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  #16  
Old 03-14-2005, 02:35 PM
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mplafleur mplafleur is offline
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Quote:
Originally Posted by Waiter
Thats my question also, hows the "T" know which tank I'm using, and where to dump the return fuel. Waiter
It doesn't need to know. Just draw from both and return to both. At least that's what I'm going to do. No valve either. Don't have one in the car.

What contamination?
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  #17  
Old 03-14-2005, 02:53 PM
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Quote:
Originally Posted by mplafleur
It doesn't need to know. Just draw from both and return to both. At least that's what I'm going to do. No valve either. Don't have one in the car.
yes you do - if there are two tanks, like in some trucks, ok ok ok a truck is not a car, but then neithor is a plane
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  #18  
Old 03-14-2005, 03:31 PM
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Quote:
It doesn't need to know. Just draw from both and return to both. At least that's what I'm going to do. No valve either. Don't have one in the car.
Thats the problem, I'm not drawing from both! I'm either drawing from the left or the right. My sump tank has the capability to be converted to a single sump system, simply by removing two plugs and install a 5 inch section of tubing. But I'm still beating this around in my head.

The fuel valve gives me a low risk option. I.E. being able to stop fuel flow in case of fire, or some type of failure that presents less risk if the fuel is shut off

Waiter
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  #19  
Old 03-14-2005, 03:42 PM
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Quote:
Originally Posted by Waiter
... I.E. being able to stop fuel flow in case of fire, or some type of failure that presents less risk if the fuel is shut off

Waiter
My buddy, the DAR, accident investigator, did nothing for 25 years except investigate airplane crashes, at one time a 210 a week, and NEVER did a fire. Hates shut off valves, i wish mine was just a left tank and a right tank. Come to think of it - it has a safety that will not allow turning it to the off position, unless it is moved.

fuel starvation = no fuel from current source.
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  #20  
Old 03-14-2005, 03:57 PM
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ok, you HAVE to return fuel injected fuel to the top of the tank, no back pressure allowed.

So i guess a check valve per tank vent line is the solution or at least a requirement
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  #21  
Old 03-14-2005, 05:11 PM
HM Andersen HM Andersen is offline
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Thumbs down Check valves

If you mount a checkvalve I assume it is ment to let air in the tank and stop fuel to get out.It would also stop air from escaping.
How about the air inside the tank expanding during climb, with the dusty altitudes around 25k ft and the climb of the turbocharged engine .
Would the tank start looking like a baloon ?
I am against putting valves of any kind in a safe open safety line.
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  #22  
Old 03-14-2005, 05:43 PM
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Trucks, well they don't have a sump that they can both drain into, do they?

You can't have checkvalves. You need air to go both ways.
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  #23  
Old 03-14-2005, 06:14 PM
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No check valves!

And it doesn't matter where the fuel from the T fitting goes because all three tanks act like a big water level. Pour extra liquid in one side of the level... the other side INSTANTLY rises. Try it Dust! I think it will help you visualize what is going on!

And there is no siphoning. The vents go up to the top on the turtleback and then straight down to open up on the bottom of the fuselage. Upside down (turned turtle) and the vent is higher than the top fuel level of the tanks. Right side up and you need to find a way to get the tanks higher than the turtle back in an uncoordinated turn.

The only way a siphon could happen is if you land on your side... which is about as rare as a quarter landing on its side when you flip it for heads or tails.
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  #24  
Old 03-14-2005, 08:28 PM
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Quote:
Originally Posted by MarbleTurtle
And it doesn't matter where the fuel from the T fitting goes because all three tanks act like a big water level. Pour extra liquid in one side of the level... the other side INSTANTLY rises. Try it Dust! I think it will help you visualize what is going on!
I know, I know, I know - but this is not a static system, pumps are a pumpin and fuel is a movin. you have 40-50 gph comin out of a central tank and 20 40 gph goin to a "t", who says the pull from the two tanks will be even at all times or that the flow will be even at ALL times or that air preasure bubbles won't have bad effects.

air preasure bubble stops flow to one tank, gravity helps things along in the wrong direction. - if logic alone worked globalflyer would not have lost 2500 POUNDS OF FUEL.

45 degree banks, slipin, skidin, climbin, decendin, decending bankin. slow standard rate turns and decents and climbs.

i can see 20 gph comin out of the tank that for some reason is gettin 30 gph returned to it, fluids in motion, along with gasses in motion can and do do strange things, vapor lockin

TEST IT
TEST IT

(if it were one big tank, i would not be talkin and talkin)
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  #25  
Old 03-15-2005, 04:18 PM
Chanler Chanler is offline
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So how do fighter planes do it? You can't tell me they're switching between 7+ fuel tanks in the midst of a dogfight or dumping hundreds of pounds overboard when they roll and loop.
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  #26  
Old 03-15-2005, 04:52 PM
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The most common approach is to put the fuel at the CG.

The L39 has five internal tanks, They all gravity feed to the header tank. Also, two tip tanks, and some are plumbed for 2 or 4 wing tanks. (All of them are at the CG)

The tip and wing tanks are feed into the centerbody tank by pressurizing the tanks to about 3psi. Leave the cap off one tank and all external fuel now becomes unusable baggage. The only fuel control the pilot has is an ON/OFF valve to the engine. Very simple and foolproof system. The Czech Engineers did a fantastic job designing it.

On a KC 135, most fuel is carried in the wings and center body tank. It has a forward and aft body tank that must be maintained manually. Fuel is pumped to the center body, The pilot selects what tank he wants to burn each engine from (4 engines)

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  #27  
Old 03-15-2005, 06:04 PM
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OK Gentlemen, be gentle, go to http://www.cozygirrrl.com/chapter21d.htm
and critque our proposed fuel circuit.
Marc suggested our original plan to just drain both strakes to the sump and return the EFI to the sump.
Feedback please
...Chrissi
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  #28  
Old 03-15-2005, 06:45 PM
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I had originally looked at returning fuel directly to the center sump, but I now have concerns that the fuel heats up too much and needs the larger displacement tanks in the strakes to cool down.

Maybe I need to draw a picture for Dust so he can visualize what I have been describing!
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  #29  
Old 03-15-2005, 07:47 PM
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Quote:
Originally Posted by MarbleTurtle
I had originally looked at returning fuel directly to the center sump, but I now have concerns that the fuel heats up too much and needs the larger displacement tanks in the strakes to cool down.
I discussd that with Al Wick and Tracy Crook and niether thought it would be an issue with the sump, at greater issue is a pump that can pump you sump dry and put all the fuel into the strakes, better have big tubes feeding it back to the sump but also if slightly nose down it's all going to be in your leading edges. Thats what made us stick to feeding back to the sump.
...Chrissi
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  #30  
Old 03-15-2005, 08:37 PM
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Quote:
Originally Posted by Cozy Girrrl
Marc suggested our original plan to just drain both strakes to the sump and return the EFI to the sump.
Feedback please
...Chrissi
am i reading this right - fuel has to be pumped to the other tank to be used? if so - you WILL forget the pump on and pump overboard.

The fuel returns have to be to the top of a tank - the one pumping from, with no back pressure, has been know to stop flow. just looked at the flow further- the return line goes into the sump - back pressure - not good

What is the ball valve for?

how many gallons is the sump

how big are the lines from the tank to the tank, tank to sump return line to sump

I don't think you want to here more from me
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