Fuel Tank Question

[bagarre]

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

That's a good tip!

[wingnut]

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.

What Bruce is suggesting with the vice-grips happens after you remove the tank top. DON'T use a punch/hammer to drive the screw shank down enough to slip skin out; You WILL destroy the nut plate. If you can drill the head of the screw (carefully), removing enough of the shank to slip the tank top out, you are good to go, and then use Bruce's suggestion with vice-grips by griping the bottom of the offending screw, below where it protrudes thru the nut plate (after tank top has been removed, and depending on location you may need to remove the tank). Use the vice-grips to rotate the screw out the bottom of the nut plate.
If for some reason you destroy the nut plate, use care drilling it out. You will notice the heads of the two rivets that attach the nut plates to the spar flange are underneath the leading edge skin, and will cause some folks to scratch their head wondering how to shoot those rivets when replacing a nut plate. Getting these two rivers out without elongating the river holes, or worse, damaging the spar is the critical operation. Best to drill the rivet buck tails from the bottom and let the nut plate fall off. Then you can use a small punch/hammer to drive the rivets upward a small amount at a time to avoid damaging the leading edge skin. Drive the river up a bit, then use a sharp stout "putty" knife to shear the protruding rivet at the top. Wash, rinse, repeat, until the rivets are out.
Now, re installation of the new nut plate and rivets. You can often lift the leading edge skin enough to place the new rivets back into the river holes you just removed the old ones from. In this case, lift the skin, install the rivets, and then slide the nut plate into position on the rivets. Then install a temporary screw to hold the nut plate in place. Don't use a rivet gun. Instead, squeeze the rivets with a rivet squeezer, or a "C" clamp........this avoids pounding on the leading edge skin.

Now let's back up to a time/place before this problem occurred and the screws were damaged. Excellent advice was already given above on first using a sharp pick to remove paint from the screw, and also using valve grinding compound that'll help grip. Also, bits come in all varieties. PanAmerican sells the best I know of. They have teeth that grip the screw. I use a Makita cordless light duty impact. Don't know the model but my Darlin Companion bought it for me a few years ago. It's amazing. It works better than those screw extractors that are used with a rivet gun/air hammer. It also helps to use a good penetrant several hours before attempting to remove the screws. There are a lot that work well. We use Seafoam and PB Blaster.
It's always a good idea to run a screw in and out of each nut plate before you begin reassembly. I like using the corrosion resistant "structural stainless" MS27039C1 screws, and putting a little smidge of Boe-Lube on the threads.

[wingnut]

Thanks Arayana.........it is not difficult after you've done it once. Anybody can do it. I'm well aware of first time instruction. It's helped me many times. If I can pay it forward to save a skin, or some bodies skin. I will.

[c170b53]

When I first saw this post, I thought of Del right away and the likelihood he would have the best answer. Thanks Del for the extra info once the damage has been done.

[mdsmith]

All of this is great info: thank you. The EZ-out recommended to me that I first attempted to use is called a "Grabit." I couldn't get it to drill into the screw head. Trying the traditional EZ-out approach, I then broke off a small diameter drill bit in a screw head to be a pilot hole for an Irwin Hanson #1 (final 5/16 inch drilling) extractor, but I did not use any oil when drilling (a mistake). I have been able to slightly turn this screw, but very little. I switched my approach to slotting heads with great success for about 12 screws. Only these two screws remain. (I do not have Jim Wildharber's procedure. Where can I find it?)

Let me recap the present scenario. One screw, as mentioned above, has a small drill bit broken off in the shank. This screw has been slotted, but the slot is presently worn. After applying Corrosion-X and several-day soak, I have been able to slightly turn this screw, but very little. (I might be able to carefully dress and clean-up the slot edges with the Dremel grinding tool, then use a slotted screw driver with an appropriate edge thickness that would lock into the slot better.)

The other screw was also slotted and now has half the head sheared off the shank. I am considering creating a flat on the head, opposite to the other flat so to create surfaces that I can get vice grips to clamp onto: very tedious process. Beyond this, looks like a drill out would be forced, trying an EZ-out in the process.

IDEA ? I used Corrosion-X as a penetrant before now. I understand it is non flammable. Would applying heat with a soldering iron (portable propane type) to these screws at their center-heads be a viable solution to loosen them? The aluminum skin would be heated some, around the screw head; would this create a problem in changing the Al metal properties? Properties of 2024-T3 online suggest it being safe for application of 200-300 degrees F for a few minutes, with "solution" (precipitation) temperature of 493 degrees F, but I'm not an expert in metallurgy. Also, I don't know if any prohibitions from the FAA exists on doing this? Would 200-300 degrees F be sufficient to loosen the screws? This idea may not feasible, but I it never hurts to ask. If not feasible, I could try application of another penetrant.

I'm also brainstorming for possible ways to get the broken drill bit shank out of the one screw, if all else fails.
I look forward to your comments.
Mike

[ghostflyer]

Never go near a aircraft with a propane soldering iron. About 30 years ago when working in a shop some half wit thought he would heat up the heads of some screws on the main spar to remove the panel that covers the fuel tank. Yes he removed the panel in one fowl swoop and nearly killed everybody in the hanger. The screws were rusted in and really bound in . But he forgot about vapour fumes that stay in the tank area. there is a drain in the filler neck that drains directly over the tank . This is supposedly to keep water away from the filler cap. However when refilled to the top some spills into this area and drains over the tank and cavity. The fuel in the tank didn't ignite [or I wouldn't be writing this ] but the wing was totalled.
mouse milk is the best for removing screws or automatic transmission fluid mixed 50/50 with acetone.

[170C]

Jim Wildharbers procedures should be within the 170 site but I don't know specifically where. Mmaybe Bruce or Jim or other members can post how to access those procedures. I don't recall that they address stuck screws, but maybe he did. Jim's step-by-step method is very well set out.

[jlwild]

Frank, the pictorial procedures can be found in The MX Library, on section titled "Fuselage, Wings, and Tail Section", and topic "Fuel Tank Removal (55 B model). Bruce posted the information for me as I lack his computer skills if some one could post the link here it would be great.

[170C]

Thanks Jim. I was just trying to get our member with the fuel tank issues to access your data as that is what he really needs to follow in order to have a successful conclusion to his project (in my opinion). He has had some issues with stuck screws in the leading edge and I don't recall if you addressed those issues or not.
Frank

[mdsmith]

Thanks for the advice. To be clear, the issue of gas vapor fumes was not overlooked. The area in and around the empty tanks, etc. have adequately ventilated and devaporized for a sufficiently long time. But with the risk scenario you mention being even remote, I'll try another penetrant to be safe.

Thanks for the link. Jim, did you address stuck screws in your procedure?

Mike

[jlwild]

Thanks for the advice. To be clear, the issue of gas vapor fumes was not overlooked. The area in and around the empty tanks, etc. have adequately ventilated and devaporized for a sufficiently long time. But with the risk scenario you mention being even remote, I'll try another penetrant to be safe.

Thanks for the link. Jim, did you address stuck screws in your procedure?

Mike

Mike, Yes I did, the slide show pictures show the highlights and "bullet comments" on fuel tank removal issues. I believe joining the 170 Assoc. And having access to the Members Only section will provide you with information worth far more then the cost of dues. The MX library contains a wealth of documentation and information. Jim

[Bruce Fenstermacher]

But specifically Mike, Jim's procedure does not offer any more secrets for removing screws than we have already shared. Though looking at pictures might give you ideas.

Bruce