Elevator Deflection

How to keep the Cessna 170 flying and airworthy.

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n2582d
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Re: Elevator Deflection

Post by n2582d »

c170b53 wrote:... I got to think the wrong part is installed somewhere beginning with the aft crank, the rod (now ruled out), the control horn and the attachment points of that horn. After that what's left? other than the elevators themselves. dimensional checks of these parts would help steer the thread.
This is an attempt to "help steer the thread." As these are different part numbers I wonder if it is even possible to accidentally interchange them. If it is, does the angle from the pivot point to the control rod mounting hole change? Tim has the correct amount of travel, it's just not divided correctly above and below 0 degrees.
Gary
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jlwild
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Re: Elevator Deflection

Post by jlwild »

Check if part Fig. 25-11 & -12 is installed correctly. This elevator Bellcrank stop can be rotated to change deflection angle.
Jim Wildharber, Kennesaw, GA
Past President TIC170A (2010-12) and Georgia Area Representative
'55 170B, N3415D, SN:26958, O-300D; People's Choice '06 Kelowna, B.C., Best Modified '07 Galveston, TX, Best Modified '08 Branson, MO.
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GAHorn
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Re: Elevator Deflection

Post by GAHorn »

n2582d wrote:Depending on where you look there are differing numbers for the degrees of elevator travel. The TCDS says 26 up and 20 down, The 1952 C-170B owners manual adds some tolerance by stating on page 52: 26 degrees up +1, -0, and 20 degrees down +1, -0. But take a look at the illustration. This must be a cut and paste from the 170A manual which slipped by the proofreader.
The attachment Unknown.jpg is no longer available
Swixtt, As your down travel is OK but your up travel is 6 degrees short I would start by confirming that the elevator rear bellcrank (fig. 67-36, p/n 0510108) in the tail is hitting the up stop. If it is not, it could be that the forward elevator bellcrank (fig. 67-1, p/n 0510159) is hitting the forward elevator stop (fig. 21-86, p/n 0713497-1 now revised to p/n 0713497-3) located on the gearbox cover. The stop bolt, fig. 21-87, p/n 0431141-1 has been revised to NAS428H3A12. This bolt is unusual in that it has UNJF threads.
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I was perplexed as to the purpose of this second up stop. The answer is found in the 100 series service manual on page 8-6:
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This stop bracket is missing on my '52 rebuild project and there is no evidence of rivet holes on the landing gear box cover where one would have been. I may have a cover from a 170A or maybe Cessna didn't add this stop until later serial number 170B's.
Gary, YOU HAVE JUST SOLVED A MYSTERY I've been working on for 12 years! (Hmmmn....not to mention startled me!)

I have a NOS, Chromated PN 0713497-3 which the previous owner/rebuilder of my airplane handed me when I bought the airplane. He said to me, "If you ever find out what this is and where it goes... let me know." :lol:
PN0713497-3.jpg
The UP movement of my yoke did indeed slightly-touch the backside of one of my gyros until I re-located it during a dual-gyro modification.
Now I have to go check my gearbox.

Just goes to show... no one knows it all!

Thank you, again!
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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n2582d
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Re: Elevator Deflection

Post by n2582d »

George, Glad I could help solve the mystery. I am curious whether this part is common to all 170B's or whether they introduced midstream in the production. If you're not planning on using the stop I'd be interested in buying it (depending on the price).
Last edited by n2582d on Wed Feb 15, 2017 2:55 am, edited 1 time in total.
Gary
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johneeb
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Re: Elevator Deflection

Post by johneeb »

Gary and George,
Just completed this years annual and because of this thread I looked for the pictured stop and can report that 25501 does not have one installed.
John E. Barrett
aka. Johneb

Sent from my "Cray Super Computer"
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c170b53
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Re: Elevator Deflection

Post by c170b53 »

I'll look at mine but I'm pretty sure, this stop has not been fitted. It's definitely in the IPC but as we all know, it can cause hair loss at times.
For another member, I recently contacted a wrecker as they had just obtained a fresh 170B to part out. The 170 owner needs parts to rebuild her gearbox, so I inquired as to whether the entire gearbox could be purchased. Yep no problem but sit down, they wanted 9500 Canadian for it. Seems they cater to the 180 crowd and according to the wrecker the gearbox is the same for the "B" as the early 180 and hence the price. Not all the parts are the same but most of the parts can be interchanged between models, thus the question.
Gary could your gearbox on your project possibly be a combination of parts, some newer than others ?
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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n2582d
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Re: Elevator Deflection

Post by n2582d »

c170b53 wrote:... Gary could your gearbox on your project possibly be a combination of parts, some newer than others ?
Yes, the double row of rivets on the angle that attaches the outer gear bracket to the lower skin is indicative of a 180/185 part. This is what I have on the left side. I believe the right outer gear bulkhead on mine is original; it just has a single row. My gearbox didn't have the four circular doublers on the front and rear bulkheads. I've had to fabricate these. I wonder if these are like the control stop -- something that was added to later aircraft in the production run?
Gary
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c170b53
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Re: Elevator Deflection

Post by c170b53 »

Gary I saw the post with the double row and your dilemma in determine which side was right, so my question wasn't really a stretch. I guess a better question from me would have been, how much of the gearbox area do you think has been changed ?
Regardless it's a great catch on your part :D . Now it would be great to have others have a look so that the collective group can determine at what point this part might come into play in rigging a plane.
To that end, I'm guessing the part might live in the tunnel forward of the trim wheel and could been seen resting atop the gearbox top surface. Is that close ? And if so lifting covering up on one side of the tunnel should be all it would take for an owner to confirm whether the part is there.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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c170b53
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Re: Elevator Deflection

