Tailwheel steering malfunction

We were about 30mph on the landing roll in my RV-4...friend in the back, when it started left. Right rudder was not working, right brake was not bringing it back very quickly, due to the aft CG. We were headed for the ditch on the side of the runway, but as we slowed, the correction finally took hold and we managed to only whack a runway light with the left flap, with minor damage.

What the hell had just happened, ran through my mind. Tailwheel steering had worked to the left and not to the right, giving a ratchet effect. In the "ride the bicycle" mode, every time I moved the rudder a little left, the tailwheel did the proper thing, but to the right...nothing.

Back on the ramp, I pulled the tailwheel assembly apart and found the spring loaded key gummed up with grease and dirt. It was not fully engaging the slot in the steering bar. Due to slight differences in tolerance, it was catching the slot to the left, but not to the right. It was a minor mechanical issue, with major impact.

I cleaned up the shaft and flushed the spring and key with WD-40. I had been using wheel bearing grease, and did again on the shaft, but this time, I oiled the key and spring area with 30W motor oil. It's working fine now, but it's one of those minor details to pay attention to.

The next day, at a local RV fly in, a friend was familiar with the problem said to only use motor oil on the tailwheel shaft, pulling it apart for re-lub every 6 mo. or so. He further stated that newer assemblies don't have the zerk fitting, since grease can gum up the works, especially on sod runway operations. Also, there is the fact that grease never really gets to the shaft properly using the zerk fitting anyway.

I'm probably "Johnny come Lately" on this issue, but wanted to get this version of tailwheel steering problems on the forum.

Dave Dollarhide

2x so far

Had the tailwheel steering go on me twice so far. Here's the deal:



The "key" wears and actually builds up little burrs on the corners that can prevent it from sliding in and out of the slot properly. You might think it's just "gunk" and grime in there, but mic the key and you'll see what I mean. In the crappy photo above, the little burrs on the corners caused the key to "widen" inadvertently and jam up. The result was that the key would get forced into the slot as the horn turned on it, and then the spring didn't have enough force to overcome the friction of the now very close tolerance fit in the slot.

In fact, when I took it apart, the key refused to come out regardless of degreaser spray and cleaning it up. Fortunately the slot is open on the other side of the shaft and I could poke something in there to force the key out.

A quick rub on the Scotch Brite wheel polishes these burrs right out (go light, just enough to square off the corners) and it's back to 100% for another 400 landings or so.

Any time you have your tailwheel apart, do yourself a favor and check for these "corner burrs." If you don't, then you may be in for a surprise sometime on landing.

)_( Dan
RV-7 N714D (725 hours)
http://www.rvproject.com

Twice here too

I agree 100% with Dan and ditto his comments.....
my -6 did exactly the same thing and my hangarmates did too.

We bought new full swivel tailwheel assemblies and converted from the original design, non full swivel and chains to the full swivel with steering link and love it......but when they came from Vans with no zerk fitting I asked Vans why and they said the grease would not travel up and down the shaft, so just service it very 25 hours!!
sorry, but I'm too lazy and like to fly too much, so I had a machine shop mill a groove on the inside up and down to let the grease move along the shaft.
But......that didn't keep the burring problem from happening.
I read with interest about the motor oil for lubing.
Fly Safe
and know thy airplane.
Love this forum.
Bob Martin

Twice here too...two

Additionally, we didn't have any landing problems when we found ours burred, but noticed the steering arm had crossed over to the wrong side and looked funny. The burred pin wouldn't extend and it let the wheel castor around to the other side. I now see we were LUCKY......thanks for the heads up!
Bob Martin

It would be nice if there was a permanent fix

I remember reading about this before on Dan's web site. It's not something that I'm looking forward to when I'm flying my 7. Would it help to use hardened steel keys?

A hardened steel key wouldn't be a *great* solution. You want the key to be the part that wears, not the rest of the assembly, because the key is much easier to replace than the parts it wears against.

sticky tailwheel steering

It's not something that I'm looking forward to when I'm flying my 7. Would it help to use hardened steel keys?

Click to expand...

