The Cessna 120-140 Association Forum

Just before the old website went down, I asked this question. Never got to read any replies if any so I'll repost. During my annual last month, I found a crack as shown in the picture. Does this down the plane until fixed? What are my choices for a repair? Is it structural?

Yes, it's structural. That panel forms the end for the gear box, the structure about which the rest of the plane is built. It is a very heavy plate, as well, for a reason. That said, I doubt that break compromises the strength that much because of where it is. That damage may be due to improper handling of the lift strut rather than stresses on the airframe.

Have your IA look in AC43.13-1c (I think) and see if you can come up with a repair that matches your circumstances. If you can, that can be used as approved data for the repair. Or, you could replace the whole plate, but it's a compound curve, so you can't just cut one out of a sheet and rivet it in place.

HTH

Thanks. No telling how long the crack has been there. It didn't happen in the couple of months I've owned the plane, but now that I know it's there, I will have to address it. Was hoping it doesn't ground me. Looks like it will take some time to repair. Wondering if there is room behind that piece to install a doubler or something.

That part is not that hard to replace. I did it and as I recall I did it with the gear leg in place. It's .050 thick and structural.

I doubt there is room behind it to install a doubler. You could probably install a doubler from the outside, but it wouldn't be that much less work than replacing the whole part.

As an owner you can fabricate the part, assuming you can't find the Cessna part.

I agree with John C, I doubt that comes from a structural load, most likely it's from somebody being clumsy with the strut. (I could be wrong, do look around the area for other signs of structural damage!! but a "rip" there is typically a human induced error)

Victor and John,
Thanks for the input. Your right, as in I might as well replace the part as opposed to a repair. I know a guy that is good with an English wheel so perhaps he can get the proper curves for me. It is pretty thick metal. .050" huh? I'll have to bite the bullet on this one and just dig in!
Thanks guys...

Mine has a small crack like that that started from one of the screw holes for the closeout panel for the gear. It was stop drilled by the previous owner and hasn't migrated. Mine isn't in the web that connects to the gear box but rather just in the sheet metal. I am going to watch it for now and fabricate a new panel and replace it in the next few weeks when it gets too hot to fly. I will post a picture next time I am at the hangar if I remember.