Another fuel tube question?

[Buckaroo]

Today the wife and I flew over the mountains to Anaconda Mt for a fly in and car show. This route his heavy mountain and forest. We left with about 28 gallons of fuel for a round trip two hour flight requiring a climb from 4K to 11k to clear the mountains. On the way back I could see my left fuel tube showing about 1/2 so I pushed the ball towards the left wing flew straight which lowered the left wing. After 20 minutes or so I cleaned up the rudder and the left tube was bouncing in and out of empty. The right fuel showed full. Continuing to descend with wife scared the tube was still bubbling near empty. Seeing this action I was afraid of any hard banking as I approached the field. After landing the tube was almost full again. I checked the tanks and the left 9 and the right showed the same. 

Why is this happening?

 

[Ed Cesnalis]

You have to both be empty on one side and unported on the other so you were fine with good reserves.  Its slipping or skidding to fear not banking.

You expected the fuel to follow the ball but it didn't?  The ball was probably lying, you were probably on the right track but the correction wasn't large enough.  Your ball is likely off.  I calibrated my ball in flight recently looking at only 1 tube that had a mid-tube gas level.  I was trimmed to fly hands off, and moved my rudder trim left and right two times.  Too far right the level goes up, too far left the level goes down (or visa versa).  This allows you to find the middle, the ball position that indicates coordination.

Coming home with one sight tube empty and the other with 9 is no big deal at all.  One empty and the other at 3 you are getting both below legal reserves and at risk for porting remaining.

If your coming home with 9 gallons or more your not getting into a range of concern.  You can test for yourself, even with full rudder deflection could you make that much gas (more than 50%) slosh and remain outboard where it can't be seen?

[Buckaroo]

Im starting to wonder if my right wing fuel system is restricted or blocked. When fueling my right tank is always at 14 gallons and my left always needs the gas. Of course my airplane sits 31/2 inches lower on the right. 

In flight today I could visually see me left wing low in a slipping configuration then cleaning up the left tube instead of indicating fuel showed the opposite burbling in and out of empty. My right tube was full and at that time my imagination went wild about a restricted right fuel port. 

[Ed Cesnalis]

2 minutes ago, Buckaroo said:

In flight today I could visually see me left wing low in a slipping configuration then cleaning up the left tube instead of indicating fuel showed the opposite burbling in and out of empty. My right tube was full and at that time my imagination went wild about a restricted right fuel port. 

This is what you might expect if the ball is not calibrated and you rely on it.  You can rely on bank if you hold a heading.

Chances are the flow rate from either is more than adequate.  After you get empty on the left it runs fine from the right?

If flow rate is your issue might as well rule out ball calibration 1st, its very easy.  Sitting uneven messes with both dipping and sight tube viewing.  Can  you fill both sides past the 17 mark?

The critical skill comes later in flight after your left tank is now very low like less than 3.  You have to maintain a slip that keeps that remaining fuel visible to you and the motor so you know when its time to call it quits and land and also so you don't run out with fuel on board.

 

[Buckaroo]

One would think that after I've lowered the left wing visually keeping a heading after 20 minutes the left site tube would look happy but instead it was bouncing off zero. It's got me baffled because I was in coordinated flight in this condition. 

Ive noticed the slush in the tube in turbulence can go from full to empty and back and forth. 

I wish up here there was a way to check fuel flow from the right wing!?

 

[Roger Lee]

Even though the ball is centered you may still be out a tad due to instrument alignment.

[Buckaroo]

Is there a way I can quickly force fuel transfer from my right wing to the left? Say in an exaggerated level left wing real low condition that after say 10 minutes I will see a positive result in the left site tube. 

Todays demonstation to the wife of fuel transfer to the left wing had us comeing in on final with a darn near empty left fuel tube. This is after flying left wing low for 20 minutes. I'm confused at this point!

 

[Tom Baker]

To help set your mind at ease check the fuel flow from the right tank. Remove the top cowling and use a clamp like this http://www.tooltopia.com/kd-tools-3791.aspx?utm_source=google&utm_medium=cpc&utm_campaign=paid_search_google_pla&adpos=1o3&scid=scplpKD+3791&sc_intid=KD+3791&gclid=EAIaIQobChMInIi-lfz11QIVDoNpCh0uewmXEAQYAyABEgKM2fD_BwE to pinch off the left fuel line that comes out of the front door post. Open the fuel valve and gascolator drain valve and check the fuel flow. It should flow at a rate of more than 10 GPH, and more than likely it will be closer to 20 GPH. For giggles you can check the left too.

Find your self a piece of wood or something to roll the tire on the side with the low wing to level it up when you park the airplane.

[Ed Cesnalis]

In the hangar transfer happens via the crossover tube which is very small diameter and has a slow flow rate.

In flight with the fuel valve open I bet transfer could happen quicker but the only tools you have to work with are slip and skid (bank while holding a course works) so the more severe, the farther the ball is out of the cage the greater the force acting on the fuel and resulting in transfer.

