left turns -airwork, observations who knows.



I've always search for the worst case just to clarify or.. justify..



Torgeir





On Thu, 01 Feb 2007 03:19:16 +0100, Lowell Fitt <lcfitt(at)sbcglobal.net> 

wrote:



[quote] 



 Torgeir,



 I think I see a problem with your figure (fuel_4). My water manometer 

 shows a column of water 4.5" tall will create the pressure at the pitot 

 tube to register 100 mph. which is a bit more than the avarage Kitfox 

 will fly (sorry to the 5 through 8 guys, but average is average and you 

 guys will come in later). A rough estimate gives a column of fuel at 

 say 6 inches at that speed. Conversely an airplane flying at 100 mph 

 will has the ability to lift a column of fuel about 6 inches. What that 

 indicates to me - if the header tank is full and the left tank is full 

 as you show, there will be fuel to some level in both the fuel line and 

 the vent line on the right side due to head pressure from the full 

 tank. The level will be somethiing like 6: below the tank fuel level. 

 As I measure it I have about 10 inches from the level of the fuel tank 

 outlet to the header tank inlet. There is insufficient pressure 

 generated from the "pitot tube" type air vent on the non leaking tank to 

 force a breach into the header tank as long is there is at least some 

 fuel in the (leaking gasket) tank and the airspeed is no higher than, 

 say 115 mph. Air at .04 psi won't lift a column of fuel 10 inches.



 Further all aircraft sold after about 1994 - the aircraft capable of 

 higher speeds have the header tanks low behind the seats with a pressure 

 head of more like 18 to 20 inches. With these airplanes the .04 psi 

 from the intact fuel cap won't force air in the fuel line or vent line 

 more than about 11inches below the fuel level in the system even at 

 VNE. I doubt there is any way to introduce air into the full tank to 

 header tank feed line in our airplanes in the scenario you illustrate.



 Also the diagram of the header tank reflects the round header tank of 

 several models ago consistent with the diagram of (Fuel_5) The newer 

 header tank has the inlets from both tanks on the top surface as well as 

 the vent line. Provision is made for a quick drain on the bottom and 

 fuel outlet about an inch or two above that on the forward facing side.



 Lowell

 ---

donpearsall
Guest

Posted: Fri Feb 02, 2007 9:02 am Post subject: Fuel flow, summary so far.

Torgeir,

The list did not get any messages from you yesterday, but there were plenty

of other messages posted. So the problem must be on your end. Your posts are

appearing now, so perhaps it is fixed.



Don Pearsall



--

torgemor(at)online.no
Guest

Posted: Fri Feb 02, 2007 10:26 am Post subject: Fuel flow, summary so far.

Hi Jim,



Got this message as a reply of all my posting to the list yesterday, see  

below.



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



The original message was received at Thu, 1 Feb 2007 20:09:40 -0800

 from barracuda.matronics.com [64.81.74.21]



    ----- The following addresses had permanent fatal errors -----

"|/lists/cto DoMIME | /lists/at Kitfox-List kitfox-list | /lists/hf  

kitfox-list Kitfox-List DoMIME"

     (reason: 554 5.4.6 Too many hops)

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



    ----- Transcript of session follows -----

554 5.4.6 Too many hops 39 (25 max): from <torgemor(at)online.no> via  

barracuda.matronics.com, to <kitfox-list(at)matronics.com>



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



Thanks for the flowers Jim.



My planned trip up North was cancelled, so now some more writing.  



Torgeir.



On Thu, 01 Feb 2007 02:51:44 +0100, James Shumaker  

<jimshumaker(at)sbcglobal.net> wrote:



Excellent Torgier



Another keeper for my archives and another change to be made on my plane.



Jim Shumaker



-- 

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

torgemor(at)online.no
Guest

Posted: Fri Feb 02, 2007 10:34 am Post subject: Fuel flow, summary so far.

Hi Noel,



Hmm, maybe there was a thunderstorm in cyberspace yesterday ... ?



See below.



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



The original message was received at Thu, 1 Feb 2007 22:02:21 -0800

 from barracuda.matronics.com [64.81.74.21]



    ----- The following addresses had permanent fatal errors -----

"|/lists/cto DoMIME | /lists/at Kitfox-List kitfox-list | /lists/hf  

kitfox-list Kitfox-List DoMIME"

     (reason: 554 5.4.6 Too many hops)

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



    ----- Transcript of session follows -----

554 5.4.6 Too many hops 47 (25 max): from <torgemor(at)online.no> via  

barracuda.matronics.com, to <kitfox-list(at)matronics.com>



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



Hi Noel,



I'll put the answer in beetween below.

 	  Quote: 	
		   On Thu, 01 Feb 2007 03:53:24 +0100, Noel Loveys <noelloveys(at)yahoo.ca>  

 wrote:


	


 	  Quote: 	
		   


	


 	  Quote: 	
		   Torgeir:


	


 	  Quote: 	
		   On the second diagram you showed the left tank dribbling fuel into the

 header tank.   I expect that you won't get a pressurized head of air over

 the fuel in the tank but neither will you get a vacuum to hold the fuel  

 up

 in the tank. Let alone suck air from the empty tank. Even though the cap

 isn't properly fitted the pitot effect should be enough to brake the low

 pressure ( hardly a vacuum) on the top of the wing.


	


See the mail just posted to Lowell.