This isn't something to spend a lot of time worrying over. Just inspect the pin each time you service the tailwheel at the condition inspection and you shouldn't have any surprises. The time the pin froze up on my RV-6 I was able to tell the swivel mechanism was getting a little sticky during preflight inspections and while pushing the plane around the gas pump. As others have stated, a minute or so with a piece of sandpaper was all it took to fix the problem.

On a related note, one of our local RV-4 pilots had the aftermarket tailwheel steering link on his plane break recently. He didn't know the link had broken on the preceding takeoff until he started taxiing to parking at a pancake breakfast. The landing was without incident and he subsequently flew the plane home and landed at his grass strip after removing the link. The taildragger RVs are pretty docile even without the normal tail steering.

Sam Buchanan (RV-6, 700 hrs)

New swivel.. er

I just finished installing my fs tw. I replaced the tailspring also since the original is not compatible.

I taxied the plane around and am somewhat taken aback by the ground handling. The steering is generally looser than it was but the real thing that has me a bit concerned is this: When I lock the brake on one side and spin the plane around, the swivel works fine. However, when I want to stop the turn, I have do it with brake since there's no rudder connect. The catch is that it seems to take a lot of rolling straight ahead for the tailwheel to straighten itself out. I can't really tell how to make it re-engage nor can I feel it click in like some do.

I taxied over some bumps and felt the tailweel break free. Didn't expect that. I guess I'm concerned that if I were given a "no delay" takeoff, I might take off with the wheel cocked at an angle. I sure wouldn't want to land with no tailwheel steering.

Anyway, I decided not to fly it, although I desperately wanted too :-(
Anybody else a little uncomfortable with this setup ?

Thanks

John

My Fix

Just as another data point, A friend of mine nickle plated my whole tailspring and tailwheel fork assembly and at the same time coated the inside of the tailwheel fork with a industrial coating called "Rulon" I believe, don't hold me to that name. It is a heavy duty coating used in very big and heavy machines(like earth movers) he told me it is a self lubricating substance and the more it wears the more it protects. Now I only have a little over 85hrs on the plane but I have pulled the tailwheel twice just to check and you can't even tell that there has been any wear at all, none on the key and none on the inner surface of the tailwheel fork.
Anyway just another thing to consider..

John RV4
If you keep your tires a little on the soft side (25lbs) you can pull the tire right off the rim by locking up one brake and spinning the airplane. Ask me how I know...... Airshow 400 miles from home, tire went flat grounding the wheelpant to the tarmac. No tube to replace. Not fun,
Tom
RV3 2000 +

Add me to this list

Probably the single most frustrating thing about my RV-8 (the poor rear seat heat comes close but that's another story).

My tailwheel unlocks if you push on the right rudder pedal. The problem is more pronounced if I have someone in the backseat.

So far I have tried:

1) Replaced the tailwheel springs with the Janzi rocket link.
2) Used light oil on the tailwheel shaft
3) Used heavier grease on the tailwheel shaft
4) Replaced the key with a brand-new from Van's spring and key ($7 + shipping for the darn thing).
5) Replaced the tailwheel assembly with the Doug Bell version.

I honestly have not got the slightest idea what to do next. The burring is part of the problem (that causes it to sometimes not lock in) but the latest incarnation of the problem is that it will come unlocked (always on the right pedal) if you are trying to correct a little yaw during taxiing.

BTW, Van's tech support was pretty cavalier on this matter. Their answer when I called them to discuss it was basically "Jeez, all tailwheels suck, get used to it".

Bruce
RV-8 Flying (422 hrs)
N297NW

Unlocked tailwheel

My 8's tailwheel would not lock up and I had to use brakes to make any right turn. Took the assy. apart and polished and put a small spacer in to make the spring stronger and still not right. Finally, I recleaned all the new grease out and used just a little bit of moly grease and didn't put any in the zirc fitting and that fixed it. Somehow in mine, the grease packed in and wouldn't let the key lock.
I have since put on a rocket link with new steering bar and have had no more problems.
I am also going to a Doug Bell fork to get more tailwheel yoke clearance.
And lastly, I don't think ANY tailwheel sucks.

Will try to make it work...

