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raimo.toivio(at)rwm.fi
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 Posted: Mon Sep 16, 2013 10:50 am Post subject: Fuel return line one-way-valve |
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Hi Ron,
I try to elaborate this a bit:
Think what happen if you will get a leak to this line. Return fuel is then coming out from engine as well as direct from the tank by gravity. Remember – if installed as per manual – a fuel return line is connected to the reserve side bottom of the tank.
Even worse scenario: during succesful forced landing your ac will suffer minor damages to the fire wall etc. Before landing you have closed as per POH your fuel valve but you have no valve in the fuel return line. If it is broken your tank will go empty under you. Maybe you are not able to escape in time. How is then sitting as jammed in the ac, listening fuel splitting out and waiting the possible flames?
Of course it is possible to have also a manual fuel valve in the return line also. Intead of that one-way-valve is automatic and works well if located as close as possible from the tank.
Before installing my one-way-valve I closed the entire fuel return line and I did not noticed any difference (there is a risk for a vapour lock /fire upp engine difficulties when semi warm and reserve side of the tank is then also not refreshed ie. always full).
If I were building now, I would like to instal the fuel return line joint to the top of the tank instead of the bottom of it. That´s bad only if you are inverted...and damaging the ac same time.
How was my elaboration?
Cheers, Raimo Toivio
[img]cid:206AC962AE4241E0BF4E7F05E2E748EC(at)Asus[/img]
Europa XS Mono OH-XRT #417
Updated flight hours /landings: 376 /604
(no damaged props so far)
37500 Lempaala
FINLAND
p +358-3-3753 777
f +358-3-3753 100
www.rwm.fi
From: rparigor(at)suffolk.lib.ny.us (rparigor(at)suffolk.lib.ny.us)
Sent: Friday, September 06, 2013 5:21 AM
To: Europa (europa-list(at)matronics.com)
Subject: Re: Fuel filters
Hi Raimo
You mentioned: | Quote: | Notice:
- Adding one-way-valve to the fuel return line
(idea by Frans Veldman) is a great must (and
mandatory at least for me).
|
Can you elaborate a little on why you might want to put a one-way-valve on the fuel return line? Is this for a 914 fuel system?
Thx.
Ron Parigoris | Quote: |
href="http://www.matronics.com/Navigator?Europa-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Wed Sep 18, 2013 9:08 pm Post subject: Fuel return line one-way-valve |
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Hi Raimo
Thx. for your elaboration.
From what you wrote, you must have a 912S?
The 914 returns a lot of fuel to the tank compared to the 912S. By returning fuel to the top of the tank, I think I remember reading it may not be a great idea to let fuel (especially auto fuel) cascade as I think it may somehow accelerate spoiling the fuel? Did you ever hear of this? I suppose could put a dip tube to the bottom of the tank to prevent this? On the 914 you don't want much in the way of back pressure as it can cause problems with proper functioning of the fuel pressure regulator.
Ron Parigoris
Hi Ron, > > I try to elaborate this a bit: > > Think what happen if you will get a leak to this line. Return fuel is then > coming out from engine as well as direct from the tank by gravity. > Remember – if installed as per manual – a fuel return line is > connected to the reserve side bottom of the tank. > > Even worse scenario: during succesful forced landing your ac will suffer > minor damages to the fire wall etc. Before landing you have closed as per > POH your fuel valve but you have no valve in the fuel return line. If it > is broken your tank will go empty under you. Maybe you are not able to > escape in time. How is then sitting as jammed in the ac, listening fuel > splitting out and waiting the possible flames? > > Of course it is possible to have also a manual fuel valve in the return > line also. Intead of that one-way-valve is automatic and works well if > located as close as possible from the tank. > > Before installing my one-way-valve I closed the entire fuel return line > and I did not noticed any difference (there is a risk for a vapour lock > /fire upp engine difficulties when semi warm and reserve side of the tank > is then also not refreshed ie. always full). > > If I were building now, I would like to instal the fuel return line joint > to the top of the tank instead of the bottom of it. That´s bad only if > you are inverted...and damaging the ac same time. > > How was my elaboration? > > > > Cheers, Raimo Toivio > > > > Europa XS Mono OH-XRT #417 > > Updated flight hours /landings: 376 /604 > > (no damaged props so far) > > 37500 Lempaala > FINLAND > > p +358-3-3753 777 > f +358-3-3753 100 > > www.rwm.fi > > > > > > From: rparigor(at)suffolk.lib.ny.us > Sent: Friday, September 06, 2013 5:21 AM > To: Europa > Subject: Re: Fuel filters > > Hi Raimo > > You mentioned: > > Notice: > > - Adding one-way-valve to the fuel return line > (idea by Frans Veldman) is a great must (and > mandatory at least for me). > Can you elaborate a little on why you might want to put a one-way-valve on > the fuel return line? Is this for a 914 fuel system? > > Thx. > > Ron Parigoris > > > > > [quote][b]
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frans(at)privatepilots.nl
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| Posted: Thu Sep 19, 2013 12:56 am Post subject: Fuel return line one-way-valve |
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On 09/19/2013 07:07 AM, rparigor(at)suffolk.lib.ny.us wrote:
| Quote: | The 914 returns a lot of fuel to the tank compared to the 912S. By
|
I have a 914 AND I have a one-way-valve in the fuel return line. No
problems, although with the engine at idle the fuel pressure tends to
climb to the upper edge of the green zone of my fuel differential
pressure gauge. But maybe that would even be the case without the one
way valve. At anything else than idle the fuel pressure is in about the
middle of the green zone.
