Landing gear bulkhead repair

Maintenance, parts and services related to Cessna 120/140's

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Landing gear bulkhead repair

Postby David Sbur » Fri Aug 01, 2003 7:20 pm

Found an apparent <.5" crack on the left 0411495 gear steel attachment during annual inspection (bulkhead plate to a cross webbing). There is a small chance I can repair it by removing the main gear leg (suspending/bracing the fuselage) and getting to it from the outside. Any experiences in repairing this weldment either inside or outside the aircraft? Worse case for me will be to remove a zillion rivets on the inside (and some outside) and lifting the sheet above. Darn, just painted the plane... Comments or words of wisdom? Thanks!

Dave Sbur
N110V, Vancouver WA
David Sbur
 

Re: Landing gear bulkhead repair

Postby Carl » Fri Aug 01, 2003 9:25 pm

May God bless you. You are in for a big job if you have to take the floor panels out. I have heard of people welding them in place with a tig welder. The thing is from what I understand they are heat treated After they are welded up.May God bless you.

Carl
N2488N
Carl
 

Re: Landing gear bulkhead repair

Postby D Sbur » Sat Aug 02, 2003 8:49 pm

Thanks Carl. From what I am finding out it seems to weld properly (my standards) I need to remove the whole fitting. I'll double check on the heat treatment but so far have found nothing on that. Seems the plane did a bad landing in 1981, enough for an NTSB report. Recently found an A&P/IA who caught the old crack and is talented enough to do something about it. Just a bunch of rivets...groan... I will sure check out everything thoroughly while I'm in there!

Dave
D Sbur
 

Re: Landing gear bulkhead repair

Postby Mike Smith » Sun Aug 03, 2003 8:10 am

David Sbur wrote:Found an apparent <.5" crack on the left 0411495 gear steel attachment during annual inspection (bulkhead plate to a cross webbing). There is a small chance I can repair it by removing the main gear leg (suspending/bracing the fuselage) and getting to it from the outside. Any experiences in repairing this weldment either inside or outside the aircraft? Worse case for me will be to remove a zillion rivets on the inside (and some outside) and lifting the sheet above. Darn, just painted the plane... Comments or words of wisdom? Thanks!

Dave Sbur
N110V, Vancouver WA


Dave,

This can be an extensive repair job. To make the job easier gather some additional information from the following individuals:

David Lowe at tele 270-736-5392 or email lowaviate@earthlink.net.

Tom Julian at telephone 850-537-5500. (I think that Tom's email has changed, and I don't know the new address)

Bill Rhoades at pilot140@aol.com. or telephone 952-652-2221.

These gents more than likely have done this job in the past, and can give you some very good information and insight to what you need to do. Rest easily, you aren't the first one to have had this problem.

Mike
Mike Smith
 

Re: Landing gear bulkhead repair

Postby Mike » Sun Aug 03, 2003 8:12 am

Dave,

Dave Lowe's email should be loweaviate@earthlink.net

Mike
Mike
 

Re: Landing gear bulkhead repair

Postby Bill Rhoades » Mon Aug 04, 2003 1:16 pm

I think over half the gearboxes I've seen have been welded and but I haven't heard of any failures caused by welding. They are heat treated and only Cessna has that(official)information. You might want to give their customer support a call.

Bill
Bill Rhoades
 

Re: Landing gear bulkhead repair

Postby Dave Sbur » Mon Aug 11, 2003 2:13 pm

Landing gear attachment woes.

