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Jimmy Young

Joined: 24 Nov 2007
Posts: 182
Location: Missouri City, TX

Posted: Sun Aug 30, 2009 3:35 pm Post subject: always do your preflight!

I found this cracked tailwire tang while doing my preflight this morning. It's the one on my left-side vertical tail. I happened to have a fresh new one on hand, so a little bend on the vice and 10 minutes of work and I was good to go. 



Prior to this happening, I had been thinking of a possible better way to assemble the Kolb tailwires by copying what is done on a lot of other GA planes in our hanger. They use the solid rods, threaded on both ends, with fork attachments and jam nuts. They also have tangs, but they are thicker than ours. I think I've seen one on a Kolb somewhere, just can't remember whose it was. Seems that would be better, if you never fold/unfold your plane. I have always looked very closely at those tangs on my preflights, looking for signs of a stress crack forming, but I never saw any indications on this one until I found it in this condition this morning. It had to have happened yesterday while I was out flying, because it wasn't there yesterday morning.



Jimmy Y

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_________________
Jimmy Young
Missouri City, TX
Kolb FS II/HKS 700

zeprep251(at)aol.com
Guest

Posted: Sun Aug 30, 2009 3:54 pm Post subject: always do your preflight!

Jimmy,

 Do you think that failure was caused by air loads or the amount of tension?

   G.Aman 

 

   

 

   

 

 --

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sun Aug 30, 2009 4:11 pm Post subject: Re: always do your preflight!

Hi Guys and Gals,



This is what this list is about...keeping everyone safe . Thanks Jimmy!



chris ambrose

m3x/jab/

N327CS

albertakolbmk3

Joined: 13 Jun 2009
Posts: 69
Location: Innisfail, AB

Posted: Sun Aug 30, 2009 4:36 pm Post subject: Re: always do your preflight!

Why so many adjacent holes. I would think that would have something to do with the failure.

_________________
Tony B.

Kolb MKIII C
Rotax 582
C Gearbox 3.00:1
WD 66" 3 Blade Prop

slyck(at)frontiernet.net
Guest

Posted: Sun Aug 30, 2009 5:20 pm Post subject: always do your preflight!

That is a good point.  Although Kolb supplied the original kits with  

the multi-hole tangs

because that was the only adjustment (aside from a small one possible  

by twisting the cable)



In this case I would fab a plain steel tang with one hole because of  

the turnbarrel.  (sorry, had to call it by its real name)

BB



On 30, Aug 2009, at 8:36 PM, albertakolbmk3 wrote:



 	  Quote: 	
		   

 <cheriebraun(at)xplornet.com>



 Why so many adjacent holes. I would think that would have something  

 to do with the failure.



 --------

 Kolb MKIII C

 Rotax 582

 C Gearbox 3.00:1

 WD 66&quot; 3 Blade Prop





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 60542#260542

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Aug 30, 2009 5:43 pm Post subject: always do your preflight!

 	  Quote: 	
		   I found this cracked tailwire tang while doing my preflight this morning. 

 It's the one on my left-side vertical tail. I happened to have a fresh new 

 one on hand, so a little bend on the vice and 10 minutes of work and I was 

 good to go.



 > Jimmy Y
	




Jimmy Y/Gang:



I don't like those multi-hole tangs, especially stainless steel, plus being 

bent to fit.



Glad you caught that one.



I have never used that style.



I have used the SS tangs with one hole each end with good success.



My mkIII is equipped with 4130 tangs I made from strap and turn buckles to 

adjust the tension.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Aug 30, 2009 5:56 pm Post subject: always do your preflight!

I'm not Jimmy Y, but I'd like to  respond.

  

 My best guess would be vibration and a stress riser  where the tang was bent across punched holes in SS.  SS is much less stress  resistant as 4130.

  

 Jim's photo shows two bends in the tang.  One  of those bends goes right through the hole that broke.  If my old eyes are  seeing correctly.

  

 john h

 mkIII

  

  

  	  Quote: 	
		      

   Jimmy,

Do you think that    failure was caused by air loads or the amount of tension?

  G.Aman    



    

	
   [quote][b]

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Aug 30, 2009 6:10 pm Post subject: always do your preflight!

