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Arksey(at)aol.com
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 Posted: Mon Aug 31, 2009 7:23 am Post subject: always do your preflight! |
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Thanks Dennis for your input...makes sense to me and makes me feel a lot better....jswan
Kolb-List message posted by: "Dennis Souder" <flykolb(at)pa.net>
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.
JIM SWAN
firestar ll, 503, N663S
Eaton Rapids, Mi. 48827
PH 517-663-8488 runway 2300' E & W (42-28.58N 084-44.69 W )
[quote][b]
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JetPilot
Joined: 10 Jan 2006
Posts: 1246
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| Posted: Mon Aug 31, 2009 7:57 am Post subject: Re: always do your preflight! |
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I posted a warning about this here on the Kolb List last year. These tangs have a history of cracking like this. Rans even posted an AD on this same type tang last year for their aircraft. Rans speculated that this can happen due to incorrect bending, and over tightening of the tail wires. Rans said these tangs shoud be inspected with a 10 X magnifying glass, which I do regularly.
http://forums.matronics.com/viewtopic.php?t=42213
Attached to this post is a copy of the Rans AD on these tangs.
Rans aircraft have two sets of tail wires, Kolbs only have one set. If one tail wire were to fail on a Kolb, the airplane would tumble. Given the AD, and close calls like this one, I recently did the work to install a second set of tail wires on my Kolb MK III.
Mike
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_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Kolb MK-III Xtra, 912-S |
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Jimmy Young
Joined: 24 Nov 2007
Posts: 182
Location: Missouri City, TX
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| Posted: Mon Aug 31, 2009 11:09 am Post subject: Re:Re: always do your preflight! |
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Rick Neilsen wrote:
>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,
Will do, thanks for the advice.
I did more "metal fatigue" to my Kolb last year when I pancake-landed it and ripped the left gearleg socket clean off, due to my lack-of-piloting skills. It could be the tang got jerked down pretty hard on that incident, starting a crack. I think that's what some call Kolb-quit, when you stall the plane and you haven't landed yet.
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Jimmy Young
Missouri City, TX
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albertakolbmk3
Joined: 13 Jun 2009
Posts: 69
Location: Innisfail, AB
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| Posted: Mon Aug 31, 2009 5:27 pm Post subject: Re: always do your preflight! |
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Dennis,
I would have to disagree with you. Any failure at all whether top or bottom WILL be a disaster. You know the cable will stretch over time, maybe fractionally, but it will. As everything loosens up you start to get more vibration because you have no way to adjust the tension. Of course you need to be careful not to over-tighten. The tangs have almost cut all the way through the cable thimble on mine, much like the others have noted.
I'm not sure how much time john H. has put on the old tangs but if I remember correctly he had re-done them a few times before going to the system he has now. There is obviously a problem here.
Whether or not the turnbuckle really adds any concern is questionable.
I believe the tang is the problem or at least the way it is being used.
Tony
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Tony B.
Kolb MKIII C
Rotax 582
C Gearbox 3.00:1
WD 66" 3 Blade Prop |
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flykolb(at)pa.net
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| Posted: Mon Aug 31, 2009 7:05 pm Post subject: always do your preflight! |
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Tony,
.. "WILL be a disaster"
Not necessarily!
When I was in Taiwan, I saw a maxair drifter lose its hs stab cables and the
hs stab was loose and flipping around. It got my attention because it
looked like an impending disaster and also because I had just flown the
drifter before this flight. We had just assembled it and I did the first
flight - then another pilot took it up. But the pilot was able to land the
airplane with careful use of the throttle.
At Oshkosh one year, I was sitting at the shore at the seaplane base
watching an ultralight amphibian flying by at 500 ft altitude or so, over
the water. The whole tail broke completely off - the composite fuselage
tube just broke apart - and it went straight in. That WAS a disaster, both
pilot and passenger will killed.
The main point I wanted to make was if one wanted to use turnbuckles, then
put them on the bottom wires - not the top wires. John uses 4 I think, but
others have done it with 2 which still provides good adjustability. Putting
them above provides additional failure points and if I had to choose which
cables to lose, I would choose to lose the lower cables. John seldom folds
his Mark-III so turnbuckles are less problematic with his flying style. To
have turnbuckles on the top wires and fold regularly - you are setting
yourself up for some potential binding problems because the turnbuckle will
get sandwiched between the vertical stab and the horiz stab and since the
tang is projecting out at an angle the turnbuckle will be held to that same
approximate angle and it WILL put pressure on the tang. With the turnbuckles
on the bottom wires, they are on the outside and much less susceptible to
being stressed.