Folks,

If you ever find cracks in your gear attach weldment then be prepared for a LOT of work to repair it. First, you need to remove 3 floor plates: the one by your foot, the one over the gear bulkheads, and the one under the seat. Disconnect the fuel and trim wheel to remove the bulkhead floorplate (drain all the fuel also). This is neccesary to access the rivets that need to be removed (and there are some real big ones in there). Second, you need to shore up your plane as you need to remove the affected gear leg (removal of the leg found the crack to be MUCH worse). I used a telephone cable spool and sawhorse under the main belly of the fuselage with lots of padding. It also helps to level the plane by putting the tail on some sort of drum. A motor hoist attached to the engine provides a little insurance also. You will then need to shore up the wing on the opposite side of the affected weldment and attach a rather heavy weight to it also to provide some sort of security to prevent the aircraft from tipping in the direction of the side without the gear leg. After all this, the wing with the affected weldment will have to be loosened at it's mounts as you will need to remove the jury strut assembly and then detach the strut from the fuselage-the strut unfortunately overlaps the weldment so off it comes. Next, you have some serious rivets to remove, do it carefully. Removal of the weldment found a previously undiscovered small crack. The weldment in my case is to be TIG'd and stressed relieved-no amount of calls to Cessna would provide me any other information. It is steel and apparently not hardened. Now is also a good time to check the bulkheads on either side of the weldment for damage and repair them PROPERLY-my aircraft had some illegal and improper repairs on some cracks in the rear bulkhead. Remember, if your aircraft had a bad landing and crunched the gears you are bound to have some sort of damage. You can choose either to ignore it/look the other way or repair it properly and have the satisfaction of knowing your bird is stout once again. In my case, had I landed cross with a heavy side load on the left gear I would have been asking for trouble. My final suggestion is to seriously look at your weldments with inspection mirrors and be truthful with yourself if you find any damage. Cost me a few grand to repair but it's much better than having a gear fold on me. We are about halfway through the process so if anybody has any comments or suggestions feel free to let me know. Oh, I found out about the previous damage by reading the NTSB reports as suggested in a previous reading on this site-excellent advise by whoever and a little detective work on your part may be of value.

Dave Sbur/N110V
Vancouver WA
Dave Sbur
 

Re: Landing gear bulkhead repair

Postby Carl » Mon Aug 11, 2003 2:34 pm

Dave
I have seen this same work done on a friend's C-120 that is why all I could say is God bless you. Take some pictures of it up on the pads etc. Be very sure and careful about alignment of the gearboxes when you put it back together (very important if you change gearboxes) Be careful with the welding as it can make the gear box bow and twist. You do want it to set level when you put it back on it's feet.

Carl
N2488N
Carl
 

Re: Landing gear bulkhead repair

Postby frank sottile » Thu Aug 21, 2003 9:44 am

I have a 48, 140 that I am in the process of rebuilding. The right gear box was cracked at the tube and bulk head along the weld. The 140 was damaged in a ground loop years ago they tried to weld it up and straighten bulk head but it cracked again along the weld this is a heat treated part and welding on it is not approved repair.This was done long be for I owened it. The best way to fix a gear
box is to replace it which I have done, or send it to an approved repair station where they can do the repairs and heat treat it.

FRANK
frank sottile
 

Re: Landing gear bulkhead repair

Postby David Sbur » Thu Sep 18, 2003 7:30 pm

Well folks, finally after 71 billed hours got thru annual and the gear weldment/bulkhead repairs. Will have pictures soon for anyone interested-I can send them on. Of course some major league headaches to get the repairs legal, proper, and bullet proof but worth it. Will probably need a weight and balance with the additional bracing/rivets! Then again my wallet is probably that much lighter so who knows. Of course now the weldment/bulkhead area is the strongest place on the plane...The worst thing is I missed a heck of a lot of good flying weather here in the PNW!

Dave Sbur N110V
Vancouver WA
David Sbur
 

Re: Landing gear bulkhead repair

Postby Carl » Fri Sep 19, 2003 12:01 am

Dave
Happy to hear you are back up and running. Did everything come out straight :)

Carl
N2488N
Carl
 

Re: Landing gear bulkhead repair

Postby Rick Jorgensen » Fri Sep 19, 2003 12:36 am

David Sbur

I have gearbox issues....

Would you email me at rpjorgen@dcn.davis.ca.us

Thanks

Rick Jorgensen
Rick Jorgensen
 

Re: Landing gear bulkhead repair

Postby Bob Tofsrud » Fri Sep 19, 2003 10:14 am

In regards to the gear boxes being heat treated, They are made of 4130 chrome moly. When it is welded with oxy acetelene it doesn't require annealing but when tig welded the heat is concentrated to such a small area that it requires annealing to relieve the stress in the area surrounding the weld. I certainly would not be afraid of a repair as long as it conforms to 43.13 and is done by a qualified welder.
I heliarced the engine mount for the Harmon Rocket I'm building, before I started the real thing I welded up some test pieces and destroyed them with a hammer. It's amazing what it takes to break a good weld. I've noticed alot of pinholes in the welds on my gearboxes that Cessna built and am a bit surprised they past their quality control even in 1947.
Bob
2388N
Bob Tofsrud
 


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