Tinnerman nuts

Briar Rabbit

Briar Rabbit

Line Up and Wait
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Albion, Nebraska
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Rob
We have a couple of tinnerman nuts on the tailcone with one side of the internal metal flap broken off. The screws going into the nut hold ok if we use an oversize screw but then they do not match the rest of the screws in the access panel. To replace the nuts it is necessary to disassemble part of the horizontal stabilizer/elevator and also the vertical stabilizer/rudder, costly. It is not really a safety factor as if the screws do fall out it does not affect the structure and the several screws still there adequately hold the inspection panel. If the A&P does drill out the tinnerman nut I am told it will fall into the tail and not be retrievable, does not sound like something I want bouncing around in there forever. Anyone experienced this problem before and have a simple fix that does not cost 5 figures for two tinnerman nut replacements?
 
Briar Rabbit said:
Anyone experienced this problem before and have a simple fix that does not cost 5 figures for two tinnerman nut replacements?
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Aircraft type? IPC diagram where these nuts are located?
 
Cessna single engine, access panels at the base of the vertical stabilizer and inboard edges of the horizontal stabilizers on the tailcone.
 
Briar Rabbit said:
access panels at the base of the vertical stabilizer and inboard edges of the horizontal stabilizers on the tailcone.
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Are you talking about the fairing strips at the dorsal/vert fin to fuselage junction (Fig 11, Item 30 below)?
http://www.vac.flights/index_htm_files/Cessna_C210K-Parts-Catalog.pdf

Are they this type of tinnerman?
upload_2021-3-16_13-55-2.png

And you can not see the backside of the broken ones through the tailcone aft belly panel? Or when the tailcone aft fairing/stinger is removed?

What type of nutplate will be used to replace the tinnerman once drilled out?
 
I am 70 miles from the airplane so I am dealing from memory. I believe they are shown in figure 13 items 60 and 61. And yes I believe them to be the type of nut you pictured in your post. Apparently not all of these nuts are visible from the back side of the skin and requires quite a bit of disassembly to get to the back side of a couple of them. I know this A&P has replaced some other ones that hold these fairings in place previously but apparently there are a couple that are not easily accessible. So we are wondering if there are any alternatives? Appreciate your thoughts!
 
You run a long piece of lockwire though the hole and nut and work it around until the far end comes out of the elevator pushrod hole or whatever other opening is handy, then twist a knot in the wire at the locknut end. Then you drill out the two rivets and pull the nut out of the elevator pushrod hole, with the knot making sure it comes. That wire has to be long enough that it doesn't disappear into the screw hole. You put a new nut on the wire and make a knot behind it and pull it into place, lining it up with a small awl, and secure it with 3/32" flush Cherry rivets made for this purpose. Then you remove the wire.

It ain't impossible at all.

Edit: I think these are the rivets: https://www.aircraftspruce.ca/catalog/hapages/CCC32cherryRivets.php?clickkey=3009160
 
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I received another suggestion with a similar technique only to use weed wacker string instead of safety wire. The suggestion was the OD of the string is close to the ID of the tinnerman nut and makes it easier to maintain control of the loose nut.
 
Briar Rabbit said:
I received another suggestion
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You'll find there are quite a few tricks out there. Others include using magnets, unique hardware set ups, modified mechanical fingers, extensions using SO tubing, etc. The key is to ensure your trick set up also provides a path to get the new part in as well if needed. And don't forget the old-fashion find a small guy to crawl down the tailcone too. Good luck.
 
[QUOTE="Bell206, post: 3060568, member: 31758". And don't forget the old-fashion find a small guy to crawl down the tailcone too.[/QUOTE]
When I worked in engineering at the Cessna Wallace plant (twins) in 1973 we occasionally would have to crawl down the tail cone to measure something. And of course it was always the new guy stuck with the task. So out to the factory and try to find a partially completed bird that no one was working on. It never failed that you would get to the very rear of the tailcone on your hands and knees and a pair of riveters (or more) would magically appear to buck some rivets on that big megaphone you were inside. I think the plant guys watched the new guy with the clip board crawl in there and timed it for the most effect! o_O Could not help but wonder if it was a planned initiation - sure taught you to wear hearing protection.
 
Bell206 said:
And don't forget the old-fashion find a small guy to crawl down the tailcone too. Good luck.
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There is a film available on YouTube, produced by Ford, which tells the story of the Willow Run plant that built B-24s during WWII. The plant construction was nothing short of miraculous. The land was originally used as a farm by Ford, and it took just 18 months to place the mile long production line in operation. The numbers are staggering. For example, there were over 15 miles of piping in the airfield subsoil drain system.

But to the point, the film shows the production line in operation, and when the outer wing panels were mated to the wing, little people, or "midgets", as the film called them, worked inside the wings to effect joining of the parts.

In mid 1944, the plant was rolling out a completed B-24 every 50 minutes. The original Consolidated Aircraft factory in San Diego needed days to accomplish the task.
 
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