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The American Aviation 2-seat variations have a very robust fuel tank setup. The fuel is actually carried in the aluminum spar (very safe place for it) so crash ruptures are quite rare. That with the visual sight fuel gauges make for a nice system with no electrical problems. However, I digress.
Take the tank itself, it has an inboard plug (with o-ring) and an outboard plug (with o-ring, fuel neck, baffles, etc) and the spar. These 2 plugs form the tank of the 2-seat planes. The o-rings seal the fuel, the plugs are locked into place with AN bolts into blind nutplates and then the seals are further reinforced with fuel tank sealant.
Here is a picture of the outboard plug with the fuel tank baffles attached (these restrict how the fuel flows in the wing in turns, etc).
Next is a picture of the inboard plug with the o-ring.
Finally a closeup of the outboard plug with the new o-ring.
Additionally while I was getting my guru training under the master, Ken, got the t-shirt and the beers under my belt, at AirModsNW, we had a plane come in that had had the tanks resealed with RTV just a year ago. Now this RTV had swelled with the fuel and debonded making getting the plugs out, so to say, very problematic. Once we had removed the outbaord one (with twisting and pulling attached to the airframe) the inblo0ad one was removed with a 4 x 4 wooden post 8 feet long used as a battery ram to drive out the inboard plug. Most owners care to skip this part of the process.
Here is a picture of the inboard plug after removal with the clear RTV still attached.
Do Not Do This is you reseal. Don;t ask me how I know this! -
Have AA-1B. Fuel slowly disappears from the right tank when parked (~1/2 tank in a week). However, there is no leak showing from the outside. If the inboard plug is leaking, where will the fuel come out?
Ware Fuller -
If the inboard plug is leaking, it will come out the same place mine did… from the center of the fuselage. It will leak into the center spar, where there is a hole to drain from. If it’s leaking that much, I suspect you’d see evidence under the plane.
If you’re not seeing any fuel leaks, I’d suspect you might have the same problem I did… the short length of fuel tubing between the sump drain and the fuel tank sump fitting may have split and is weeping.
In the attached file, the first is the left tank, and you can see how clean and dry it is underneath the hose. The second picture is of the right tank, and you can clearly see how fuel has been weeping and discoloring the aluminum for quite some time.
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I don’t see any attached file.
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Hi, Thank you for the pictures, it is better than the book and easier to understand, my question why dont they recommend PRC (the lighter one for the fuel tank access doors) we wouldn’t have to remove the outboard ends (some work to clean out if you have to remove the inner plate one day) but maybe not as much as removing the outboard end. did anybody tried that or your inputs on it would be welcome.
did anybody tried to remove the inner plate with a succion cup used to install window glass..
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