The International Cessna^® 170 Association

Good Morning everyone,

I have spent several hours reviewing multiple posts related to tailwheel springs, shimmy and slack cables but cant quite solve my lack of steering issue. I have a 52' 170B.
I just got done replacing the tailwheel channel retainer bracket (which had the tab broken off) then I replaced all four tailwheel springs from Univair and put on a new Alaskan Bushwheel 3200 tailwheel.

I am at a loss for a couple of reasons. My steering on the ground is slim to none. (which was part of the reason I went this far. After thinking my Scott could have been overhauled I found out a new one was $150 more). I placed the aircraft on the ground and configured the steering chains so there was no slack. But my steering on the ground is slim. I am using a lot of brake to turn and an awful lot of brake to get the tailwheel back in line after I break it free to make a tight turn. I am thinking that the opposite side chain is adding tension so the steering arm is not moving. If I add a link of chain the only thing that happens when I move the rudder is the slack is taken out and the steering arm does not move.

My second issue seemed to come on a couple of test flights with about a ten knot direct crosswind. Both times after landing I needed to tap the downwind brake to keep the aircraft tracking down the centerline and not weathervaning. (could just be bad pilot) Seriously It seemed as though the tailwheel was not straight when I put it down.

A lot of threads talked about the cable slack and chain slack in the new model but I did not see a lot of rigging on the earlier models. Any expert help or Cheap shots on my landings would be greatly appreciated

Brad

For a while, I had a '55 model with the steering cables coming out of the fuselage like the later C-180s. It would not steer for sour owl s--t either. I strongly suspect that a good set of double puck brakes are the best answer.

Don't take this the wrong way, but, if your cables are run thru the plane correctly with the proper tension and your tailwheel springs are correct and tensioned properly with the tailwheel exactly in trail with the rudder, use more brake.

We have all dealt with the same exact thing.

I'd guess the previous posters are correct but you might confirm that your kingpin nut torque is correct and that you have the Scott 3239 steering springs rather than the lighter Scott 2151 springs.

Brad,
A lot of problems with lateral control during landing can be caused by improper main wheel alignment. A 170 with proper main wheel toe is a pussycat and a 170 with improper main wheel toe is an ally-cat with crossed eyes.

Another question, how many springs (Cessna part # 0442010-17) do you have installed? Our 170's only require three, heavier airplanes like the 180 require 5.

Besides all the other make sure it is right comments, Gary and John have hit the last thing to check. As John points out our aircraft Scott 3200 only had 3 springs in the tailwheel. Heavier applications I presume would use 5. These springs, along with the king pin nut set the friction or dampening inside the tailwheel. The king pin nut will be different depending on how many springs you have. Less springs, tighter nut, more springs looser nut. What you are adjusting for is that amount of friction that just does not allow any shimmy.

How do you find this magic king pin nut adjustment. Trial and error. We will assume yours is to tight. Remove the cotter pin and loosen the nut 2 flats or a 1/4 turn. Try it. No shimmy, repeat unless the tail wheel has loosened up to your satisfaction then stop. Otherwise repeat until you think its better or you get shimmy. If you get shimmy tighten up a flat or 1/8th turn till no shimmy and stop.

BTW you will be not able to sit on the ground stopped, move the rudder and have the tailwheel arm move.

And a picture of your setup is worth a thousand words to us remote arm chair tailwheel mechanics.

Brad, first of all, .... although these tailwheels are called "steerable".... they are mostly castering, in actuality.
You've got to know your history.
Clyde Cessna was one of the first, if not THE first, to install a tailwheel instead of a tail-SKID on airplanes. He tired of the skid tearing up his landing area.
The advantage of a skid is that it adds DRAG and helps prevent the airplane from swapping-ends in a ground-loop. The disadvantage is that the pilot needs help (or a lot of power and a large rudder) to get an airplane turned-around on the ground. Ground-handlers were required to lift the tail, and swing the airplane around.
Clyde installed a wheel, and made it "swiveling" so that by using differential braking, one could maneuver the airplane on the ground.... Ground that was not full of furrows from tailskids.

Two further developments of the tailwheel were "locking" tailwheels...which could be locked into a straight-ahead position for takeoff, in order to prevent those silly excursions towards the edge of the runway....(now that folks started using straight runways with defined edges, instead of large pastures and round aerodromes that always allowed landing and taking-off directly into the wind).... and then "steerable" tailwheels, which in-fact are not strictly steerable, but only vaguely follow the input from the rudder steering system. This is what the Scott (and copy-cat Bushwheel) tailwheels are.

Jack your airplane tail off the ground and grab your tailwheel and try to turn it left/right. It should not freely do so. It should be reluctant due to a distinct detent locking it in the trailing position.
Now move your rudder full left. The tailwheel should follow that movement. Same as to the right. (But, with effort, if forced out of the detent, it should swivel with only minor friction.
Now place the tail back onto the gr)ound. Move the rudder left/right. The tailwheel should not move, but should remain "in trail" with the fuselage (despite the steering chains slight--movement and tensioning of the steering springs.)
Now, have someone hold the rudder full right, while you place your butt against the fuselage immediately forward of the horizontal stabilizer. Use your butt to shove the airplane tail to the RIGHT (opposite direction from what right-rudder would actually move the tail if under-way.) The tailwheel should UN-lock, and swivel so as to allow the tail to move to the right, contrary to the rudder's input.
Now,pushing the airplane straight-ahead...with the rudder straight. the tailwheel should fall back into-line and trail properly.

If your steering chains are taut but not stretching the steering springs, if it is castering at the proper angle, as we've displayed in several photos here in the forums (top of kingpin aft of bottom of kingpin), then it should not shimmy.

The compression clutch-plates and the compression springs which adjust their pressure-plate friction (3 springs for 120/140/170 aircraft, 5 springs for 180/185 and heavier...but not especially critical regardless) merely help transmit steering inputs to the tailwheel and dampen any shimmy caused by uneven terrain.

IN other words, I think you are probably placing too much faith in the word "steerable". A great deal of differential braking is always required to operate and maneuver these airplanes. In very strong crosswinds (20 kts or greater) they can become quite difficult to taxi straight ahead or to turn down-wind. That is the reason we tailwheel-qualified pilots are better than those who fly only "trikes".