The International Cessna 170 Association

Frank, unusable fuel is considered "unuseable/undrainable" in the 3-point attitude.

Started the fuel tank job today. Based on the condition of the rubber strips, the filler cap adapter gaskets, and the vent line interconnect hoses, I don't know if either tank has ever been removed. Both tank bays contained a good amount of red clay dust, maybe from the airplane's early years in LaSal, Utah, near Moab. If they've been removed before, it was a long time ago.

I removed the tanks because of fuel seeping out across the upper wing skins. The fuel gauge corks were shot. The bays were nice and clean, except for the dust. No corrosion anywhere.

Always check in behind that wooden block. I found a heap of corrosion behind mine and also a 170b that was in the shop with a fuel leak had a heap of corrosion also .we ended up replacing a section of spar .

Aft block removed, all clean underneath. Forward block is not removable because its screws pass through the main spar from the front, with the heads in the bay between the wing leading edge and the spar. There's no access. Inspecting the spar under the block would mean destroying the block and inventing a way to affix it from the tank bay side. How do you do it?

We replaced the wood with a hard wood soaked in 2 PAC epoxy glue and used this to position it in the fuel,bay . We had to reopened the tank after a suspected fuel leak report from the owner . The block was still ok after about 340 hours and 13 months . The fuel leak was water after the owner had washed the aircraft and this "fuel" was leaking out of the lower wing fuel bay drain hole .

How did you remove the forward block?

Very carefull drilling of the wooden block in a vertical line until it was split and the corroded screw was removed by a magnet on a stick and string through holes in the leading edge D ribs . I did not personally do the job but but shown the results . I have been told that the wood is often replaced by a hard rubber block and glued into position .

The block should be an "owner produced part" by reverse engineering, of course.

Ok, so I'm not missing something. There is no trick, the forward block isn't removable in one piece, it must be destroyed. Thanks for the details! The aft block is removable if you have long skinny arms. Reaching through an inspection hole forward of the aft spar, I can just get a screwdriver on the screws.

I'm planning to use a self-etching primer and some sort of top coat in the bay and on the tank. What have you guys used for this?

I replaced the blocks on my wings. As the wings were off the plane removing the front blocks was not a problem. If I was to do this with the wings on I would cut off the old blocks, install rivnuts in the existing two .250" dia. holes, and then countersink the blocks for 10-32 screws.

FInally finished the tank job. It was a lot more work than I expected. Nothing very difficult, but a ton of small but time-consuming tasks. I was surprised by how difficult it was to R&R the tank cover skins and the tanks themselves. There's no finessing them, and they don't come out with a single movement. They're both firmly wedged in place, especially if like mine they've never been removed. Be prepared to push and shove to get stuff to do what you want. With all the cleaning, priming, painting, and learning, I probably put 40 hours into it. My 80-year-old mechanic was happy to let me go up and down the ladder!

My contributions to the knowledge base: Put about three inches of blue painters tape on the upper wing skins all around the tank cover skin to protect against scratching during R&R. Use a good quality ladder that fits under the lowered flap. You need to get right up against the wing. It helps to have a two people when reinstalling the tank cover skin.