Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle - Stab

How to keep the Cessna 170 flying and airworthy.

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c170b53
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by c170b53 »

Del, You understand what I'm thinking but gee wouldn't there be an easier way to make this adjustment.? So as much as I like my theory, I don't understand why the fitting can be found on various s/n 's in a somewhat sporadic fashion. We might find it easier to determine the why if we could create a map of the serial numbers and the type of holes in this fitting from a majority of members. With that info we might better understand the why and if the change meant some other form of change that goes hand in hand with each hole type.
My tail is apart right now, I might try playing with it to see what the real world results are of moving the horizontal stab forward. Anyone have dimension's of the slot?
Jim McIntosh..
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by c170b53 »

Digging in and digging out :D ( Yes Gary I might have to yell for a smaller shovel :oops: )
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Swixtt could you have a look at your rear horizontal stab 's lower aft attachment point and advise whether those (your) attachment holes are elongated ? In trying to solve the mystery of some holes elongated and some not, I tried moving my stab fore and aft and as Del and I thought it's obvious it changes the pivot point of the elevator aft bellcrank in a big way and thus will affect the elevator travel.
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by wingnut »

Interesting information;
The Cessna 195, Cessna 170, and Cessna 170A, all use the same elevator pylon PN# 0310262. The 170B uses pylon PN# 0534107
The Cessna 170 and 170A use the same elevator push/pull tube PN# 0510111-2. The 170B uses push/pull tube PN# 0510111-5. The 195 uses tube PN# 0310174-3
All of the 170 series use the same horizontal attachment angle PN# 0512108-5. The 195 uses attachment angle PN# 0312108

I do not know what the differences in these parts are. Cessna changed the angle of incidence of the horizontal stab beginning with the B model. The 170 and 170A are -4 degrees. The 170B is -2 deg 48 min. I have heard from a couple members that they have noticed an obvious difference in the vertical position of the leading edge of the hor stab in relation to the fuselage closure skin lap. It was rumored that when Cessna moved their jigs from one building to another, the jig was not set up correctly, and that some aircraft left the factory with incorrect angle of incidence. This would cause a problem with rigging the elevator travels, as the A and B models are different; The A model is 28 up and 17 down, the B model is 26 up and 20 down. Being able to move the horizontal stab fore/aft would allow correct adjustment of elevator travels on the aircraft that were built incorrectly, if this mistake did indeed occur (it may also have been possible to install an A model pylon on a B model, or a B on an A, to permit correct travels. Who knows what happened.........)
As to the elongated holes in the attachment brackets, which seem to be sporadic throughout the years these planes were built, all I can offer is these aircraft have been damaged and repaired, some numerous times. It is not a stretch to assume parts have 'traded' throughout 7 decades of service history. I don't know the answer, but I am not at all concerned about the elongated holes, and in fact I like being able to fine tune the symmetry.
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by wingnut »

Aryana wrote:Regardless of the approval issue that's been discussed, if you're not concerned with the brackets with elongated holes Del, then I believe we have no issue with safety on the fleet of 170s that have this style of bracket IMO.

The explanation you give above seems quote plausible. It's interesting to try and figure out what actually happened to put these brackets on some of the fleet. I bet there is someone alive who was on the assy line when this happened and knows the whole story!
Imagine the effect of a fuselage or tail feather jig being set up improperly. Then realize, Cessna didn't have just one or two, or five jigs......... They likely had a couple dozen or more to crank out these planes in that post war era. If just one jig was set up wrong.........just one out of 10 or 20 jigs used to build these series planes, then I can fathom a notion that this problem we are discussing could skip serial numbers, and appear random. Someone, likely a principal, called a meeting of the brightest and most open minded individuals. In my minds eye, I see less than a handful of Cessna's best behind closed doors.........and I'll bet they solved a problem over a cup of coffee and a fine cigar, in a few hours, maybe less.
As a child, and even still as an old phart, I dream(ed) of being able to go back in time. It'd be awesome to know so many things about the past......long gone.
But then, we wouldn't have so much to post about here.
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by c170b53 »

No concern here.
I too thought of those working at the time of the builds but doing the math I think it's unlikely we would find someone who would know. As for those no longer with us, I'm not sure if they are having a small chuckle now at our dilemma or busting a gut.
Jim McIntosh..
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by n2582d »

c170b53 wrote:Digging in and digging out :D ( Yes Gary I might have to yell for a smaller shovel :oops: )
Back to this post http://www.cessna170.org/forums/viewtop ... tor+travel
Swixtt could you have a look at your rear horizontal stab 's lower aft attachment point and advise whether those (your) attachment holes are elongated ? In trying to solve the mystery of some holes elongated and some not, I tried moving my stab fore and aft and as Del and I thought it's obvious it changes the pivot point of the elevator aft bellcrank in a big way and thus will affect the elevator travel.
Jim, The discussion you linked to above tried to solve the mystery of incorrect elevator travel. We theorized incorrect pushrods, pylons, etc. The mystery ended unsolved. It seems to me that this thread may very well close the loop on that discussion. That said, I don't think the purpose of those slots in the attach angle are to adjust elevator travel. As others have said, the slots are there to align the rudder pivot points. On the B model Cessna changed their method of alignment (or maybe added a second way of aligning the rudder hinge points?) by adding a shim behind the bottom rudder hinge, p/n 0512000-60. (Fig. 25-28). The earlier models IPC's do not show this shim.
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by c170b53 »

