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KeysFox
Joined: 05 Jan 2009
Posts: 137
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 Posted: Mon Nov 02, 2009 8:12 am Post subject: Fuel flow stop after unport tank |
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Lynn,
Thanks for the suggestion.
Once on the ground, I can see the entire vent line run in my application.
There is no fuel trapped in it in low spots and no low spots to hold fuel.
So for fuel not to flow when I cover the fuel tank pickup with gas Almost
seems to defy laws of physics as I understand them.
I susspect low head pressure and marginal resistance from the inline
filter element that others have alluded to is at play.
The left wing tank feeds faster so I generally put more gas in it prior to
departure, consequently the left tank may not have unported in the
descents. I am tempted to try clear fuel lines on all runs from wing
tanks to header tank to see if fuel is caught in pockets on the feed lines
and to see if fuel is still being drawn from the left wing tank.
A couple of times when I have unported the right tank and stopped fuel
flow thru that inline filter, I have climbed to altitude over my local
airport (5,000' long) to see if I run the header tank dry while I still
have fuel in both wings or whether fuel will start to flow again when the
header tank gets low enough but due to heavy traffic with jet ops mixed in
and being a bit nervous about it, I have not given this an nadequate
trial.
BJ
N154K model IV
Rotax 912
about 600 hours
| Quote: |
Could it be that your vent line has a uphill/downhill portion in it?
That could be one reason that the fuel won't fill the filters. What I
*think* is happening is this: You run the header tank low by using
fuel from it instead of the tanks when you unport the wing tanks in
your descent. Then with the plane at ground attitude, fuel tries to
come down the fuel lines through the filters and into the header
tank. Some does (maybe), but apparently not all unless you "crack the
seal". I believe that when the fuel tries to flow into the header
tank it is trying to overcome air trapped inside the header
tank....trapped because of fuel that is trapped in the uphill/
downhill vent line, and can't be pushed uphill by the downflowing
fuel in the fuel lines. I've had the same thing happen with my
plane.....watching the vent line empty during the descent (and of
course the fuel line is emptying at the same time....and I've been
lucky enough to tip the plane to an attitude that allows for a "mid-
air re-fueling" if you will. But I was very careful to make certain
of there being NO uphill/downhill sections in my vent line.
It would seem to me that this scenario that I just suggested would
require just a certain amount of fuel trying to come down the fuel
lines *versus* a certain amount of fuel trapped in the uphill/
downhill vent line, or a certain amount of volume of lines for this
to happen.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 805.4 hrs
Countdown to 1000 hrs--195 to go
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying (and learning)
On Nov 2, 2009, at 7:38 AM, bjones(at)dmv.com wrote:
>
>
> This extended discussion on fuel flow issues has been just the sort of
> thing I want out of the list sereve.
>
> When I unport my right wing tank during a prolonged descent with
> low fuel
> (model IV with large tanks) I watch fuel drain down out of the vent
> line
> until the glass tube inline filter housing empties and does not refill
> unless I crack the seal on it on the ground, then fuel instantly
> flows.
>
> This has occurred several times even with new filter elements, clean
> finger strainers in the tanks, new fuel lines throughout, and lots of
> attention to straight fuel lines between wing tanks and header tank.
>
> Rather than removing the in line filter elements, I may try placing
> some
> larger openings in the elements. The idea being less resistance but
> ability to monitor for crud.
>
> Thanks to those who have posted comments and to the list serve
> manager for
> making this (and other discussions possible.)
>
> B J
> N154K model IV
>
>>
>> <flyboytr(at)bellsouth.net>
>>
>> Sorry...I missed that... No, I have baffles in the tank. Can't
>> see that
>> area of the tank. ...which I could! 
>>
>> --------
>> Travis Rayner
>> Mobile, AL
>> Skystar Vixen, N-789DF
>> Continental IO-240, Prince P-Tip Prop
>> ADI-II Autopilot
>> AnyWhereMap Navigation with weather
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p 70320#270320
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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_________________
B Jones
N154K
443-480-1023 |
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Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
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| Posted: Mon Nov 02, 2009 10:43 am Post subject: Fuel flow stop after unport tank |
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Hmmmmm.....I was hoping that the vent line was partially obscured,
like mine is, behind the root rib of the right wing. I can't see
every inch of my clear vent line, but I know that it is straight
downhill. Well, that shoots that theory all to hell! : )
I'm curious as to why the left tank feeds faster. From time to time
my right tank will feed faster than the left, but not often. This may
be due to me gawking out the left side of the plane, and banking to
get a better view, which is what got me into a low-fuel/out-of-fuel
predicament a few weeks ago.
I have played (the first time wasn't playing!) with the un-porting of
the tanks on several occasions...to the point of the low-fuel warning
light coming on....and it is quite satisfying to (bank the plane,
and) see the fuel flow into the clear filters, and up the clear vent
line, making the low-fuel light go back off, and letting me know that
I've got about 15 more minutes of flight left. But like you
mentioned, a jet or two getting in the way of your carefully schemed
plan will rattle your cage. : )
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 805.4 hrs
Countdown to 1000 hrs--195 to go
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying (and learning)
On Nov 2, 2009, at 10:27 AM, bjones(at)dmv.com wrote:
| Quote: |
Lynn,
Thanks for the suggestion.
Once on the ground, I can see the entire vent line run in my
application.
There is no fuel trapped in it in low spots and no low spots to
hold fuel.
So for fuel not to flow when I cover the fuel tank pickup with gas
Almost
seems to defy laws of physics as I understand them.