[Buckaroo]

Today my wife asked why are you flying rolled so left? I told her I was transferring fuel to the lower line and pointed out the left tube at 1/2 or so and the right full. On the way home I'm doing the same thing and I tell her to check out the left tube now in coordinated flight. By now we're in turbulence and the fuel is sloshing from 1/4 to 3/4 depending on the bounce. That parts ok but slightly descending out of 10 to 5k we're both glued to a tube bubbling from nothing to 1/2 of a inch. Now the right tube is full and I reassure her we're ok as we have fuel visible. By now she's getting figity and so am I fearing a possible blockage in the right system. I ask myself why is this aircraft so hell bent on eating fuel out of the left side? ?

[Buckaroo]

19 minutes ago, Tom Baker said:

To help set your mind at ease check the fuel flow from the right tank. Remove the top cowling and use a clamp like this http://www.tooltopia.com/kd-tools-3791.aspx?utm_source=google&utm_medium=cpc&utm_campaign=paid_search_google_pla&adpos=1o3&scid=scplpKD+3791&sc_intid=KD+3791&gclid=EAIaIQobChMInIi-lfz11QIVDoNpCh0uewmXEAQYAyABEgKM2fD_BwE to pinch off the left fuel line that comes out of the front door post. Open the fuel valve and gascolator drain valve and check the fuel flow. It should flow at a rate of more than 10 GPH, and more than likely it will be closer to 20 GPH. For giggles you can check the left too.

Find your self a piece of wood or something to roll the tire on the side with the low wing to level it up when you park the airplane.

Thanks Tom I will test this out!??

[Tom Baker]

18 minutes ago, Ed Cesnalis said:

In the hangar transfer happens via the crossover tube which is very small diameter and has a slow flow rate.

In flight with the fuel valve open I bet transfer could happen quicker but the only tools you have to work with are slip and skid (bank while holding a course works) so the more severe, the farther the ball is out of the cage the greater the force acting on the fuel and resulting in transfer.

The fuel valve would have ne effect on the rate of transfer.

[Ed Cesnalis]

1 hour ago, Tom Baker said:

The fuel valve would have ne effect on the rate of transfer.

Why not?

Is there a diagram?

[Roger Lee]

"

  1 hour ago, Tom Baker said:

The fuel valve would have ne effect on the rate of transfer.

Why not?

Is there a diagram?

 

Because the fuel valve only separates the fuel  tanks from the engine. The fuel valve is downstream of the hoses that pass fuel from wing to wing. Wing to wing is an open circuit. That's why when the fuel valve is off and you park on a wing down slope fuel flows to the low wing and will eventually overflow the down slope wing. The hose size from wing to wing is 5/16". Fuel flows slow between wings during a flight. You can transfer, but not fast, fuel by flying 1 ball out to the low fuel wing. To keep it fairly equal during a flight fly 1/2 ball out to the fastest draining wing.

This isn't unique to FD. Other aircraft including GA have the same issue. It is because of the flat wing tank design and an instrument that may not be perfect.

[Tom Baker]

The fuel comes down the door post and goes to a "Y" fitting. The passage from wing to wing is through thid "Y". The third leg of the "Y" goes through the firewall, and then to the valve.

[Ed Cesnalis]

33 minutes ago, Roger Lee said:

"

  1 hour ago, Tom Baker said:

The fuel valve would have ne effect on the rate of transfer.

Why not?

Is there a diagram?

 

Because the fuel valve only separates the fuel  tanks from the engine. The fuel valve is downstream of the hoses that pass fuel from wing to wing. Wing to wing is an open circuit. That's why when the fuel valve is off and you park on a wing down slope fuel flows to the low wing and will eventually overflow the down slope wing. The hose size from wing to wing is 5/16". Fuel flows slow between wings during a flight. You can transfer, but not fast, fuel by flying 1 ball out to the low fuel wing. To keep it fairly equal during a flight fly 1/2 ball out to the fastest draining wing.

This isn't unique to FD. Other aircraft including GA have the same issue. It is because of the flat wing tank design and an instrument that may not be perfect.

Thanks,

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

[Anticept]

Or just don't worry about the low fuel in the one wing. Just don't get silly and sideslip to a landing with the empty tank high.

[Buckaroo]

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. 

Question? Please advise me a technic on how I can distribute fuel to the left tank! 

Im thinking that if we can just ignore left vs right tank usuage I can ignore the tubes as we landed with a total load of 18 gallons.

But after my engine starvation field landing last winter with 8 plus gallons still in the right tank slinging outward starving the engine im concerned. I was lucky to be over field crops at the time!

I love this aircraft but need to sort out the fuel management question! It seems I cannot manage the fuel from one tank to the other. 

If just flying level with at least 6 gallons of fuel on board regardless of tube indications is the way to go please advise. I can deal with this total fuel management as long as I don't have to expect fuel transfer management to keep us safe! Today I dropped the left wing for a long time hoping to show the wife how I can fill the lower tank. Instead as a result the left tank was indicating empty. WTF!!