| Quote: | I think I remember reading it may
not be a great idea to let fuel (especially auto fuel) cascade as I
think it may somehow accelerate spoiling the fuel? Did you ever hear of
this?
|
I have the same fear. Remember the returning fuel has an increased
temperature (might even be hot) due to its travel through the heated
engine bay, pumps, pressure regulator, etc! That's the reason why we
have a fuel return line after all; by keeping more flow in the system
than the engine requires we prevent vapor lock. Fuel consists of many
components, and they all vaporize at a different rate. It doesn't feel
right to have hot fuel cascading downwards from the top of the tank,
splattering around, having its components vaporize partly, then
condensing against the cold tank walls, and dripping into the fuel pool
again. Also the surrounding oxigen together with the high temperature of
the return fuel vapor might oxidize some of the fuel components at an
increased rate. We all know that fresh fuel is different than "old" fuel
and elevated temperatures and lots of contact with oxigen might play a
role in this "aging" process. My feeling is that it is healthier to
arrest the returning fuel immediately on arrival in a pool of cold fuel
without letting it get into contact with air and oxigen first.
For what it is worth, I try to use Mogas as much as possible, even when
flying in the French Alps (around FL100), have done this dozens of times
(Ilona's parents live there so we tend to visit them often with our
little aircraft) and I never had any problems with the fuel. Maybe it
just helps to keep the fuel temps down and not inviting too much
interaction with oxigen molecules.
| Quote: | I suppose could put a dip tube to the bottom of the tank to
prevent this?
|
So then what would be the point to route the fuel to the top of the tank
first while there is a shorter route to the same spot?
| Quote: | On the 914 you don't want much in the way of back pressure
as it can cause problems with proper functioning of the fuel pressure
regulator.
|
One more reason to feed the fuel back at the underside of the tank.
Shorter hose, and less elevation of the fuel required to deliver it
where it ends up anyway.
Of course, a one way valve gives some resistance, but apparently it is
not too much. A valve can fail, but the most dangerous fail is when it
remains shut. If this happens, you will discover it during engine start
up. With the low fuel demand during that stage there is much return
flow, and if the valve stays shut it will quickly flood the engine
(apart from your fuel pressure needle pegging against the stop) Once
open, it seems utterly unlikely that the valve will spontaneously close
against the fuel pressure during flight. Once open, it will stay open as
long as fuel pressure is pushing against it and holding it there.
It gives some piece of mind that there is not an unclosable fuel hose
going to the engine bay. If the hose breaks, the fuel flow will stop by
itself.
Frans
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raimo.toivio(at)rwm.fi
Guest
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| Posted: Thu Sep 19, 2013 8:43 am Post subject: Fuel return line one-way-valve |
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Hi Frans,
you are absolutely as right
******as usually*********
(ask Ilona about these stars 
but still I am brave enough to consider that fuel
will not be significantly "aged" when dropping or
in fact spraying it from top of the tank. That
spray will contact air just a split second during
the drop distance from 0 to max say 40 cm. Notice
you will use this fuel in hours or at least mix it
soon to the fresh fuel when refueling again.
Anyway - if you have a manual tap or an automatic
one-way-valve - there is no reason to instal it (a
return line) to the top of the tank.
BTW have you any idea what´s a typical fuel
temperature rise from the tank outlet to the tank
inlet? My guess is it is just couple of degrees
only or even zero - flow rate is so high.
