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Fuel flow

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cjpilot710(at)aol.com
Guest

Posted: Tue May 18, 2010 7:53 pm Post subject: Fuel flow

Let me see if I can elucidate what I think happens.

    

   While a plug vent will definitely cause fuel to flow from just one tank, I just don't feel that the vent line placed closer to one tank than the other will cause the problem. If we have two tanks with equal amounts of fuel in them AND they are level with each other, they both will exert the same pressure head at the outlets. Hence the fuel in the header tank, which is full at all times, will have that same pressure. The flop valves will only open when pressure from the tank side is greater than what is in the header tank and thus fuel will flow. So it bear to reason that if the airplane is sitting on a slope, fuel from the high side will flow. Since the head pressure builds up in the header tank the flop valve on the lower side will close.

    

   Now lets get the airplane moving. Now both tanks AND the header tank, will not only have the head pressure but inertia forces acting on them. IF you make coordinated turns forces are the same in the tank AND the header tank. 

    

   But lets say you have a slight yaw either in a turn or wings level, the inertia forces of the fuel tank will actually increase head pressure will force one flop valve open and fuel will feed from that tank. Assume you have yaw left (left rudder peddle down), the inertia in the left tank will effectively increase the head pressure and force open the left flop valve, and the left tank will feed fuel. The right tank may have exactly the same amount of fuel, but its inertia is a way from the flop valve thus its head pressure is effective less.

    

   The inertia of the fuel in the header tank will react the same - helping keep the opposite flop valve closed.

    

   Anyway that's what I think happens. A engineer type agreed with me, but I think he was in a hurry to get to the bar. Would appreciate a back up check on my theory.

    

   Jim "Pappy" Goolsby

 

   [quote][b]

ph451(at)yahoo.com
Guest

Posted: Tue May 18, 2010 8:13 pm Post subject: Fuel flow

So are you saying if the right tank is not feeding, step on the right rudder.  Others have said apply rudder on the low tank side (left).



--- On Wed, 5/19/10, cjpilot710(at)aol.com <cjpilot710(at)aol.com> wrote:

  	  Quote: 	
		  

From: cjpilot710(at)aol.com <cjpilot710(at)aol.com>

Subject: Fuel flow

To: yak-list(at)matronics.com

Date: Wednesday, May 19, 2010, 4:44 AM



 



  Let me see if I can elucidate what I think happens.

  

 While a plug vent will definitely cause fuel to flow from just one tank, I just don't feel that the vent line placed closer to one tank than the other will cause the problem. If we have two tanks with equal amounts of fuel in them AND they are level with each other, they both will exert the same pressure head at the outlets. Hence the fuel in the header tank, which is full at all times, will have that same pressure. The flop valves will only open when pressure from the tank side is greater than what is in the header tank and thus fuel will flow. So it bear to reason that if the airplane is sitting on a slope, fuel from the high side will flow. Since the head pressure builds up in the header tank the flop valve on the lower side will close.

  

 Now lets get the airplane moving. Now both tanks AND the header tank, will not only have the head pressure but inertia forces acting on them. IF you make coordinated turns forces are the same in the tank AND the header tank. 

  

 But lets say you have a slight yaw either in a turn or wings level, the inertia forces of the fuel tank will actually increase head pressure will force one flop valve open and fuel will feed from that tank. Assume you have yaw left (left rudder peddle down), the inertia in the left tank will effectively increase the head pressure and force open the left flop valve, and the left tank will feed fuel. The right tank may have exactly the same amount of fuel, but its inertia is a way from the flop valve thus its head pressure is effective less.

  

 The inertia of the fuel in the header tank will react the same - helping keep the opposite flop valve closed.

  

 Anyway that's what I think happens. A engineer type agreed with me, but I think he was in a hurry to get to the bar. Would appreciate a back up check on my theory.

