CT Fuel Tank Failure Ruins Both Wings

[ctspain]

Left wing

[ctspain]

Outside view of left wing. It is difficult to see but there is an small bubble separating sandwich.

[Jim]

Looking at that picture, I have to wonder if excessive wing flex, either landing or in the air might have been a contributing factor.

[Rich]

There are places to save weight, every little bit helps but the fuel tanks are not the place to shave points.

The tanks should be aluminum, period! When you spend upward of 140/150 K for an aircraft you shouldn't need to be concerned about the tanks leaking.

 

We need to write to our respective manufactures and demand a better product. Better yet, just keep getting the word out about the leaking composite tanks, I'm sure that will get their attention.

 

R.

[FlyingMonkey]

Aluminum tanks can leak too.

[Rich]

Yes they can. But you wouldn't need to be concerned about the fuels you use which may be causing the problems.

The chemicals in mogas or the E-10 would not be a concern. You also wouldn't have to worry about the coating or coatings breaking down.

 

One of the previous posters had stated that it's not a matter of if but when. I agree with that.

 

If you buy an aircraft that is touted to use mogas or mogas with 10%E then it should be able to do just that.

 

IMO we're much safer with aluminum tanks.

[FlyingMonkey]

Aluminum reacts with water forming aluminum oxide.  That is a form of corrosion that can powder and flake into the fuel, getting in filters, fuel lines, and carb jets.  Fuel with ethanol is hydrophilic, and attracts water.  So ethanol fuel can still cause fuel tank damage with aluminum tanks.  You'd want to be careful using E10 fuel.

 

I'm not slamming your suggestion, just pointing out that there is no perfect solution to fuel tank leaks.  It's tough to find substances that resist gasoline, water, and ethanol equally well and yet still have the strength you need.

 

A better material would be, IMO, rotationally-molded one piece polythethylene tanks.  A lot of racing fuel cells are made from that, as is the fuel tank in the Sonex I was building.  It's very tough material with great resistance to all the chemicals mentioned.  But it's also heavy, and over time I don't know if it would become brittle enough to compromise it.  I know a lot of similar fuel tanks have been around for decades, but you never know.

 

But also, how many CTs have tanks that have leaked?  I know of two.  That's a pretty good record with probably five hundred or more airplanes flying.  The Sting has a different structure and chemical lining, so I can't speak to those.  But overall I have a CT and use E10 in it and never have seemed to have an issue, as have many others.  Sure, repairs in the event of a large fuel leak might be painful, but the likelihood of that happening appears very low, on par with other major repairs that might occur.  

[Anticept]

Someone suggested bladder tanks once. Combined with witness holes in the bottom of the wing, that would work decently well (until you saw the cost of the replacement every 10-15 years that is).

 

All things considered though, what we have is really the best option... There is no perfect option unless e10 can be removed.

[FastEddieB]

The tanks should be aluminum, period!

No reason a properly constructed composite or even plastic tank could not work reliably if properly designed. Rubber bladders have also been used successfully forever, as have sealed aluminum wing structures.

 

I had an aluminum tank on a BMW motorcycle begin to leak from pinholes around the fuel valve - water could collect there and begin to corrode it from the inside out. Modern motorcycles most often have plastic tanks which tend to be trouble free.

 

As an aside, my Sky Arrow has a composite tank that has never had an issue. I think I prefer it over an aluminum tank, though either should work, again if properly designed.

[gbigs]

The Flight Design fuel tanks and the other fuel system components are designed to be used with 91E10 ethanol fuel.  We have used nothing but 91E10 in our plane since day one with no ill effects.  In fact, the absence of lead in the engine makes it run cleaner and we are able to use full syn Mobil 1 racing oil which helps with temp control and easily lets us have 100 hour oil change intervals which we cut in half to 50 hours to baby the engine.

 

After two years I have not once seen water in the gas.  I have seen water in planes using 100LL.

[IrishAl]

It seems that every CT with leaky wings has the leak in both wings and it seems to me that this is a big clue in identifying cause. 

 

If you were talking about random imperfections in the manufacturing process, you would expect the occasional plane to to suffer with one wing only - the chances of random imperfections occurring in both wings would be very small.  

 

Therefore, it's reasonable to conclude that either the planes concerned were exposed to something during their lifetime that cause the breakdown in both wings or a poorly trained technician coated both tanks during the manufacturing process and didn't do it properly. (Of course, this assumes that wing tanks were sealed in pairs rather than on a production line.) 