So,
I flew my full slobber tailwheel today. The takeoff felt very weird. It definately left me feeling like I was flying a different airplane. I went out and did some airwork and I think my mind was convincing me that the tailwheel was going to be cocked and I was going for a wild ride on touchdown. The wind started changing direction and gusting up. In the end though, the landing was fairly normal except for an odd noise it seemed to make when I was braking.

I suspect ( but can't prove yet ) that the new tailwheel/tailspring combo is slightly shorter than the original. That may be leading to an enhanced sense of sloppiness as the chains may be looser. I put the rudder over to the stop and I think I could remove 1 link from the chain and still make the stop or come very close. I think I'll try this first. I'll search the archives for some detail.

Do you believe in curses ? While I was taxiing around yesterday and deciding NOT to fly the airplane, a friend of mine was working on his tailwheel endorsement. His usual Citabria was unavailable, so the owner took him up in a Birddog. Apparantly a very nice Birddog. Anyway, 3pt landing and as soon as the tailwheel touched, the airplane headed for the weeds. Opposite brake was not enough (left skid marks on the runway) and they groundlooped damaging the dog.

Net effect of the weekend: 2 seriously bummed out pilots, 1 damaged airplane and 1 unhappy but otherwise unscathed RV driver :-(.

John.

oh BTW, thanks Tom for the tip on the flat tire. No more doughnuts in the parking lot for me .

Ditto for me

Glad I saw this thread. I struggled with the same problem about 100 hours into my -8. Nice to know the final culprit appears to be the key.

Thankfully it happened prior to a take off, so I taxied back. Ripped into the thing and found, well, nothing. I kept looking at the arm as a source of the problem - as in maybe I polished the internals too much, etc. In fact it worked beautiful on the bench. Cleaned and reinstalled, I taxied back out only to have it happen again.

Took it apart again and checked thru everything trying to figure out what I was missing. Still nothing, so taxi test and fly it.

I found that once it locked it would stay locked, so I was able to enter the runway, get it straight and locked and it would remain that way until the landing (wheel landing of course given the scenario). I basically treated it like a locking Pitts TW.

Long story short - I finally gave up since I hated the Vans TW anyway due to such poor ground clearance. It is a nice simple design, but I was always concerned about rough field performance and taxiing from pavement to grass and ripping off something in the back. So... I bought an Aviation Products TW and LOVE it. That and the Tail Lynx with no slack (tail up) allowing some minor slack with the TW on the ground due to flex from the TW rod.

I have quite a bit of tail time in the slower to tricker varieties and found the Av Products TW and the Tail Lynx to be the nicest compromise.

The Bells do make a high quality product, but I was too impatient to wait and I wanted something different other than the Van's caster given the mystery locking problem.

My 2c.

MSFT-1 said:

My tailwheel unlocks if you push on the right rudder pedal. The problem is more pronounced if I have someone in the backseat.

Click to expand...

Bruce - This may not be your problem, but I had a similar issue once on my RV6. It turned out to be the bushing inside the tail wheel assembly. (Where the TW swivel shaft actually slides up into.) These bushings are pressed in and have the groove for the steering key machined out of it. In my case, the bushing had turned and the groove was, in effect, shortened on one side causing the TW to break out too soon. I just took a large vice grip pliers and was able to grab the bushing, where it sticks down below the assembly, and turn it back to the appropriate position. It was a one time thing and worked fine for several hundred hours after that. I don't know why it happened in the first place. Hopefully this helps.
Good luck.

Tail lynx??

What is this????

Tail Lynx

cawmd82 said:

What is this????

Click to expand...

Van's now sells these as an alternative to the old screen door springs. They are great...

http://www.vansaircraft.com/cgi-bin...5558551-138-357&browse=misc&product=tail-lynx

If you follow the assembly instructions you might end up with these too slack. They weren't clear on how they were measuring the slack from what I recall - i.e. with our without weight on the tail and this makes a difference. I bought a couple of extra attach pieces so I could experiment. I found that the best feel was to have this installed so that there was zero slack (but no compression on the springs) when the tail was off the ground. Once you put the tail on the ground it gives you a small bit of slack due to natural bowing of the tailspring rod.

