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New failure mode for Siver Bullet Tailwheel link

rvator51

rvator51

Well Known Member
Here is a failure mode I wasn't aware of for my Silver Bullet tail-wheel link. I had did a preflight and it looked ok before the flight, but I think it was probably already backed out some.

I put some locktite on the threads and tightened it back up and everything seems ok, but going to look closely at it from now on in preflight inspections.


img_1540.jpg
 
How did that happen Tom? There appears to be a jam nut at the aft end. Does that keep the two sections from loosening?

I don't have one of those so knowing details helps me apply it to similar hardware if I even encounter it.

If the jam nut (if it exists) is supposed to keep the aft section from turning, would TWO jam nuts be a suitable solution?
 
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Thanks for the heads up

Thanks for the heads up........
I'll surely be looking closer next time out!
 
Hi Tom, Would it help to install a small roll pin to keep the two halves from unscrewing? Larry
 
There is no jam nut on the two center pieces. They just screw together.
I like LARCOs idea. I wonder if you could use a cotter pin or safety wire through a small hole also? Checking it regularly to make sure it hasn't started to unscrew would probably work too. The locktite that I put on might help.
 
So, how did it handle?

Tom,
I assume it detached in flight? If so, what was the experience like when you landed?
 
Louise Hose said:
Tom,
I assume it detached in flight? If so, what was the experience like when you landed?
Click to expand...

One of the rod end bearings on my Rocket tailwheel link broke during taxi over a very rough strip of new pavement. I discovered the broken link during taxi to takeoff when the tailwheel failed to "lock". Since the RV-6 could be easily steered with the brakes I elected to fly the plane to my home 'drome.

Control wasn't a problem, steering just felt sorta "loose" until airspeed got high enough for the rudder to kick in. Landing likewise was a non-event (light winds) and the plane never acted like it was going to get unruly. A crosswind landing/rollout would have the potential to be sporty, however. ;)
 
Scott Chastain said:
Tom:

I played around with the steering link during Phase One, then tried out the Tail Lynx sold at Van's . . . just for the heck of it! Now, there is no going back to the steering link. I still have a ready-made gust lock with the Lynx installed, excellent handling in X-winds or otherwise, and an aesthetically pleasing connection to the rudder with the stainless steel design of the Lynx.

I'm glad you avoided any incident with this failure, but it only bolsters my opinion that these things are inherently unstable (reads unsafe). My pair o' pennies.
Click to expand...


Interesting opinion Scott. I am not sure what you mean by "unstable" - I have been flying with one for many hundreds of hours, and haven't seen a problem - have known many folks with close to a thousand hours on them that haven't had any problems with the Silver Bullet either. The Tail Lynx looks quite nice, and if I was going back to springs, I'd go with them just for looks, but really, they're just fancy springs, aren't they? It also locks the rudder the same way springs did - at least for me it does - with a little "give".

I think that there is a lot of personal preference involved in choosing between springs and a link, and how you like the tail wheel to feel, but I don't know of a stability problem with either.

(Of course, I've had the standard springs fail due to the screen-door clip that Van gives us for attachment - fixed that with sailboat shackles....)
 
No Scott, I'm not kidding - that isn't what I would have refered to as an instability, I'd call that a mechanical problem, but as long as we define out terms, that's OK. I could post pictures of tailwheel springs hanging loose, but that just rpoves that everything has failure modes. I was more concerned that you were referring to a dynamic/control instability of some sort.

If the link does fail in flight, you land with a free-castoring tailwheel - not a disaster, as that can happen if the lock-pin gets stuck or hung up (another common failure for people), even with springs.

Paul
 
Works fine

I'm knocking on 400 hours with my Silver Bullet link. No problems at all. As will with all aspects of our planes, they need constant monitoring and inspection.
 
I've got about 200 hrs. between 3 Silver Bullet links on the RV8's and haven't seen anything like this, nor would it worry me if it broke.
But then again I sometimes use Jet-A in my smoke system while flying with my canopy open.:rolleyes:
 
Scott Chastain said:
Paul:
You're kidding, right? By unstable (unsafe), I mean this . . .

. . . or this . . .

