Fuel Tank Mods - With A Twist

[Catbird]

I'm down to the final home stretch now on Kit #120221 and hope to fly by Memorial Day. The engine is mounted and practically ready for first start. Skyview is in-hand and the wiring modifications are going as well as can be expected. Which brings me to the fuel tank.

This past weekend I was showing my completed and leak tested fuel tank to a friend who has built an RV-9. We discussed the sight glass and the problems many RV-12 builders are having with leakage in this area. I described to him how the Moeller fuel gauge is being used as a retrofit with the sight glass area blanked off after E-LSA certification has been received. We then discussed Service Bulletin 11-12-14 (Frangible Bolts), which requires removing the access opening from the front of the tank and subsequent resealing. His suggestion was so simple, that I was kicking myself mentally for not thinking of it first.

Install the fuel tank as-is, optain E-LSA certification, and fly the plane. Order all parts for a replacement fuel tank from Van's, including the Moeller fuel gauge from another source. Build the replacement tank with all the desired/recommended modifications and then install it during the first annual inspection or when the first leak appears in the in-service tank, whichever comes first. Why go to the trouble of tearing into a perfectly good fuel tank, which will delay project completion? Brilliant!!!

Any differing opinions?

[rvbuilder2002]

Originally Posted by Catbird

Any differing opinions?

No differing opinion (seems like a reasonable plan), just a question of my own.

Where is the evidence that shows that "many RV-12 builders are having leakage problems at the site glass"?

As far as I am aware, there has been nothing mentioned in this forum for quite some time and those couple of instances (if I am remembering correctly) were related to leaks present from the initial assembly, not something that developed over time. There will always be a few builders that have a leak (even happens in the other RV models), but there has been no indication that problems are any more prevalent than in any of the other RV models (but if you have info indicating otherwise, please share it).

[Catbird]

You are correct and I apologize. I have no evidence or data to support my claim that a lot of builders are having leaks around the sightglass area.

[Mich48041]

My DAR required a list of all service bulletins and had me sign a paper stating that they were complied with. It might be considered perjury or fraud if a false statement is made. Your DAR or FAA inspector might be knowledgeable about the fuel tank service bulletin because it is one of the most important ADs.
If the RV-12 is flown without the fuel tank upgrade, the tank could rupture during a forced landing on rough terrain. And forced landings are more likely during the testing phase. The fuel tank did rupture in one RV-12 that made a very hard landing. The pilot was sprayed with fuel and was lucky that there was no fire. That incident was the reason for the service bulletin, to prevent similar incidents.
Although there was a problem with the original sight glass, the revised one has not been a major problem. Fuel leaks are unlikely in a properly constructed tank. While the fuel tank access port is open for the service bulletin upgrade, a hole can be cut and a reinforcing ring can be installed in preparation for the future installation of the Moeller fuel gauge after certification. See Don's post on the subject:
http://www.vansairforce.com/communit...29&postcount=4
Joe Gores

[mikerkba]

Its pretty hard to beat the reliability, accuracy, and low weight of a sight glass. I was wondering, if a builder had leak problems with a sightglass, would sealing it up and adding a different gauge reduce the liklihood of leaks? Catbird's idea of building a new tank without the sightglass sealing areas would avoid that, but it does cost some time and money to have the two tanks.

Van's designs are pretty well thought out and they function as advertised. If I was building again, I would build closer to the plans and modify only for true performance reasons (e.g. extended tanks, I would do again. Copilot EFIS, I would not.) I would definitely build lighter.

[BigJohn]

Originally Posted by Mich48041

My DAR required a list of all service bulletins and had me sign a paper stating that they were complied with.....

My DAR didn't even ask about SB's.

[Snowflake]

How does changing the sight glass out for something else affect the E-LSA certification?

[rgmwa]

Originally Posted by Snowflake

How does changing the sight glass out for something else affect the E-LSA certification?

E-LSA rules require the aircraft to be an exact copy of Van's factory-built S-LSA original. That aircraft has the sight glass, therefore the E-LSA aircraft has to have one - at least until after certification.

[J.Coles]

Why would you want to block out the sight glass and install a fuel gauge which means you have to go back to tank dipping to check your fuel level?

Cheers

Julian 120316

[Gagarin737]

The main reason for me to install the Moeller fuel gauge is that you can see the fuel level during refueling. You can't see the sight glass during refueling or during flight when you have luggage in the compartment. The mechanical fuel gauge is always visible.