The International Cessna 170 Association

During the annual inspection on my "53 C170B, my mechanic found intergranular corrosion in the left side, outboard landing gear bracket. (page 40 diagram #47 part number 0713495 of the C170B parts catalog). The corrosion and crack that developed from it is significant enough to warrant replacement. I have already ordered a replacement part from P-Ponk, but I am wondering if anyone has made this repair, and, are there any tips or deep dark secrets, to make this repair as efficiently as possible. I searched the forums and did find some discussion about this issue, but nothing concerning the actual repair process. Any advice would be appreciated. By the way I just paid for my TIC170A membership for a couple of years since P-Ponk gives an association discount! Thanks again TIC170A!

N8293A wrote: By the way I just paid for my TIC170A membership for a couple of years since P-Ponk gives an association discount! Thanks again TIC170A!

And besides you have to be a member to be on the board making big bucks.

Sorry to hear that Steve, your machine is a beauty

Thanks Jim and Bruce I only hope there is someone who has made this repair and has some words of wisdom to pass along. I really don't want my maintenance folks learning as they go! Here is a picture of what got us digging deeper. This is looking at the outboard face of the bracket. The really telling view is after they removed the gear leg and seeing the slot the leg slides into. The top of the lower edge of the slot was split open. More to come.

Generally I believe that's what I've seen happen when iron oxide is mechanically worked into an aluminum alloy, dissimilar metal corrosion sets up corrosion which runs through the grain structure of the extrusion and eventually the part fails. Likely a good reason to make sure that the wedges are checked tight and preventing any relative movement between the parts during your annual. As well all these parts should have some surface protection.
Steve it would be interesting to know the condition your gear leg's surfaces where the gear makes contact through the fitting/wedges and whether there was relative movement between in the parts.

N8293A wrote:During the annual inspection on my "53 C170B, my mechanic found intergranular corrosion in the left side, outboard landing gear bracket. (page 40 diagram #47 part number 0713495 of the C170B parts catalog). The corrosion and crack that developed from it is significant enough to warrant replacement. I have already ordered a replacement part from P-Ponk, but I am wondering if anyone has made this repair, and, are there any tips or deep dark secrets, to make this repair as efficiently as possible. I searched the forums and did find some discussion about this issue, but nothing concerning the actual repair process. Any advice would be appreciated. By the way I just paid for my TIC170A membership for a couple of years since P-Ponk gives an association discount! Thanks again TIC170A!

This link Might help you visualize the issue.
http://www.cessna170.org/forums/viewtop ... ox#p118176.
In any case you will need to remove (drill off) the upper cover or lower skin over the gear box to gain access. P-Ponk has a little video on his there web sight of how the P-Ponk gear beef up kit works that shows the arrangement of all of the parts. The are a number of issues to be addressed with riveting parts that have to be installed. In any case I would Give Steve Knopp a call at P-ponk and ask to discuss it with him as he has done this a few times.
Regards,
Jim

Thanks Jim and Jim for the advice. We will definately contact Steve at P-Ponk for some tips. Jim I will try to take some pix as we go along, including the area at the top of the gear leg and the wedges. I believe you are right Jim, there is/was some movement in that area that set about this process.

IIRC, the outer landing gear bracket is riveted to the cabin floor and belly skin and bolted to the two bulkheads immediately fore and aft. Several years ago I converted a C182 to a C180 and remember having to remove the belly skin and peel up the cabin floor to gain access. I don't know you'll have to do all that, but suspect you may. The good news is that it's mostly grunt work you can do yourself under supervision. If you know or can learn how to rivet, you'll be miles ahead money-wise. Good luck!

Dave

Well the repair is well underway. Thanks to those who chimed in. Most importantly thanks to P-Ponk for supporting our aircraft, and our association. The replacement bracket is of high quality and the advice from P-Ponk has helped this process go relatively smoothly. I tried to upload some photos but they are all too large. Here is a link to photobucket where photos of the parts can be viewed.
http://s328.photobucket.com/user/smcgre ... .jpeg.html

Wow, you're making great progress!!

Dave,
Thanks for the encouragement. Although I can't take much credit for the repair. Other than cheerleading and taking photos, I am leaving this repair to the pros. I know my limitations and I have a great shop here at the airport where we live. So this is in their hands.

Steve, was the corrosion bulge on the inboard or outboard side of the bracket? How did you find it?

Are you doing both gear or only one? Do you have a picture of the new P-ponk part, it would be interesting to see a comparison of an original bracket and P-ponk's version.

Dave,
Inboard side, and during the annual the mechanic used an inspection camera just to take a peak inside the gear box area. The first picture in the post shows the crack that caught his attention. This was reason enough to pull the gear leg and have a more detailed look. At that point we saw the bulge caused by the corrosion, and also caused the crack.

John,
We are only doing one side. The inspection of the right side showed no anomalies. Their is a picture of the new part in the photobucket link. The new part is beefier, and rather than a stamped or extruded part, this part is milled from a solid block of aluminum.

How did you jack the airplane? Do you have a picture of that?