New 170B owner

How to keep the Cessna 170 flying and airworthy.

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hilltop170
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Re: New 170B owner

Post by hilltop170 »

I don't recall anything in the manual but just-taught with no slack is what I have always been told and have used with good results. This leaves the most positive control without undue stress on the rudder horn because of too much tension or any dead zone without steering authority if there is slack. When the tailwheel leaves the ground, tension increases in the springs and puts downward bending stress on the rudder horn. I have seen broken rudder horns due to too much spring tension held over time. When necessary, adjust slightly tight vs. slack or twist like Gene suggests to get zero-slack/tension. The steering is bad enough as it is without introducing any extra slop.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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gfeher
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Re: New 170B owner

Post by gfeher »

I couldn't have said it any better than Richard (hilltop170). But if you need to show your A&P documentation, show him/her the Scott 3200 Installation Instructions for the 170, which you can download from this thread http://cessna170.org/forums/viewtopic.php?f=40&t=8168. It says:

"NOTE: Tension on connector springs not required or advisable. Use sufficient chain links to remove slack in each connection assembly on installation."
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
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GAHorn
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Re: New 170B owner

Post by GAHorn »

hilltop170 wrote:...When the tailwheel leaves the ground, tension increases in the springs and puts downward bending stress on the rudder horn..
I heard this many times and simply couldn’t believe Cessna would do that to us, so at the Branson Convention Steve Grimsley made that comment and I determined to see if it’s true. So, with Steve’s airplane on the ground we saw his chains were “taut” and no slack and no steering-spring stretch. We measured the distance from rudder-horn to steering-arms. He then got on all fours and, with his back, LIFTED the fuselage until the tailwheel was IN THE AIR. Guess what? NO DIFFERENCE!

The tailwheel descends, but IN AN ARC (after-all, it IS attached to the tailwheel mounting bracket with leafsprings that DO NOT lengthen) and the steering springs remained EXACTLY TAUT with NO SLACK, and no additional tension on the steering springs or steering arms. The distance from the rudder steering horn and the tailwheel steering arm DOES NOT CHANGE.

AS for the recommended tension on the steering chains: Think about this. If the chains are NOT TAUT.... how the hell are they going to STEER? Small rudder inputs will have NO INPUT until the chains are taut and pull on the tailwheel steering-arm.

The tailwheel steering chains should be TAUT (no slack) but not so taut as to place any stretch in the steering springs.
'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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Bruce Fenstermacher
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Re: New 170B owner

Post by Bruce Fenstermacher »

Once again George, you and I will not see eye to eye on this. We've been round and round on it before.

While they may have all left the factory with the same geometry, changes in tail wheel parts since then mean the geometry changed. The biggest geometry change is the myriad of tail wheel springs that are now installed. There are so many variants from over the years that not even the PMA manufacturer is absolutely sure.

One of my two 170s got tighter when the tail wheel is lifted of the ground. Might even be both of them. I'm also not surprised you and Steve saw no difference. I tell folks when adjusting the springs there should be no tension or slack. As that is difficult to attain side on the slack side with the wheel on the ground in case your geometry gets tighter when the tail wheel is off the ground.
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rnealon1
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Re: New 170B owner

Post by rnealon1 »

Thanks Guys,

As always I appreciate all the collected experience.

Bob
Bob Nealon

Southbury, CT
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GAHorn
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Re: New 170B owner

Post by GAHorn »

Bruce Fenstermacher wrote:...One of my two 170s got tighter when the tail wheel is lifted of the ground. .
Then I’d reply your system was likely not original or is out-of-specification.

One likely difference is wear-and-tear (and perhaps mfr’g differences in a PMA leafspring...which by the way, would mean the PMA is NOT MET because by definition a PMA’d part is a dimensional exact replacement to the OEM. (My own 170B has a Spruce/Univair/PMA’d main leafspring and it behaves exactly as I just described like Steve’s.)

If the owner has changed his steering-chain/spring from the OEM version... yes it will introduce differences. That is one reason to do it as Cessna/Scott intended and as depicted in their manuals/instructions and to use only approved parts.

But suppose the leafspring has lost it’s shape and the tailwheel is riding higher than normal because of a weak leafspring and the owner adjusts his steering chains “taut”.... or suppose the leafspring is not OEM and is some truck-spring-company replacement... or some other “similar” part.
Regardless...when the tailwheel is ON THE GROUND the steering springs should still be “taut” in order for them to have any input. Otherwise any rudder movement would be ineffective ...until the slack is taken-up.

So what is the purpose of the heavy-duty steering-springs we use in the steering chains?

