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Fuel tank leak on CTLS


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Noticed this staining on the wing seal tape and CTLS fuselage near the wing root this morning.  Last flew two weeks ago.  Removed tape and could see by the staining that fuel had come through the narrow horizontal opening mid wing where wing and fuselage meet.  No smell of gas, wet area or any sign of ongoing leak.  Fuel level is where I last recall it at 25 gallons.  I have flown twice since topping off the tank.  

Wondering if this is a tank leak or failing hose?  No sign of any discoloring or composite failure on bottom of wing.  Also not sure whether safe to fly to my mechanic so he can remove wing to inspect.  As always, appreciate any insights from the board.  

 

 

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I have been through this. It is likely from the access port on the wing root. The first thing I would try is tightening the six nuts on that port (this was advice from Adrian at FDUSA). If that does not work you will need to pull the wing, remove the plate covering the port and reseal it with a thin layer of Hylomar. 

There is one more possibility for the leak and that is the fuel nipple which would also require the removal of the wing and removing the port to get access to back side of the fuel nipple.

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One other thing I have seen, especially if the tank was full is a leaking vent line.

If it is not dripping I wouldn't be afraid to fly the airplane somewhere to get it fixed, but I would talk with your mechanic first.

In addition to the Hylomar Doug mentioned there is also a gasket.

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This leak is would be very rare to come from around the bulkhead fuel plate. 95% of the time that leak comes from the fitting coming out of the fuel tank bulkhead plate fitting that feeds the "A" post. It is easy to repair and only requires sliding the wing back. You do not need to remove the fuel bulkhead plate. I have repaired many and never had it leak again. You will need some Universal Hylomar. I have helped several repair this without a big hassle.

 

You need to call me and I'll tell you how to fix it. It's quite easy.

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I guess I am a rarity. And, Arian said that the leaking around the bulkhead fuel plate is often fixed by tightened Nguyen the nuts, so evidently he has seen it before. So maybe not that rare.

Roger, are you saying that it is possible to put Hylomar on the fitting without accessing it from inside the tank and have it seal?

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Hi Doug,

 

I just re-read the original post and noticed it was a CTLS. I was going to give the fix for the SW until a saw this. You can tighten those 10mm nuts on the fuel bulkhead plate, but this is rarely the case even for the LS. In the LS's case I would be looking at the hose and clamp where it attaches at the bulkhead. The fitting is almost too short. I find different types of clamps here from different mechanics. If it's a worm drive serrated clamp toss it. These clamps have no place in a fuel system. It should be either a fuel injection clamp or an Oetiker clamp. The main problem here is the factory hole that the fitting and clamp go into on the fuselage side at times is barely big enough so putting the wing on or off plays with this clamp. I ALWAYS take my Dremel tool during a wing inspection and open this hole up so as not to pull or bang on the clamp which is on the short fitting.

 

So if this were my plane I would pull that wing out and do try and tighten those 10mm nuts. You may or may not get 1/2 turn out of them. I have never seen on get a full turn or more.  If you actually got 1-2 turns out of them I would be surprised, but I guess stranger things have happened. Maybe someone even took this off once before and didn't torque them down? Then I would address the hose, clamp and hole size. Doing both of these should take care of your leak.

 

p.s.

If you need a wing inspection anytime soon now would be a good time to just do the other side too and get it out of the way. Do the sight tubes to.

 

p.s.s

I'll post the SW leak fix shortly.

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Okay once upon a time:

Oops wrong story. :)

 

To fix a CTSW fuel bulkhead leak that appears by coming from under the door seal tape and or fuel smell in the cockpit.

Drain the fuel, pull back the offending wing about 15"-18". You will need some Universal blue Hylomar gasket fuel sealer (Amazon, sorry Ace Aviation doesn't carry this) and a 17mm open end wrench. The huge majority of the time the fuel leaks come from under the fuel out fitting that your rubber fuel hose fits on. It may be very small and hardly detectable, but it's there. If you look you may see a tiny bit of brown or greenish blue fuel stain  just under the fitting and if you put your nose up there you may smell it. First take a long piece of safety wire (about 12" long) and just tie it around the end of the fitting. This will keep you from losing the fitting back inside the fuel tank. Then remove the 17mm nut. Now the fitting is loose. Push the fitting back into the tank about 1/2" just so the fitting threads are back out of the way and the nozzle end of the fitting is still sticking out. The other side of the fitting you can't see has a small flange on it. Now take a small tipped flat screwdriver and put some of your Hylomar on it and push it back into the fitting hole.. The fitting throat is still sticking out and there is plenty of room to pass a small tip screwdriver past the fitting that is sticking out. Push Hylomar in through the fitting opening all the way through and do it all around the fitting. The idea is to get the Hylomar on the back side of the fuel bulkhead plate so when you pull the fitting back in place the flange on the back side of the fitting pulls up and squishes the Hylomar between the flange and plate. Remember DO NOT push the fuel fitting all the way back inside the tank while doing this. The nozzle end will always being sticking out with your safety wire on it. Once you have Hylomar pushed back inside then pull the fitting back up in place and put the 17MM nut back on and tighten it, tight. Make sure your fitting is pointed downward which can be felt because the strainer on the inside is resting on the tank bottom. It will be in the same position as you found it. It's its own resting position.  Now wipe off any excess Hylomar you may have smeared on the exterior of the fitting and bulkhead. You're done.

p.s.

