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Thread: Carbon Cub-Aileron Cable Wear

  1. #1
    Steve Pierce's Avatar
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    Carbon Cub-Aileron Cable Wear

    Doing a condition inspection on a high time (600 plus hours/2 yrs) Carbon Cub FX3. The aileron cable that goes over the spar is worn at the pulley. This pulley is smaller than on Piper aircraft as the pulley is on top of the spar rather than behind it thus making a smaller radius. I think between that and the higher cable tensions 40 plus/minus 5 lbs are causing this issue. I wasn't expecting to find anything but ran my finger along the cable where it runs across the pulley and it felt rough. After picking at it with my thumb nail I exposed cable strands. Curious if anyone else finds anything like this since the Carbon Cub SS, EX/FX2 and EX/FX3 are designed this was. The X Cub uses a push rod.

    Also, there is no IPC (illustrated parts catalog) for these airplanes and when you order parts be aware that what I call the top aileron cable from the top of the aileron bellcrank to the bottom of the rear stick is called a bottom aileron cable (prt# SK97410) by Cub Crafters and the balance cable from the bottom of the aileron bellcrank on one side, through the fuselage to the bottom aileron bellcrank on the other side is considered the top aileron cable (prt# SC97400) by Cub Crafters. Hope this saves some else having to wait a week when they chose not to spend the extra money on overnight shipping for the parts. This is not a dig at Cub Crafters but a shout out to the folks who fly and maintain these aircraft as to what to look for in the field.

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    Steve Pierce

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    spinner2's Avatar
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    Thanks for the Head's Up Steve. I read your post while eating breakfast and checked my EX this afternoon. I've got about 900 hours on mine and they are whisker-free.

    Such a nice day here I went for a flight too.

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    "Fast is fine, but accuracy is everything." Wyatt Earp

  3. #3
    RaisedByWolves's Avatar
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    Good luck if you ever have to change the balance cable. That conveniently runs through the torque tube. I think the later models have a Clevis on the cable on the left wing. Giant pain in the rear replacing the cable. You can’t get to any of the pulleys.


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  4. #4
    courierguy's Avatar
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    [QUOTE=spinner2;766874]Thanks for the Head's Up Steve. I read your post while eating breakfast and checked my EX this afternoon. I've got about 900 hours on mine and they are whisker-free.

    Such a nice day here I went for a flight too.

    Makes me wonder if your system is running less tension. When I had very stiff rudder cables on my RANS, I was surprised to see the cable grow whiskers after less then 1000 hours, especially as they didn't turn any corners, just some minor angles. When I got much softer springs, the lesser tension solved the issue.

  5. #5
    mike mcs repair's Avatar
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    [QUOTE=courierguy;766880]
    Quote Originally Posted by spinner2 View Post
    Thanks for the Head's Up Steve. I read your post while eating breakfast and checked my EX this afternoon. I've got about 900 hours on mine and they are whisker-free.

    Such a nice day here I went for a flight too.

    Makes me wonder if your system is running less tension. When I had very stiff rudder cables on my RANS, I was surprised to see the cable grow whiskers after less then 1000 hours, especially as they didn't turn any corners, just some minor angles. When I got much softer springs, the lesser tension solved the issue.
    Minor angles are ALWAYS worse than sharp angles for some reason.... go figure...


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    [QUOTE=mike mcs repair;766881]
    Quote Originally Posted by courierguy View Post

    Minor angles are ALWAYS worse than sharp angles for some reason.... go figure...


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    Really? I wouldn’t have guessed that. Any idea why?

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    mike mcs repair's Avatar
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    [QUOTE=CamTom12;766890]
    Quote Originally Posted by mike mcs repair View Post

    Really? I wouldn’t have guessed that. Any idea why?
    no

  8. #8
    SteveE's Avatar
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    Just curious, how many whiskers do you let it grow before it becomes unairworthy?


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  9. #9
    courierguy's Avatar
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    On my plane and my crane rigging, any whiskers at all and it gets replaced. Wire rope is so cheap, why not? Lesser angles, less wear.... Interesting, news to me but yeah that seems to be the case.ca'nt imagine why?!

  10. #10
    Steve Pierce's Avatar
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    Quote Originally Posted by SteveE View Post
    Just curious, how many whiskers do you let it grow before it becomes unairworthy?