I propose they are there to accommodate any need for such matters as well as to avoid rudder-system-cable damage in the event of a tailwheel which fails to disengage it’s detent-pawl or in some other tailwheel-damage-event or in the event a twig or grass-clump gets tangled up in that system. (Hitting a limb on takeoff or landing might engage/tangle the steering chains and the steering springs would relieve the shock/tension.)
'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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gfeher
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Re: New 170B owner

Post by gfeher »

If you do as we suggest (no tension, no slack), to the extent the tension may increase when the tail wheel is lifted, it will be negligible and not enough to bend the arms on the tail wheel. (I don’t express any opinion one way or the other on the debate between George and Bruce, other than to say that when I lift my fuselage at the tail end, the tension doesn’t increase in any amount that I have noticed, and certainly not enough to bend anything.) :)
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
hilltop170
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Re: New 170B owner

Post by hilltop170 »

Geometry of the tailwheel assembly installation says the chains will tighten when the tailwheel leaves the ground.

Reality shows there is not enough spring deflection to make any/much difference.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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Bruce Fenstermacher
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Re: New 170B owner

Post by Bruce Fenstermacher »

hilltop170 wrote:Geometry of the tailwheel assembly installation says the chains will tighten when the tailwheel leaves the ground.

Reality shows there is not enough spring deflection to make any/much difference.
Richard, you hit the nail on the head with your first sentence. I would just add under most circumstances to your last sentence.
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n2582d
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Re: New 170B owner

Post by n2582d »

hilltop170 wrote:Geometry of the tailwheel assembly installation says the chains will tighten when the tailwheel leaves the ground.

Reality shows there is not enough spring deflection to make any/much difference.
This discussion was started by Bob Nealon who owns a '54 C-170B which has the later style tailwheel steering system shown in Fig. 65A. Here Charlie has shown that with this style the cable has less, not more, tension on it when the tailwheel leaves the ground. I'm guessing Bruce and Richard are thinking about the earlier style tailwheel steering. The angle of the spring and sash chain more closely parallel the tailspring with this arrangement which would reduce the difference in tension between when the tailwheel is on or off the ground.
Tailwheel back on ground Chains shortened.jpg
Tailwheel back on ground Chains shortened.jpg (142.17 KiB) Viewed 11982 times
Gary
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GAHorn
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Re: New 170B owner

Post by GAHorn »

n2582d wrote:
hilltop170 wrote:Geometry of the tailwheel assembly installation says the chains will tighten when the tailwheel leaves the ground.

Reality shows there is not enough spring deflection to make any/much difference.
This discussion was started by Bob Nealon who owns a '54 C-170B which has the later style tailwheel steering system shown in Fig. 65A. Here Charlie has shown that with this style the cable has less, not more, tension on it when the tailwheel leaves the ground. I'm guessing Bruce and Richard are thinking about the earlier style tailwheel steering. The angle of the spring and sash chain more closely parallel the tailspring with this arrangement which would reduce the difference in tension between when the tailwheel is on or off the ground.
Tailwheel back on ground Chains shortened.jpg
Gary, that pic should help folks understand this better. Thanks for posting.
In that pic, the red-line which Gary depicted demonstrates the geometry when a Scott 3200A tailwheel is utilized. That tailwheel is not the same steering-arm as the one specified in the Type Certificate and which Cessna used. Cessna used the 3200, which has a straighter/flatter steering arm and which is even MORE CLOSELY parallel to the tailspring.

What sometimes happens is that owners or their maintenance technicians, either inadvertently or purposefully, in search of “improving” tailwheel steering will substitute parts not originally intended which can lead to more and more complications to the system. Examples are: Adding more compression springs to the tailwheel friction plates. (The L19 and other aircraft heavier than the 170 use 5 springs while the 170 and other light aircraft use only 3.). Switching to the 3200A (upright) steering-arm in the mistaken belief it will improve tailwheel steering. (This is also sometimes done when owners find their original 3200 steering arm is bent. Scott mistakenly issued some defectively-soft steering arms which were susceptible to bending. Parts-sellers sometimes suggested switching to the 3200A steering arms (believing this would improve things) when the “more-correct” repair would have been a properly-tempered 3200 arm. This switch may be thought appropriate because the 3200A is described as a “Heavy Duty” version tailwheel. Just because something is “heavy duty” does not equate to “appropriate” or necessarily mean “correct for the purpose.” (This thinking is similar to that of “If a little torque on a bolt is good then a LOT of torque must be BETTER! )
The HD 3200A has a different arm because it also has 5 springs instead of the 3 the 170 should use, and it is intended to be used with different geometry/strength tailwheel-bracket springs such as the L19 or tubes such as in the case of the 185.) Another ill-advised attempt to “improve” tailwheel steering is to replace original “heavy-duty” tension-springs in the chain with Maule-type compression springs. This alteration can damage the tailwheel steering system (depicted in Gary’s pic above) when excessive force is inadvertently applied to the steering-cables and rips the pulleys (internal to the fuselage) from their mountings.

