FYI - All 170 rudders are not the same

[Lopez]

Short story...I am rebuilding a 54 B model that got flipped on its back. Of course the rudder was damaged. It was fixable but I decided to try to find a decent used one. Found one on Ebay for a reasonable price and even though it looked okay, I decided to reskin it since the rest of the rebuild was going to look really nice. I ordered skins from our good friend up in Bow, WA and made it look brand new. I even bolted it on the rebuilt vertical to admire my work while I reskinned the elevators. I finished the elevators yesterday and again was so excited that I decided to bolt them on the airplane as well. I couldn't get the right one installed because the cutout in the rudder for the elevator torque tube is too small. After inspecting my buddy's A model, It turns out that the A model elevator hinge line is closer to the stabilizer spar by about 1" which makes sense because the cutout in the rudder is about 1" smaller on the A model rudder.

I spent a long time researching this before I bought it and searched "rudder" all the way back to 2005 on this site and never tripped on this info so I thought I'd share it to save someone else some headache. My quick reading of the 2 parts manuals tells me that the only difference is the small stub spar located just aft of the cutout. Figure 15 item 26 in my A model book, and Figure 15 item 11 in my b model book, both downloaded from micro-tools. The skins have a different suffix but are shaped the same as far as I can tell. I am debating on whether to just buy the different spar and install it in my rudder or try to find a B model rudder and reskin it. I have been moderately fanatical about my repairs looking original and this one would require about 4 extra rivets per side which 99.9% of the people who saw it would never know.

After reading how that sounds I've decided to just fix mine, I don't need to be that anal.

A few final thoughts...

-My conclusion at this point is that a B model rudder will fit an A model but not the other way around. Their balance specs are identical as well.

-Every 170 rudder I have looked at has cracks around the middle hinge point at the lower end of the spar. I believe this to be due to misalignment of the hinges but that is just my theory. I ran a string through the hinges on the vertical and they were perfect, but the rudder was way out and I had to add almost 1/4" of shim to the upper hinge point under the pillow block to get them straight. Check your rudders because I'm sure there are a few cracked ones out there.

[GAHorn]

The "spar" is actually called the "bellcrank support" and the IPC illustrates that the channel which forms the support is "reversed" with the "open" channel facing aft in the B model whereas earlier supports faced fwd. I presume this is to allow for the torque-tube clearance difference.

A-model PN: 0533000-7

A-model 0533000-7.JPG

B-model PN: 0533000-13 (which will fit either rudder)

B-model PN 0533000-13.JPG

[ccondit]

I've got a 1952 C-170B, and on the rudder bellcrank, it has an enlarged hole on the top of where the centerline bolt fits through. (see atached image, red arrow). The hole is just slightly smaller than the actual bolt head, but larger than the bolt's shaft.

My mechanic tells me we need to replace the bellcrank, which leads me to a couple of questions:

I gave him my C170 parts book, and he came back with a PN of 0433113, which seems at odds with that given here PN053300-13. Can anyone tell which is correct?

He also gave me a prices of about $600 where he could get it - does that sound right? and if so, can anyone suggest where i can get one at a better price?

Also should a washer be placed on the top of the centerline bolt? It would seem to me to provide a braoder wear surface for the bellcrank, but as of now, it doesn't have one on it. Should it have one?

I tried to attach a jpeg image of the bellcrank with an arrow showing the centerline hole I'm talking about, but it didn't seem to show up in this message.

Appreciate any help you all can give me

Chris

[GAHorn]

Sound as if your mechanic has a 100% mark-up on parts.



http://www.aircraftspruce.com/catalog/a ... dderbc.php

Here's where you may purchase a bell crank (PN 0433113) for about $277. (The other part number 053300-13 is for the channel-support, or "spar".) There is no washer beneath the bolt "head" nor inside the bellcrank inside, but there is above the lower nut. Hope this helps.

[Bruce Fenstermacher]

I might be wrong but I believe Univair has the PMA to make these. In any case according to their on-line catalog they sell them for about $3 cheaper at $274.
http://univairparts.com/shopping/advanc ... mit=Search

Your mechanic is probably shopping at Cessna were they list this part at $572.

From CessnaParts.com:
Part No. Description Your Price (Units)
Order 0433113 BELLCRANK AY
(List Price: $ 572.00) Stock Available $ 514.80 (EA)