Fuel Tanks

[Richard Blair]

As part of the renovation of N99997, I removed the 9 gallon main tanks.  Inspection revealed a blue stain around the outlet fitting attachment point on both tanks.  I assumed that it was due to a loose or improperly seated fuel line.  After removing the stain, I found that on each tank one of the rivets holding the fitting to the tank had been replaced by a POP rivet.  This turned out to be the source of the leak.  I drilled out about 30 or so rivets around the fitting in order to lift that corner to be able to buck the missing rivet.  When the interior was inspected, I found that one other rivet had corroded down into the fitting and three or four others were deeply pitted. The tank and the fitting were untouched by corrosion, only the rivets, Why?  I dont't know.  I also noted that the inside of the tank had been coated (sloshed) with what looked like varnish.  Based on the history of this aircraft it may be dried up fuel.  What is important is that the stuff was dried and very brittle.  Rub it with a hand and it would flake off.  Guarenteed to plug up a filter or fuel line.  I drilled out the rest of the rivets, cleaned the inside of the tanks and will replace all of the rivets in all of the fittings. I have photo's of the inside of a 9 gallon tank and if anyone is interested in what they look like inside, let me know and I'll scan them in. Richard Blair  [EMAIL PROTECTED]  415C         N99997 4J6, St. Marys, Ga