> In this case I would fab a plain steel tang with one hole because of  

 	  Quote: 	
		   the turnbarrel.  (sorry, had to call it by its real name)

 BB

 
	




Bob B:



Isn't the "turnbuckle barrel" one part of the turnbuckle?



The other two parts being a pin or cable fork???



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

slyck(at)frontiernet.net
Guest

Posted: Sun Aug 30, 2009 6:41 pm Post subject: always do your preflight!

The old west coast aviation guys used to call them turnbarrels as do  

some UK countries.  I just like to call them that

because I don't see a buckle there.  I would still call the hardware  

store variety a turnbuckle though.

The aeronca C-3 and some others actually used them for lift struts.  

I shall now yield to common usage.

I shall also think about a design change on mine, plus closer  

preflights until then.

BB

On 30, Aug 2009, at 10:05 PM, John Hauck wrote:

 	  Quote: 	

 > In this case I would fab a plain steel tang with one hole because of

> the turnbarrel.  (sorry, had to call it by its real name)

> BB

 Bob B:

 Isn't the "turnbuckle barrel" one part of the turnbuckle?

 The other two parts being a pin or cable fork???

 john h

 mkIII

WhiskeyVictor36(at)aol.co
Guest

Posted: Sun Aug 30, 2009 7:12 pm Post subject: always do your preflight!

In a message dated 8/30/2009 8:38:10 P.M. Eastern Daylight Time,  cheriebraun(at)xplornet.com writes:

  	  Quote: 	
		     Why so many adjacent holes. I would think that would have something    to do with the failure.



    

   cherie/all

    

   The tang with several holes was designed so as to be able to    adjust the length of the cable for proper tension.  By moving the bolt    from one hole to another, it will either tighten or loosen the    cable.

    

   On the tangs with only one hole (at each end of    course) they could be adjusted by installing or removing washers placed under    the tang.  My builders manual mentioned this and suggested installing at    least one washer between the tang and the tail surface when being built so if    adjustment was needed later it could be done as described.     

   Bill    Varnes

Original Kolb FireStar

Audubon  NJ

	


 

  [quote][b]

flykolb(at)pa.net
Guest

Posted: Sun Aug 30, 2009 7:50 pm Post subject: always do your preflight!

Jimmy,



It looks like the clevis end of the turnbuckle may have been pressing on the

tang as there appears to be an indented marking on the tang matching the

curvature of the clevis end.  (Sometimes photos are deceiving, but it does

give this appearance.)  I don't know if at some point in the life of the

airplane that when the wings were folded the turnbuckle was leveraging the

tang and flexed it ... possibly when folding the tail, the turnbuckle had

some pressure on it and in turn flexed the tang?



I know the tang is not 4130 and there are holes in it - but even still there

is a lot of strength in the tang. I have a hard time thinking that the crack

resulted from tension loads alone. 



The tang is designed to replace a turnbuckle and consequently most Kolbs

would not have the turnbuckle.  So this is probably a relatively rare set-up

and possibly the turnbuckle and tail folding had something to do with it?



Dennis

--

Fran Losey

Joined: 21 Feb 2009
Posts: 61
Location: Boca Raton, FL

Posted: Mon Aug 31, 2009 3:24 am Post subject: always do your preflight!

Has anyone else experienced this?



Do you have a photo of where the failure occurred?  I am in process of building, info as you supplied sure tells me to beef up the tangs if this is not an isolated case.



Thanks for sharing this!

---

_________________
Fran Losey
N62FL (reserved)

loseyf@comcast.net

mdnanwelch7(at)hotmail.co
Guest

Posted: Mon Aug 31, 2009 3:48 am Post subject: always do your preflight!

Fran C

  

   Did you miss Jimmy's photo link C in his original post C at the bottom of his email??  It has a photo of his broken tang.   Scary stuff C BTW!!!

  

 Mike Welch

 MkIII

 

[quote] 

 Has anyone else experienced this?

 

 Do you have a photo of where the failure occurred? I am in process of building C info as you supplied sure tells me to beef up the tangs if this is not an isolated case.