Anyway - thanks you helped me/us to understand
that return line potential danger IN TIME (and to
do something to it). Among us is living at least
one person who would have been very happy about
that extra valve during his awful incident (IMHO).
Funny, we (me & my wife) feel comfortable over the
shoreless sea or in the most thickiest cloud but
so far we cannot even think about flying VFR over
hostile & high terrain like Ilona´s parent´s Alps.
I understand it´s just our lack of information.
And also lack of turbo, oxygen and BRS...
Raimo
HA-MDO
http://www.flyfinland.fi/view/10153/
OH-XRT
http://www.flyfinland.fi/view/9490/
-----Alkuperäinen viesti-----
From: Frans Veldman
Sent: Thursday, September 19, 2013 11:55 AM
To: europa-list(at)matronics.com
Subject: Re: Fuel return line
one-way-valve
<frans(at)privatepilots.nl>
On 09/19/2013 07:07 AM, rparigor(at)suffolk.lib.ny.us
wrote:
| Quote: | The 914 returns a lot of fuel to the tank
compared to the 912S. By
|
I have a 914 AND I have a one-way-valve in the
fuel return line. No
problems, although with the engine at idle the
fuel pressure tends to
climb to the upper edge of the green zone of my
fuel differential
pressure gauge. But maybe that would even be the
case without the one
way valve. At anything else than idle the fuel
pressure is in about the
middle of the green zone.
| Quote: | I think I remember reading it may
not be a great idea to let fuel (especially auto
fuel) cascade as I
think it may somehow accelerate spoiling the
fuel? Did you ever hear of
this?
|
I have the same fear. Remember the returning fuel
has an increased
temperature (might even be hot) due to its travel
through the heated
engine bay, pumps, pressure regulator, etc! That's
the reason why we
have a fuel return line after all; by keeping more
flow in the system
than the engine requires we prevent vapor lock.
Fuel consists of many
components, and they all vaporize at a different
rate. It doesn't feel
right to have hot fuel cascading downwards from
the top of the tank,
splattering around, having its components vaporize
partly, then
condensing against the cold tank walls, and
dripping into the fuel pool
again. Also the surrounding oxigen together with
the high temperature of
the return fuel vapor might oxidize some of the
fuel components at an
increased rate. We all know that fresh fuel is
different than "old" fuel
and elevated temperatures and lots of contact with
oxigen might play a
role in this "aging" process. My feeling is that
it is healthier to
arrest the returning fuel immediately on arrival
in a pool of cold fuel
without letting it get into contact with air and
oxigen first.
For what it is worth, I try to use Mogas as much
as possible, even when
flying in the French Alps (around FL100), have
done this dozens of times
(Ilona's parents live there so we tend to visit
them often with our
little aircraft) and I never had any problems with
the fuel. Maybe it
just helps to keep the fuel temps down and not
inviting too much
interaction with oxigen molecules.
| Quote: | I suppose could put a dip tube to the bottom of
the tank to
prevent this?
|
So then what would be the point to route the fuel
to the top of the tank
first while there is a shorter route to the same
spot?
| Quote: | On the 914 you don't want much in the way of
back pressure
as it can cause problems with proper functioning
of the fuel pressure
regulator.
|
One more reason to feed the fuel back at the
underside of the tank.
Shorter hose, and less elevation of the fuel
required to deliver it
where it ends up anyway.
Of course, a one way valve gives some resistance,
but apparently it is
not too much. A valve can fail, but the most
dangerous fail is when it
remains shut. If this happens, you will discover
it during engine start
up. With the low fuel demand during that stage
there is much return
flow, and if the valve stays shut it will quickly
flood the engine
(apart from your fuel pressure needle pegging
against the stop) Once
open, it seems utterly unlikely that the valve
will spontaneously close
against the fuel pressure during flight. Once
open, it will stay open as
long as fuel pressure is pushing against it and
holding it there.
It gives some piece of mind that there is not an
unclosable fuel hose
going to the engine bay. If the hose breaks, the
fuel flow will stop by
itself.
Frans
browse
Un/Subscription,
FAQ,
http://www.matronics.com/Navigator?Europa-List
Forums!
List Admin.
