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Another fuel tube question?


Buckaroo

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Yeah, I wish the lines were a true T at the valve, so that with the fuel valve closed fuel would not transfer at all.  Since my right wingtip is lower then the left, if I'm not careful how I park, especially on grass, I can have fuel transfer while parked.  Twice with full tanks I have come back to an airplane with a dripping wet wing where fuel has sloshed out of the right vent.

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Yeah, I wish the lines were a true T at the valve, so that with the fuel valve closed fuel would not transfer at all.  Since my right wingtip is lower then the left, if I'm not careful how I park, especially on grass, I can have fuel transfer while parked.  Twice with full tanks I have come back to an airplane with a dripping wet wing where fuel has sloshed out of the right vent.

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13 hours ago, Ed Cesnalis said:

Thanks,

Transfer in flight is frustratingly slow. Buckaroo can adjust the rate of slow transfer by moving the ball farther from the 'center'

True, but be careful, it's easy to overdo it.  I wanted to get a fast transfer once and set trim about two balls out, and ten minutes later I had to swing the trim the other way because I had transferred too much.  :rolleyes:

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3 minutes ago, FlyingMonkey said:

True, but be careful, it's easy to overdo it.  I wanted to get a fast transfer once and set trim about two balls out, and ten minutes later I had to swing the trim the other way because I had transferred too much.  :rolleyes:

I have come home with one tank empty at the sight tube at least, so many times now that I am no longer concerned about having fuel in one wing only, I'm just fine with that.

In fact I have not put any fuel in my right tank in the last year, I never need 34 gallons, topping off 1 wing always suits my needs but my initial imbalance is often 17 left and 3 right.  Tends to equalize pretty fast in flight without effort, by the time I'm looking its as though I started even.

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Im out at my plane and re measured my return fuel from yesterday. I have 13 gallons in the right (low wing) and 7 gallons in the left. So yesterday flying back home I'm indicating full right and bubbling on emty left. That's 17 gallons all in the right 17 gallon tank with I guess sloshing in the left. Now this is after I work hard on low canted left wing slightly slipping to avoid the very thing that happened!?

Anyway im leveling the bird and checking the ball.

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12 hours ago, Buckaroo said:

My CTSW is a left wing tank hog! She sits low right in the hanger and then we fly sucking lots of fuel from the left tank. Then today over hostile Montana 9000 foot mountains she continues to suck fuel from the treasured left tank and finally runs it dry after a return flight after 2 hours of mostly climbing out to clear huge mountain ranges with some down drafts. 

 

Get a piece of 1"-1.5" thick wood and park with the right wheel up on the wood.  You can even throw it in the airplane and park like that when away from home.  That will slow, reduce, or prevent fuel transfer when sitting on the ground.

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1 hour ago, Ed Cesnalis said:

I have come home with one tank empty at the sight tube at least, so many times now that I am no longer concerned about having fuel in one wing only, I'm just fine with that.

In fact I have not put any fuel in my right tank in the last year, I never need 34 gallons, topping off 1 wing always suits my needs but my initial imbalance is often 17 left and 3 right.  Tends to equalize pretty fast in flight without effort, by the time I'm looking its as though I started even.

I agree there is no problem with a tank imbalance, as long as you have enough in the full tank to never unport in any flight condition.  I still think keeping balanced tanks is a little safer practice.  Unless both tanks are *very* low, then you might be better off with all the fuel in one tank.

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13 minutes ago, Buckaroo said:

When I set her in the field I slung 8 gallons out long enough to unport the right tank after seeing the left empty. This still concerns me, ok freaks me out!?

 

 

Did you realize a power loss or was the landing still precautionary? 

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I understand the uneasy feeling one gets when the sight tubes show zero fuel.  What makes matters worse, it becomes very hard to maintain the proper attitude so the sight tube on the side with fuel always shows fuel. Especially when flying in gusty conditions.  A test I have done tells me that I would be able to get away with unporting fuel for a few minutes when running at low engine speed.  At my last wing removal, I left a few gallons of fuel in the each wing and pinched off the fuel line running into the wing root.  This allowed fuel to remain in the pillar and down into the gascolator and in the fuel lines. I then drained the remaining fuel from the system. It took over 5 minutes for this fuel to drain.  Granted, some of this fuel came from the gascolator and the lines below the carbs.  I would guess that there is probably at least 2 minutes of fuel available to the carbs when fuel is no longer viewed.  There is a good amount of fuel remaining in the "A" (front) pillar.  This  contains a square tube which is about 3/4" square and runs the length of the pillar.  Even after the fuel is no longer visable at the sight tube, there is quite a lot of fuel in this square tube and in the fuel pump/fuel lines running down to the carbs. Buckaroo, inquisitive minds want to know.  What has your hangar test showed you?  Once you leveled your CT, were the drain rates equal?  Were you able to calibrate your ball?  Please remember that your mushroom is easy to move and this requires you to check your calibration occasionally.

 

 

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You guys are overthinking this. This has been an item since we first had a forum. FD addressed it in a letter many years ago.  It is a flat tank design item not a problem with your plane. Other than playing with your instrument leveling there is nothing you can do. If you spend all the time trying to make everything perfectly level with the instrument panel it will all be for nought when people press on it or shifty it around. Then that was on the ground and pilot orientation and flight characteristics will undo whatever you did on the ground. You might as well save tons of frustrating hours that won't change much. If yours is way out on the panel you may help it some, but not so it's perfect.