I thought hard on that one as well. Not sure it's the answer because as you mention a simple shim or shims solves the problem. But you could be correct.
Jim McIntosh..
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by c170b53 »

I've thought myself into many corners, its nothing new to me, but here's more with respect to my last post ( but help me out if you think I'm stuck again :D ). It appears that the slots allow for the HS to be moved forward which would move the vertical stab forward as the VS is fixed to the top of HS and shimmed at the forward attachment point. Rudder misalignment could be cured and obviously was with a shim at the lower rudder attachment point moving it aft, no need to move the VS/rudder upper attach forward.
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by wingnut »

Of the many qualities required for_______________, persistence is the ticket. If I had a torch to pass, I'd be passing to you, Jim :D
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by c170b53 »

Del, I went to school and studied electronics when Bill and Steve were just coming out of their garages. I decided at that time there wasn't much money to be made in computers, left the field and carried on as a mechanic for an airline. I have over time suffered a somewhat flatten forehead over that call. :D When I was an aircraft apprentice, I did quite a bit of flashlight holding, it does teach patience. Persistence..ah that I'm not sure of.
My plane has been rebuilt numerous times as noted in the logs, no doubt not all the repairs made it to paper. Again if my machine had this type of fuselage fitting, it would not bother me in the least. Much like Del said, those that have a straight machine, should consider themselves very very lucky.
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by GAHorn »

Showboatsix wrote:... , documentation from Cessna says they did not do it ....
That's not what was documented. What was discovered was the existence of one dwg that indicated round holes. That does not prove they "did not do it" in other examples. Cessna often modified assy's and sometimes even created dwgs that support the mod. (And on several encounters it's been well-accepted that Cessna no longer has a complete library of dwgs on this airplane model. They call us on such matters from time to time searching for lost data.)
The two angles I have are elongated and round. Neither appear to be modifications, but instead "as built". I doubt anyone but Cessna made these things and it appears they made them both ways since we have both types.
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by Showboatsix »

gahorn wrote:
Showboatsix wrote:... , documentation from Cessna says they did not do it ....
The two angles I have are elongated and round. Neither appear to be modifications, but instead "as built". I doubt anyone but Cessna made these things and it appears they made them both ways since we have both types.
And what data did you use to come to your "expert" conclusion?
If there was a large block of continuous serial numbers that had elongated holes then I might consider that your expert conclusion is a correct one, however since they are hit and miss with wide gaps of serial numbers I doubt that Cessna modified onesie twosies and heresie theresies and sent them out the door to the unsuspecting customers like that!
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by wingnut »

Showboatsix wrote:
gahorn wrote:
Showboatsix wrote:... , documentation from Cessna says they did not do it ....
The two angles I have are elongated and round. Neither appear to be modifications, but instead "as built". I doubt anyone but Cessna made these things and it appears they made them both ways since we have both types.
And what data did you use to come to your "expert" conclusion?
If there was a large block of continuous serial numbers that had elongated holes then I might consider that your expert conclusion is a correct one, however since they are hit and miss with wide gaps of serial numbers I doubt that Cessna modified onesie twosies and heresie theresies and sent them out the door to the unsuspecting customers like that!
It is inappropriate to think todays rules and "logic" are the same as back then. Remember, the FAA did not exist, and government looked to the private sector for solutions, unlike today where the private sector must get some alphabet agencies blessing before performing a minor change or "fix" such as described here. Although the linked article is not related to this specific subject, it is aviation related, very interesting, and gives the reader an idea of how things worked back then. I think it is highly likely Cessna altered these angles, as required, for the purpose of adjusting/correcting symmetry issues.

http://www.enginehistory.org/Frank%20WalkerWeb1.pdf
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by Bruce Fenstermacher »

Del hit the nail on the head. While I haven't talked to a Cessna factory floor employee who built our Cessna's, I have talked to those that built Pipers in the 40s and 50s. At Piper, number one was completing a airframe that could be sold at profit. If a minor change was needed to make that happen, it happened. They did not ask a Fed for approval. Many but not all of this was documented and available today not because Piper will supply it, in fact they can't. Piper upon closing their Lock Haven plant ordered all records of aircraft built and many drawings to be disposed of. Luckily the person in charge of disposing of such material kept it (with permission) and makes it available today. Also because many of their aircraft where sold to the military, those blue prints are in the public domain. Piper would like to deny they ever built a J3, they certainly won't admit they ever changed anything on the factory floor. Fact is people at Piper today don't know. We know better. Do you think Cessna was different?

We have evidence in the angles that changes seem to have been made in production. Try to fit a door from one 170 to another or a door window to a different door and you will quickly realize there was some hand manufacturing and fitting going on on the factory floor. We know, because Cessna engineers have admitted to us, that they don't have access to every drawing of everything they made or did.

What you do with this information is up to you.
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Re: Need Fig.25-24, p/n 0512108-5 Bulkhead Assembly Angle -

Post by hilltop170 »

Just maybe, who knows?, a sub-contractor making one batch of the subject angles might have drilled the holes in the wrong place, and Cessna engineers to save money instead of junking the parts and knowing it wouldn't make any difference anyway said, slot the holes? That would explain why the drawings were not changed. Stranger things have happened.
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