Sam Buchanan said:
One of the rod end bearings on my Rocket tailwheel link broke during taxi over a very rough strip of new pavement. I discovered the broken link during taxi to takeoff when the tailwheel failed to "lock". Since the RV-6 could be easily steered with the brakes I elected to fly the plane to my home 'drome.

Control wasn't a problem, steering just felt sorta "loose" until airspeed got high enough for the rudder to kick in. Landing likewise was a non-event (light winds) and the plane never acted like it was going to get unruly. A crosswind landing/rollout would have the potential to be sporty, however. ;)
Click to expand...

. . . or any number of other horror stories out there regarding the one-sided steering links. But to each his own. Good luck!
Click to expand...

Whoa, Scott!

You totally misread my quote about the rod end bearing failure on my Rocket link. The whole point of my post was that the link failure was not a control problem (what you called a "horror story").

Please do not let your lack of objectivity obscure the facts stated in the posts you quote.
 
No sense in letting it go to waste

Hey Scott,
If your steering link isn't being used I may be interested in it.....seeing as you're going to stay with the Lynx.

Scott Chastain said:
Tom:

I played around with the steering link during Phase One, then tried out the Tail Lynx sold at Van's . . . just for the heck of it! Now, there is no going back to the steering link.
Click to expand...
 
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I gotta side with Scott here. Looking at the photo, it appears that it would take very little for the forward half of the link to get onto the opposite side of the tail spring, thereby possibly jamming the rudder, or at least preventing left rudder deflection much past neutral. If it happened in the air, it could have consequences far more dire than mushy ground handling.

It looks like a hard application of full right rudder would do the trick, say like doing a right hand spin. With the forward half of the link jammed against the tail spring, full left rudder (and thus spin recovery) would be impossible.

However, this wouldn't scare me away from using this link on my plane (still happy w/ Van's screen door springs...) but I think it is a bit more serious than first meets the eye.
 
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Tail lynx failures

Don't think by using the tail lynx you won't have problems. I've had one fail on landing. We just took it off and flew home. It's like going back to more vintage aircraft that didn't have any tailwheel steering at all! Not too difficult but you have to be aware that the steering is more rudder and brakes.
My mate has had 2 lynx fail on him. He seemed to think that had a bad batch that were weak.

Peter
 
Lynx failure modes

kiwipete said:
Don't think by using the tail lynx you won't have problems. I've had one fail on landing. We just took it off and flew home. It's like going back to more vintage aircraft that didn't have any tailwheel steering at all! Not too difficult but you have to be aware that the steering is more rudder and brakes.
My mate has had 2 lynx fail on him. He seemed to think that had a bad batch that were weak.

Peter
Click to expand...

Peter,

How about some details on the failure modes? If it's at the bend in the tang, most likely the bend was done over the sharp edge of a vice.

http://picasaweb.google.com/tonyboytoo/RV3BMiscellaneous#5136871339099572018

Otherwise, what's to break?

Tony
 
Tony

It was when I was flying a friends RV. I landed and went to turn off.
It broke where the tang goes into the spring unit itself. From memory at that point the tang reduces in size and this is were it broke. I'll have to ask Mark to be 100% sure.

Peter

PS I have the rocket steering link and love it. Wayne Hadath has been a pleasure to deal with. My link got damaged by accident and he sent a replacement free of charge.
 
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Louise Hose said:
Tom,
I assume it detached in flight? If so, what was the experience like when you landed?
Click to expand...

Hi Louise,

It came off as we came to the end of our taxi when we were swiveling 53L around to do the runup.
We just taxiied back to the hanger using brakes and rudder to turn, investigated, and put some locktite on the threads and retightened the two parts together and continued on to the Coolidge pancake breakfast.
I believe that this probably loosened over several flights so I take the blame for not noticing it. I was looking at the rod end bearings at the each end of the link in the preflight not the center of the link. In hindsight, it should have been obvious to me that it was coming unscrewed. I emailed the manufacturer to see if it is ok to put a small hole through the threads for a roll pin or cotter pin or safety wire to keep the parts from backing out. However, I suspect a good preflight would catch the same problem in the future.
I really like flying with the combination of the silver bullet link and the Rocket tailwheel and dont plan to change.
 
