Fuel Tank Leak - What to do?

[Flying Bozo]

OK if you care to call me I can tell you about the good experience I had at Airtime. who fixed  this problem. 408-821-6902

I am not much on writing up stuff like that but would be happy to tell you about it on the phone.

Larry

[Andre]

I took a picture of the inside of my tank.  That funny buildup is either where the leak is from or very close to it – I am guessing it is.  Is this something that somebody has seen before?

[Brudy]

I have 1/6th in a 2006 CTSW with 300 TT, I found it in Iowa with 100 TT.

Right wing tank developed a Leak , the same sick ugly feeling came to us.

We had it repaired in here Michigan, Arian and the Factory got involved when the thought there may have been damage to the wing structure from the leaking fuel.

It was determined that the wing structure is fine.

I can supply the name of the repair shop, They are well known and great to work with, including borrowing the wing trailer for transport.

 

[Runtoeat]

Brudy, please provide name and phone number of shop that repaired your wing.  Thanks.

[Andre]

Here is an update about my fuel leak.  It is still not repaired nor do I have a definitive plan to get it repaired.  I will start with a bit of general information.

The first picture shows the inside of a normal fuel tank showing the hatch epoxied inside the tank (Courtesy of John Neves).  This is for a CTSW circa 2006 like mine.   The fuel leak usually occurs where the hatch edges meet the fuel tank.

Repair can include the replacement of the hatch and/or using a tank sealer such as Caswell or Kreem Weiss, both of which have been used successfully in the past.   IMO, based on what I know now, replacing the hatch is probably an overkill for this type of leak and there is no guaranty that the replacement job will be any better than the factory job.   I would recommend the tank sealer first. 

The second picture shows what the hatch area looks like after using a tank sealer.  This is an actual picture of my tank.  Unbeknownst to me, my tank had already been repaired in 2015.  There is a vague one-liner in my Aircraft Log which I misinterpreted when I read it in the past.  I thought that the fuel leak it referred to was at the fuel sight plate since the next sentence was about replacing the sight gauge and fuel lines.  

The reddish "growth" is what may be causing me a problem (based on its location).  I do not know what it is and I do not know if it existed after the original repair was done or if it developed since then.    Nobody has yet been able to tell me what is it.

In my case, the two repair options are possible.  I can add more tank sealer to cover the area where the red growth is to try to stop the leak.  Or I can try to replace the hatch.   

Adding more tank sealer may be problematic because that stuff is quite runny and it may be difficult to seal the red growth.  Also, not knowing what that red growth is, there is no guaranty that the repair will hold this time.

I do not know how difficult it would be to replace the hatch.  The tank sealer is epoxy and there is quite a large layer of it.  Removing it may require a lot of delicate work.  I have never work with this stuff so I do not know. 

So I have no definitive plan as how to proceed at this point.  I have disconnected the fuel tank and the aircraft is flying quite happily on one tank so it is only a minor inconvenience at this point.  One tank is 3+ hours of flight at economy cruise which meets 99% of my requirements.  I still want to get it repaired but I want to make sure it will be done right (by me or another party) before I proceed further.

One thing that I have learned from others is that you should drain a leaky fuel tank.  If you do not, then fuel could soak into the foam of the wing.  It will expand the foam, which in turn will expand the carbon covering and make a permanent deformation.

Any insight into my problem by others who have experience with it is much welcomed.

Andre

  

 

 

[AGLyme]

Have you considered purchasing a whole wing of the same vintage, post accident?

[FlyingMonkey]

Sorry you are dealing with this, Andre.  It really looks like a scary and annoying problem to have, and it's compounded by the "one-liner" repair that gives you no information on the methods used.

I think my first stab at the problem would be to try to squirt a new bead of sealant around and covering the reddish blob.  If you can encapsulate it and seal all around it , that might solve your issue.  Of course precise application of the sealant might be a problem.  Maybe some kind of syringe with a long tube or hose attached?  If you can get the syringe hose *and* your borescope in there, you might be able to get the goop where you want it.

Did FD give a recommendation?

[FlyingMonkey]

1 minute ago, AGLyme said:

Have you considered purchasing a whole wing of the same vintage, post accident?

