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03-28-2016, 12:27 PM
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Join Date: May 2014
Location: KBVY Massachusetts
Posts: 1,100
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"To measure fuel drop in a tank might be tricky, even at 35 gph, a minute is 1/2 gal, how much is that on a dip stick? Think about that one."
I have been...and so far I don't have many ideas. One thought was to plug the vent for the tanks I'm testing to stop the flow while the pump is on.
Have to think on this one some more.
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Flying RV-8 N880BC
2019 Dues - happily paid.
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03-28-2016, 12:40 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by Saville
"To measure fuel drop in a tank might be tricky, even at 35 gph, a minute is 1/2 gal, how much is that on a dip stick?
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Not much.
You will have to run the pump for a while.
If the airplane is protected from wind and you don't bump it, the fuel in the tank should be steady enough that if a plastic ruler is sitting in the filler opening, you should begin to see the level go down after a few minutes.
This will be easier to see if the tank is nearly full because there is a smaller cross section area at the top surface of the fuel.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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03-28-2016, 12:45 PM
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Join Date: May 2014
Location: KBVY Massachusetts
Posts: 1,100
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"For a recent fuel test we grounded the airframe to the discharged fuel with a bare wire dropped into the fuel container. Ground and un ground it at the clip end, not by dropping in the container."
Can you describe this a little more?
Metal container?
Mostly closed? Open bucket?
was it the wire touching the container that did the grounding?
Thanks
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Flying RV-8 N880BC
2019 Dues - happily paid.
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03-28-2016, 01:02 PM
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Join Date: Jul 2013
Location: US
Posts: 2,251
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Why don't you just open up the housing for the fuel valve and see how it's connected? While you're at it, you can replace it with one that's *correct* for a low-wing plane:
http://www.andair.co.uk/product/fuel-selector-fs20x2/
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03-28-2016, 01:11 PM
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Join Date: Oct 2007
Location: Salmon Arm, BC
Posts: 933
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I don't understand the need to measure the fuel level decrease in the fuel tanks. Just mark a container at 1 gallon and, for each tank, pump fuel in to the mark. Use your watch to determine how long it takes for each tank. You'll now know if each tank pumps at the same flow rate, and by doing a little math you can figure out the gpm the pump is capable of when free flowing.
As a data point, IIRC my Andair pump puts out ~50 gpm free flowing.
__________________
Mark Olson
1987 RV-4 Sold
2003 Super Decathlon - Sold
F1 EVO Rocket, first flight May 31/14
First in line for the Sonex JSX-2T kit
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03-28-2016, 03:26 PM
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Join Date: May 2014
Location: KBVY Massachusetts
Posts: 1,100
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Quote:
Originally Posted by SMO
I don't understand the need to measure the fuel level decrease in the fuel tanks. Just mark a container at 1 gallon and, for each tank, pump fuel in to the mark. Use your watch to determine how long it takes for each tank. You'll now know if each tank pumps at the same flow rate, and by doing a little math you can figure out the gpm the pump is capable of when free flowing.
As a data point, IIRC my Andair pump puts out ~50 gpm free flowing.
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The issue is that while the selector was on BOTH it was drawing only from the Left Tank whereas before it was drawing form both.
I need to know why even if I never use BOTH again.
Now I have no confidence that when I switch it to RIGHT, I'll be drawing fuel from the Right.
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Flying RV-8 N880BC
2019 Dues - happily paid.
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03-28-2016, 04:48 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Quote:
Originally Posted by Saville
"For a recent fuel test we grounded the airframe to the discharged fuel with a bare wire dropped into the fuel container. Ground and un ground it at the clip end, not by dropping in the container."
Can you describe this a little more?
Metal container?
Mostly closed? Open bucket?
was it the wire touching the container that did the grounding?
Thanks
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A little explanation - fuel flowing through an plastic insulated hose can collect a static charge, so if the gasoline flowed into a plastic (HDPE) container it could collect quite a static charge voltage. So - the wire is dropped into the gasoline container- in the liquid. It is grounded back to the airplane. We did this because we used the clear vinyl hose. The aircraft teflon hose is (should be) self grounding.
The container, we used, was a rinsed windshield fluid jug so we could see the fuel level. Large open containers are scary. I would ground any gasoline "can". If you actually have a metal container like an old gas can, that would be grounded to the container, but you can't see the level as easy.
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Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
Last edited by BillL : 03-28-2016 at 04:59 PM.
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03-28-2016, 07:21 PM
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Join Date: Apr 2012
Location: West Fargo, ND
Posts: 1,073
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it seems the common denominator with no matter what you do is to replace that valve with the correct valve. Perhaps do that first and then conduct the fuel flow tests, this way you will understand how your new system operates.
Isnt it possible the valve with L/R/B works fine but if you're flying with the slightest slip or skid the tank draw may favor one side or the other?
I know my 182 draws heavily from the right tank, even when on BOTH, I often switch to the left tank in cruise just to draw it down.
I know I could manipulate the reading on my -9A fuel guages by just the slightest rudder input, effectively moving fuel to either the inboard or outboard end of the tank 
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Derek Hoeschen
EAA Tech Counselor
RV-9A #92103 - N803DK
G3X, Superior XO-320, Dual Pmags, Catto 3B
www.mykitlog.com/dbro172/
1974 Bellanca Super Viking - N16AW - Flying
RV-8 #83565 - N184DK - building
1968 Mooney M20C - N6801N - Sold
1956 C-182 - N744W - Sold
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03-28-2016, 07:25 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by Dbro172
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Isnt it possible the valve with L/R/B works fine but if you're flying with the slightest slip or skid the tank draw may favor one side or the other?
I know my 182 draws heavily from the right tank, even when on BOTH, I often switch to the left tank in cruise just to draw it down.
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I was taught that if the plane is slightly uncoordinated, wing low, etc, the fuel will drain from one tank before the other in a high wing.
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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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03-28-2016, 07:40 PM
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Join Date: Oct 2012
Location: New Ulm, Minnesota
Posts: 283
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One of the fuel caps are not sealed and so there is no air pressure from the fuel vent on that tank... The same thing happened to me just last week...
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Robin Mckee
New Ulm, MN 56073
RV3b N219BB
420 hours and counting
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