4-way valve on CTSW

[Ulmo133]

Hello everyone,

I'm asking for your opinion on the installation of a four-way valve (https://www.aircraftspruce.com/pages/ap ... xvalve.php) on my CTSW.
I understand that the new FD units are equipped with one. For my part, I only have the ON/OFF valve that hide the start key hole.
I'm considering this not because it doesn't work as it is, but because I'm not able to empty the tanks symmetrically (and yet I'm doing my best to keep the ball in the center) and I'm "afraid" of ending up with one tank empty and not the other, because I don't know what that could cause.
What do you think about this installation of a 4-way valve?

Otherwise, the current fuel circuit meets in the engine compartment on a Y before going through the firewall to the valve and back. So I was thinking of drilling a second hole for the second hose to pass through to connect this.
One of the questions I have are where to position the fuel filter that's currently in the dashboard: upstream or downstream of the valve? If upstream I have to put two.

Now, some people will tell me that you can't solve a skills problem with equipment, but by improving skills (and that saves money).

Second part : Does somebody have the fuel circuit sketch for the CTSW ? he is missing on my CTSW manual and it's not the same for the vent parts as the one I saw in the fuel starvation topics.
Does anybody have the fuel circuit sketch for a CT with a 3/4-way valve ?

Thank you.

 

[FlyingMonkey]

Do you know how to balance the tanks by flying slightly uncoordinated?  It's simple to put the ball out 1/2 to 1 ball using the rudder trim wheel.  Leave it there 5-15 minutes depending on how much you want to transfer, and then re-check.  The fuel will "follow the ball", so if you want more fuel in the right tank put the ball out to the right.

You can keep your tanks very close to perfectly even this way.  I personally wouldn't modify the fuel valve setup when we have an easy work around.

[FlyingMonkey]

Also to address your concern about flying with one empty tank:  You can fly with one tank completely dry and it's not an issue as long as you have fuel in the other tank and don't unport fuel (slosh it away from the pickup in the wing root under the fuel sight tube) from the tank with fuel in it by flying uncoordinated.  Generally if you can see fuel in either sight tube fuel will get to the engine.

The way to avoid this is to balance the tanks as I described above, and to land before your fuel gets so low that you could too easily unport the remaining fuel.  The CT has such large tanks and is easy enough to manage, that there's not really any good excuse for fuel exhaustion or starvation (other than a mechanical problem of course).

[Tom Baker]

I have only seen the fuel injected engines with the 4-way valve, and they still have parallel shut off valves behind the panel. 

The vent system for the CTSW is very simple, it is just the standpipe on the fuel cap. There is no other venting. 

Ball centered is a misnomer when it comes to fuel balance in the CT. First and foremost, is your ball calibrated? With the wings leveled is it in the center? Second a slight restriction in the fuel line on one side compared to the other will allow the tank with the least restriction to flow more fuel. This can be checked by leveling the airplane in the hangar and draining fuel and watching that the tanks drain evenly. Flying with the ball off center can help this issue. If flying with the autopilot look at the wing tips and use the rudder trim to level them visually, trim towards the low wing. Don't worry if the ball is off center a little when you do this. It will keep the tanks even. 

[Ulmo133]

@FlyingMonkeyThanks for the information. I will check this. Sometimes I have in the right wing less than 10 liters and in the left 25 even if I do my best to fly horizontal and centered and the make me nervous even if I know I'm vey far from starvation. Maybe I have to change a little the orientation of the vent stub. The one on the left wing is 30° angle and the one on the right wing is in the flight direction. It was made by the previous owner.

@Tom BakerThank you for the vent information it's not what I saw in the CTLS manual in this topics :

and I was  pretty surprise because I was pretty sure that the vent system was only the standpipe on the fuel caps.

Yes the ball is calibrated and I have the same information on my D10 and the analogic one. I will check the restriction too. I have no rudder trim on my CT only the stabilator one.

Thanks

[Ulmo133]

1 hour ago, FlyingMonkey said:

Do you know how to balance the tanks by flying slightly uncoordinated?  It's simple to put the ball out 1/2 to 1 ball using the rudder trim wheel.  Leave it there 5-15 minutes depending on how much you want to transfer, and then re-check.  The fuel will "follow the ball", so if you want more fuel in the right tank put the ball out to the right.

You can keep your tanks very close to perfectly even this way.  I personally wouldn't modify the fuel valve setup when we have an easy work around.

I have no rudder trim but on my manual they say to slide for some minutes to equilibrate.

[Roger Lee]

So equal fuel drain has always been an issue in a CT.. It’s because of two reasons. First the tanks are a flat design and second only a few have a perfectly level panel and instrument mounting. You many say their left wing drains faster. Your fuel system is open from tank to tank. So remember this. “The fuel follows the ball”. So if the left wing drains faster fly 1/2 ball out to the left. This will make the fuel drain pretty equal. If you did drain the fuel in the left wing down to let’s say three gallons and there’s fifteen in the right then fly one whole ball out to the left. This will not only supply the engine, but will transfer fuel back over to the left wing. Once both tanks are fairly equal then go back to 1/2 ball to the left.

