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Re - Question about fuel flow from only one tank?

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peterlthomson(at)gmail.co
Guest

Posted: Sun Sep 07, 2008 11:51 pm Post subject: Re - Question about fuel flow from only one tank?

Curt, perfect timing !



I've flown my CZAW 701 for about 9 mths and 150 hrs. In that time, it

has always drained from the RIGHT TANK first. After my 1st flight I

drained the RHS tank manually on ground to make sure the fuel kept

coming from the left. It did.



But last week during a 3 ½ flight, I decided to select the left for

some time. When I did this and switched back to both, the LHS tank

kept draining more than the right ! To the extent that I selected RHS

for a time.



It made me think perhaps it was something in the Andair fuel valve.



However, I see it has now reverted back to the old procedure, draining

the RHS tank first.



Beats me – I was told has been doing this since new (2005).



Bit more, fly slats off, VG's wings and elevator. 16l/hr of E10

95octane blend, 80kts



Peter

CH701/912ULS

egelhoffl(at)juno.com
Guest

Posted: Mon Sep 08, 2008 4:32 am Post subject: Re - Question about fuel flow from only one tank?

I purchased my 701 already built. The previous owner/builder had the same

situation as reported here. He finally determined

that the drain balance depended on the dominant direction of turns.....

Left turns moved more fuel to the right tank and vice versa.

I have not flown enough to verify this.



Larry,

Tennessee



On Mon, 8 Sep 2008 14:51:10 +0700 "Peter Thomson"

<peterlthomson(at)gmail.com> writes:

 	  Quote: 	
		   

 <peterlthomson(at)gmail.com>

 

 Curt, perfect timing !

 

 I've flown my CZAW 701 for about 9 mths and 150 hrs. In that time, 

 it

 has always drained from the RIGHT TANK first. After my 1st flight I

 drained the RHS tank manually on ground to make sure the fuel kept

 coming from the left. It did.

 

 But last week during a 3 ½ flight, I decided to select the left for

 some time. When I did this and switched back to both, the LHS tank

 kept draining more than the right ! To the extent that I selected 

 RHS

 for a time.

 

 It made me think perhaps it was something in the Andair fuel valve.

 

 However, I see it has now reverted back to the old procedure, 

 draining

 the RHS tank first.

 

 Beats me – I was told has been doing this since new (2005).

 

 Bit more, fly slats off, VG's wings and elevator. 16l/hr of E10

 95octane blend, 80kts

 

 Peter

 CH701/912ULS

 

 

 

 

 

 

 

____________________________________________________________
	


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Inge

Joined: 08 Sep 2008
Posts: 1

Posted: Mon Sep 08, 2008 5:21 am Post subject: Re: Re - Question about fuel flow from only one tank?

My CZAW 701 (540 hours, 120 hours by me, slats off, Feathers VGs wings and elevator, 912/80 Hp, 14 liters per hour, 90 miles per hour) also drains the right hand tank first, as did my previous plane (ICP Bingo/HKS, 430 hours). If it is the plane or the pilot? Most people get a consistent flow from both tanks, but then again, most people do not x-country as long as it takes to be sure there is a difference. A friend reported this phenomenon on his Kitfox 3. I noticed the same in another friend's slick, racy 130 kts CTSW during a six hour x-country. Discussing this phenomenon (is it likely to start draining from the other tank soon?) over the high seas is certainly one of the stronger spices of life. By the way, as you may have come to expect, these four planes all level out between their tanks while left for a while.

NYTerminat(at)aol.com
Guest

Posted: Mon Sep 08, 2008 2:46 pm Post subject: Re - Question about fuel flow from only one tank?

Larry, I believe that there is a lot of truth to what you said, also I find  that if you have a slight uncoordinated flight it will favor one or the other  tank. I also have the individual fuel shut off valve for each tank and use them  if they become too uneven. More important is if you park on uneven ground you  can shut off one of the tanks so that the high one won't overflow into the lower  one, as Gary mentioned. Any unbalance in my tanks is balanced out when the plane  sits on my level hanger floor.

  

 Bob Spudis

 N701ZX/ 164hrs

  

  

  

  

 In a message dated 9/8/2008 8:34:28 A.M. Eastern Daylight Time,  egelhoffl(at)juno.com writes:

  	  Quote: 	
		  I    purchased my 701 already built. The previous owner/builder had the    same

situation as reported here. He finally determined

that the drain    balance depended on the dominant direction of turns.....

Left turns moved    more fuel to the right tank and vice versa.

I have not flown enough to    verify this.



Larry,

Tennessee

	


 

  



Psssst...Have you heard the news? There's a new fashion blog, plus the latest fall trends and hair styles at StyleList.com.

  [quote][b]

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Tue Sep 09, 2008 7:02 am Post subject: Re: Re - Question about fuel flow from only one tank?

