rudder hinge point cracks

[Keith M Johnson]

is there an accepted fix for the crack that occors nears the middle hinge point on the rudder. I read about alingment of the hinges being a problem and to check that. Is it something to be concerned about. will it continue to crack futher.

[Bruce Fenstermacher]

is there an accepted fix for the crack that occors nears the middle hinge point on the rudder.

First I've heard of the rudder cracking there.

[bagarre]

Welcome to the forum!

You can't post pictures directly to the forum unless you're a paying member of TIC170A

But if you own a 170, joining the Association is a really great idea!

[edbooth]

Wonder what caused this crack? Been a 170 owner for 43 years and in the club since 1977 and don't believe I have ever heard of a crack at this location. Something must be bent focusing stress here ?????? Be nice to see picture.

[Keith M Johnson]

The aircraft with the rudder hinge crack has had apretty rough life. It was all but destroyed in a bad ground loop early in its life where it got B model Tail section still has A wings. It belongs to my nephew while he has had it he was doing something bad on a landing and broke the tail wheel spring damaging the lower rudder skins. I was replaceing the skins and found the crack quite by accident. I unbolted the middle hinge to get it out of my way and under the left bolt just outside of the bolt hole was a crack about .5 inches long going vertcal in the main spar and lower rib. I would have never seen it had I not removed the hinge. It is possible to see with a mirror looking at the skin edge near the hinge. You will have to clean the area good to see it very well , I think you can see it with the rudder installed. In the B model parts manual pg 28 fig 75 bolt# 21 just outboard of bolt hole from bottom of spar to just above hinge assembley

[Bruce Fenstermacher]

Keith, I guess we'll all be running to the hanger and checking ours close.

As for doing something bad and breaking the tail spring, your nephew may have been. But you don't have to do anything bad to break that spring, that we know about. They break, it just a matter of time. We tell folks to change them every 500 hours no matter what to help avoid what your doing at 4 times the expense.

Please it you wouldn't mind. Send a picture of the crack to my email listed below my name so we can all see what your looking at. Hopefully we find your crack to be the only one in the fleet.

Thanks

[Keith M Johnson]

Sent you some pictures have been inspecting the area can't really see any other problems. I have heard the tail wheel springs can be a problem. we installed the heavier spring in it. It has been working good I don't have much time in it but it seems to handle ver nice. I have time in Champs, Citabrias, luscombs introduced my son and nephew to the joy of flying in the champ it was alot of fun. I had'nt been in a taildragger for about 7 years but had no problem with the 170. Thanks for an help you can offer. Keith

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[Bruce Fenstermacher]

Here are the photos of the crack Keith sent me.

IMG_3645-resized.jpg

IMG_3644resized.jpg

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And I think we are looking at the area behind part 19.

[Bruce Fenstermacher]

BTW Keith that thicker main spring is a L-19 spring. They break as well, I know. I broke one.

[edbooth]

Here are the photos of the crack Keith sent me.

IMG_3645-resized.jpg

IMG_3644resized.jpg

IMG_3643-resized.jpg

IMG_3642-resized.jpg

Screen Shot 2013-02-24 at 8.56.41 PM.png

And I think we are looking at the area behind part 19.

From the look of that rivit on the right, it looks like someone attemped a repair there before. I think I would fashion a doubler in the back, re-rivit , check the alignment of the hinge points and if Ok, reinstall and get to flying....thats only IMHO based on the facts I have.

[jlwild]

Keith, is corrosion also present under the Rudder Hinge (Fig. 15-19)? Is that a stop drill hole at the end of the crack? Is the Rudder-Intermediate rib (Fig. 15-18) also cracked where it attaches to the Rudder Hinge? Hopefully not, but these were my thoughts as I looked at the expanded photos. You may need to remove the rudder skins (Fig. 15-31/32) to see if more damage and/or corrosion is present.

[Keith M Johnson]

There dosent seem to be any corrosion in the rudder. I stop drilled the crack. Looked at putting a doubler in behind the spar. The rib is cracked same as spar. The crack doesnt go thru the radius of the rib the affected area seems to be near the bolt hole on the side. The bolt was tight when removed. The lower rudder skins have been changed before. I'm thinking along the lines of a doubler just behind the hinge to the rib in the hinge mount area and keeping a close eye on it for awhile. See what happens, I removed that rivet installed a new one.

[GAHorn]

There are some suggestions for rudder gust-locks made in certain references (i.e. the SRAM, The 170 News, etc.) to use "blocks" of wood or other devices wedged between the rudder bellcrank and the stop-bolts, as a method to prevent excessive movement of the rudder while the airplane is parked/tied-down.

This sort of idea has always horrified me because of the intense stresses which may be placed upon the rudder hinges due to leveraged forces when the rudder is blown about. If you use your imagination, it's sort of like attempting to prevent a door from closing by placing your fingers between the door and the door frame at the hinges. OUCH!

Eventually something will break. In this case, the hinge brackets (Item 19 in Bruce's illustration) will have to absorb the intense forces, and pass that along to the rudder spar. It looks to me as if that possibly is the source of the stresses leading to the cracks in this picture. The hinge is only attached to the spar by those AN3 bolts, and yet if the rudder must move in the breeze while the hinge is bolted to the vertcal ...then something must give...in this case the thinner material of the rudder spar to which the hinge is bolted.

It's only a theory...but I believe that, or something similar, may be what contributed to this damage.

Rudder spars and other components are becoming quite rare and expensive. Do not used blocks in the bellcrank area as a rudder gust lock, nor use any clamps in the upper counterbalance-to-vert.stab area, as that will damage the upper rudder. Use gust locks which grab the rudder at it's trailing edge in the area of the nav light....(best, in my opinion)......or use the type which limit rudder movement by locking the rudder pedals in the cockpit....(less desireable due to the stresses imparted to the rudder control-cable/pulley system.)

The lower rudder is also at risk to damage from broken tailwheel mainsprings and broken tailwheel attach bolts and/or castings. The tailwheel, now loose from the mainsprings, yet still captive by the steering chains, will serously damage the rudder while it flails about during takeoff/landing, ...and the cost of rudder repairs will be far more than regular, preventive maintenance/replacement of those tailwheel attachment-parts.

(Replace tailwheel mainsprings, tailwheel attach bolts, and completely remove, disassemble, inspect/overhaul tailwheel assemblies every 500 hours/cycles, is the club recommendation.)

[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?