So close, so close and yet so far...

[spduffee]

Sorry if the title brings back awkward memories of roller skating to the Bee Gees....
I took everyone's advice and went to the airport to day to get 5448C annual'd so that I can quit messing around and fly her. Everything was going well until the IA looked at the back end of the plane. The rudder, painted during the winter, had been removed and was to be re-balanced. That left the rear wide open for inspection. The inspector found a horizontal crack in the aft bulkhead, stemming from the starboard rivet. The bracket assemblyis also cracked on the port side, and I understand this is a very common occurrence on the 170s. I stopped the inspection there, but then asked him to check the major structural components. If he were to find another fault, 5448C would be looking for a new home. As it is, I have no idea how much this repair will set me back. He saw I was pretty shaken up and said, "You could go to another IA, maybe they'll not see it, or not see it as severe. Me, I can't sign it off, sorry." What to do? Can the bulkhead be welded? It looks as though the bracket has been welded already. Are there any STCs or engineered fixes for this? Should I look for salvage parts?
Other squawks included three rivets in the upper door post missing (these corrode and fall out?) and the fuel vent coupling in each of the wing roots. The starboard piece looked like a gerbil with two clamps on it. I swear I jumped when he pointed it out - I thought there was a dead rodent in there....

EDIT: Forgot the pictures.

++170a_pm++ 54.pdf

(76.52 KiB) Downloaded 306 times

AND, when I Googled the part number, I saw the IC170A has several posts on this subject. Apologies. Still, if anyone has any new ideas...

Thank you,

Shawn

[c170b53]

Shawn, we need a p/n or least I need a p/n to follow, looking at the pics how about a from pic before the close up please then I might be able to understand what the scope of the issue is. Just looking at the pics I don't know what part of the tail has that number of bolts in it. Thks

[spduffee]

Part numbers, as far as I know: 0512108-3 Bulkhead fuselage aft Section station 228-687 and 0512125-1 bracket assembly tail wheel mount.
As stated, it seems these two issues plague the 170 owner, and this appears to be nothing new.
Looking at all the bolts, rivets and material in the affected area, it is not as serious as depicted, but I understand, this cannot go addressed. Have towel, will throw....

[Bruce Fenstermacher]

If your mount looks like the one in the IPC page you linked (I assume that is why you linked it) then you have the early bracket which makes sense as it would have been the type that came from the factory up into early '52. These are steel and we have seen them removed and welded.

The Cessna fix was to replace that bracket with the later style. All the parts you will need for that conversion are (where) available from Air Repair. The 'kit' cost about $650 three of 4 years ago.

I can't imagine the rear bulkhead couldn't be repaired with a doubler scheme.

Those are nice close ups but it's hard to tell exactly what parts and where they are located because the pictures are so close. One a bit farther back would give us a better over all picture.

[T. C. Downey]

Other squawks included three rivets in the upper door post missing (these corrode and fall out?)

The bracket in the tail can be replaced pretty easy. But corrosion in the upper door post to wing spar carry thru is very serious. Those rivets are what hold the fuselage to the wing.

[spduffee]

Thanks guys. Attached is a shot further out. We talked about a doubler for the bulkhead, too. The bracket appears to have been welded previously, but I can't tell until I remove it and prep it. Tom, the IA said three rivets were missing. I asked if he saw any corrosion in the spar or anywhere in that area, and he said no, that rivets will opfer themselves first before the metal they attach. I will definitely have someone else look at that. The bummer is, I was really shooting for the California meetup in September... This could take a while.

[Bruce Fenstermacher]

Sorry to have to add to the mess but that bracket was not originally held on with those 15(per side) AN bolts who's heads we see. it was riveted on. So what this means is that someone in the past drilled out the rivet holes for the AN bolts. And what look like at least AN-4 bolts when -3s probably would have worked. The bolts are overkill.

The problem is if you choose to replace it with the upgrade. So of those oversize holes might cause you fits. i might be inclined to repair what you have until you can't repair it anymore.

[spduffee]

Yeah, I think at this juncture I will go with the repair option. You do have to admit though, those bolts do add a certain ruggedness to the tail... Thanks for pointing that out. There are a number of repairs that were done to the craft a long time ago that are perfectly acceptable, but a bit shoddy on the detailmanship.

[c170b53]

Tom's concerns are valid if the rivets he refers to are the same rivets that you are having an issue with. Again another pic of those rivets from a small distance might help in this discussion. If we are discussing the rivets which Tom refers to, they may appear to be sound visually but their true state might be best verified physically with an instrument such as a hard plastic scraper.

[c170b53]

Ok, I've worked too much this week and I went to the football game last night soo my typing and thinking are a bit ....I guess neither are fast at the best of times.
I'm all for making it work but the issue of the horizontal crack may be a result of insufficient edge distance. Those bolts look as right in place as the bolts in Human Munster's neck...err.
If that's the original bulkhead it's likely on the inside the edge distance on the flanges would be close to nill. As for workmanship, It wasn't done by someone with a real licence. Sorry to be so negative but a knowledgable inspector would take one look at that and wonder about other wonders yet to be seen.

[T. C. Downey]

Tom's concerns are valid if the rivets he refers to are the same rivets that you are having an issue with. Again another pic of those rivets from a small distance might help in this discussion. If we are discussing the rivets which Tom refers to, they may appear to be sound visually but their true state might be best verified physically with an instrument such as a hard plastic scraper.

The major problem with the row of rivets that hold the door post to the spar carry thru, is that the corrosion is inside the spar carry thru and can't be seen on the outside of the assembly. When the head of the rivet falls off the entire rivet has been eaten away, and the spar carry thru is in need of a very good inspection. The only way to replace the rivets and to inspect the carry thru is to remove the top cabin skin. Every time I have done this due to the rivets being missing, I have found the carry thru needed to be replaced.
To do this replacement, the wings must be supported and the forward spar bolts removed, the wind screen must come out, and the cabin top skin removed all the rivets that hold the carry thru to the door post must be removed and a new carry thru installed. My lat work order totaled $7500.00 for parts and labor.

This is a major safety issue.

[spduffee]

Well, there goes any hope i had left. Thats more than i can take on and i'm going to have to pass this on as a project plane, i guess...

[T. C. Downey]

Well, there goes any hope i had left. Thats more than i can take on and i'm going to have to pass this on as a project plane, i guess...

You and I need to talk

[c170b53]

Shawn, please provide a pic of the rivets in question if you have time.

[spduffee]

Here is a photo. You are looking at the starboard side of the top of the door post/spar carry through, looking up.The backside of the rivets are still there, for what it's worth....