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    AC 43.13-1B 7-149. CABLE SYSTEM INSPECTION.Aircraft cable systems are subject to a variety ofenvironmental conditions and deterioration. Wireor strand breakage is easy to visually recognize.Other kinds of deterioration such as wear,corrosion, and/or distortion are not easily seen;therefore, control cables should be removedperiodically for a more detailed inspection.a. At each annual or 100 hour inspection,all control cables must be inspected for brokenwires strands. Any cable assembly that has onebroken wire strand located in a critical fatiguearea must be replaced.b. A critical fatigue area is defined as theworking length of a cable where the cable runsover, under, or around a pulley, sleeve, or througha fair-lead; or any section where the cable isflexed, rubbed, or worked in any manner; or anypoint within 1 foot of a swaged-on fitting.
    http://www.337skymaster.com/document...inspection.pdf
    Steve Pierce

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  11. #11
    SteveE's Avatar
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    Aha, thanks Steve.


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  12. #12
    txpacer's Avatar
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    What size cable does CC use on the Carbon Cubs?

  13. #13
    Steve Pierce's Avatar
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    1/8"
    Steve Pierce

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    Could it be the pulley material? The old pulleys were Bakelite. There are some plastics that eat steel for lunch.

    J3 cables last so long it is embarrassing! My cables lasted for several thousand hours after I bought my Cub, and I think they had a thousand hours on them when I bought it. I have a pair of non-Bakelite pulleys down at the bottom, and they eat cables at about 500 hours. Cable is, indeed, cheap.

    I have all the tools, so I don’t need to wait for shipment.
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    I'd guess the batch of cable. I had an aileron balance cable changed after 35 years. The replacement lasted 6 years and with not many hours. The only way to explain that is cable materials.
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    courierguy's Avatar
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    I just bought a 325' length of USA made 9/16" anti rotation wire rope for my 30 ton boom truck, $800.00, it'll pay for itself in less then a day. Plus I'll sell the old rope, with 6800 hours TT on it (but no broken strands yet felt) for maybe $100.00 to a farmer or rancher. On the other extreme, I have a reel of 1/16" stainless that I bought in '80 for rigging ultralight tip rudder controls, and continue to use for misc. things around the home and shop, I have a couple lifetime supplies of the stuff. Sorry to hear that maybe the quality is getting erratic!

    On a somewhat related subject, I just had a castellated nut on a shackle bolt somehow lose the cotter pin on some of my misc. truss rigging for the crane, and I only noticed it as the pin damn near came loose, as the nut had backed off and fallen off. Subject to a lot of wear and tear on the job site, but I still can't account for how it could have came off. It made me be more vigilante on inspecting the plane's castellated/pinned bolts. I had gotten lax on inspecting the crane rigging apparently to let this get as far as it did, this was a good wake the hell up call.
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  17. #17
    Steve Pierce's Avatar
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    Cables replaced, look worse after bending them the opposite direction.
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    Steve Pierce

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    Yow! Stainless?
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  19. #19
    Steve Pierce's Avatar
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    Quote Originally Posted by bob turner View Post
    Yow! Stainless?
    No, galvanized. Checked one with almost 500 hours last week that was set 10 lbs more cable tension than the worn ones and no issue whatsoever. I am thinking bad batch of cable.
    Steve Pierce

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    Quote Originally Posted by Steve Pierce View Post
    No, galvanized. Checked one with almost 500 hours last week that was set 10 lbs more cable tension than the worn ones and no issue whatsoever. I am thinking bad batch of cable.
    It has been building on my mind to ask if Stl or Galvanized, that is answered.
    Probably hard to answer but how much content of the CC planes would be of Chinese origin. Allot of good stuff is coming out of there but I expect it much be possible the heat treat or alloy might not be spot on with that cable.

  21. #21
    BC12D-4-85's Avatar
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    Do the strands show any flattening or shine from slippage on the pulley (as in worn strands vs just breakage)? Smooth faced hard pulleys can resist turning in other applications when (I assume) the cable moves quicker than the pulley can turn. Old micarta pulleys get wear patterns that mimic the cable twist and maybe grip better.

    I've seen nylon float plane pulleys wear cable fast.