Once this fitting has been tightened don't ever mess with it again so you don't break the seal. Leave well enough alone.

I have used this method many many times and it has never once failed me and never leaked.

The only other option if you don't like this is to get some new bulkhead gaskets from FD, remove the entire plate , loosen the fitting and put the Hylomar on from the inside. It does the same thing as my method. Then you'll need to try and clean all the old Hylomar off, apply Hylomar to the new gasket. ABSOLUTELY do not over apply this Hylomar to the gaskets because when you tighten those 10mm nuts back up it WILL squish out and since fuel won't dissolve the Hylomar it floats through the fuel system like silicone does and will clog everything and you'll be stripping and cleaning the fuel system from fuel tank to carb.

 

My way is proven since 2006 on many CT's and it takes less time, less hassle and less parts, less likely to get Hylomar throughout the system from over zealous application.

You can always call me to.

 

If something here is not clear let me know and I'll edit it.

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CTLS Fuel bulkhead plate with 6 nuts is very clean with no signs of any staining in chamber.  Must be the fuel line where it connects to the nozzle on the bulkhead as Roger suggests.  Tried to view with an endoscope but that area is closed off.  

Will slide out wing next.  Curious if anyone knows a Repairman in the Chicago metro area with Flight Design experience that could do a house call.  My plane was converted to experimental. 

Thanks all, Happy Memorial Day.  

 

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Hi Roger.  Thanks for the detailed method for sealing the fitting.  There are many types of hylomar shown on the internet.  If you might provide the number and/or name of the hylomar you use, it would be appreciated.  I'm wondering if there is a type that is specifically required for MoGas with ethanol?  I have found that hylomar did not work when used on the paper gasket used for the fuel filler fixture in my wing.  This fixture leaked soon after being installed.  When the leaking fixture was pulled out of the wing, it was obvious that fuel had worked it's way past the paper gasket which had the 'blue" sealant on it.  I believe the mechanic used hylomar but am not certain.  If he did use hylomar, I'm not sure which type he used.

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Sorry if a late contribution. I got similar thin leak at the same area, I noticed it in March, after first flights after winter. Pulling the wing back it appeared to come from the pin that connects the wing to the fuselage. That pin is located between leading edge and wing spar. It seems to have some sorts of gasket and the thin leak came from there. It needed resin work around the pin by a dedicated shop where they said they also poured some liquid sealing inside the tank and flipped the wing around long enough to get the sealing coat all the interior of the tank.

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@ Doug, many thanks for your thought,, it throws some light. I was thinkg the dark material around the pin (when the wing got pulled back) was some gasket or a black rubber,, now with what you say I better understand. That must be the reason the shop used resin to repare that area on my CT.

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The fuselage pin has nothing to do with the fuel tank.They are completely separate items.  If there is a tank leak out by the pin then yes fuel could leak there. The only places a tank can leak are either a pin hole leak in the tank someplace and all this needs is to slosh the tank with Kreeme Weiss or it is around the fittings on the fuel bulkhead plate. It can be around the gasket of the fuel bulkhead plate, but that tends to be rare. 

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Roger

What is used to bind the fuel filler fixture to the composit wing.  A lineman pryied mine out with the fuel hose nozzel.  I tried some fuel tank repair two part epoxies from Ace but the gas is breaking them down to soft and letting the fixture come loose.

Thanks.   Greg 

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You need a fuel resistant epoxy. Something like Proseal or Kreeme Weiss.

Allowing the filler nozzle from fueling to pry against the filler neck will eventually break this out. This is why I ALWAYS fuel my own plane, not to mention they always slop it out and overfill it.  

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Thanks Roger.  I totally agree with putting in fuel myself.  I was in Lakefront New Orleans and got lazy.  Never again. 

Two tips for getting home for those with loose fuel fittings.  Take the fitting and fuel cap out and pound a large aluminum foil ball in the hole until it is flat with surface. Amazing how well it works and will get you home.  Or, tape it down.  Duck tape will work for awhile but the fuel breaks it down.  Use the blue paint line tape.  Designed to be solvent resistant and easily available.  Make sure you run tape over and under the leading edge of wing.  Seal it tight or vacuum will form and prevent fuel flow from that tank. 

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