I susspect low head pressure and marginal resistance from the inline
filter element that others have alluded to is at play.
The left wing tank feeds faster so I generally put more gas in it
prior to
departure, consequently the left tank may not have unported in the
descents. I am tempted to try clear fuel lines on all runs from wing
tanks to header tank to see if fuel is caught in pockets on the
feed lines
and to see if fuel is still being drawn from the left wing tank.
A couple of times when I have unported the right tank and stopped fuel
flow thru that inline filter, I have climbed to altitude over my local
airport (5,000' long) to see if I run the header tank dry while I
still
have fuel in both wings or whether fuel will start to flow again
when the
header tank gets low enough but due to heavy traffic with jet ops
mixed in
and being a bit nervous about it, I have not given this an nadequate
trial.
BJ
N154K model IV
Rotax 912
about 600 hours
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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
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n85ae
Joined: 14 Mar 2007
Posts: 403
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| Posted: Mon Nov 02, 2009 2:22 pm Post subject: Re: Fuel flow stop after unport tank |
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Whichever tank has the header vent line run to it, will feed faster. It is
just hydraulic head pressure which causes it, and unless you vent to both
tanks there will always be a difference.
Regards,
Jeff
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KeysFox
Joined: 05 Jan 2009
Posts: 137
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| Posted: Mon Nov 02, 2009 2:55 pm Post subject: Fuel flow stop after unport tank |
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Lynn,
My plane is unusually bare bones so a lot is exposed including the vent line.
I mentioned the slower left side fuel flow just in case it triggered a
thought about fuel restriction on that side, although I suspect the cxause
is pilot technique and rigging.
Its probably time to install a low fuel warning system. Thanks for
mentioning it.
BJ
N154K
I mentioned the right fuel useage in ncase it triggered a thought about
restriction in that line>
<lynnmatt(at)jps.net>
| Quote: |
Hmmmmm.....I was hoping that the vent line was partially obscured,
like mine is, behind the root rib of the right wing. I can't see
every inch of my clear vent line, but I know that it is straight
downhill. Well, that shoots that theory all to hell! : )
I'm curious as to why the left tank feeds faster. From time to time
my right tank will feed faster than the left, but not often. This may
be due to me gawking out the left side of the plane, and banking to
get a better view, which is what got me into a low-fuel/out-of-fuel
predicament a few weeks ago.
I have played (the first time wasn't playing!) with the un-porting of
the tanks on several occasions...to the point of the low-fuel warning
light coming on....and it is quite satisfying to (bank the plane,
and) see the fuel flow into the clear filters, and up the clear vent
line, making the low-fuel light go back off, and letting me know that
I've got about 15 more minutes of flight left. But like you
mentioned, a jet or two getting in the way of your carefully schemed
plan will rattle your cage. : )
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 805.4 hrs
Countdown to 1000 hrs--195 to go
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying (and learning)
On Nov 2, 2009, at 10:27 AM, bjones(at)dmv.com wrote:
>
>
> Lynn,
>
> Thanks for the suggestion.
>
> Once on the ground, I can see the entire vent line run in my
> application.
> There is no fuel trapped in it in low spots and no low spots to
> hold fuel.
> So for fuel not to flow when I cover the fuel tank pickup with gas
> Almost
> seems to defy laws of physics as I understand them.
>
> I susspect low head pressure and marginal resistance from the inline
> filter element that others have alluded to is at play.
>
> The left wing tank feeds faster so I generally put more gas in it
> prior to
> departure, consequently the left tank may not have unported in the
> descents. I am tempted to try clear fuel lines on all runs from wing
> tanks to header tank to see if fuel is caught in pockets on the
> feed lines
> and to see if fuel is still being drawn from the left wing tank.
>
> A couple of times when I have unported the right tank and stopped fuel
> flow thru that inline filter, I have climbed to altitude over my local
> airport (5,000' long) to see if I run the header tank dry while I
> still
> have fuel in both wings or whether fuel will start to flow again
> when the
> header tank gets low enough but due to heavy traffic with jet ops
> mixed in
> and being a bit nervous about it, I have not given this an nadequate
> trial.
>
> BJ
> N154K model IV
> Rotax 912
> about 600 hours
|
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
B Jones
N154K
443-480-1023 |
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KeysFox
Joined: 05 Jan 2009
Posts: 137
|
| Posted: Mon Nov 02, 2009 2:55 pm Post subject: Fuel flow stop after unport tank |
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Oddly my right tank which has the header tank to wing tank vent line draws
fuel slower.
BJ
N154K
| Quote: |
Whichever tank has the header vent line run to it, will feed faster. It is
just hydraulic head pressure which causes it, and unless you vent to both
tanks there will always be a difference.
Regards,
Jeff
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 70634#270634
|
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
B Jones
N154K
443-480-1023 |
|
| Back to top |
|
|
n85ae
Joined: 14 Mar 2007
Posts: 403
|
| Posted: Tue Nov 03, 2009 3:11 pm Post subject: Re: Fuel flow stop after unport tank |
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There was a post on the Zenith list a while back where the guy did extensive
pressure measurement recording of the internal pressure in both tanks in
flight and he found significant pressure difference from side to side, EVEN
with the same vented caps.
So I think it's probably a lot more complicated than it would seem.
I have a a header low warning, and I ignore the differences between
the tanks in flight. Once I get down below 1/4 fuel remaining it starts
flickering more and more.
I've stood on a rudder pedal until the tanks were balanced, but once the
foot comes off it goes right back where it wants to be.
Jeff
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
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