  

 Jim "Pappy" Goolsby



 	  Quote: 	
		  



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               [quote][b]

cjpilot710(at)aol.com
Guest

Posted: Tue May 18, 2010 8:51 pm Post subject: Fuel flow

In this case the right tank has the most fuel in it.  Raise that wing (stick left) while at the same time applying right rudder.  You'll do two things.  Increase the head pressure of the right tank and induce a yaw to use inertia to increase its effective pressure to open the flop valve.  - - - - - - -  I think.

    

   Jim "Pappy" Goolsby

 

 

   

 

 

   --

wlannon(at)persona.ca
Guest

Posted: Tue May 18, 2010 9:07 pm Post subject: Fuel flow

Jim;

  

 I agree with you as well - but this engineer type  just came FROM the bar.

 Yes the same quantities of fuel in both tanks will  result in the same pressure being applied to both sides of the flapper valve. 

 But that same pressure does not translate into the  same force being applied on each side of the valve.

  

 Pressure, whether described in pounds per sq. ft,  grams per sq. cm. or whatever produces equal force only when applied to an equal  area.

  

 That is precisely the problem with the CJ flapper  valve. The closing force is actually 3 to 4 times the opening force with  equal pressure.

 In fact with absolutely no fuel sloshing (ie: no  yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance of  about 50 liters to open.

  

 Fortunately we rarely ever find a day, or a pilot,  that can deliver a non fuel sloshing flight. 

  

 That it is invariably the right side hung up  is I believe a result of the vent system design.  The left side vents  much more directly than the right.

  

 Walt

  

 [quote]   ---

KingCJ6(at)aol.com
Guest

Posted: Tue May 18, 2010 9:33 pm Post subject: Fuel flow

All â€“ I think there have been 50+ posts  on this subject in the last few days, not counting the 100+ in years past.  Bill Blackwell sells a simple,   very inexpensive kit consisting of some PVC tubing, two manual cockpit  mounted toggle shut-off valves and a few T-fittings that takes about 3-4 hours  for a novice A&P wana-be to install.   Simply flip the non-venting tank switch off for 5-10 minutes in-flight,  and problem solved. 

  

The beauty of our â€œexperimentalâ€  class! 

  

Dave  

  

  In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time,  wlannon(at)persona.ca writes:

 [quote]   Jim;

    

   I agree with you as well - but this engineer type    just came FROM the bar.

   Yes the same quantities of fuel in both tanks    will result in the same pressure being applied to both sides of the flapper valve. 

   But that same pressure does not translate into    the same force being applied on each side of the valve.

    

   Pressure, whether described in pounds per sq. ft,    grams per sq. cm. or whatever produces equal force only when applied to an    equal area.

    

   That is precisely the problem with the CJ flapper    valve. The closing force is actually 3 to 4 times the opening force with    equal pressure.

   In fact with absolutely no fuel sloshing (ie: no    yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance    of about 50 liters to open.

    

   Fortunately we rarely ever find a day, or a    pilot, that can deliver a non fuel sloshing flight. 

    

   That it is invariably the right side hung up    is I believe a result of the vent system design.  The left side    vents much more directly than the right.

    

   Walt

    

   [quote]     ---

viperdoc(at)mindspring.co
Guest

Posted: Wed May 19, 2010 5:35 am Post subject: Fuel flow

PVC?  

Doc  

       

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of KingCJ6(at)aol.com

 Sent: Wednesday, May 19, 2010 12:33 AM

 To: yak-list(at)matronics.com

 Subject: Re: Fuel flow  

  

  

     

All â€“ I think there have been 50+ posts on this subject in the last few days, not counting the 100+ in years past.Â  Bill Blackwell sells a simple,  very inexpensive kit consisting of some PVC tubing, two manual cockpit mounted toggle shut-off valves and a few T-fittings that takes about 3-4 hours for a novice A&P wana-be to install.Â  Simply flip the non-venting tank switch off for 5-10 minutes in-flight, and problem solved.  

   

The beauty of our â€œexperimentalâ€ class!  

   

DaveÂ    

    

   

      

In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time, wlannon(at)persona.ca writes:  

  [quote]    

Jim;  

    

   

    

I agree with you as well - but this engineer type just came FROM the bar.  

    

Yes the same quantities of fuel in both tanks will result in the same pressure being applied to both sides of the flapper valve.   