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frans(at)privatepilots.nl
Guest
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| Posted: Thu Sep 19, 2013 10:01 am Post subject: Fuel return line one-way-valve |
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On 09/19/2013 06:43 PM, Raimo Toivio wrote:
| Quote: | you are absolutely as right
******as usually*********
(ask Ilona about these stars
|
I will do!
| Quote: | but still I am brave enough to consider that fuel will not be
significantly "aged" when dropping or in fact spraying it from top of
the tank. That spray will contact air just a split second during the
drop distance from 0 to max say 40 cm.
|
Well, ever noticed in the shower how much the water cools down in the
same distance? It is pure interaction with the surrounding air...
| Quote: | Notice you will use this fuel in
hours
|
I often park my airplane with the tank about half filled.
| Quote: | BTW have you any idea what´s a typical fuel temperature rise from the
tank outlet to the tank inlet? My guess is it is just couple of degrees
only or even zero - flow rate is so high.
|
I don't know. But even it it were at room temperature I wouldn't think
that repeatedly cascading it down would do any good to its composition.
| Quote: | Anyway - thanks you helped me/us to understand that return line
potential danger IN TIME (and to do something to it). Among us is living
at least one person who would have been very happy about that extra
valve during his awful incident (IMHO).
|
It was at that moment of the incident I was installing the fuel hoses
and indeed considered that I didn't want to go that same route.
| Quote: | Funny, we (me & my wife) feel comfortable over the shoreless sea or in
the most thickiest cloud but so far we cannot even think about flying
VFR over hostile & high terrain like Ilona´s parent´s Alps.
|
This gets interesting. The places we feel incomfortable is when flying
in Scandinavia. With an almost blank GPS screen, and hours of flying
above just rocks, ice and maybe some trees (if you are not too far
north) beneath you. I've never observed an almost blank GPS screen,
except in Scandinavia, and I've never seen such strectched areas where
you can't find a landing area of 200 meters without hitting at least a
car sized rock. At our return flight from the North cape, at about 2am
in daylight conditions (for you not amazing but for the majority of
pilots it is) we were flying above terrain that looked very hostile and
didn't change for two hours. In these two hours we didn't see any road,
house, or whatever human structure. We felt very alone and wondered if
in case we would have to carry out a forced landing (between the endless
rocks) whether anybody would ever find our remains. Don't get me wrong,
I found it absolutely beautifull, very serene, the midnight sun, the
small amount of haze, the reddish sky, the blueish light surrounding you
and the absolute silence (radio contact got lost very soon). Even while
the engine was dutyfully whirring you could sense the silence around
you. And then to see a moon rise just in front of you. Priceless.
Then the Alps. Chances are big that if you look down at any spot you
will find an airfield beneath you. The mountains look agressive, but so
much cultivated that there is always some pasture, road, or anything
within gliding distance. There are plenty of shallow slopes. I guess it
is difficult to land uphill but of course it means that once in the
landing flare you will very quickly come to a halt. If in doubt, just
land uphill and gently fall down when your speed reaches zero just above
the tree tops.
I haven't seen much of these escape possibilities in Scandinavia. The
terrain, although filled with enormous rocks, is most of the time very
shallow. And even if you were to survive such a landing, you will freeze
to death, eaten by wolves or bears (no beers unfortunately!) before
someone finds you. If something is left at all.
Anyway, you are invited. If you want to go to the Alps, just let us
know. We can guide you in and probably offer some accommodation.
Frans
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Thu Sep 19, 2013 1:29 pm Post subject: Fuel return line one-way-valve |
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Hi Frans
Thx. for the reply.
If there is a trauma to the return line, we want the break or leak to occur upstream of the 1 way return valve (closder to the fuel pressure regulator).
Did you do anything to stack the cards in favor when the engine gets ripped off that the 1 way return valve stays connected to the fuel tank?
Ron Parigoris
[quote][b]
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frans(at)privatepilots.nl
Guest
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| Posted: Thu Sep 19, 2013 1:59 pm Post subject: Fuel return line one-way-valve |
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On 09/19/2013 07:00 PM, rparigor(at)suffolk.lib.ny.us wrote:
| Quote: | Hi Frans
Thx. for the reply.
If there is a trauma to the return line, we want the break or leak to
occur upstream of the 1 way return valve (closder to the fuel pressure
regulator).
Did you do anything to stack the cards in favor when the engine gets
ripped off that the 1 way return valve stays connected to the fuel tank?
|
Good to mention this!
I have the one way valve very close to the fuel outlet. The rest of the
hose is securely tied to the aircraft at numerous places before it
enters the cowling. I'm quite confident that if the engine gets ripped
off the one way valve stays connected to the fuel tank.
Frans
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