Post by c170b53 »

Ok, First 25656 does not have this part and as the 180 came out in 53 I doubt it will be found on earlier 170 s/n's.
I had to look at a 180 today to see where this fitting is located. If it can be found on a 170,(and possibly it will be) it will be located forward of the forward elevator bellcrank and when looking at the picture provided by George the stop faces aft (aircraft forward would be to the right in that picture) and the elevator torque tube from the control T runs underneath the hat section of the fitting to the bell crank. The IPC suggests (at least to me) it's at the front of the gearbox but the fitting is positioned in the middle of the top plate of the gearbox. If you had to replace this part riveting it in would be, well, not too good.
Again if folks could think of looking at their planes, look inside the tunnel, atop the gearbox, just forward of the trim wheel and see if you can solve one of our mysteries.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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n2582d
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Re: Elevator Deflection

Post by n2582d »

c170b53 wrote:Gary ... how much of the gearbox area do you think has been changed ?
Hard to say. I'm guessing it was replaced piecemeal rather than as a whole unit. Frustrating that they didn't primer the parts -- especially the steel angles -- before they repaired the gearbox.

Here's a shot from the right (copilot) side looking inside the center tunnel where the stop would go. The landing gear box cover is off. Note the trim wheel housing above the tunnel. As Jim said, the stop assembly would straddle the push-pull tube. As noted here the IPC has the bellcrank 180º off in the vertical axis. I also see that they show the wrong end of the push-pull tube attached to the bellcrank. It should show a slot "cut" deeper for the bellcrank to clear at full deflection.
Up is forward - sorry, can't rotate it
Up is forward - sorry, can't rotate it
Elevator bellcrank.JPG (40.96 KiB) Viewed 27581 times
Bellcrank.jpg
Bellcrank.jpg (33.85 KiB) Viewed 27581 times
Last edited by n2582d on Fri Feb 17, 2017 1:59 am, edited 1 time in total.
Gary
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DaveF
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Re: Elevator Deflection

Post by DaveF »

No elevator bellcrank stop on my airplane. S/N 26498, late 1954. No sign one was ever installed.
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ghostflyer
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Re: Elevator Deflection

Post by ghostflyer »

It was a very good point of n2582d about the bell crank that bolts the 2 halves of the elevator torque tube together. I was building up a tail feathers of a 170A and had major issues during the reassembly of this area. The elevator torques tubes and and bell crank bolted together ok??, but the pitch change rod would not align . A inspection panel was cut on the under surface of the fuselage for easier access. After 2 days [yes 2 days] we couldn't work out why the pitch change rod was mis-aligned .every thing was removed that could be and a part number check of all components was done .Some parts had been paint striped and 2 pak silver painted which didn't help th cause . A TEMPERORY spacer was made up,between the pitch change rod and the horn to see if the travel was there . The elevator travel was no where were it should have been . Rigging was checked from the control column back many times but with the same result. Enter the 4 th day . The tech rep from Cessna was brought in for a look. HE spent about 4 hours on the job and consulting with his company with photos emailed etc etc . Cessna came back that the fuselage was twisted. B..l Shi..How come the horizontal stab and vertical fin are at 90 digs to each other . [The vertical fin is off set too] By this time we were using a laser to measure the angles of the horizontal stab and cord lines etc ,it was all good . We didn't have another 170 or a early Cessna to compare . We had a early Cessna 180 on the field so it was look time with this aircraft. It has similar bits so the build up was being examined . It was noted that they are very different in part numbers but the principal is the same . Then the penny dropped with a crash. That pitch change horn that we were trying to fit was a Cessna 180 pitch change horn as it was the same shape and dimensions . BUT It was slightly different . OMG 3 persons on this job for this period .it was the only part we couldn't identify with a part number due to painting ,we assumed it was the correct part. Back to the paint shop and the painter had this bin of lost parts . In it was the pitch change horn . 4 hours later the job was finished correctly . I "me" had grabbed the wrong part off the drying rack after the painter had finished .

"Speedy"the painter was painting some parts for a customer of his that came from another airfield .
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c170b53
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Re: Elevator Deflection

Post by c170b53 »

Or maybe some other twists :D Cessna, use this part until exhausted then use this part or this part superseded by.....
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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DaveF
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Re: Elevator Deflection

Post by DaveF »

n2582d wrote:
elevator_bellcrankrsz.jpg
elevator_bellcrankrsz.jpg (63.36 KiB) Viewed 27502 times
Here's a shot from the right (copilot) side looking inside the center tunnel where the stop would go. The landing gear box cover is off. Note the trim wheel housing above the tunnel. As Jim said, the stop assembly would straddle the push-pull tube. As noted here the IPC has the bellcrank 180º off in the vertical axis. I also see that they show the wrong end of the push-pull tube attached to the bellcrank. It should show a slot "cut" deeper for the bellcrank to clear at full deflection.
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Mine looks just like your photo. When the yoke is full aft and the elevator hits the up stop, the bellcrank is all the way into the slot. There's only about 1/16" of travel left before the bellcrank hits the slot end, which could be done with a harder pull on the yoke, stretching the cables (as George noted). The bellcrank stop would need a very fine adjustment to make the bellcrank and elevator hit their stops simultaneously.
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GAHorn
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Re: Elevator Deflection

Post by GAHorn »

Once again.... just proves how/why the IPC is not an approved document... It's only a "parts-ordering-catalog". (Glad I have all the parts, including the one I don't need.) :?
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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