rudder hinge point cracks

[Keith M Johnson]

That is my theory also that it was wind gust lock induced. It has signs of a gust lock installed at the top hing point pushing both sides of the skin in some.

[snellbob]

Keith:
Did you repair the rudder spar at the hinge point? If so, any pics?

[GAHorn]

In discussions with a good sheet metal man in FTW he mentioned that he's seen cracks in these areas when the airplane has been used extensively in flight training, especially if training SPINS. This might be due to the rigorous use of rudder in anti-spin recoveries.

[wingnut]

I will start giving this area more attention during inspection. I received a call from a fellow this past week with the same problem. I can't remember if he was a member, nor his name . He preferred to replace the spar rather than repair (which I agreed could require some thoughtful engineering, and even then would likely take more time than simply replacing the spar. A few minutes on the phone, and digging in the 170A and B, and Cessna 195 IPC's show the part numbers for the spar to be exactly the same for these models. I suggested to this man to call The 195 Factory. I have not heard back from him if he was successful in getting one of their PMA spars, and I don't presently have access to my IPC's (deer season presents some limitations). But I suggest to all, the best method of repair is to replace the spar (which is also the leading edge; a one piece roll formed L/E spar).
I will post the part number, and contact info Monday if someone else doesn't get to it first.

Edit to add, I think I made certain the 195 rudder spar PN# was identical to BOTH the "A" and "B" models 170's, but certain it was the same as his 170 model he was calling me about. I will verify on Monday that it is the same for all.

[snellbob]

Hello to all:
Del that was I that mooched 20 minutes of wisdom from you last week. Thank you for your valuable time!
After searching high and low on the web and talking to the 195 factory I have not been able to find a spar. 195 factory does not make the spar currently so I have to repair it.
After consulting a sheet metal shop close by it looks like the plan of attack will be open the skin on one side, cut the rib out behind the spar, install a doubler in behind the spar and then repair the rib that was cut out. Sounds easy but it always sounds easy!!
Will provide pics when I can.

[n2582d]

In addition to the front rudder spar, p/n 0333132, being identical on the C-170A, C-170B, and C-195, it is also common to the C-170 and the L-19. Air Repair's online L-19 IPC shows the part in the illustration 161-13 but skips it in the text. So I wrote Pete and he said, "the spar is the same. no new ones available but we do have some nice drill off units."

[snellbob]

Pics attached that show the repair to the rudder spar crack in nearly the same location as Keiths. A "U" channel doubler was formed and installed behind the spar so that hinge alignment would not be impacted. Just a few rivets were removed from the skins on both sides in ordered to slide the doubler in behind the spar. Note that the rib behind the spar was cut to facilitate this and then a repair to the rib was done as well.

[snellbob]

Pics. Note stopdrilled crack at top of hinge block.