I’ve done this for a few thousand hours without any issues and many here do the same thing.

if the right wing drains faster then 1/2 ball out to the right. 
There is no need to install valves and many years ago FD had left / right valves, but took them out because people kept forgetting to switch tanks. Plus because of the flat tank design it is possible to have fuel starvation even with fuel in a tank. If you’re out of trim you can shift the fuel left to the outboard part of the tank and end up with no fuel to the engine.

[FlyingMonkey]

39 minutes ago, Ulmo133 said:

I have no rudder trim but on my manual they say to slide for some minutes to equilibrate.

Ah...is this a 2004-2005 model?  It can still be done, it's just more fatiguing as you have to hold the rudder position with your foot.

Adjusting the vent is easy, just loosen the 10mm nut at the base of the vent tube, rotate it to where you like it, and cinch it back down.  Both vents should have the open side directly aligned into the direction of flight. That might help a little if the tank draining more slowly is the one with a misaligned tube.

Also there is no speed penalty in the CT for flying with the ball out 1/2 to 1 ball.  Physics says there must be more drag doing this, but it's negligible and you won't see it on your airspeed indicator.

[Eddie Cesnalis]

Some of us are comfortable using 1 side. I used to fill my right wing only unless I was flying somewhere distant.  I fly coordinated and don't sweat keeping fuel balanced and I don't sweat running out of one wing only.

Try it?

[Ulmo133]

Yes it's a 2004.

I will reorientate the vent tube and try like this and follow your advice.

@Eddie CesnalisI'm a "young" pilot so for now "everything" make me sweat  except flying  

Thanks everybody.

[FlyingMonkey]

BTW if you experience starvation on one tank you can push the rudder to put the ball opposite of the full tank and re-port the pickup.  You might also need to bump the starter.  It's only a problem if you panic.

[Tom Baker]

4 hours ago, Ulmo133 said:

 

@Tom BakerThank you for the vent information it's not what I saw in the CTLS manual in this topics :

The CTLS vent system is very different than the CTSW.

[Roger Lee]

Like Tom said the vent system on an SW is totally different than an LS. An LS has the same flow issues.
 

Changing the vent tube position does zero. When I researched this back in 2007 I tried all four positions with the stock vent. Zero difference. Then I took two 10” tubes. Bent them 90 degrees and threaded the end and replaced the stock vents. I aimed the open end towards the front in hopes of a slight pressure. These made zero difference. I did leave them on for 1500 hours because no fuel ever splashed out and it can splash out with stock vents.
This issue still has to do with flat tanks and the panel and ball not perfectly level and coordinated with the wings.

[Roger Lee]

5 hours ago, Ulmo133 said:

Yes it's a 2004.

I will reorientate the vent tube and try like this and follow your advice.

@Eddie CesnalisI'm a "young" pilot so for now "everything" make me sweat  except flying  

Thanks everybody.

This will do no good.

[Jim Meade]

My Rans S-7S developed a very tiny leak in one fuel tank.  I found that if I turned the vent tube backward, it would not leak.  If I turned the vent tube in the normal forward position, the tank leaked.  The leak was about a drop at a time.  My assumption was the orientation of the vent tube could induce a very slight pressure in the tank.  Likewise, when I wrapped tape around the vent, the leak did not manifest itself.  Different airplane, of course.

[Mike Koerner]

Balancing the fuel in the wings by shutting off the flow from one wing with a 4-way valve would be effectively the same as running one side completely dry in that fuel would then only be available from the other side. 

I agree with Flight Design: aircraft scrape yards are full of planes that went down with fuel in one wing and the fuel valve set to the other. On our early model CTs they eliminated that problem.

With respect to Ed's comment, there's a significant amount of fuel in the fuel lines below the wing. Momentarily un-porting the only wing that still has fuel would not be a problem. You just need to slosh fuel over one of the tank outlets periodically to keep the engine running. But by running one tank try, you introduced a whole bunch of additional failure modes: Is the tank dry because there's a flow restriction in the line from the other wing, which is now the only wing with fuel? Is it dry because the rudder or aileron trim are misadjusted, or because you have a slightly heavy foot on one rudder pedal? In either case, the force that drained one wing first is now pushing the fuel away from the outlet port in the other wing. After emptying the one tank, can you be distracted by some other emergency and fly slightly uncoordinated for a while with the wing that still has fuel low?  When asked to "Fly direct to the numbers and expedite your landing", will you remember to slip in the right direction?

Long-time readers of this forum know of at least two CTs that went down after running one tank dry. There were probably others that we didn't hear about.

When one tank gets down below about an inch showing in the sight glass, I rebalance the fuel as Roger & Andy suggest. I make sure I can see fuel in both sight glasses during coordinated flight, and I land before that becomes impossible.

[Roger Lee]

FD in the early days used fuel shut off valves, but they had accidents from pilots not switching tanks when needed so they got rid of the original fuel valves. 
A tool, instrument or in this case a plane is only as good as it’s operator. Even a screwdriver can cause damage when used wrong. Maybe changing some old habits will work better.