This is just an issue about knowing your plane.

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ct9000, good point.  I've used a straight board across the fuselage so it contacts each wing and put a level on this.  I found that my floor is level so I just measure distance from floor to wingtips now.

Tom, yes, no need to drain the tanks.

Roger.  I'm not thinking about making things perfect, just about the big picture.  If Buckaroo is ending up with 3 gallons in one tank and 17 gallons in the other, he's got a "gross" problem and a situation that makes for very uncomfortable flying.  For this, if it were me, I would want to understand how things could be this far off.  Speaking for myself, I must understand inaccuracies and variables in order that I'll be able to get to know my plane. You have to remember that you have been at this for a long time and for most of the problems we discuss here, you already been to the rodeo and it's old hat for you.  For those of us that are new at this, we need to work thru these issues and understand them to be comfortable when we fly.  I do agree with you regarding pilot orientation, etc.  For a while, I was finding that my fuel tanks had 3 or 4 gallons difference after some fairly long flights even though I was flying coordinated according to my ball .  I guess it's my nature to want to understand why.  First I checked fuel flow thru both tanks.  When I found this OK, I next looked into my ball calibration.  It was apparent that the ball was quite a bit off.  But, as you point out, this system is only good until the next time someone pushes or pulls on the mushroom.  Now, I have my ADS-B with a sensitive AHRS system. My electronic ball is calibrated to my CT and is unaffected by mushroom movement.  My fuel usage is now pretty even between tanks.  You'll note I didn't say it is perfect but I'm still working on it! :rolleyes:

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13 hours ago, Roger Lee said:

You guys are overthinking this. This has been an item since we first had a forum. FD addressed it in a letter many years ago.  It is a flat tank design item not a problem with your plane. Other than playing with your instrument leveling there is nothing you can do. If you spend all the time trying to make everything perfectly level with the instrument panel it will all be for nought when people press on it or shifty it around. Then that was on the ground and pilot orientation and flight characteristics will undo whatever you did on the ground. You might as well save tons of frustrating hours that won't change much. If yours is way out on the panel you may help it some, but not so it's perfect.

This is just an issue about knowing your plane.

I don't share Roger's stance, because I know of a few cases where there was a problem. Not necessarily with the calibration of the ball, but with the fuel system itself. For the CTSW the fuel flow test on the ground should show if there is an issue. For the CTLS the fuel flow test on the ground might not show a problem, but the airplane still have flow issues in the air.

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33 minutes ago, Tom Baker said:

I don't share Roger's stance, because I know of a few cases where there was a problem. Not necessarily with the calibration of the ball, but with the fuel system itself. For the CTSW the fuel flow test on the ground should show if there is an issue. For the CTLS the fuel flow test on the ground might not show a problem, but the airplane still have flow issues in the air.

Buckaroo found himself on the ground with too much gas on board for it to be his fault.

Landing with a 17 / 3 balance in a CTSW means you are losing fuel from your vent too.

You are right Tom, this needs to be confirmed.

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I called airian at flight Design. I then called the prior owner and ran the situation by them. 

First prior owner: "we could never figure out why it fueled from the left tank so aggressively". He said they used to prop the right side up in the hanger. He suggested I call FD. 

Second call FD: Pinch off full lines and conduct a flow test. He said he's heard of a kinked line in the wing root but never had one himself. 

I'll try this and advise! Both advised they would never fly with an uneven usage this extreme. 

 

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Do you have fuel streaks from your filler caps to the backs of the wings?  You could have some fuel leaking from the epoxy seals which has broken down over time.

You should definitely do a drain test.  Level the wings using boards to shim under the right wheel or a ladder under the right wing with towels padding against the wing to get the correct height.  Fill both tanks up with about five gallons, enough that they fill about half the sight tubes.  If on filling the tubes don't look roughly even, investigate why.  If they look even, drain fuel from the gascolator into a container, while watching the sight tubes (don't get in the airplane to do this, it might "unlevel" it).  If one empties completely, and there is still significant gas in the other tube, you have some kind of fuel flow problem on the still full side.

Also, you can check the ball once the airplane is leveled this way to see if it's way out.  You can do a quick eyeball coordination check in flight...in calm winds, when your ball shows centered, look at your wingtips.  If they are each the same distance from the horizon, your instrument is close to correct.

BTW, it's all too easy to fly these airplanes with one wing down, I end up doing it all the time and have to correct myself when I catch it.  But with three axis trim you should be able to get it flying pretty straight in calm winds.

 

 

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Great advise FlyingMonkey! Yesterday I leveled her by shimming the right tire which took her way high so using my side by side under the high wing I used a strap design to pull her down to perfect level. The ball was 1/2 out left which suspected as before out of butt feel I'd always fly in that position when level. Now it's straight and correct.

Now she's back in a 4 inch right wing position with the shim still under the right tire. Both tubes are indicating 10.5 gallons with the right high wing dipping 3.5 gallons and the low left wing at 14 or so. ? I suspect the high right wing has clumped all the full up to the wing root. At this severe 4 inch high difference wouldn't all the right wing fuel go to the left wing? Unless the right tube has the only fuel showing 10.5 but it just in the tube?

Tomorrow I'll work on first level again and checking site tubes for comparison and then a flow test. Gotta find a fuel pinch tool. Andy your idea of emptying etc sounds good as well. Gotta get rid of some fuel first.

 Thanks everyone we'll get to the bottom of this soon!????

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