Pics of stuck TW steering key and cleaning/assy

Gents,

I experienced the loss of TW steering in my RV-6, and this thread was extremely helpful in finding the solution and gettin' it corrected. Thought I'd add this post, with pictures, to say thanks and help others that run into this. I let my TW get too dirty, and found that even after cleaning, the key still stuck, even though I saw no visible burrs. However, the edges of the key felt a bit rough, and after a little sanding with fine sandpaper, the key moved nicely. I've inserted some before, during and after photos, and hope it adds value to the thread. Thanks again for the insight and gouge in all the posts!

Bob
"Rocket" RV-6
N600SS - 4SD
Pics Follow

1. Here's the (very dirty, my bad!) TW shaft showing the key stuck in the retracted position (a nail set points to the key):

http://img250.imageshack.us/img250/9839/1twshaftwithstuckkeyez5.jpg

2. Here's the TW assy (post-cleaning, pre-greasing), ready to go back together:

http://img337.imageshack.us/img337/6421/2twassyreadytoreassemblhc2.jpg

3. Here's the TW shaft with the key properly protruding (the spring is installed):

http://img337.imageshack.us/img337/8536/3twshaftwithkeyproperlyhc9.jpg

4. Here's the TW assy without the steering link connected, showing the key properly riding in the channel (this channel gives the steerable range of travel):

http://img222.imageshack.us/img222/8371/4twshafttopinsteeringchmo3.jpg

5.Here's the TW assy with the steering link installed (nut and washer still removed). The key rides in the u-shaped cutout duringTW steering, and retracts during free castering/swiveling:

http://img250.imageshack.us/img250/550/5twshaftwithkeyengagedmr1.jpg

6. The next two pics show the TW as I swiveled it past the steering range and into the free castering/swiveling range. The first shows the key starting to retract, and the second shows the key fully retracted (pushed in). Apologies for the slight blurriness, my point and shoot digicam couldn't quite hack the close-ups:

http://img222.imageshack.us/img222/589/6twshaftwithkeypartiallzh7.jpg

http://img222.imageshack.us/img222/1167/7twshaftwithkeydisengagnu8.jpg

7. Finally back together! Took about an hour, thanks to all the help here in the forum! Thanks again!

http://img252.imageshack.us/img252/7505/8twassybacktogetherzo9.jpg

original tailwheel

Has anyone considered converting back to the original style non-castering tailwheel? Not sure if it's still available, but this is what I have on my RV-3 and it works fine. My chains are just loose enough that the tailwheel can acheive a near 90 deg. position with just a little tension on the spring. If you try to spin the plane around too fast, you'll get a little tailwheel hop, but if you're gentle with it, it allows just about as much maneuverability as one that breaks into caster mode.

loss of tailwheel steering?

When you guys say loss of steering do you mean that the tailwheel became free to swivel independant of the of rudder movement? ( free as if not connected to rudder horn?) Or do you mean that the tailwheel would not turn at all. ( Stuck in one position?)

I have flown my RV-4 without any connection between rudder( no chains to tailwheel) and tailwheel numerous times. When I do have chains on they are loose so that they only pull the tailwheel when the rudder pedals are more than 1/2 displaced. I have found that I can land and taxi in the same max crosswind without the springs on. ( xwinds bad enough that the main gear could not hold the runway)

>>> Has anyone considered converting back to the original style non-castering tailwheel?

Yes !! But after 60 or so hours using the new setup, I am used to it. It hasn't given me any operational issues and I have a reasonably good feel for it now. I did remove one link from the chain and that made the whole setup feel much less sloppy but not too twitchy either.

I would just go with the standard in the kit and not sweat it. The only thing I would probably change would be get a fork from Vince F. to give it more ground clearance.

John

Clarification on "loss" of TW steering

Chris,

In my case I meant that the TW became free swiveling. Apologies if the term "loss" was confusing! Did not mean to infer that the a/c was non-steerable. On the day it happened, the landings and taxi-in were very controllable (light winds probably helped!). Good question for clarification though!

Cheers,
Bob