Metalized Wing fuel tank cover

[6643]

Nonetheless, CAA designee signed it off as approved for return to service in block 6. Block 7 accepted by the CAA aviation safety agent.

OK, that's an older form 337. Does it have anything written on the back?

[dcannon]

Nonetheless, CAA designee signed it off as approved for return to service in block 6. Block 7 accepted by the CAA aviation safety agent.

OK, that's an older form 337. Does it have anything written on the back?

Yes, form ACA-337 (4-52). On the back is block 8, description of work accomplished. It contains a weight and balance table and the text "Fabric removed and 020 metal installed"

[6843]

Dan, Did you have a chance to look to see if the portion (about 3/8") of the tank cover that slides underneath the fuselage top skin is riveted to the butt rib on your plane?

Thanks,
Dave

[dcannon]

Dave, my apologies. Forgot, then got busy, haven't been to the hangar in a while. Im trying to visualize what you are describing. Ive never had the tank cover off in the few years Ive owned it. Cover does slide under inboard panel but confirming whether it is then riveted to the rib I think would require some disassembly?

Does this image help? All PK screws securing the cover

Screenshot_20250823_121151_Photos.jpg (38.39 KiB) Viewed 2114 times

Screenshot_20250823_120819_Photos.jpg (38.25 KiB) Viewed 2114 times

[dcannon]

PS Can I get you this info by removing the wing root fairing?

[6843]

Dan,

Wow! your plane looks great! I don't think you can see anything by removing the fairing. If their were rivets, unless they were flush rivets, you'd see the cabin skin sit off the surface of the wing by the height of the rivet heads. I don't see that in your pictures so I'm thinking it's not riveted. I'm thinking more and more about using machine screws but still haven't convinced myself cutting the threads won't cause spar cracks down the road.

I appreciate your sending the pictures.

Dave

[ken_k]

The 1946 140 I used to own had metalized wings before I installed fabric wings sometime later. The fuel tank covers were attached with screws and the panel slipped under the top skin of the cockpit. The skin was drilled at each screw location with an oversized hole to allow removal of the screws and panel without removing the wings.

[bill_e]

Hi Dave, I went through a similar issue with my '46 140. Per my logs, my wings were metallized with the Ruleto drawings listed in the A-768 TCDS. The cover panels over the fuel tanks had cracks in them last annual, so my A&P and I wanted to replace them. My A&P was very surprised and concerned over the PK screws that we found threaded into the spar caps holding down the front and back edges of the panels and asked me to find documentation substantiating that as an acceptable condition. Since the Ruleto drawings are thus far unobtainium, I got in touch with Victor Grahn about finding any documentation for wing metalization. He was able to get me a copy of STC SA4-89 for the application of .020" 2024T3 aluminum skins to the wings and it specifically calls out installing the fuel tank cover panels with #8 PK screws installed in the existing rivet holes in the spar caps. While it's not the engineering used to actually install the metal on my wings, it is CAA approved data for the tank covers, if nothing else. I still share your concern about the stress risers that threads in those holes may cause, but my wings were metalized back in 1955 and we found no signs of cracks around any of the holes. Reach out to Victor if you're looking for a copy of the paperwork and hopefully that can help you with your issue.

[dcannon]

And more great detail from Mr. Wright:

https://www.cessna120140.com/Forum2018/ ... php?id=179