Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Fuel Return Line

Matronics Email Lists Forum Index -> Europa-List

View previous topic :: View next topic

Author Message

raimo.toivio(at)rwm.fi
Guest

Posted: Thu Apr 26, 2012 10:12 am Post subject: Fuel Return Line

All,



   



  



  We have a fuel selector valve in fuel line. We try to remember  to close it before a possible emergency landing. Some pilots close it always  when not flying and some people close it only during a long storage  time.



   



  



  There is also a fuel return line. That is connected to the  tank bottom (starboard side /reserve side) if built as per a BM (issue 6, page  6-3). 



   



  I have two guestions:



  



  



  1) would it be wise to have a 2nd fuel valve in a fuel return  line also to get an ability to close it or one-way-valve in the case of  emergency?



  



  



  2) why this line is connected to the fuel outlet which locates  in the bottom of the tank? Why not to the upper corner of the (reserve side)  tank?



   



   



  BTW: During this winter I changed all the  rubber parts under the cowling (oh boy there are really many of them!). I  noticed the fuel restrictor (FS02) was totally blocked. It was quite hard to  open it. I assume it has maybe been blocked since almost new because I had  during those days (2007) an issue with a fuel contamination and suffered a scary  engine stoppage because of a totally blocked filter during a flight # 7. It was  good to have a 2nd filter and way to use it by selecting  “RES”.



   



  So, I have noticed no problems to use my engine with return  line which is off-line. There are also many Rotax aplications with no plans for  return lines in use. What is a main reason we should have a fuel return line? To  get more fresh cool fuel or what?



   



   



  Cheers, Raimo



  OH-XRT



  Finland



    [quote][b]

grahamsingleton(at)btinte
Guest

Posted: Thu Apr 26, 2012 10:46 am Post subject: Fuel Return Line

Raimo

the top of the tank is the right place for the return line, as you suggested. That way hot fuel gets mixed with the whole tank content instead of being drawn straight back to the tank.

Graham

        From: Raimo Toivio  <raimo.toivio(at)rwm.fi>

 To: europa-list(at)matronics.com 

 Sent: Thursday, 26 April 2012, 19:11

 Subject: Fuel Return Line

     All,

  We have a fuel selector valve in fuel line. We try to remember  to close it before a possible emergency landing. Some pilots close it always  when not flying and some people close it only during a long storage  time.

  There is also a fuel return line. That is connected to the  tank bottom (starboard side /reserve side) if built as per a BM (issue 6, page  6-3). 

  I have two guestions:

  1) would it be wise to have a 2nd fuel valve in a fuel return  line also to get an ability to close it or one-way-valve in the case of  emergency?

  2) why this line is connected to the fuel outlet which locates  in the bottom of the tank? Why not to the upper corner of the (reserve side)  tank?

  BTW: During this winter I changed all the  rubber parts under the cowling (oh boy there are really many of them!). I  noticed the fuel restrictor (FS02) was totally blocked. It was quite hard to  open it. I assume it has maybe been blocked since almost new because I had  during those days (2007) an issue with a fuel contamination and suffered a scary  engine stoppage because of a totally blocked filter during a flight # 7. It was  good to have a 2nd filter and way to use it by selecting  “RES”.

  So, I have noticed no problems to use my engine with return  line which is off-line. There are also many Rotax aplications with no plans for  return lines in use. What is a main reason we should have a fuel return line? To  get more fresh cool fuel or what?

  Cheers, Raimo

  OH-XRT

  Finland

    [quote]http://www.matro====================

[b]

frans(at)privatepilots.nl
Guest

Posted: Thu Apr 26, 2012 3:26 pm Post subject: Fuel Return Line

On 04/26/2012 08:11 PM, Raimo Toivio wrote:

 	  Quote: 	
		   I have two guestions:

 1) would it be wise to have a 2nd fuel valve in a fuel return line also

 to get an ability to close it or one-way-valve in the case of emergency?


	


I have a one-way valve in the return line for exactly this reason.



 	  Quote: 	
		   2) why this line is connected to the fuel outlet which locates in the

 bottom of the tank? Why not to the upper corner of the (reserve side) tank?