Taking care to maintain the two systems (early or late) as originally-designed and avoiding “ad-hoc” field-modifications is the best way to maintain the system and avoid troubles, IMO. There is no need to imagine increased “stress” or “tension” that does not need a modified system to accommodate forces that Cessna engineers had already figured-out in their design.

I don’t mean to come across as so didactic. Just hoping to help.
'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: New 170B owner

Post by n2582d »

Charlie,
I noticed your rudder has two nav lights which means you have an L-19 rudder. I’m curious if the bellcrank on your rudder is also from an L-19 or is it a stock C-170 bellcrank? The L-19 bellcrank, p/n 0660340, measures 8” between the tailwheel steering tab holes while the C-170 bellcrank is around 5” between the holes. One would think a larger bellcrank would help the anemic tailwheel steering on the C-170.
L-19 bellcrank p/n 0660340
L-19 bellcrank p/n 0660340
Gary
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Bruce Fenstermacher
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Re: New 170B owner

Post by Bruce Fenstermacher »

rnealon1 wrote: Hi All,

In regard to the slack/tension, is this addressed anywhere in the 100 Service Manual or elsewhere? My A&P says there should be slack but he is not a 170 expert.

Thanks,

Bob
Yes it is addressed in the Scott instructions which according the the TCDS is the only instructions to be used when a 3200 tailwheel is installed.
http://cessna170.org/forums/download/file.php?id=3148 to download the Scott instructions.
CAUTION - My forum posts may be worth what you paid for them!

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goodair
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Re: New 170B owner

Post by goodair »

well, its anual time again for our N138WW. Our families have put another 125 hours on it with no problems and many fantastic memories. We took it to Gastons for a great week of fishing among omany other trips.
This year is an easy anual with onlt the 500 hour mag check and a few other minor items. Note!! Be very careful choosing a shop for these mag checks. I sent these mags with 523 hours total time since new to a mag shop that only specializes in magneto servicing. They told me that they "were not economically rebuilfable". And that the " impulse rivets were cracked". The quote for repair was more than a factory new mag. So, I had this shop send the mags to Aircraft Accessories in Tulsa. They are a Slick service center and can acually overhaul the mags. The previous shop could not. The Tulsa folks could not find a single discrepancy and did the normal parts replacement for a 500 hour inspection. Under 1k for the pair. I used to do these 500 hours myself but will no longer have my name in a logbook for an accessory for the next 500 hours, which might take some folks 20 years.
Back to the anual, I did install rhe flap ratchet part to give us a 10 degree notch. Found a new one (nos) on ebay for 120$. Not too bad and an easy install.
My partner has hinted that our good ol 138WW could be up for sale in the future. He needs a traveling airplane and although we absolutely love this thing my lifetime cabin Waco project is about ready for final assembly, so I will have another toy.
This is not a show plane but a very straight and sound airplane. A previous owner lost the logbooks so no books before 1987. They contacted the previous mechanic and accuratly restarted the total time. It has under 600 hours smoh and around 3k total time.
Does anyone have an idea of value for a 54 170B. s/n 26189. I did put in a JPI fs450 - fuel flow computer. Darn thing is accurate to less than a gallon per tank. New Scott 3200 tailwheel, New 4 place sterio, music intercom, pulled and re-installed the tail surfaceses with new hardware last year. New generator and regulator last year. No visible damage history in that the gear/door posts and fuse/wing skins are all original. It could use rudder skins in its future and has a few little dents and dings in the normal places. No stabilizer boots yet. I have new wing tips for it. Clevelands...new tires....It has a reasonable airtex interior with new carpet. Just wondering as i am not seeing many B models for sale. It is NOT being listed yet but I will post here first when it goes on the market.
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daedaluscan
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Re: New 170B owner

Post by daedaluscan »

n2582d wrote:Charlie,
I noticed your rudder has two nav lights which means you have an L-19 rudder. I’m curious if the bellcrank on your rudder is also from an L-19 or is it a stock C-170 bellcrank? The L-19 bellcrank, p/n 0660340, measures 8” between the tailwheel steering tab holes while the C-170 bellcrank is around 5” between the holes. One would think a larger bellcrank would help the anemic tailwheel steering on the C-170.
14774262-3B13-456B-A305-9F4682BD0146.jpeg
Very interesting question, I will look. I had no idea they were different.
Charlie

1956 170B C-GDRG #27019
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