    

But that same pressure does not translate into the same force being applied on each side of the valve.  

    

   

    

Pressure, whether described in pounds per sq. ft, grams per sq. cm. or whatever produces equal force only when applied to an equal area.  

    

   

    

That is precisely the problem with the CJ flapper valve. The closing force is actually 3 to 4 times the opening force with equal pressure.  

    

In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance of about 50 liters to open.  

    

   

    

Fortunately we rarely ever find a day, or a pilot, that can deliver a non fuel sloshing flight.   

    

   

    

That it is invariably the right side hung up is I believe a result of the vent system design.  The left side vents much more directly than the right.  

    

   

    

Walt  

    

   

  [quote]    

---

viperdoc(at)mindspring.co
Guest

Posted: Wed May 19, 2010 5:43 am Post subject: Fuel flow

In the YAK, have done exactly that as well as have snap rolled the aircraft into the heavy wing and away from the heavy wing with pretty much equal results. On the ground on Dennis’s advice have taken a rubber hose that will fit the main drain and force low pressure air through it until air bubbling could be heard in the right tank. If it was fuel in the siphon for the vent that clears it out.  

Doc  

     

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of cjpilot710(at)aol.com

 Sent: Tuesday, May 18, 2010 11:51 PM

 To: yak-list(at)matronics.com

 Subject: Re: Fuel flow  

  

     

In this case the right tank has the most fuel in it.  Raise that wing (stick left) while at the same time applying right rudder.  You'll do two things.  Increase the head pressure of the right tank and induce a yaw to use inertia to increase its effective pressure to open the flop valve.  - - - - - - -  I think.  

    

   

    

Jim "Pappy" Goolsby  

  

     

--

William Halverson

Joined: 27 Feb 2010
Posts: 88

Posted: Wed May 19, 2010 6:48 am Post subject: Fuel flow

Exactly.  Doesn't PVC + AvGas = Goo?

+--

KingCJ6(at)aol.com
Guest

Posted: Wed May 19, 2010 8:37 am Post subject: Fuel flow

Sorry, it's a gas-friendly flex fuel tubing, about 3/8" OD 

  

  In a message dated 5/19/2010 7:48:12 A.M. Pacific Daylight Time,  william(at)netpros.net writes:

 [quote]-->    Yak-List message posted by: "William Halverson"    <william(at)netpros.net>



Exactly.  Doesn't PVC + AvGas    = Goo?

+--

gill.g(at)gpimail.com
Guest

Posted: Wed May 19, 2010 11:54 am Post subject: Fuel flow

Donâ€™t install vent control valves on metal tanks unless you want smaller tanks!  

   

Gill  

       

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Roger Kemp M.D.

 Sent: Wednesday, May 19, 2010 6:34 AM

 To: yak-list(at)matronics.com

 Subject: RE: Fuel flow  

  

  

   

PVC?  

Doc  

       

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of KingCJ6(at)aol.com

 Sent: Wednesday, May 19, 2010 12:33 AM

 To: yak-list(at)matronics.com

 Subject: Re: Fuel flow  

  

  

     

All â€“ I think there have been 50+ posts on this subject in the last few days, not counting the 100+ in years past.  Bill Blackwell sells a simple,  very inexpensive kit consisting of some PVC tubing, two manual cockpit mounted toggle shut-off valves and a few T-fittings that takes about 3-4 hours for a novice A&P wana-be to install.  Simply flip the non-venting tank switch off for 5-10 minutes in-flight, and problem solved.  

   

The beauty of our â€œexperimentalâ€ class!  

   

Dave    

    

   

      

In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time, wlannon(at)persona.ca writes:  

  [quote]    

Jim;  

    

   

    

I agree with you as well - but this engineer type just came FROM the bar.  

    

Yes the same quantities of fuel in both tanks will result in the same pressure being applied to both sides of the flapper valve.   

    

But that same pressure does not translate into the same force being applied on each side of the valve.  

    

   

    

Pressure, whether described in pounds per sq. ft, grams per sq. cm. or whatever produces equal force only when applied to an equal area.  

    

   

    

That is precisely the problem with the CJ flapper valve. The closing force is actually 3 to 4 times the opening force with equal pressure.  

    

In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance of about 50 liters to open.  

    

   

    

Fortunately we rarely ever find a day, or a pilot, that can deliver a non fuel sloshing flight.   

    

   

    

That it is invariably the right side hung up is I believe a result of the vent system design.  The left side vents much more directly than the right.  

    

   

    

Walt  

    

   

  [quote]    

---

byronmfox(at)gmail.com
Guest

Posted: Wed May 19, 2010 12:11 pm Post subject: Fuel flow

I have Blackwell's vent valve kit on my metal tanks, and indeed you must be careful.  Our thin-walled CJ tanks will collapse if you fail to cycle the vent valve switch frequently. I was shocked at the oil-canning I heard when pulled a fuel cap off after failing to turn the switch off. Now, I cycle the switch about every ten minutes until balance is achieved. No fuel tank leaks have appeared, and I've had the systems in place for about five years.  ...Blitz

  

On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g(at)gpimail.com (gill.g(at)gpimail.com)> wrote:

[quote]              

Don’t install vent control valves on metal tanks unless you want smaller tanks!  

   

Gill  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of Roger Kemp M.D.

 Sent: Wednesday, May 19, 2010 6:34 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: RE: Fuel flow  

  

  

   

PVC?  

Doc  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of KingCJ6(at)aol.com (KingCJ6(at)aol.com)

 Sent: Wednesday, May 19, 2010 12:33 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: Re: Fuel flow  

  

  

     

All – I think there have been 50+ posts on this subject in the last few days, not counting the 100+ in years past.  Bill Blackwell sells a simple,  very inexpensive kit consisting of some PVC tubing, two manual cockpit mounted toggle shut-off valves and a few T-fittings that takes about 3-4 hours for a novice A&P wana-be to install.  Simply flip the non-venting tank switch off for 5-10 minutes in-flight, and problem solved.  

   

The beauty of our “experimental” class!  

   

Dave    

    

   

      

In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time, wlannon(at)persona.ca (wlannon(at)persona.ca) writes:  

  [quote]    

Jim;  

    

   

    

I agree with you as well - but this engineer type just came FROM the bar.  

    

Yes the same quantities of fuel in both tanks will result in the same pressure being applied to both sides of the flapper valve.   

    

But that same pressure does not translate into the same force being applied on each side of the valve.  

    

   

    

Pressure, whether described in pounds per sq. ft, grams per sq. cm. or whatever produces equal force only when applied to an equal area.  

    

   

    

That is precisely the problem with the CJ flapper valve. The closing force is actually 3 to 4 times the opening force with equal pressure.  

    

In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance of about 50 liters to open.  

    

   

    

Fortunately we rarely ever find a day, or a pilot, that can deliver a non fuel sloshing flight.   

    

   

    

That it is invariably the right side hung up is I believe a result of the vent system design.  The left side vents much more directly than the right.  

    

   

    

Walt  

    

   

  [quote]    

---

gill.g(at)gpimail.com
Guest

Posted: Wed May 19, 2010 1:41 pm Post subject: Fuel flow

Blitz,  

   

I designed the vent control valves to work with rubber bladders where permanent deformation is not a issue like it is on metal tanks.  The engine fuel pump is a positive displacement device which can cause nearly a full atmosphere of negative pressure which is sufficient to collapse the flat sides on the standard metal tanks, even thick walled ones.  As a minimum I suggest you install a spring check valve with a low break pressure so a to limit the pressure differential between the inside of the tank and the ambient pressure.  

   

Gill  

     

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Byron Fox

 Sent: Wednesday, May 19, 2010 1:10 PM

 To: yak-list(at)matronics.com

 Subject: Re: Fuel flow  

  

   

I have Blackwell's vent valve kit on my metal tanks, and indeed you must be careful.  Our thin-walled CJ tanks will collapse if you fail to cycle the vent valve switch frequently. I was shocked at the oil-canning I heard when pulled a fuel cap off after failing to turn the switch off. Now, I cycle the switch about every ten minutes until balance is achieved. No fuel tank leaks have appeared, and I've had the systems in place for about five years.  ...Blitz

      

On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g(at)gpimail.com (gill.g(at)gpimail.com)> wrote:      

Don’t install vent control valves on metal tanks unless you want smaller tanks!  

   

Gill  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of Roger Kemp M.D.

 Sent: Wednesday, May 19, 2010 6:34 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: RE: Fuel flow  

  

  

   

PVC?  

Doc  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of KingCJ6(at)aol.com (KingCJ6(at)aol.com)

 Sent: Wednesday, May 19, 2010 12:33 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: Re: Fuel flow  

  

  

     

All – I think there have been 50+ posts on this subject in the last few days, not counting the 100+ in years past.  Bill Blackwell sells a simple,  very inexpensive kit consisting of some PVC tubing, two manual cockpit mounted toggle shut-off valves and a few T-fittings that takes about 3-4 hours for a novice A&P wana-be to install.  Simply flip the non-venting tank switch off for 5-10 minutes in-flight, and problem solved.  

   

The beauty of our “experimental” class!  

   

Dave    

    

   

      

In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time, wlannon(at)persona.ca (wlannon(at)persona.ca) writes:  

  [quote]    

Jim;  

    

   

    

I agree with you as well - but this engineer type just came FROM the bar.  

    

Yes the same quantities of fuel in both tanks will result in the same pressure being applied to both sides of the flapper valve.   

    

But that same pressure does not translate into the same force being applied on each side of the valve.  

    

   

    

Pressure, whether described in pounds per sq. ft, grams per sq. cm. or whatever produces equal force only when applied to an equal area.  

    

   

    

That is precisely the problem with the CJ flapper valve. The closing force is actually 3 to 4 times the opening force with equal pressure.  

    

In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance of about 50 liters to open.  

    

   

    

Fortunately we rarely ever find a day, or a pilot, that can deliver a non fuel sloshing flight.   

    

   

    

That it is invariably the right side hung up is I believe a result of the vent system design.  The left side vents much more directly than the right.  

    

   

    

Walt  

    

   

  [quote]    

---

byronmfox(at)gmail.com
Guest

Posted: Wed May 19, 2010 1:55 pm Post subject: Fuel flow

Excellent thought, Gill, and easy to install. Where might I locate such a check valve? Thanks, Blitz



On Wed, May 19, 2010 at 2:49 PM, Gill Gutierrez <gill.g(at)gpimail.com (gill.g(at)gpimail.com)> wrote:

 [quote]             

Blitz,  

   

I designed the vent control valves to work with rubber bladders where permanent deformation is not a issue like it is on metal tanks.  The engine fuel pump is a positive displacement device which can cause nearly a full atmosphere of negative pressure which is sufficient to collapse the flat sides on the standard metal tanks, even thick walled ones.  As a minimum I suggest you install a spring check valve with a low break pressure so a to limit the pressure differential between the inside of the tank and the ambient pressure.  

   

Gill  

     

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of Byron Fox

 Sent: Wednesday, May 19, 2010 1:10 PM



 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: Re: Fuel flow

  



  

   

I have Blackwell's vent valve kit on my metal tanks, and indeed you must be careful.  Our thin-walled CJ tanks will collapse if you fail to cycle the vent valve switch frequently. I was shocked at the oil-canning I heard when pulled a fuel cap off after failing to turn the switch off. Now, I cycle the switch about every ten minutes until balance is achieved. No fuel tank leaks have appeared, and I've had the systems in place for about five years.  ...Blitz

    

  

On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g(at)gpimail.com (gill.g(at)gpimail.com)> wrote:  

    

Don’t install vent control valves on metal tanks unless you want smaller tanks!  

   

Gill  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of Roger Kemp M.D.

 Sent: Wednesday, May 19, 2010 6:34 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: RE: Fuel flow  

  

  

   

PVC?  

Doc  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of KingCJ6(at)aol.com (KingCJ6(at)aol.com)

 Sent: Wednesday, May 19, 2010 12:33 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: Re: Fuel flow  

  

  

     

All – I think there have been 50+ posts on this subject in the last few days, not counting the 100+ in years past.  Bill Blackwell sells a simple,  very inexpensive kit consisting of some PVC tubing, two manual cockpit mounted toggle shut-off valves and a few T-fittings that takes about 3-4 hours for a novice A&P wana-be to install.  Simply flip the non-venting tank switch off for 5-10 minutes in-flight, and problem solved.  

   

The beauty of our “experimental” class!  

   

Dave    

    

   

      

In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time, wlannon(at)persona.ca (wlannon(at)persona.ca) writes:  

  [quote]    

Jim;  

    

   

    

I agree with you as well - but this engineer type just came FROM the bar.  

    

Yes the same quantities of fuel in both tanks will result in the same pressure being applied to both sides of the flapper valve.   

    

But that same pressure does not translate into the same force being applied on each side of the valve.  

    

   

    

Pressure, whether described in pounds per sq. ft, grams per sq. cm. or whatever produces equal force only when applied to an equal area.  

    

   

    

That is precisely the problem with the CJ flapper valve. The closing force is actually 3 to 4 times the opening force with equal pressure.  

    

In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance of about 50 liters to open.  

    

   

    

Fortunately we rarely ever find a day, or a pilot, that can deliver a non fuel sloshing flight.   

    

   

    

That it is invariably the right side hung up is I believe a result of the vent system design.  The left side vents much more directly than the right.  

    

   

    

Walt  

    

   

  [quote]    

---

wlannon(at)persona.ca
Guest

Posted: Wed May 19, 2010 2:56 pm Post subject: Fuel flow

Gill;

  

 Over the years I have seen two T6 (actually 1 T6, 1  Harvard) fuel tanks "reworked" by plugged vents.  These are not light wall  tanks.  You could touch the tank bottom with your fingers through the  filler opening.

  

 Also recall one of our Bristol Brittanias sched.  run Mexico City to Toronto .  Emergency landing in the US (can't remember  where) due running out of fuel.  These were all bag tanks,  all were  sucked to the top.  Vents all plugged by some Mexican  bugs! 

  

 Walt

 [quote]   ---

gill.g(at)gpimail.com
Guest

Posted: Wed May 19, 2010 2:56 pm Post subject: Fuel flow

Blitz,  

   

Aircraft Spruce has spring loaded check valves with low break pressure.  You can always adjust break pressure by changing the spring.  I can’t tell you the pressure you need but I would think something under 12”wg which is equivalent to 20”fuel gauge and under 0.5 psig.  You can use a simple U-tube water filled manometer to test with.   The other concern I have has to do with metal fatigue and ultimately a crack developing as a result of pressure pulsing the tank sides.  You should locate the check valves so that they are between you vent control valves and the tanks.  That will require a tee in each line to accommodate the new check valves.  Also, remember that the collector tank is vented through one of the wing tanks, assuming you didn’t separate the vents when you installed the valves.  

   

Gill  

     

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Byron Fox

 Sent: Wednesday, May 19, 2010 2:55 PM

 To: yak-list(at)matronics.com

 Subject: Re: Fuel flow  

  

   

Excellent thought, Gill, and easy to install. Where might I locate such a check valve? Thanks, Blitz    

On Wed, May 19, 2010 at 2:49 PM, Gill Gutierrez <gill.g(at)gpimail.com (gill.g(at)gpimail.com)> wrote:      

Blitz,  

   

I designed the vent control valves to work with rubber bladders where permanent deformation is not a issue like it is on metal tanks.  The engine fuel pump is a positive displacement device which can cause nearly a full atmosphere of negative pressure which is sufficient to collapse the flat sides on the standard metal tanks, even thick walled ones.  As a minimum I suggest you install a spring check valve with a low break pressure so a to limit the pressure differential between the inside of the tank and the ambient pressure.  

   

Gill  

     

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of Byron Fox

 Sent: Wednesday, May 19, 2010 1:10 PM      



 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: Re: Fuel flow  

  

  

      

   

I have Blackwell's vent valve kit on my metal tanks, and indeed you must be careful.  Our thin-walled CJ tanks will collapse if you fail to cycle the vent valve switch frequently. I was shocked at the oil-canning I heard when pulled a fuel cap off after failing to turn the switch off. Now, I cycle the switch about every ten minutes until balance is achieved. No fuel tank leaks have appeared, and I've had the systems in place for about five years.  ...Blitz

    

  

        

On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g(at)gpimail.com (gill.g(at)gpimail.com)> wrote:  

  

          

Don’t install vent control valves on metal tanks unless you want smaller tanks!  

   

Gill  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of Roger Kemp M.D.

 Sent: Wednesday, May 19, 2010 6:34 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: RE: Fuel flow  

  

  

   

PVC?  

Doc  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of KingCJ6(at)aol.com (KingCJ6(at)aol.com)

 Sent: Wednesday, May 19, 2010 12:33 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: Re: Fuel flow  

  

  

     

All – I think there have been 50+ posts on this subject in the last few days, not counting the 100+ in years past.  Bill Blackwell sells a simple,  very inexpensive kit consisting of some PVC tubing, two manual cockpit mounted toggle shut-off valves and a few T-fittings that takes about 3-4 hours for a novice A&P wana-be to install.  Simply flip the non-venting tank switch off for 5-10 minutes in-flight, and problem solved.  

   

The beauty of our “experimental” class!  

   

Dave    

    

   

      

In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time, wlannon(at)persona.ca (wlannon(at)persona.ca) writes:  

  [quote]    

Jim;  

    

   

    

I agree with you as well - but this engineer type just came FROM the bar.  

    

Yes the same quantities of fuel in both tanks will result in the same pressure being applied to both sides of the flapper valve.   

    

But that same pressure does not translate into the same force being applied on each side of the valve.  

    

   

    

Pressure, whether described in pounds per sq. ft, grams per sq. cm. or whatever produces equal force only when applied to an equal area.  

    

   

    

That is precisely the problem with the CJ flapper valve. The closing force is actually 3 to 4 times the opening force with equal pressure.  

    

In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance of about 50 liters to open.  

    

   

    

Fortunately we rarely ever find a day, or a pilot, that can deliver a non fuel sloshing flight.   

    

   

    

That it is invariably the right side hung up is I believe a result of the vent system design.  The left side vents much more directly than the right.  

    

   

    

Walt  

    

   

  [quote]    

---

gill.g(at)gpimail.com
Guest

Posted: Wed May 19, 2010 3:06 pm Post subject: Fuel flow

Walt,  

   

You are right, if the vents get plugged, metal and/or bag tanks will collapse.  It’s just harder to get the metal tanks back into shape.  

   

Gill  

       

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Walter Lannon

 Sent: Wednesday, May 19, 2010 3:57 PM

 To: yak-list(at)matronics.com

 Subject: Re: Fuel flow  

  

  

     

Gill;  

    

   

    

Over the years I have seen two T6 (actually 1 T6, 1 Harvard) fuel tanks "reworked" by plugged vents.  These are not light wall tanks.  You could touch the tank bottom with your fingers through the filler opening.  

    

   

    

Also recall one of our Bristol Brittanias sched. run Mexico City to Toronto .  Emergency landing in the US (can't remember where) due running out of fuel.  These were all bag tanks,  all were sucked to the top.  Vents all plugged by some Mexican bugs!   

    

   

    

Walt  

  [quote]    

----- Original Message -----   

    

From: Gill Gutierrez (gill.g(at)gpimail.com)   

    

To: yak-list(at)matronics.com (yak-list(at)matronics.com)   

    

Sent: Wednesday, May 19, 2010 2:49 PM  

    

Subject: RE: Fuel flow  

    

   

  

Blitz,  

   

I designed the vent control valves to work with rubber bladders where permanent deformation is not a issue like it is on metal tanks.  The engine fuel pump is a positive displacement device which can cause nearly a full atmosphere of negative pressure which is sufficient to collapse the flat sides on the standard metal tanks, even thick walled ones.  As a minimum I suggest you install a spring check valve with a low break pressure so a to limit the pressure differential between the inside of the tank and the ambient pressure.  