	


This fuel might be quite warm. Imagine when your tank is half empty. The

hot fuel will have to make a free fall before it reaches the pool of

fuel, and it will probably evaporate before it even gets there. No big

deal as the tank will vent it away, but you might find that your fuel

consumption is a tad high. It is better that the return fuel immediately

enters the cold fuel in the tank, so even when some fuel has already

evaporated and produced bubbles, it will condensate back into useful

fuel when it contacts the cold fuel. So the bottom of the tank is the

correct position, and so it is depicted in the build manual anyway.



 	  Quote: 	
		   So, I have noticed no problems to use my engine with return line which

 is off-line. There are also many Rotax aplications with no plans for

 return lines in use. What is a main reason we should have a fuel return

 line? To get more fresh cool fuel or what?


	


I can't say this for the 912, but for the 914 it is to avoid vapor lock,

so yes, to get cold fuel all the time and to avoid keeping it longer

than necessarily in the hot engine compartment.



Frans

klinefelter.kevin(at)gmai
Guest

Posted: Thu Apr 26, 2012 6:58 pm Post subject: Fuel Return Line

If the return fuel enters the top of the tank (under a little pressure) and expands while falling to the level of fuel in the tank, would that not cool and therefor not evaporate?

This also does away with any need for a second fuel valve and it's weight and complexity in an emergency.

Kevin

On Apr 26, 2012, at 5:20 PM, Frans Veldman <frans(at)privatepilots.nl> wrote:

 	  Quote: 	

 On 04/26/2012 08:11 PM, Raimo Toivio wrote:

> I have two guestions:

> 1) would it be wise to have a 2nd fuel valve in a fuel return line also

> to get an ability to close it or one-way-valve in the case of emergency?

 I have a one-way valve in the return line for exactly this reason.

> 2) why this line is connected to the fuel outlet which locates in the

> bottom of the tank? Why not to the upper corner of the (reserve side) tank?

 This fuel might be quite warm. Imagine when your tank is half empty. The

 hot fuel will have to make a free fall before it reaches the pool of

 fuel, and it will probably evaporate before it even gets there. No big

 deal as the tank will vent it away, but you might find that your fuel

 consumption is a tad high. It is better that the return fuel immediately

 enters the cold fuel in the tank, so even when some fuel has already

 evaporated and produced bubbles, it will condensate back into useful

 fuel when it contacts the cold fuel. So the bottom of the tank is the

 correct position, and so it is depicted in the build manual anyway.

> So, I have noticed no problems to use my engine with return line which

> is off-line. There are also many Rotax aplications with no plans for

> return lines in use. What is a main reason we should have a fuel return

> line? To get more fresh cool fuel or what?

 I can't say this for the 912, but for the 914 it is to avoid vapor lock,

 so yes, to get cold fuel all the time and to avoid keeping it longer

 than necessarily in the hot engine compartment.

 Frans

frans(at)privatepilots.nl
Guest

Posted: Fri Apr 27, 2012 1:21 am Post subject: Fuel Return Line

On 04/27/2012 04:53 AM, klinefelter.kevin(at)gmail.com wrote:



 	  Quote: 	
		   If the return fuel enters the top of the tank (under a little pressure) and expands while falling to the level of fuel in the tank,


	


Fuel is not compressible.



However boiling temperature decreases with lower pressure. So if the

fuel is hot, the free fall will promote evaporation of the fuel due to

the sudden drop of pressure.



So, the only way to release hot fuel properly is to release it below the

fuel level.



 	  Quote: 	
		   This also does away with any need for a second fuel valve and it's weight and complexity in an emergency.


	


Well, a one-way-valve is a low weight and low complexity solution. Fuel

can only flow into the tank but never out of it.



Even when you have the fuel return in the top of the tank, I would still

advise a one-way valve. Fuel fumes also burn excepionally well, and of

course it is always possible that you end up inverted.



I recall the story of one Europa-flyer (I believe it was PH-ZZZ ) who

had an emergency and ended up unharmed but inverted. The doors where of

course blocked, and fuel started dripping on the trapped pilot. Luckily

a fire was not started and he was rescued in time.