My guess is due to slight differences in vents, and lacking a line to

balance pressure between tanks this is the real culprit.



In Kitfoxes this is very common, the reason for it is the header vent line

returns to only one tank. This causes a a pressure differential inside the two tanks. The only real solution is to put a balance line between the 

two tanks to balance the internal pressure. 



All it takes is a slight pressure difference between tanks to cause this to

happen. The plus is that at some point when one tanks gets lower in fuel

than the other the fuel flow will equalize. But with one tank having lower

quantity that the other. It's a good reason to use a header as well. 

Because regardless how the fuel from the tanks is flowing to the header,

the feed to the engine is constant.



Jeff

Roland Smith

Joined: 02 Jul 2006
Posts: 14

Posted: Tue Sep 09, 2008 7:32 am Post subject: Re: Re - Question about fuel flow from only one tank?

Plumbing in my 701 ( N701AA reserved) is for one tank at a time.  Never both on.  This has worked well in my old Taylorcraft BC12D, albeit, with a header tank and also with my Cessna 140 that I fly to stay current while finishing the 701. 



This serves me best for fuel management.  For example:  Should my engine splutter when the fuel in my left tank runs dry I know there is fuel in the right tank.   My preflight dipsticks are calibrated for each tank.  I also marked the gages at one hour remaining.  



If anyone sees a problem with this setup for the 701, please comment.

_________________
701 kit, Rotax 912 ULS, SensorNetics EFIS, Flying.

lgold(at)quantum-associat
Guest

Posted: Wed Sep 10, 2008 12:32 pm Post subject: Re - Question about fuel flow from only one tank?

My 701 has 4 10-gal wing tanks but I have had no occasion to use the outer

two yet. The wing root fuel control valves on each wing allow me to select

inside or outside tanks or shut them both off. Because of this I can drain

any one tank or drain two tanks at once, one from each wing. The fuel flows

from each valve into its own filter. The lines come together in the

gascolator, finally the fuel goes through and an auxiliary pump (which I

normally leave off), before going up to the 912 engine. 



To avoid the possibility of forgetting to switch tanks, I usually allow the

fuel to drain from both inside tanks at the same time. The inside tanks

often drain at different rates (but not always). I have notices that the

right side often drops down more than the left. However, with this fuel flow

configuration, unless I have a clogged line or am in weird attitudes, with

both valves open, I do not see how the fuel will stop flowing into the

engine if one tank runs dry. On one occasion I had under 1/2 gal in the

right tank and an almost full left tank and did not feel it was necessary to

cut off my right tank because I knew fuel had draining from my left tank,

indicating it wasn't clogged and left tank would siphon down when needed. 

Is there anything wrong with this logic?

Les

N67MG    



[quote] --

b.carl@sympatico.ca

Joined: 20 May 2008
Posts: 77

Posted: Sun Sep 14, 2008 3:53 am Post subject: Re - Question about fuel flow from only one tank?

Rolland,

The biggest improvement I made to my 13 year old 701 fuel system was to add 

an 8 liter collector tank.

Carl

---

ggower_99(at)yahoo.com
Guest

Posted: Mon Sep 15, 2008 10:11 pm Post subject: Re - Question about fuel flow from only one tank?

Hello friends,

  

 The Kitfox rear header tank  (about a galon capacity) is also a good idea, is attached to the back side of the seats.  this tank conects both wing tanks in one over the gascolator. comes with a float switch that will light a bulb in the instrument panel in case of the fuel is low in this header tank.  At least will give the pilot a few minutes to aproach a landing place before the engine stops...   

  

 Someone knows if Kitfox sells them, or where can be bought?  at least the float switch,  I can make my own tank with alum or vinilester resin...

  

 Saludos

 Gary Gower.



--- On Sun, 9/14/08, carl <b.carl(at)sympatico.ca> wrote:



 [quote]From: carl <b.carl(at)sympatico.ca>

Subject: Re: Re: Re - Question about fuel flow from only one tank?

To: zenith701801-list(at)matronics.com

Date: Sunday, September 14, 2008, 7:53 AM



[quote]--> Zenith701801-List message posted by: "carl" <b.carl(at)sympatico.ca>  Rolland, The biggest improvement I made to my 13 year old 701 fuel system was to add  an 8 liter collector tank. Carl ---

rvickski(at)yahoo.com
Guest

Posted: Tue Sep 16, 2008 3:05 am Post subject: Re - Question about fuel flow from only one tank?

I am glad to know that Gary, I did the same but without prior firsthand knowledge of the effectiveness. My tank has a submersible high pressure pump and fuel cell foam in it and will be hard to retrofit a level sender. Perhaps I will investigate oil level senders used on lawn mowers or cars. Thanks for the info.

Cheers

Roy Szarafinski

701 plans, corvair

roysgarage.com



---

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