 

With Windows Live C you can organize C edit C and share your photos. Click here.   	  Quote: 	
		  [b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Mon Aug 31, 2009 4:05 am Post subject: always do your preflight!

 	  Quote: 	
		   It looks like the clevis end of the turnbuckle may have been pressing on 

 the

 tang as there appears to be an indented marking on the tang matching the

 curvature of the clevis end.



 The tang is designed to replace a turnbuckle and consequently most Kolbs

 would not have the turnbuckle.  So this is probably a relatively rare 

 set-up

 and possibly the turnbuckle and tail folding had something to do with it?



 Dennis


	




Dennis/Gang:



You may have something there.  Would be easy to side load the tang with the 

turnbuckle (turnbarrel for BB) during tail folding and handling.



I use four turnbuckles on my mkIII tail wires.  Normally, I do not fold, but 

if I do, all the wires come off the tail section first.



Looking at the photo, looks like there may be some scoring/scratching by 

wrench or socket around the high temp lock nut in the area of the break. 

Doesn't look like there is a washer under the nut either.



If the tail wires were loose in flight, would induce a lot of vibration to 

the SS tang.



Another thought from my foggy old mind, the further the bend from the 

attaching bolt, the more side load at the bolt.  When I make up my tail wire 

tangs, I bend them at the edge of the washer under the nut or bolt head to 

reduce possibility of side load.



My thoughts prior to my first cup of coffee this morning, as I contemplate 

finishing loading and heading to the Rock House, this morning, to harass 

Larry Cottrell for a few weeks, along with the jack rabbits, coyotes, and 

antelope.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Mon Aug 31, 2009 4:06 am Post subject: always do your preflight!

 	  Quote: 	
		   



 Has anyone else experienced this?



 Do you have a photo of where the failure occurred?  I am in process of 

 building, info as you supplied sure tells me to beef up the tangs if this 

 is not an isolated case.


	


Fran/Gang:



The url for the photo is at the bottom of Jimmy Y's msg.



This is the first failure of these particular SS tangs that I have knowledge 

of.  I believe it is an isolated case.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Jimmy Young

Joined: 24 Nov 2007
Posts: 182
Location: Missouri City, TX

Posted: Mon Aug 31, 2009 4:31 am Post subject: Re: always do your preflight!

I agree it looks like a combination of the bend being too close to the holes and the weakness caused by the holes being close together that helped get the failure going. 



To Dennis' reply, I have not to my knowledge ever folded up the tail causing the turnbarrel to leverage some tension on the tang, but it could have happened with a previous owner. I think the main thing to learn is, regardless of what caused it, the crack developed at the weakest point of the tang where the holes are all close together.

 

I'm going to locate some SS single hole tangs and wil be replacing the entire tail wire assembly.

_________________
Jimmy Young
Missouri City, TX
Kolb FS II/HKS 700

Fran Losey

Joined: 21 Feb 2009
Posts: 61
Location: Boca Raton, FL

Posted: Mon Aug 31, 2009 4:40 am Post subject: always do your preflight!

Thanks John, safe journey!

---

_________________
Fran Losey
N62FL (reserved)

loseyf@comcast.net

flykolb(at)pa.net
Guest

Posted: Mon Aug 31, 2009 5:20 am Post subject: always do your preflight!

Jimmy and others with turnbuckles (or barrels),



John mentioned that he was not aware of any such tang failure previously and

I have none either, these are not just used on Kolb, they are extensively in

all sorts of ultralight aircraft.  So, logic would seem to indicate that the

that the presence of the turnbuckle is probably related to the failure in

some way.



The tang, I feel certain, is quite strong enough for its intended tensions

loading.  So all this to say, make sure you don't replicate a scenario that

would not eliminate the real problem.  Any tang will fail if flexed sideways

a sufficient number of times.



I would not put the turnbuckle on the top wires for several reasons:



(A) These are the wires that will get you home when all else would fail. The

bottoms are really along for the ride - the tops carry the downward force on

the horizontal stabilizers.  If the top wire support fails, you probably

will not make it home.  So keep the failure modes for the top wires as few

as possible.  The turnbuckle itself represents several failure modes: (1)

whatever happened to yours (2) the turnbuckle could fail itself (3) there is

an additional connection points/links to come apart(4) the safety wire could

fail if incorrectly done or forgotten (5) the turnbuckle could be

incorrectly assembled with too few threads inserted.  These are all

potential failure modes - most not likely - but how likely was your tang

failure when none has failed before?