So for this reason I don't want any port in the tank where fuel can

escape. This includes the sight gauge. I have consequently scrapped the

sight gauge.



Frans

Duncan McFadyean

Joined: 18 Jan 2011
Posts: 222

Posted: Sun Apr 29, 2012 2:15 am Post subject: Fuel Return Line

The  LAA was averse to the idea of discharging the fuel return to the bottom of the  tank on the basis that, if fuel lines firewall-forward were ruptured in an  accident or engine fire, then there would be the possibility of fuel siphoning  from the tank via the fuel return line, This makes sense, although mitigation of  that possibility could be to place the vent line restrictor behind the firewall.  Or arrange for the addition of  a non-return valve at the same  location.

  

 Duncan  McF.

 [quote]   

   --

Remi Guerner

Joined: 14 Dec 2010
Posts: 284

Posted: Sun Apr 29, 2012 3:16 am Post subject: Re: Fuel Return Line

It is always instructive to have look at what is done on type certificated aircraft. Attached pages from the Diampnd Katana show the aircraft fuel system. As you can see: the return line goes to the top of the fuel tank, which is located behind the seat, as in the Europa. There was a one way valve in the return line of the first 90 production aircraft. Then the one way valve was removed on subsequent production aircraft and a Service Bulletin was issued to allow the retrofit of this modification, probably for a good reason.



Another thing is the diameter of the restrictor. The diameter of the restrictor supplied with the kit by Europa is .75 mm while ROTAX specifies .35 mm in their 912 series Installation Manual. I believe .35 is appropriate whenever the return line goes to the top of the tank and the bigger diameter is necessary in the Europa configuration due to somme back pressure caused by the line returning to the bottom of the tank.



Remi Guerner

F-PGKL

DA20-A1_AMM_Rev11 p276,277.pdf

Description:

Download

Filename:

DA20-A1_AMM_Rev11 p276,277.pdf

Filesize:

95.13 KB

Downloaded:

352 Time(s)

budyerly(at)msn.com
Guest

Posted: Sun Apr 29, 2012 7:28 am Post subject: Fuel Return Line

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Interesting discussion on fuel return and battery placement and to review  long ago topics.

 The return line was plumbed to the bottom because it was easy and it  works.  All points are valid that have been made.

 914 Engines require no orifice and must have little restriction or poor  performance will result.

 912/Jabiru normally aspirated engines so equipped with returns must  use the recommended restrictor by that engine manufacturer and hose size.

 Return fuel back to the tank to the top requires more plumbing and is  perfectly fine provided the fuel size and fitting size is maintained.   Slightly more head pressure is required on the return but in my opinion is minor  as the pressure would be similar when the tank is full and a normal return  fitted.  As a technique, plumb a 5/16 fitting into the cobra neck for  the return or use the same fitting as on the long ranger tank for the return  interface.  Then buy  a pump for your long ranger tank and figure out  something else for its plumbing and the tank vent.  Nothing comes easy on a  modification.

  

 Battery location in the trigear with most configurations follows from my  shops construction logs:

 912 with fixed prop any panel put the battery on the passenger  footwell.

 912S same as above.

 912S with Airmaster or equivalent prop, move the battery to the baggage  floor behind the flap tube.

 914 with Airmaster or equivalent prop, move the battery to the baggage  floor behind the flap tube.

 Jabiru 3300 may be put on the footwell, or the baggage bay  floor with fixed prop and VFR panel.

  

 Mono wheel configurations 912, 912S or Jabiru 3300 are same as above but  the CG will tend to be about 1/2 to one inch forward of ideal of 60 inches  empty.

 For the 914/Airmaster with IFR panel, and autopilot, the battery must be  installed near the mass balance support bracket.  If installed in the  baggage bay normally a 5 pound weight attached to the tail spring bolt attach  point or similar is going to be required.  Otherwise mount the battery to  the tail spring.

  

 We use the Odessy PC680 as our standard battery as it is reliable and  reasonably light (15 pounds).  We use the metal battery box supplied as an  option.  This is based on price, availability options such as the metal  battery box premade, and US lack of restrictions.

