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Fuel Tank Mods - With A Twist

C

Catbird

Well Known Member
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?
 
Catbird said:
Any differing opinions?
Click to expand...

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).
 
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.
 
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/community/showpost.php?p=638229&postcount=4
Joe Gores
 
simple

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.
 
How does changing the sight glass out for something else affect the E-LSA certification?
 
Snowflake said:
How does changing the sight glass out for something else affect the E-LSA certification?
Click to expand...

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.
 
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
 
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.

IMG_2031.JPG
 
Gagarin737 said:
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.

IMG_2031.JPG
Click to expand...

Although my fuel tank is still on the workbench waiting for the sealant to cure, after looking at a friend's -12 sight glass, I agreed with his statement as well as Gagarin's that it is useless during refueling and hardly useable for pre-flight check. I am wondering though if for refueling some contraption using a miror could help. This would require just to view the top 3 windows, i.e., those to check when topping off. the mirror could hang from the top of the tank and reflect toward the filling neck. Just an idea...
 
Fill the tank

When would you not want to fill the tank? I always aim to fill the tank. Minimises the risk of condensation, and you can always estimate the amount of fuel used based on time flown. I typically fly at 100+ knots at 4700rpm burning 16 or so litres an hour. I calculate based on 17 litres an hour. The float fuel gauge is my backup indication, and the contents based on the fuel flow is my second backup indication.

Cheers...Keith
 
gblwy said:
When would you not want to fill the tank? I always aim to fill the tank. Minimises the risk of condensation, and you can always estimate the amount of fuel used based on time flown. I typically fly at 100+ knots at 4700rpm burning 16 or so litres an hour. I calculate based on 17 litres an hour. The float fuel gauge is my backup indication, and the contents based on the fuel flow is my second backup indication.

Cheers...Keith
Click to expand...

I think the problem is over filling the tank. You can't see the fuel level down the neck.
 
Fuel Tank mods & refueling

WingedFrog said:
Although my fuel tank is still on the workbench waiting for the sealant to cure, after looking at a friend's -12 sight glass, I agreed with his statement as well as Gagarin's that it is useless during refueling and hardly useable for pre-flight check. I am wondering though if for refueling some contraption using a miror could help. This would require just to view the top 3 windows, i.e., those to check when topping off. the mirror could hang from the top of the tank and reflect toward the filling neck. Just an idea...
Click to expand...

Actually, the sight window is not intended for use during refueling since it can't be seen from the starboard side at all. Even if you could see the sight gauge and even if you have the Moeller gauge on top of the tank, it won't register the top gallon or two, putting the last gallon or so into the tank is the problem especially if you are using 100LL out of an av gas refueling pump. Those nozzles put out a fast flow that is hard to control and the opening on the 12 will just spray out fuel if you are not super careful. With a hand pump setup you can go very slow at the final last gallon and actually hear the fuel coming up into the filler neck. When away from my home airport and using an airport filling station I place a thin rubber pad over the filler opening to avoid the chance of a spill on the lexan window:
i-THp7KKJ-L.jpg

The picture shows the pad in place and my home base refueling setup. I normally run on car gas from the local Chevron.

The point of all this being that even with the Moeller gauge in the tank, please be really careful putting in the last couple of gallons to avoid fuel burping out on you and the airplane :eek:.

Without the Moeller gauge, a quick glance at the Dynon fuel gauge before shutdown will tell you how much fuel you will be putting in (obvious, I know).

Regarding preflight, if you look at the sight glass window, you will NOT see the fuel since the fuel is clear. If you place your hand on the trailing edge of the wing and gently shake the wing up and down while looking at the sight glass you WILL see the fuel bobbing up and down (obvious, again), unless the tank is chock full.

All that said, I am seriously considering installing a Moeller gauge since I have to pull the cover off the tank to do the Service Bulletin reinforcement. But by gosh I would be keeping my sight glass, so I can visually check my fuel at preflight.

I don't think I have driven the thread off topic since the point of the thread was installing the Moeller ;).

Tony
 
Dip stick

I agree - the sight glass is next to useless. And I too can also hear when the fuel level has reached the bottom of the filler neck. I have a moeller fuel guage installed. But I always rely on my old fashioned dipstick when I do my preflight or to know how much fuel the tank will take when I refuel.

The tanks are all the same. so the dipsticks should all be the same. Except mine is in litres.

I know Tony at Pt Macquarrie has one too.