Replacing a whole wing seems kind of extreme (and expensive) -- since every CT is hand made, I'm not sure how the fit might be with the new wing.

[johnnyjr]

I've been traveling and have not had a chance to circle back on this thread to comment.  My CT is the one that the first picture above came from.  My mechanic and I spent a lot of time with FDUSA and other composite experts working on a solution that didn't involve removing and replacing the patch.  We finally settled on using the Caswell tank sealer as suggested by Arian at FDUSA.  

We started by a full inch by inch inspection of both wing tanks and both cavities within each tank.  For this we used a good quality borescope (the key to the entire process is the borescope) and inserted addition lights into the tanks to get enough light for a clean picture.  once we found the patches we attempted to knock the red epoxy lose to insure it was secure and verify we did not have to work it down before sealing.  Once this was all confirmed we moved on to tank prep, for this we followed the Caswell instructions, simple process.  

When it came to sealing the challenge was how we would direct the sealer to the patch, for this we strung the wings up from the hanger rafters and got to the level point that would allow the sealer to settle over the patch.  Now for the fun part, we rigged up a disposing rig that was made of a large syringe with a tube on the end and a spring steel rod (very thin rod and flexible).   We setup the borescope camera to get an overhead view of the patch and used the rod with the tube taped to it to move the end of the tube over the patch.  After mixing the Caswell we graciously injected the Caswell over the patch making sure all the red "mountains" had complete coverage and at least an inch surrounding the entire patch (we ended up with about 2 inches of coverage around the patch once the sealer settled.  

During inspection we found a few pin holes on the leading edge so we covered the entire leading edge as well to insure we didn't have to get back in there at a later date.

Very important part of the process is to bring the tanks and Caswell up to 70* F before starting application, as well as maintaining that temp (or slightly lower, see Caswell instructions for temp and cure times) to insure a proper cure of the material.  I've had the plane back for 3 weeks and have kept the tanks topped off.  So far, no leaks, but I wouldn't expect any right away.  Only time till tell if this process is successful.

We also sampled a drop of the Caswell near the sight tube port so that we could attempt to remove it post cure, this would give us confidence that the bond was strong, and yes, it was rock hard and would not detach from each other.

 

Good luck to you all, this was not as difficult as it sounded.  Aside for the investigation the entire process took less than 8 hours including wing removal and install.  Remember the success is all in the prep, make sure it is clean.

[Brudy]

5 hours ago, Runtoeat said:

Brudy, please provide name and phone number of shop that repaired your wing.  Thanks.

https://mwskysports.com/maintenance

 

[AGLyme]

A new (used) wing solution isn't extreme if the gas tank is beyond repair.

[Flying Bozo]

I think that there is almost no gas tank repair that is beyond repair. There is one that I have seen that was almost totally re-skinned at the tank and the final result is beautiful and looks like brand new. It was really a mess and it is now fixed from what I thought was a total loss.

Larry

[Tom Baker]

4 hours ago, AGLyme said:

A new (used) wing solution isn't extreme if the gas tank is beyond repair.

From what I remember from composite class the wings are not interchangeable between airplanes. even thought these are factory built airplanes they are still primarily built by hand.

For the SW I remember someone lost a baggage door, and ordered a replacement, and it didn't fit. Come to find out there were at least 3 different baggage doors with slightly different shapes. You had to have the one that was matched to your airplane. 

[AGLyme]

one of the F-2 (new plane) bragging rights is that the composite layup is "robotic".  Naturally, removes labor out of the cost and the Parts will be uniform.  

From what I know about production, I agree with what you said - almost.  I agree with your doors and baggage doors comment... after reviewing the fit and finish on our planes, it is obvious that the tolerances are indeed custom for both the fuselage and the doors.

I don't agree with the wings however.  The wings are separate "Parts"... made and brought into the Plant for attachment.  The wings aren't made to fit a particular fuselage.  I am sure there is some shimming between the wings and the fuselage, but when done there is a relatively sizable gap - after install.  Which is white-taped over for anti drag and water, etc.