[Ed Cesnalis]

I hardly give it a 2nd thought if I come back with one tank empty and the other with six.  Done it many times.

[Anticept]

If you had fuel in the right tank and still lost your engine power, then you either have an actual fuel system problem that remains unseen, or you unported fuel for far too long.

Level the airplane then check the ball indication. If it's more than half out, you really need to adjust your instrument mounting.

[Runtoeat]

Listen to Corey.  Get your plane level however you can do this in the hangar by measuring at the end wing tips to ground and placing blocks of wood under the wheel on the low side. Once you are level with the wings, adjust your ball to show level.  Understand though, that the mushroom is not rigidly held to the firewall and will move around if you lean or push on it. This is typical with our CTSW's (and probably CTLS's too).  This causes your ball callibration to change if you lean or pull on the mushroom after callibration.  Once calibrated, find out if you do have a restricted fuel flow.  While you still have your CT level, drain both tanks.  Fill first one tank with a couple of gallons of fuel.  Time how long it takes to drain this tank thru your gascolator.  Fill the other tank.  Time the drain of this one.  Are they both equal?  Does the time to drain meet Fight Design's spec? This then leads to following the advice of others here, which is, don't panic if you see one side low while flying.  If you get in a situation where you see fuel only on one side and not the other, you still are providing fuel for the engine from the side with fuel.  Just make sure you keep the CT in an attitude where you always see fuel on at least one side.

I would keep the wood block you use to level your CT and make a ramp which allows you to push your CT onto this when parking in the hangar.  This keeps the fuel in both tanks level and allows you to accurately dip the tanks before flying.

[Roger Lee]

Hi Dick,

 

Doing a drain test through the gascolator when the wings are level in the hangar won't tell you how it is affected during a flight. There are no other forces in play except gravity sitting static in the hangar.

All the instruments would have to be perfect in flight and when people put their elbows on the console getting out of the plane it can move it since it is only held in place by a few screws.

It's just too easy to look at the tube in a long flight and to fly 1/2 ball out to your left to keep things equal.

[Ed Cesnalis]

59 minutes ago, Roger Lee said:

Hi Dick,

 

Doing a drain test through the gascolator when the wings are level in the hangar won't tell you how it is affected during a flight. There are no other forces in play except gravity sitting static in the hangar.

All the instruments would have to be perfect in flight and when people put their elbows on the console getting out of the plane it can move it since it is only held in place by a few screws.

It's just too easy to look at the tube in a long flight and to fly 1/2 ball out to your left to keep things equal.

Roger,

This is a good test in my opinion. Gravity is the only force at play in the hangar just like level 1g flight.  Otherwise Gravity is adequate force to simulate any situation except when less than 1g.

If flow rates are not even it will never be fixed by learning to keep  your nose in the wind.

[Ed Cesnalis]

2 hours ago, Runtoeat said:

Listen to Corey.  Get your plane level however you can do this in the hangar by measuring at the end wing tips to ground and placing blocks of wood under the wheel on the low side. Once you are level with the wings, adjust your ball to show level.  Understand though, that the mushroom is not rigidly held to the firewall and will move around if you lean or push on it. This is typical with our CTSW's (and probably CTLS's too).  This causes your ball callibration to change if you lean or pull on the mushroom after callibration.  Once calibrated, find out if you do have a restricted fuel flow.  While you still have your CT level, drain both tanks.  Fill first one tank with a couple of gallons of fuel.  Time how long it takes to drain this tank thru your gascolator.  Fill the other tank.  Time the drain of this one.  Are they both equal?  Does the time to drain meet Fight Design's spec? This then leads to following the advice of others here, which is, don't panic if you see one side low while flying.  If you get in a situation where you see fuel only on one side and not the other, you still are providing fuel for the engine from the side with fuel.  Just make sure you keep the CT in an attitude where you always see fuel on at least one side.

I would keep the wood block you use to level your CT and make a ramp which allows you to push your CT onto this when parking in the hangar.  This keeps the fuel in both tanks level and allows you to accurately dip the tanks before flying.

I think what you are 'saying' with this test is  that 'uneven head results in uneven flow'  I'm currently low fuel I think I'll try this myself.

We don't use a valve to control flow but instead allow the fluid to choose based on head and available paths.

Tom pointed out that our systems are a simple Y so flow on either side has two direction choices. 1) towards the engine 2) towards the wingtip

As well both sides have variable rates based on current head.  Relative baselines from your test in the hangar will reveal a lot. The bigger the differential the less control we will have in the cockpit even if we know where middle really is.

 

[Buckaroo]

I'm reading these posts with real interest! Today I'm going to level my plane and check the ball. Then I'm going to conduct Toms flow test so I can be convinced my right always heavy with fuel is draining. 

I'm baffled at this point why my downward wing tank showed almost empty after our two hour flight!