Fuel Tank Question

[GAHorn]

By George, George, I think you are right regarding the Scrubbing Bubbles slowing down the airplane However, there still remains that question, never resolved, of which plane it slows down "the most", a red one or a green one Must be that having the belly so slick, shiney & clean that the air somehow is attaching itself to that surface for a longer period of time just so it can admire how nice it really is Maybe we can get our resident rocket scientist, Miles, to give us a better explanation of this via some formula

I'm afraid to bring this subject up again. (Joe is much better connected than I these days, and likely in a better position to influence such things.)

(I still don't know how he managed to get a green robe.)

[170C]

The green robe---Joe has connections in higher places

[flyguy]

By George, George, I think you are right

AAAAAAAAAAAAAARRRRRRRRRRRRRRRRGGGGGGGGGGGGG!!!!!!!!!!!!!!!!!!!!!!!!!!!!
GEORGE RITE????????????????????????? OOOOOOOOOOOOOHHHHHHHHHHHHNNNNNNNNNNNNNNNNNNNNNNOOOOOOOOOOOO

[mdsmith]

As this seems to be the same or similar assembly for my 1957 C172, have a related question about removing frozen screws. Two, one in each wing won't budge. The popular EZ-out from Lowes didn't work for me. I ground slots in the others after the Phillips head stripped. I expect to lose the heads of these two remaining screws trying to get them out. I'm not sure what type of anchor nut is used along the rear of the leading-edge when these two are located, but I am wondering if a punch could be used to push the screw shaft done to clear the fuel cover plate holes, assuming an NAS444-5 is used. The longer screws along the leading edge might indicate this type of tinnerman anchor nut is not correct: unclear in the parts manual. Please comment as possible.
Mike
King George, VA

[DaveF]

Bathe them in penetrating oil for a week or so, then try a left-hand drill bit. You'll either drill out the screw or the vibration will cause it to loosen and back out. That worked for me, removing rusted screws on my old Cherokee.

[mdsmith]

I have used Corrosion-X hoping it would creep under the head and down the screw. There is a drill bit broken off in one screw -- may not be able to drill into it. The other screw has half the head sheared off flush with the skin. Perhaps Liquid-Wrench would creep better. The anchor nuts are not assessable directly inside the wing.
Mike

[Bruce Fenstermacher]

Mike, I'd just try to get the screw head off the two then lift the skin up over them. Once that is off you can see the nut plate and perhaps more penetrate oil and a vice grip in the screw left going out the bottom will remove it and leave the nut plate in tacked. 'work for me on a few of the screws.

[c170b53]

Bruce sounds like this is a screw in the leading edge area where you can't get at the nut plate. Those that took in Benton Harbor might remember during the MX session how a front spar corroded due to a loose screw / nut plate working. This might be expensive.
Tank screw removal is a job you never rush.

[170C]

Might try some Mouse Milk to hopefully loosen the threads.

[edbooth]

As this seems to be the same or similar assembly for my 1957 C172, have a related question about removing frozen screws. Two, one in each wing won't budge. The popular EZ-out from Lowes didn't work for me. I ground slots in the others after the Phillips head stripped. I expect to lose the heads of these two remaining screws trying to get them out. I'm not sure what type of anchor nut is used along the rear of the leading-edge when these two are located, but I am wondering if a punch could be used to push the screw shaft done to clear the fuel cover plate holes, assuming an NAS444-5 is used. The longer screws along the leading edge might indicate this type of tinnerman anchor nut is not correct: unclear in the parts manual. Please comment as possible.
Mike
King George, VA

The nut plates used for the fuel tank covers are mostly AN366F832.

[mdsmith]

Thank you, Bruce, but Jim is correct. Both screws are along the leading edge, one on each side of the airplane. (See my first posting.). There are screw locations that are worse than others for a stuck screw: this location is one of the worst. It does't look like the skin could be raised high enough to allow the tank cover thickness to clear over the remaining screw with their heads off. I doubt that mere skin thickness would allow me to get vice grips on the screw, even if space were to exist for the end of small pliers. As a side note, it looks like working the cover out with three edges having skin over the tank cover edge is going to be bit tricky, even with all screws out, although I am sure it can be done.

Jim, believe me: I haven't rushed getting theses screws out. I don't know why theses two have not wanted to budge. Is there a threaded nut plate in this location? The parts manual is not clear. Due to all these screws along the leading edge being longer, I expect they are going through a spar. Should I try using Kroil (with the expectation of lifting paint)? I 'm thinking liquid wrench would be the next safer penetration oil to attempt. What is the worst case scenario if I end up not being able to get these two screws out? (Typo in the original posting: "done" should be "down.")
Mike

[170C]

If memory serves me, all the screws in the fuel tank cover go into nut plates. No, you likely won't be able to lift the leading edge sufficient to slide the cover up & over the screw shank. In my opinion, and I have been there, you will have to drill out the screw (s) even if it ruins the nut plate. You can replace the nut plate later with the tank out. The tank cover will slide out once all screws are removed. I don't remember if you have access to the step-by-step procedures that Jim Wildharber developed, but that is THE way to accomplish this task.
If you are going to remove the fuel tanks, be sure to remove or cut the hoses on the fuel tank vent tube before attempting to remove the tank itself. When I removed my tanks, the hoses were old and hard--difficult to even cut with a kitchen knife due to the limited access. I failed to remove the short piece on one of the vent nipples and when I managed to lift up the outboard back corner of the tank, I broke the vent line nipple on one of the tanks. Be careful!

[c170b53]

Mike, I sometimes get visual progress focused thus my comments. I'm not suggesting you rushed this, I only know, generally the first shot at these screws is the best. I always use an exacto knife to pick out the paint and junk out of the screw recesses (wear eye protection). If I think it needs juice, I soak and leave it work on the screw. I like using a rattler but it's easy to apply too much pressure and do damage. Last resort; if the Phillips head slots have opened up, I will use a sharp small drill and an easy out knowing that a shallow precise hole is required. The peril here is if either break they are virtually impossible to drill out.

[c170b53]

Re-reading Mike's post, sounds like his approach is no different from what I might have done. Not sure what easy out your using. There's two types I use, I'll try to find them and post a pic: both are or were available from Aviall. One uses a socket and the other uses a tap wrench for which I substitute needle nose vice grip pliers.

[170C]

Another tip-----put a little valve grinding compound on the screwdriver tip. This will help it gripe the screw head.