 	  Quote: 	
		   Why bother connecting a vent from the header to the cross vent in the  

 last

 diagram?  Once you have the cross vent tube installed the air pressure on

 top of the fuel should be consistent across both wing tanks regardless of

 whether or not one cap is not properly installed..  The header will self

 purge because you don't fill both tanks at exactly the same speed to trap

 air in the header.... That is assuming of course you ran or drained the

 header dry.  One other thing... On my plane the inlets to the header tank

 are "almost" at the very top of the header tank....  The vent comes off  

 the

 same level as the inlets.


	


As my tank has a colletion camber for air and vented at the top, it's a  

must to be able to vent.

In your newer system,perhaps with 3/8" lines, the system will self vent.





 	  Quote: 	
		   Nice diagrams.  I do like the idea of the cross vent.  Then again I like  

 the

 idea of controlling the fuel flow too.


	


 	  Quote: 	
		   Noel


	




Thanks



Torgeir.





-- 

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

rjdaugh

Joined: 30 Aug 2006
Posts: 195

Posted: Sat Feb 03, 2007 9:40 am Post subject: Fuel flow, summary so far.

"And this one, let's say that the left only have say 5 Gallon and the pilot 

make some left turns -airwork, observations who knows.

I've always search for the worst case just to clarify or.. justify.."

Torgeir

Hey Torgeir,

I always fly coordinated (Yah, You betcha,  sure...), so it doesn't matter

if I am turning right or left or flying straight.   The situation you refer

to only applies to slips or skids.



Thanks for the drawings and discussion.  Also thanks to Lowell and Guy for

the head pressure calculations.  This helps educate all of us on the list!



Randy  - Fuel tank caps now part of preflight!

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

torgemor(at)online.no
Guest

Posted: Sat Feb 03, 2007 12:15 pm Post subject: Fuel flow, summary so far.

Hi Randy,



Sure you're sooo right, it's so easy to forget the most elementary things..



I've also trying to be coordinated, but..



Thanks Randy.



Cheers



Torgeir

On Sat, 03 Feb 2007 18:38:24 +0100, Randy  Daughenbaugh  

<rjdaugh(at)rapidnet.com> wrote:



 	  Quote: 	
		   

 <rjdaugh(at)rapidnet.com>

 "And this one, let's say that the left only have say 5 Gallon and the  

 pilot

 make some left turns -airwork, observations who knows.

 I've always search for the worst case just to clarify or.. justify.."

 Torgeir

 Hey Torgeir,

 I always fly coordinated (Yah, You betcha,  sure...), so it doesn't  

 matter

 if I am turning right or left or flying straight.   The situation you  

 refer

 to only applies to slips or skids.



 Thanks for the drawings and discussion.  Also thanks to Lowell and Guy  

 for

 the head pressure calculations.  This helps educate all of us on the  

 list!



 Randy  - Fuel tank caps now part of preflight!


	


-- 

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 Feb 03, 2007 4:52 pm Post subject: Fuel flow, summary so far.

After spending quite a few hours contemplating the turn co-ordinator in my

plane I read the best way to fly co-ordinated was to try to feel the

movements in the controls through, for lack of a better term, your derriere.

I tried on a couple of flights and it is remarkable just how well you can

co-ordinate "by the seat of your pants".



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Beemer

Joined: 26 Aug 2006
Posts: 87
Location: Middle Georgia

Posted: Sat Feb 03, 2007 5:07 pm Post subject: Fuel flow, summary so far.

I've heard that some pilots are very sensitive to that feeling. I, myself,

find it a little hard to judge. Not sure why, just could never really rely

on my ass to push the rudders.



Now, the Lancair IV my buddy just finished, I can feel a hair's width of

slip in that thing. Again, I don't know why, but he once almost made me

sick, it was yawing so much. No problem keeping that one centered by touch.



My 'fox flies like yours, but for me it seems a little hard to get centered

by feel. I think it may be due to the fact I am a Cessna baby, and the

rudders on those hardly work at all (at least in comparison to a 'fox). So,

I probably didn't really learn to feel it in my initial training.



Bradley



--

_________________
Beemer
KF2 (and now an M3!)
Suzuki G10 three-banger
Middle Georgia

Bob

Joined: 24 Oct 2006
Posts: 89
Location: Damascus, Maryland, USA

Posted: Sun Feb 04, 2007 6:42 am Post subject: Re: Fuel flow, summary so far.

In Cessnas, Kitfoxes, and the like, your head, the CG, and the CL are all within a few inches.  Basically, the airplane maneuvers about this small sphere that your head is in and yaw is not as pronounced.  In the Glasair, Lancair, and some of the other pocket rockets, the pilot's inner ear is actually pretty far aft of this; naturally the pilot can better feel yaw.  As an interesting aside, yaw dampers in airliners typically only have max rudder authority of a few degrees, but turn them off and people in the ends of the cabin can get sick or have trouble standing.



The Kitfox was designed to be a light airplane and here comes the tie-in to altering an airplane's design.  We all like to have "stuff" that adds weight.  If we put that weight in the center of the airplane, it diminishes our useful load.  However, as we add say a heavier engine in the front and ballast in the tail, bigger tailwheel, aft batteries, etc, we don't just diminish the useful load, we diminish the inertial stability of the design that the flight controls are sized to manipulate.  Handling a cross-wind gust at low speed can come closer to the limits of rudder control, ground-loops become easier, and spin recovery takes more effort.  Keeping your airplane light will help keep the inertia, and controllability, as it was designed to be.  



Bob

Aero Eng, A&P

Do not archive

_________________
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