[Towner]

The uneven fuel flow issue on the SW’s was never brought up when I got my check out in the plane, even though the instructor was someone with CT experience. I think this can be a dangerous situation for someone new to the plane if it is not explained. I would have never known about it except for this forum.

Once it is understood by the pilot, including how to transfer fuel from one tank to another during flight, it’s not a big deal. Should a pilot accidentally run one tank dry, it should also be explained how to safely keep the fuel flow going from the tank with fuel.  

Of course I understand that all pilots need to monitor fuel and keep a safe amount in the plane, but I’ve flown some pretty long cross country flights where the tanks get pretty lop sided after hours of flight. Someone who doesn’t understand the way the system works and how to transfer in flight could get themselves in trouble. 

All I’m trying to say is make sure anyone new to the plane gets a good explanation of this early.
 

 

[Ulmo133]

Thanks.
So to resume :

• when you want equilibrate the tanks you put 1/2 ball out on the side of the tank you want to "fill" with the rudder trim or with a little pressure on the rudder pedal for some minutes
• when you have an empty tank and one almost empty, you put 1/2 ball out on the side of the tank empty tank to be sure to feed the motor with the remaining fuel.

Am I correct ?
Thank you.

PS : just a kind reminder  , be indulgent, I am a "new" pilot and I just hit 130 hours a little while ago so I still have to learn a lot.

[Towner]

1 hour ago, Ulmo133 said:

Thanks.
So to resume :

• when you want equilibrate the tanks you put 1/2 ball out on the side of the tank you want to "fill" with the rudder trim or with a little pressure on the rudder pedal for some minutes
• when you have an empty tank and one almost empty, you put 1/2 ball out on the side of the tank empty tank to be sure to feed the motor with the remaining fuel.

Am I correct ?
Thank you.

PS : just a kind reminder , I am a "new" pilot and I just hit 130 hours a little while ago so I still have to learn a lot.

When transferring, fuel follows the ball during normal flight. So yes, keep the ball on the side you want to transfer the fuel towards. Half a ball to a full ball outside. Depending on how much you want to transfer, it may take more than a few minutes. Also, when the ball is outside, the fuel will not show the level accurately in the sight tubes. To determine where you are at, check the levels with the ball centered. If you still aren’t level, move the ball outside again.

If you get down to one tank (don’t!), you can still fly safely to an airport. Just make sure you can continue to see fuel in the sight tube on the side that has fuel. If you can’t see fuel, it has moved to the outside of the tank and isn’t feeding the engine. There will be a little fuel in the lines from the tank to the engine, so It’s not going to immediately die, but get the fuel back to the sight tube. 
 

If you are down to one tank, it is safe to turn that direction or do other basic maneuvers without unporting the fuel. Just remember all the stuff we learned about coordinated flight and uncoordinated flight and how it affects the g’s, which can pull the fuel away from the port.

Pretty easy to practice too. You don’t have to empty a tank. You can leave 3-4 gallons in one tank, but make sure you have plenty in the other. Go out and play and notice what the fuel does in the sight tubes in different flight configurations. Even with 3-4 gallons in one tank, it isn’t hard to pull that much away from the port during uncoordinated flight.

Sorry, I’m not the best at explaining things, but hopefully you can make sense of this.

[Mike Koerner]

I agree with Towner.

The only thing I would add is that you can only check your fuel status with the wings are level in coordinated flight. When your transfering fuel, you have to move the ball back to the center to check progress.

[Towner]

1 hour ago, Mike Koerner said:

I agree with Towner.

The only thing I would add is that you can only check your fuel status with the wings are level in coordinated flight. When your transfering fuel, you have to move the ball back to the center to check progress.

Much clearer explanation of what I was mumbling! Thanks! It always sounds so good while I’m typing, just reads sooo different later….

[Ulmo133]

Thank you both very much.

I'll be performing a few tests on my next flight.

[Towner]

I think it’s a big deal, and can be dangerous when you don’t understand it. Once you understand it, it just takes a little monitoring and it’s not a big deal at all. 

This forum can answer just about any question you may have on the plane, both flying it and maintenance. I read it everyday for new posts, but often do searches on any questions I have. 
 

I have owned a handful of airplanes, but the CT is the most fun! If you only need two seats, it’s hard to beat!

[Eddie Cesnalis]

It is best to understand yet so many are confused.  I came up with the phrase 'the fuel follows the ball' about 17 years ago for a simple explaination.  I have seen many times on other forums that fuel flows from the high wing to the low which isn't necesarrily true.  I can transfer from the low wing to the high in my CTSW.

There is no transfer in a coordinated turn yet you have a high and low wing. Better said we transfer from the leading wing to the trailing wing when in a slip regardless of bank or lack of it.

I envision my sight tubes as a giant slip skid instrament that I can use to confirm the calibration of my slip/skid ball.  When you are wings level and coordinated both sight tubes are correct. Add left rudder (trim) and the level on the left goes up as it sloshes inboard and the level on the right goes down as fuel sloshes outboard.  Do this left and right a few times and you will see where the middle is, where there is no transfer, where there is no yaw.  Angles on panels and bias a mechanical slip/skid ball for instance so I learned to confirm it with the sight tubes long ago.