I am in Woodstock on the next good weather flying day I'll ask the guys there if they have ever seen wings "sold" by the junkman  for scrap to folks who need them.

[Tom Baker]

I was just relaying what I was told by the engineer from Flight Design Techique who taught the factory composite training that I attended.

[AGLyme]

Right, but it isn’t accurate.  There is a time during the production process when the wings meet up with the fuselage for shimming — which occurs in the area where the wing meets the fuselage ... which makes sense right ?

[FlyingMonkey]

19 minutes ago, AGLyme said:

Right, but it isn’t accurate.  There is a time during the production process when the wings meet up with the fuselage for shimming — which occurs in the area where the wing meets the fuselage ... which makes sense right ?

Sure...but remember the wings are all hand built too.  They might not all be completely uniform, which would mean the factory shimming on the fuselage side might not give correct geometry with a different wing.  

[Tom Baker]

46 minutes ago, AGLyme said:

Right, but it isn’t accurate.  There is a time during the production process when the wings meet up with the fuselage for shimming — which occurs in the area where the wing meets the fuselage ... which makes sense right ?

It is not just about matching the fuselage. The wings must also be perfectly matched to each other. Where the pins go through the wing spar the bushings must match perfectly. 

[AGLyme]

Guys... the customization is in the shimming.  Fortunately the same process can be applied to plane #2 where the spars meet in the box.  Sanding here, epoxy there... it can be done.

[AGLyme]

FYI... same process with the CTLS landing gear Leg replacement.  The gear “box” is similar in concept as the wing spar box.  I saw that done in person.  I built a boat once, epoxy is incredibly versatile.

[FlyingMonkey]

1 hour ago, AGLyme said:

Guys... the customization is in the shimming.  Fortunately the same process can be applied to plane #2 where the spars meet in the box.  Sanding here, epoxy there... it can be done.

I don't think anybody argued it *can't* be done, only that it doesn't make sense to do so for a fuel leak unless the fuel has significant;y damages the wing structure.  I'd probably have the entire bottom of the skin under the tank replaced before entertaining a wing replacement.

[AGLyme]

I agree with that strategy Andy if replacing the bottom skin can be done without any compromise to the stress tolerances.  Having worked with epoxy (boat, which has significant stresses as well), I am a firm believer that almost anything can be repaired.  I would love to see a 3D modeling of the wing stringers, gas tank area and balance of the wing parts.  

[Tom Baker]

3 hours ago, AGLyme said:

FYI... same process with the CTLS landing gear Leg replacement.  The gear “box” is similar in concept as the wing spar box.  I saw that done in person.  I built a boat once, epoxy is incredibly versatile.

I have first hand experience removing wings and replacing gear legs, and it is not the same process. I can see how you might think that, but it is not.

[Tip]

5 hours ago, AGLyme said:

Guys... the customization is in the shimming.  Fortunately the same process can be applied to plane #2 where the spars meet in the box.  Sanding here, epoxy there... it can be done.

Where are these shims located? Do you have a part number?

[AGLyme]

Tom, sorry should have stated — “similar”... Naturally, the “boxes” are different, they do different things but the engineering principals and the way the pre-made Parts (wings or CTLS struts )fit into the boxes, and shimmed, are “similar”.  
Your argument is that when the Parts (wings, gear struts, etc) are made, each Part is custom sized and made in essence in their own custom jig (custom dimensions).

 Each part is made with a goal of “jigged” consistency...however each composite Part (wing, gear leg, fuselage, door, wheel spat, etc) is different than the last because of the human aspect of layup  construction.  Literally humans spreading cloth and adding epoxy in open air factories during winter or summer conditions.

Then the Parts are shipped to the assembly area and each Part has to be sanded, and/or epoxied (material additions) to “fit” each human being made Part.  When the wings are put into the box in the fuselage (in front and above our heads) the shimming process happens and yes “customized”... for best fit.  there is no reason a wing cannot be transferred to another plane... with sanding and epoxy work.

The F2 is going to use robotic laying up in improved climate controlled conditions.  The weight savings are huge allowing the plane to be larger than the LS but similar weight.  Epoxy is heavy. 

thx, Andrew