READ THIS - There is a serious safety issue to be considered...!!!

sprucemoose said:
I gotta side with Scott here. Looking at the photo, it appears that it would take very little for the forward half of the link to get onto the opposite side of the tail spring, thereby possibly jamming the rudder, or at least preventing left rudder deflection much past neutral. If it happened in the air, it could have consequences far more dire than mushy ground handling.

It looks like a hard application of full right rudder would do the trick, say like doing a right hand spin. With the forward half of the link jammed against the tail spring, full left rudder (and thus spin recovery) would be impossible.

However, this wouldn't scare me away from using this link on my plane (still happy w/ Van's screen door springs...) but I think it is a bit more serious than first meets the eye.
Click to expand...

This hypothetical situation is VERY real. An RV-8 lives in my hangar and is fitted with the silver bullet (fitted on the LHS). A couple of weeks ago he was taxiing and whilst doing a tight turn on a grass strip the tail wheel arm over-rotated in a left turn and locked against the shaft effectively locking the rudder in full deflection.

The reason that it over-rotated was that the silver bullet arm was slightly bent due to wear and tear effectively shortening the operating length. Once over-rotated you CAN NOT return the rudder to the center position.

This is a SERIOUS concern because it is possible that during aerobatic flight
a full rudder deflection could cause the arm to over rotate and lock the rudder in full deflection causing an unrecoverable spin.

The pilot of the aircraft has removed the silver bullet and is currently flying with the rocket steering link from my unfinished seven with a mod which is basically a stop bolted onto the end of the spring steel to stop any chance of over rotation. Note that either steering arm can cause this problem.

He is away in his aircraft at the moment however when he returns he intends to post some images on VAF to show the problem and the fix. I will encourage him to do this ASAP.

In our review of the problem it was noted that the design of the steering links is such that during a cross wind landing (with wind coming from the left) it is highly likely that right rudder input opposes the castoring action of the tailwheel causing increased compression load on the arm and in extreme cases this could bend the link causing it to be shortened through the "z bend". It is also possible that the effective shortening could easily be missed in a routine inspection.

If in doubt check it out....

Regards

JON.
 
Jon Clements said:
This hypothetical situation is VERY real. An RV-8 lives in my hangar and is fitted with the silver bullet (fitted on the LHS). A couple of weeks ago he was taxiing and whilst doing a tight turn on a grass strip the tail wheel arm over-rotated in a left turn and locked against the shaft effectively locking the rudder in full deflection.

The reason that it over-rotated was that the silver bullet arm was slightly bent due to wear and tear effectively shortening the operating length. Once over-rotated you CAN NOT return the rudder to the center position.

This is a SERIOUS concern because it is possible that during aerobatic flight
a full rudder deflection could cause the arm to over rotate and lock the rudder in full deflection causing an unrecoverable spin.

The pilot of the aircraft has removed the silver bullet and is currently flying with the rocket steering link from my unfinished seven with a mod which is basically a stop bolted onto the end of the spring steel to stop any chance of over rotation. Note that either steering arm can cause this problem.

He is away in his aircraft at the moment however when he returns he intends to post some images on VAF to show the problem and the fix. I will encourage him to do this ASAP.

In our review of the problem it was noted that the design of the steering links is such that during a cross wind landing (with wind coming from the left) it is highly likely that right rudder input opposes the castoring action of the tailwheel causing increased compression load on the arm and in extreme cases this could bend the link causing it to be shortened through the "z bend". It is also possible that the effective shortening could easily be missed in a routine inspection.

If in doubt check it out....

Regards

JON.
Click to expand...

Excellent point. Jon. This scenario was discussed extensively several years ago either on this forum or the Matronics RV-list. If I recall correctly, those of us using a steering link (mine is the Jantzi/Rocket unit) were encouraged to make sure the link was installed with the rod end bearings adjusted so the link would be long enough to prevent the over-center problem. The link must reach the bottom of its travel before the steering arm can go over-center. I believe the releasing pin of the tailwheel would have to jam in the locked position for this scenario to occur during taxi. If the pin is well-maintained and free to slide in its groove the tailwheel would unlock as designed and prevent the steering arm from going over-center. But an inflight over-center event could be due to a damaged or improperly installed link.

The link definitely needs to be part of the preflight inspection. A photo of your friend's bolt-on stop would be appreciated.
 
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