I have recently purchased a 1961 cessna 172C with the ralph bolen tailwheel stc. During the annual inspection I noticed a crack on the plates that are riveted on to the sides of the tail under the horizontal stab. which hug the sides of the tailwheel spring. The crack is located just aft of the tail bulkhead right where the tailwheel spring comes out of the tail. These plates are mounted on both sides of the tail and both are cracked.

Just by looking at this area of these tailwheel attachment plates ( or brackets ) I can tell that alot of stress is focused on this piont on which the cracks have started. It looks a bit under engineered. With that said im sure im not the only one who has ran across this problem.

I am looking for guidance from any one who has made this repair. It looks to me like some reinforcement plates could be fabricated and bolted under the preexisting bolts to reinforce this area. Im just seeing if any one has had any luck with a repair. Thanks.

No engineer by any means, but wouldn't a larger radius in that corner be better? Seems like a small radius, and cut less than optimal, unless I am not seeing it correctly.

WWhunter wrote:No engineer by any means, but wouldn't a larger radius in that corner be better? Seems like a small radius, and cut less than optimal, unless I am not seeing it correctly.

What the pictures are showing is the tail end of those plates that are riveted on the side of the tail which hug the tailwheel spring. You can see the rudder horn right above it. You are right the corner is cut to a very narrow radius causing this crack to start.

I have the same setup on my 1956 172. I found cracks in the same location about 8 years ago, stop-drilled the cracks and they have not advanced since. Yes the radius is too narrow and I looked at having it repaired, but so far it has not gotten any worse.


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slowhawk wrote:I have the same setup on my 1956 172. I found cracks in the same location about 8 years ago, stop-drilled the cracks and they have not advanced since. Yes the radius is too narrow and I looked at having it repaired, but so far it has not gotten any worse.


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It looks like the stop drill holes failed the first try on this one. How long did the the cracks get on yours before you stop drilled it? Im trying to decide if im going to give it another try.

Both less than an inch, I can get you an exact measurement in a couple days when I get home. I would give stop-drilling another shot, so far mine has held up, as I remember, making the repair was going to be rather expensive


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I would repair it if it were my airplane or if I was doing the maintenance on this aircraft. The first stop drill was worth trying but now the crack is propagating into the meat of the tail bracket and could cause cracking of the underlying sheet metal that the bracket is attached to. If that has or is about to happen, then yes the repairs are going to get expensive and time consuming.

I would also investigate what is causing the cracks and try to correct that problem too. Is it a poor design that patching/beefing up the weak area with solve, is the tail wheel spring/attach hardware/tailwheel loose or out of alignment, or is the tailwheel springs/bearings/tire in need of repair? The tail wheel could be shimmying or cocked sideways when landing or binding when turning. All these thing will cause stress to the bracket and could contribute to the cracks especially if the design is somewhat weak.

It seems odd that those cracks formed there, if the cracks were to propagate further it doesn't seem like a catastrophe.

If you did want to fix it it would be pretty easy to remove the cracked material and fab some triangular doublers that span the gap by picking up a few of those bolts.