Dennis
--
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pj.ladd(at)btinternet.com
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| Posted: Tue Sep 01, 2009 1:43 am Post subject: always do your preflight! |
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The tangs have almost cut all the way through the cable thimble on mine,
much like the others have noted.>>
Hi,
thats interesting. Were they particularly tight?
I remember that when I was gliding everyone pulled their cables at every
annual as a matter of course. This was mainly to check cable wear round
pulleys etc, finding individual wires which had broken (usually by sticking
the end into your finger) but i can never remember anyone having trouble at
the tang.
I remember one guy landed a bit heavily, banging his feet on the rudder
pedals, and the rudder horn fell off. Nothing wrong with the cable though.
Cheers
Pat
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1planeguy(at)kilocharlie.
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| Posted: Tue Sep 01, 2009 1:21 pm Post subject: always do your preflight! |
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| Quote: |
I posted a warning about this here on the Kolb List last year. These tangs have a history of cracking like this. Rans even posted an AD on this same type tang last year for their aircraft. Rans speculated that this can happen due to incorrect bending, and over tightening of the tail wires. Rans said these tangs shoud be inspected with a 10 X magnifying glass, which I do regularly.
http://forums.matronics.com/viewtopic.php?t=42213
Attached to this post is a copy of the Rans AD on these tangs.
Rans aircraft have two sets of tail wires, Kolbs only have one set. If one tail wire were to fail on a Kolb, the airplane would tumble. Given the AD, and close calls like this one, I recently did the work to install a second set of tail wires on my Kolb MK III.
Mike
I believe the "Warning" you refer to was my message dated APRIL 15 2008
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that referenced (and attached) the RANS AD about these tangs. I do not
know who Kolb gets them from but RANS does in fact manufacture these
tangs for several other companies...they do NOT use them for the tail
wire purpose anymore. At the last inspection in July of this year I
found another tang that was starting to crack (right through the 2ND and
3RD hole just like the AD says they will, for what it is worth I have
never heard of the tangs with only 1 hole in each end ever having a
failure) For the record this tang had never been REbent and the bend was
located properly per the original plans. I am most likely going to
retrofit my cables to a 4130 steel strap with 1 hole in each end...have
another thought on the subject but haven't decided yet. My application
is a RANS S7 but same setup as Kolb for tail cables. Before anyone says
"That doesn't apply to Kolbs" I want to go ahead and say "bull-doody",
they both are subject to vibration and tension and a myriad of other
forces...and will be subject to the same failures on either plane. Only
difference will be the S7 has another complete set of cables to hold
things in their general location till you get it on the ground (albeit
wiggly)...if a Kolb has a tang failure then I hope you have a BRS.
For what it is worth this is kind of ironic that it is even being
discussed again...When someone has a failure of a particular
manufactured part , you'd think other folks with the same manufactured
part would think "Hey, that might be worth taking a look at!" Come on
guys, don't rationalize that "I did mine right , they are fine!!!"
Waste an hour and inspect those 8 little tangs holding your tail
feathers together (and keeping your TAIL in the air...so to speak)
While we are rehashing old warnings, I'll throw out another that I
mentioned around 2005. MATCO 6" aluminum rims that were optional
upgrades on many Kolbs over the years. If memory serves they were MATCO
model number MH6B and were usually anodized gold. They were a spun rim
and had some problems with the web of the rim cracking out where it bent
around and formed the flange. These were later changed ...the
replacements I got were both thicker material and a different profile
shape as well. I know of 2 that let go in use 1 during an otherwise
nice landing that then caused a pretty spectacular sudden stop...I took
the hint and pulled mine off and broke them down to inspect...lo and
behold one of mine had already cracked about 45 degrees of the web to
flange bend. So I can personally attest to 3 failures or imminent
failures of this part. While you are pulling maintenance , checking
those cable tangs why not pull the rims (if you have that style) and
give them a once over?
I am attaching a picture of my cracked rim to show you where to look...I
drew an ellipse around the crack...
Fly safe,
Jeremy Casey
__________ Information from ESET NOD32 Antivirus, version of virus signature database 4387 (20090901) __________
The message was checked by ESET NOD32 Antivirus.
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Wed Sep 02, 2009 3:14 am Post subject: Re: always do your preflight! |
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Jeremy,
Thanks for the Matco wheel information. The Slingshot I bought a month ago has 6" Matco wheels, gold in color but not sure of the model number. The airplane was built in 1999. I'll be checking mine soon. Appreciate the heads up and the photo.
do not archive
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
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