Mine is made from a flexible plastic tongue. The joiner that goes between sheets of particle board flooring. Mark the divisions with an automatic centre punch.

Anybody else use a dipstick?
Rod
 
Dipstick

3/16" dowel from Aviation Dept at Home Depot. Darker color wood shows fuel level better. I beveled one end to use as a cap pry device. Pencil markings in 2-gallon increments. Pretty high-tech.

Jim
RV-12 N233TX
flying 98 hours
 
Rod is almost exactly right...

Rod is almost totally correct. He feels that the sight glass is almost totally useless; when in reality it is totally useless. The Moeller guage unit is the only smart way to go.

Carrie and I do quite a bit of cross country flying and when we do we try and plan 200-250 mile fuel stops for two reasons. First, my bladder range is less than my airplane full fuel tank capability and 2) I really like to have a 1.5-2.0 reserve aboard when cross country.

I carry a couple of folding nice plastic gas cans that I can use to buy premium uleaded enroute (that's what courtesy cars are for) and the line staff have never complained about an ice-cream sundae on return (nor has the pilot).

Whe we fly less than 2 hour legs we rarely top off the tank...why carry around the extra weight...and the Moeller reading full is over 15 gallons in our airplane. When we aren't going cross-country, our dog Harriet almost always occupies the baggar compartment and she weighs about 45 lbs. after we stop for the $100. hamburger..

I look at the Moeller before every flight...I use the Moeller whenever I fuel the aircraft and I read the Moeller inflight any time I am showing under 6 gallons on the Dynon reading. I am wayyyy more trusting of the Moeller than any other method of determining my fuel onboard.

Jay Sluiter
N124CS
550 hours on the tach
Love our Moeller...
 
Mind telling me where you got the folding gas cans? I need a couple myself.

Threetracker said:
Rod is almost totally correct. He feels that the sight glass is almost totally useless; when in reality it is totally useless. The Moeller guage unit is the only smart way to go.

Carrie and I do quite a bit of cross country flying and when we do we try and plan 200-250 mile fuel stops for two reasons. First, my bladder range is less than my airplane full fuel tank capability and 2) I really like to have a 1.5-2.0 reserve aboard when cross country.

I carry a couple of folding nice plastic gas cans that I can use to buy premium uleaded enroute (that's what courtesy cars are for) and the line staff have never complained about an ice-cream sundae on return (nor has the pilot).

Whe we fly less than 2 hour legs we rarely top off the tank...why carry around the extra weight...and the Moeller reading full is over 15 gallons in our airplane. When we aren't going cross-country, our dog Harriet almost always occupies the baggar compartment and she weighs about 45 lbs. after we stop for the $100. hamburger..

I look at the Moeller before every flight...I use the Moeller whenever I fuel the aircraft and I read the Moeller inflight any time I am showing under 6 gallons on the Dynon reading. I am wayyyy more trusting of the Moeller than any other method of determining my fuel onboard.

Jay Sluiter
N124CS
550 hours on the tach
Love our Moeller...
Click to expand...
 
Another vantage point....

I have a lot of cross country flight time in 3 different RV-12's (some of it on trips of 1800+ miles).

I use the site window to verify fuel levels in comparison to the electronic fuel gauge and fuel computer, before and after a flight.

After some experience, it is easy to guess within a gallon or so, what the fuel level in the tank is based on what the level is in the site window.

I have never splashed fuel on me when refueling.
It is easy to recognize by sound when it is getting nearly full without having a gauge to look at. The only time it has been challenging is if a fuel truck is parked very close and is overly loud (only happened once or twice).

I am not meaning to put down anyone that chooses to install a mechanical gauge, but I do think it is a higher level of risk to rely on a mechanical device to confirm a fuel level before flight. (And I do kind of wonder when someone blocks off the site window, installs a mechanical gauge, and then uses a dip stick to verfy the fuel level...... kind of seems like a step in the wrong direction:rolleyes:)

It has been a long time standard to use your eyeball and visually verify a fuel level before flight.
That is the entire engineering basis for the site window... walk up to the left side of the airplane... jiggle the wing while you look at the window... verify that the fuel level is above the 4 gal. minimum fuel for take-off limit... go fly!
 
One gallon? What's the point? I'm going to get low on fuel, land off-airport somewhere, put in one gallon, and continue? Don't think so! Maybe for a car if you have - say - a spouse that likes to crowd EMPTY - but not a plane!
 
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