(B) The upper wires are the longest and therefore subject to the most

in-flight vibration and movement in general and adding mass to these will

likely increase any in-flight vibrations, etc.



I can understand why someone would want them: its more traditional and it

makes adjustment easier.  But given all the additional failure modes (and

things to check on preflight).  I would not have the turnbuckles on my

airplane.



If you do include turnbuckles and fold your tail, you should consider,

having wire on both sides of the turnbuckle to eliminate any potential

binding, or (remove the bolts thru the stabilizer(s).  If you remove the

bolt(s), putting it back may be a challenge - if you fold regularly you

probably don't want to do it this way.

Dennis



--

slyck(at)frontiernet.net
Guest

Posted: Mon Aug 31, 2009 5:53 am Post subject: always do your preflight!

Thanks Dennis.  Good points to consider.  In addition we may want to  

look at

the dinky little bolts that do the pass-through.  The threads would  

be the weak area. -both on the nut and the bolt.

Because of the angle they are in both tension and shear.



The loads on these wires are not great.  Vibration and work-hardening  

with hours of run time would be the real culprit.

BB



On 31, Aug 2009, at 9:19 AM, Dennis Souder wrote:



[quote] 



 Jimmy and others with turnbuckles (or barrels),



 John mentioned that he was not aware of any such tang failure  

 previously and

 I have none either, these are not just used on Kolb, they are  

 extensively in

 all sorts of ultralight aircraft.  So, logic would seem to indicate  

 that the

 that the presence of the turnbuckle is probably related to the  

 failure in

 some way.



 The tang, I feel certain, is quite strong enough for its intended  

 tensions

 loading.  So all this to say, make sure you don't replicate a  

 scenario that

 would not eliminate the real problem.  Any tang will fail if flexed  

 sideways

 a sufficient number of times.



 I would not put the turnbuckle on the top wires for several reasons:



 (A) These are the wires that will get you home when all else would  

 fail. The

 bottoms are really along for the ride - the tops carry the downward  

 force on

 the horizontal stabilizers.  If the top wire support fails, you  

 probably

 will not make it home.  So keep the failure modes for the top wires  

 as few

 as possible.  The turnbuckle itself represents several failure  

 modes: (1)

 whatever happened to yours (2) the turnbuckle could fail itself (3)  

 there is

 an additional connection points/links to come apart(4) the safety  

 wire could

 fail if incorrectly done or forgotten (5) the turnbuckle could be

 incorrectly assembled with too few threads inserted.  These are all

 potential failure modes - most not likely - but how likely was your  

 tang

 failure when none has failed before?



 (B) The upper wires are the longest and therefore subject to the most

 in-flight vibration and movement in general and adding mass to  

 these will

 likely increase any in-flight vibrations, etc.



 I can understand why someone would want them: its more traditional  

 and it

 makes adjustment easier.  But given all the additional failure  

 modes (and

 things to check on preflight).  I would not have the turnbuckles on my

 airplane.



 If you do include turnbuckles and fold your tail, you should consider,

 having wire on both sides of the turnbuckle to eliminate any potential

 binding, or (remove the bolts thru the stabilizer(s).  If you  

 remove the

 bolt(s), putting it back may be a challenge - if you fold regularly  

 you

 probably don't want to do it this way.

 Dennis



 --

NeilsenRM(at)comcast.net
Guest

Posted: Mon Aug 31, 2009 6:53 am Post subject: always do your preflight!

Jimmy / All



The turnbuckles add mass to those wires so that if there is any in-flight 

vibrations or side loading it would compound the issue. Add to that the V 

twin engine that was bolted solid to your engine mount would have added to 

the issue by transmitting engine vibrations.



I would suggest you give your plane a very close going over to check for 

other vibration related metal fatigue.



Rick Neilsen

Redrive VW Powered MKIIIC



---

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