  

 Attach to the fuselage floor using a wood or metal floor fitted to the  inside the battery box and attach with AN #10 tapered screws of your choice to a  floor mounting plate.  The flange on the bottom of the battery box can be  used to screw through but I find a 1/8 ply with glass faces as a floor to  be more expedient.  Battery hold downs are simple aluminum angles riveted  to the box, then nut plates are installed for the battery hold down  bolts.  Secure a flat bar across the battery to the metal battery box  angles with appropriate #10 hardware to suite.

 The mount to the floor is via a glassed (4 layers) in wood plate, flox  and foam.  Nut plates are installed beneath the wood so as to be aligned  with the wood floor in the battery box.

 If there is a question of CG in the Mono, I make another mount near  the mass balance guide post identical to the one in the baggage bay  floor.  

 Do the weight and balance, and if necessary move the battery if required  the extra few feet.

 I use #4 cable and attach studs to the vertical ply mount for the positive  and negative terminals.  This makes battery attachment a single cable  affair instead of a mass of junkie wires all attached to the battery for  whatever you forgot, external electrical plugs, charging jacks, or  future electrical upgrades requiring direct battery access.  To move  the battery, just make a new pair of wire attach cables to suit the new battery  location.  Affix the cables securely to the floor.

  

 Great advice from you all.

 Regards,

 Bud Yerly

 Tech Support

  

 [quote]   ---

Duncan McFadyean

Joined: 18 Jan 2011
Posts: 222

Posted: Thu May 03, 2012 1:29 pm Post subject: Fuel Return Line

<<..the bigger diameter is necessary in the Europa configuration due to some

back pressure caused by the line returning to the bottom of the tank..>>

Err....does not compute!!

The smaller size in any case would be susceptible to blockage, unless the

filter size matches.



Duncan McF

Do not archive.



--

h&jeuropa

Joined: 07 Nov 2006
Posts: 645

Posted: Thu Nov 01, 2012 11:45 am Post subject: Re: Fuel Return Line

While trying to understand our recent 914 power problems, we talked to Rob Seaton at Rotech.  



He suggested we measure how much pressure is required to return the fuel to the tank (from regulator). Remove return hose from top of regulator, plug one side of banjo fitting and blow into other (don’t ingest fuel!). it should be very easy (max is 1.5 PSI pressure loss with both pumps on: 914 installation manual sec 14.3) 



We found with the fuel tank full the pressure required was more than we could easily blow.  With the tank half empty not much pressure was required.  Our system is per Europa with the return at the bottom of the tank.  Calculations show the pressure of the column of fuel in a full tank (15 inches of fuel) is about .4 psi which is certainly less than 1.5 psi. 



The Europa setup has worked OK for over 400 hours, but perhaps it would be better to return the fuel to the top of the tank.  Opinions?



Jim & Heather

N241BW

grahamsingleton(at)btinte
Guest

Posted: Thu Nov 01, 2012 5:33 pm Post subject: Fuel Return Line

Jim

I have always put the fuel return into the top of the tank, (I used a redesigned tank fitting that incorporated the breather connection (3/8 aluminum)

fuel return and sight gauge return connection. Much less back pressure at the top of the tank and the (maybe hot from the engine driven  pump)

then mixes with the main bulk of the tank contents before going baCK TO THE ENGINE. sorry kaps lok again!

Graham



         From: "h&jeuropa" <butcher43(at)att.net>

 To: europa-list(at)matronics.com 

 Sent: Thursday, 1 November 2012, 19:45

 Subject: Re: Fuel Return Line

  

 

--> Europa-List message posted by: "h&amp;jeuropa" <butcher43(at)att.net (butcher43(at)att.net)>



While trying to understand our recent 914 power problems, we talked to Rob Seaton at Rotech.  



He suggested we measure how much pressure is required to return the fuel to the tank (from regulator). Remove return hose from top of regulator, plug one side of banjo fitting and blow into other (donâ€™t ingest fuel!). it should be very easy (max is 1.5 PSI  pressure loss with both pumps on:  914 installation manual sec 14.3) 



We found with the fuel tank full the pressure required was more than we could easily blow.  With the tank half empty not much pressure was required.  Our system is per Europa with the return at the bottom of the tank.  Calculations show the pressure of the column of fuel in a full tank (15 inches of fuel) is about .4 psi which is certainly less than 1.5 psi. 