   

Gill  

     

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Byron Fox

 Sent: Wednesday, May 19, 2010 1:10 PM

 To: yak-list(at)matronics.com

 Subject: Re: Fuel flow  

  

   

I have Blackwell's vent valve kit on my metal tanks, and indeed you must be careful.  Our thin-walled CJ tanks will collapse if you fail to cycle the vent valve switch frequently. I was shocked at the oil-canning I heard when pulled a fuel cap off after failing to turn the switch off. Now, I cycle the switch about every ten minutes until balance is achieved. No fuel tank leaks have appeared, and I've had the systems in place for about five years.  ...Blitz

      

On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g(at)gpimail.com (gill.g(at)gpimail.com)> wrote:      

Don’t install vent control valves on metal tanks unless you want smaller tanks!  

   

Gill  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of Roger Kemp M.D.

 Sent: Wednesday, May 19, 2010 6:34 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: RE: Fuel flow  

  

  

   

PVC?  

Doc  

       

From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of KingCJ6(at)aol.com (KingCJ6(at)aol.com)

 Sent: Wednesday, May 19, 2010 12:33 AM

 To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: Re: Fuel flow  

  

  

     

All – I think there have been 50+ posts on this subject in the last few days, not counting the 100+ in years past.  Bill Blackwell sells a simple,  very inexpensive kit consisting of some PVC tubing, two manual cockpit mounted toggle shut-off valves and a few T-fittings that takes about 3-4 hours for a novice A&P wana-be to install.  Simply flip the non-venting tank switch off for 5-10 minutes in-flight, and problem solved.  

   

The beauty of our “experimental” class!  

   

Dave    

    

   

      

In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time, wlannon(at)persona.ca (wlannon(at)persona.ca) writes:  

  [quote]    

Jim;  

    

   

    

I agree with you as well - but this engineer type just came FROM the bar.  

    

Yes the same quantities of fuel in both tanks will result in the same pressure being applied to both sides of the flapper valve.   

    

But that same pressure does not translate into the same force being applied on each side of the valve.  

    

   

    

Pressure, whether described in pounds per sq. ft, grams per sq. cm. or whatever produces equal force only when applied to an equal area.  

    

   

    

That is precisely the problem with the CJ flapper valve. The closing force is actually 3 to 4 times the opening force with equal pressure.  

    

In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect condition vents, etc.) it will take an imbalance of about 50 liters to open.  

    

   

    

Fortunately we rarely ever find a day, or a pilot, that can deliver a non fuel sloshing flight.   

    

   

    

That it is invariably the right side hung up is I believe a result of the vent system design.  The left side vents much more directly than the right.  

    

   

    

Walt  

    

   

  [quote]    

---

barryhancock

Joined: 09 Oct 2008
Posts: 285

Posted: Thu May 20, 2010 5:43 am Post subject: Re: Fuel flow

I have 3 axis electric trim on my plane and don't have fuel imbalance issues.  With the M-14P and 74 gallons of fuel in my bird, it's been well worth it to be able to trim hands off straight and level at any weight and airspeed.



Barry

_________________
Barry Hancock
Worldwide Warbirds, Inc.
www.worldwidewarbirds.com

wise(at)txc.net.au
Guest

Posted: Thu May 20, 2010 2:32 pm Post subject: Fuel Flow

---

wise(at)txc.net.au
Guest

Posted: Thu May 20, 2010 2:32 pm Post subject: Fuel flow

G'Day Barry,



Now that sounds like a go.



Please advise type of auto pilot and where you bought it.



Thanks and cheers,

Chris.

Chris Wise

GT Propellers Australia

__________________________________________________________

Tel.      +61 415 195 095           Fax.   +61 8 8326 7268



Email     chris(at)gtpropellersaustralia.com.au

Website   www.gtpropellersaustralia.com.au



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