 

Apart from that, it's hard to see how an occasional fault could be always occurring in pairs.

[FlyingMonkey]

Probably the same tech that made those failed tanks set my wheel geometry.   

[Tom Baker]

 

 

But also, how many CTs have tanks that have leaked?  I know of two.  That's a pretty good record with probably five hundred or more airplanes flying.  The Sting has a different structure and chemical lining, so I can't speak to those.  But overall I have a CT and use E10 in it and never have seemed to have an issue, as have many others.  Sure, repairs in the event of a large fuel leak might be painful, but the likelihood of that happening appears very low, on par with other major repairs that might occur.  

 

I think the number is around 1,800 world wide and 400+ here in the states.

[FlyingMonkey]

I think the number is around 1,800 world wide and 400+ here in the states.

 

Total, not with leaking tanks...right?  RIGHT?!?!   

[Rich]

I've used E10 for 3.5 years, since the plane was new and never had a problem. The Sting has had 3 tanks leak out of 100.

Unfortunately I must use the non E fuel due to the SB.

 

If I'm correct, as an S-LSA, the SB is gospel. Not like the normal certified AC in which the SB must be followed by and AD to make it mandatory.

 

I have checked my gascolator every ten hours to see if the tanks are shedding any fibers. To date I haven't found reason for concern.

 

We really need to write/call our Representatives to get the E out of the premium mogas. Talk to AOPA/ EAA for some assistance or we'll be paying top dollar for the Swift / Shell alternative post 2018 for the non E fuel.

[Tom Baker]

Total, not with leaking tanks...right?  RIGHT?!?!   

 

Everybody loves a smart ass.

 

I guess you missed the "five hundred"  that was in front of the "or more airplanes flying" that I highlighted in the quote from your post.

[FlyingMonkey]

I've used E10 for 3.5 years, since the plane was new and never had a problem. The Sting has had 3 tanks leak out of 100.

Unfortunately I must use the non E fuel due to the SB.

 

If I'm correct, as an S-LSA, the SB is gospel. Not like the normal certified AC in which the SB must be followed by and AD to make it mandatory.

 

 

IIRC, Service Bulletins are *not* mandatory, but serve as guidance (does not mean you should ignore them, of course).  The term for a mandatory action in the LSA world is "Safety Directive".  FAA also recognizes the certified term "Airworthiness Directive" with regard to LSA.

 

https://www.faa.gov/aircraft/gen_av/light_sport/media/LSA_Cert_8July2013.pdf

[FlyingMonkey]

Everybody loves a smart ass.

 

I guess you missed the "five hundred"  that was in front of the "or more airplanes flying" that I highlighted in the quote from your post.

 

[gbigs]

91.327 requires SLSA owners to comply with “each safety directive applicable to the aircraft that corrects an existing unsafe condition.”  These safety directives are issued by the manufacturer, so in effect they’re mandatory service bulletins—owners of certificated aircraft operating under Part 91 must comply with service bulletins only if the FAA issues an AD compelling compliance.

 

In essence, LSA manufacturers can issue their own “ADs” without having to jump through the statutory hoops that protect owners from unreasonable action by the FAA.

[Roger Lee]

We're getting off the original topic, but

 

 

Safety directives and service bulletins are different. An SB does not carry the same weight as an SD. SD's are mandatory no matter who issues it and is a flight safety issue. A mandatory SB does not carry the same weight as the SD. This came right from the top guys at the FAA. You could not perform a mandatory SB and not be violated by the FAA. They do however believe they should all be done. Just a weak loophole in the FARs.

AD's are "typically" used for certified aircraft, but it isn't exclusive. My guess is it depends on how serious the problem is.

[wlajara]

I'm having the same problem as TomH but my plane is new.  One of the first delivered from Taiwan after they had to close the plant in Ukraine.

[CT4ME]

Keep us posted... who's the dealer, and where is the work being done?  Satisfied with the efforts?

[FlyingMonkey]

My CTSW has some areas under the wings where they are not smooth, and look slightly wavy or bulged.  I have tested, and all these areas are just as hard and solid as the surrounding areas.  I'm assuming they are simply normal imperfections for hand finished composites, and that fuel damage would be softer and/or discolored.  Is that correct?

[Roger Lee]

Correct

[FlyingMonkey]

Correct