The Europa setup has worked OK for over 400 hours, but perhaps it would be better to return the fuel to the top of the tank.  Opinions?



Jim & Heather

N241BW





Read this topic online here:



http://forums.matronicsease Support ref="http://www.matronics.com/contribution">http://www.matronics.com/contbsp;             -Matt Dralle, List  Admin. --> http://www.matronics.com/Navigator?Europa-List</; http://forums.matronics.com

_==============

Europa_breather_system_sketch_copy.jpg

Description:

Filesize:

934.65 KB

Viewed:

5936 Time(s)

klinefelter.kevin(at)gmai
Guest

Posted: Fri Nov 02, 2012 2:30 am Post subject: Fuel Return Line

Jim,

I have my 914 fuel return set up as Graham describes, and no problems. I have never checked the return line pressure.

What problem are you experiencing?

Kevin



On Nov 1, 2012, at 8:32 PM, GRAHAM SINGLETON <grahamsingleton(at)btinternet.com (grahamsingleton(at)btinternet.com)> wrote:

 	  Quote: 	
		  

Jim

I have always put the fuel return into the top of the tank, (I used a redesigned tank fitting that incorporated the breather connection (3/8 aluminum)

fuel return and sight gauge return connection. Much less back pressure at the top of the tank and the (maybe hot from the engine driven  pump)

then mixes with the main bulk of the tank contents before going baCK TO THE ENGINE. sorry kaps lok again!

Graham



         From: "h&jeuropa" <butcher43(at)att.net (butcher43(at)att.net)>

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

 Sent: Thursday, 1 November 2012, 19:45

 Subject: Re: Fuel Return Line

  

 

--> Europa-List message posted by: "h&amp;jeuropa" <butcher43(at)att.net (butcher43(at)att.net)>



While trying to understand our recent 914 power problems, we talked to Rob Seaton at Rotech.  



He suggested we measure how much pressure is required to return the fuel to the tank (from regulator). Remove return hose from top of regulator, plug one side of banjo fitting and blow into other (donâ€™t ingest fuel!). it should be very easy (max is 1.5 PSI  pressure loss with both pumps on:  914 installation manual sec 14.3) 



We found with the fuel tank full the pressure required was more than we could easily blow.  With the tank half empty not much pressure was required.  Our system is per Europa with the return at the bottom of the tank.  Calculations show the pressure of the column of fuel in a full tank (15 inches of fuel) is about .4 psi which is certainly less than 1.5 psi. 



The Europa setup has worked OK for over 400 hours, but perhaps it would be better to return the fuel to the top of the tank.  Opinions?



Jim & Heather

N241BW





Read this topic online here:



http://forums.matronicsease Support ref="http://www.matronics.com/contribution">http://www.matronics.com/contbsp;             -Matt Dralle, List  Admin. --> http://www.matronics.com/Navigator?Europa-Listhttp://forums.matronics.com

_==============



 

 

   





<Europa breather system sketch copy.jpg>

	
 [quote][b]

budyerly(at)msn.com
Guest

Posted: Sun Nov 04, 2012 8:32 am Post subject: Fuel Return Line

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Jim,

 Never had a problem with return pressure as rigged.  The Rotax manual  says it is supposed to be a minimum of back pressure as you indicated.  If  you restrict the return pressure, you actually overpressurize the fuel  system.  Those with gauges that read raw fuel pressure can test this  easily, by just clamping the return line just slightly with the engine off and  not the rapid rise in pressure.

  

 You are very wise to note that the column pressure is only about 1/2 psi.  in the full tank.  I cannot blow more than 1.5 PSI when checking  against my fuel direct reading manual gauge.  Check for kinks and plugged  vents also.

  

 Off until Friday.

 Hope you find out what the matter is.  It must be something simple, as  it is hard to find.

  

 Regards

 Bud Yerly

 [quote]   ---

Display posts from previous:

	Matronics Email Lists Forum Index -> Europa-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum