The International Cessna 170 Association

I hope I can get an answer quickly as I am having an annual done now. The A&P who is very familiar with 170's found the rear most mounting holes for the horizontal stabilizer has elongated holes and not the round ones that he is familiar with.

I have look at a past message thread and found that it seams there are fair number of 170's with elongated holes but no documentation from Cessna that this is okay. Even though it is obvious that this was done at the factory.

What I wanted to know is --
1) Is there any new information on this subject?
2) What can I tell my A&P that will make him happy and not want to tare the plane apart just to replace this mount even though it has worked fine for years?

Please help me. I don't want to have my plane taken apart and waste the time and a lot of money.

Thanks
Jim Collins
N2488D 1952 170B

There’s been some thought that Cessna for reasons now lost to time, choose to produce tails with an altered design. That’s the best guess now. Those directly involved with present day aircraft manufacture know with each aircraft, there’s a build variance document recording all alterations from the standard build. You would think with present day advances in manufacturing techniques such as laser alignment and 3D computer design, that planes would be clone copies and they are on computer disc. That is until the human gets involved and the reality changes such that no two planes are the same.
Jim, you have done you homework and seen the conversations in the forum’s, so there’s some useful info. I would think an A&P would use some common sense here. Is there evidence of relative movement between the parts? Is there evidence that anything is deformed? Is there any evidence that the fasteners are damaged, as in bent or any heavy scoring?
If all is good, your A&P should be able to reason your airplane is good to go.

Jim rell your mechanic to call Del Lehman in Mena AR. His phone number is in directory. Del should be able to help him feel comfortable on this issue. Good luck

From what I have personally observed, the elongated holes are made that way, not worn that way. Cessna did it at the factory. Many examples are out there flying with current annuals.

I say this with some reluctance, but I would be changing my A/P . If he was very familiar with 170,s he would know this and know how to research such a issue .

Ouch

I think it very premature to have an opinion of the IA. He knows what he has seen and has not seen this and his immediate reaction is something must be amiss. Jim has come to a larger knowledge base for info and luckily we have some experience with it. It would be nice if we had an absolute answer, but we don't. But our collective has shown this must be a Cessna produced and slotted part as there are just to many accurances of it showing up.

What we hope is that Jim's IAs concerns are dispelled once he sees the evidence and evaluates his knew knowledge.

Be very careful when reassembling the hor stab. I have those elongated holes in my aircraft and didn’t have a clue originally , when I was originally rebuilding my aircraft where to align the hor stab. At this,point in time we had not heard of the 170 association . However if we aligned it full down in the holes the aircraft flew very slow and trim was way out . It flies just right with hor stab aligned mid way in the slotted holes plus there is [on my aircraft] 2 very small holes ,one on the hor stab and the other on the bulkhead that line up together . Like a witness hole . Was it put there by the factory ? I do not know but it works .so when in the correct position they line up so a piece of thick lock wire can go from one side to the other. Plus those shims [could swear but I wont] are totally impossible to put in the correct position . So they are super glued to the hor stab in correct position. Looking back on our project that was the hardest part of the job and “nearly “ the most expensive . Cessna wanted over $800 for those internal wrenching NAS bolts . This nearly killed the project . We had a couple of other share owners at the time and they didn’t want to spend that sort of money. They wanted to fit other type of fasteners that were not legal . I was the guy signing for the rebuild ,many heated words and I ended up buying a share . It was about 4 months of stale mate [work stopped] and I found a work shop that had about 400 of these NAS bolts . I paid $9 for the lot [4 of required] with all correct paper work .

Late response: The horiz attach brackets came in two flavors... Those with round holes and those with elongated holes. This was likely done to facilitate assembly and if examined closely it becomes obvious that the elongated holes are symmetrical and intentional... not worn or altered. I have examples of both in my hangar junk box.