    Gary

  22. #22
    kase's Avatar
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    Just replaced aileron cables to upper horn. L/R cables both starting to show a strand over the pulley that exits top of the wing. 2500 TIS
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    cubdrvr's Avatar
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    Checked mine today. Got 2 cables with 1-2 strands broken. One is near lower fuselage pulley and one where rudder cable exits the empennage. First ones in 2100 hrs.
    So......how many manufacturers are there for the 7/19 cable? The above posts have me wondering about quality control.
    Mine are stainless. Recommendations from anybody but Pierce would be appreciated
    "Sometimes a Cigar is just a Cigar"
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  24. #24
    RaisedByWolves's Avatar
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    Quote Originally Posted by cubdrvr View Post
    Checked mine today. Got 2 cables with 1-2 strands broken. One is near lower fuselage pulley and one where rudder cable exits the empennage. First ones in 2100 hrs.
    So......how many manufacturers are there for the 7/19 cable? The above posts have me wondering about quality control.
    Mine are stainless. Recommendations from anybody but Pierce would be appreciated
    Seems like the stainless wears much faster. Univair makes cables, tested and fit perfectly. Direct copy of piper.


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    mike mcs repair's Avatar
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    Quote Originally Posted by cubdrvr View Post
    Checked mine today. One is near lower fuselage pulley
    Normal spot. Also check where your shoes rub on cable by rudder pedals.


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    cruiser's Avatar
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    cubdrvr's Avatar
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    I'm changing all my stainless control cables with galvanized after 2200 hours. A couple cables were showing a few pop-up strands but the one that got my attention was a rudder cable........this is a straight run cable where it runs through the rear fairlead. During inspections I would cautiously run my fingers fore and aft of the fairlead but I missed this one.......maybe because the rudder was centered and the damage was hidden.
    Lots of dust in the photo but the broken strands left me operating with half a cable. I'll sure move the rudder stop to stop in the future.

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    "Sometimes a Cigar is just a Cigar"
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    Scott A's Avatar
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    Glad you caught that one - I've never seen a cable that bad on any aircraft ever - is the fairlead somehow messed up that it is causing that? Thanks for posting.

    Quote Originally Posted by cubdrvr View Post
    I'm changing all my stainless control cables with galvanized after 2200 hours. A couple cables were showing a few pop-up strands but the one that got my attention was a rudder cable........this is a straight run cable where it runs through the rear fairlead. During inspections I would cautiously run my fingers fore and aft of the fairlead but I missed this one.......maybe because the rudder was centered and the damage was hidden.
    Lots of dust in the photo but the broken strands left me operating with half a cable. I'll sure move the rudder stop to stop in the future.

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  29. #29
    skywagon8a's Avatar
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    RATIO OF CABLE DIAMETER TO PULLEY DIAMETER

    Desirable Minimum
    Critical Minimum
    42:1 24:1 12:1 28:1 18:1 10:1
    Cable Diameterin Inches
    6x7
    or
    7x7
    6x19
    or
    7x19
    6x31
    7x31
    6x37
    6x7
    or
    7x7
    6x19
    or
    7x19
    6x31
    7x31
    6x37
    1/16 2-5/8 ---- ---- 1-3/4 ---- ----
    3/32 2-15/16 2-1/4 ---- 2-5/8 1-11/16 ----
    1/8 5-1/4 3 ---- 3-1/2 2-1/4 ----
    5/32 6-9/16 3-3/4 ---- 4-3/8 2-7/8 ----
    3/16 7-7/8 4-1/2 ---- 5-1/4 3-3/8 ----
    7/32 9-13/16 5-1/4 ---- 6-1/8 4 ----
    1/4 10-1/2 6 3 7 4-1/2 2-1/2
    5/16 13-1/8 7-1/2 3-3/4 8-3/4 5-5/8 3-1/8
    3/8 15-3/4 9 4-1/2 10-1/2 6-3/4 3-3/4
    7/16 18-3/8 10-1/2 5-1/4 12-1/4 7-7/8 4-3/8
    1/2 21 12 6 14 9 5

    https://www.loosco.com/resource-libr...ave-diameters/

    The diameter of the pulley must be of the proper size for the diameter of the cable. The larger diameter of the cable, the larger the required radius for the bend of the cable to prevent breakage. It matters not how many degrees around the pulley the cable travels, the angle of bend of the cable will be the same. The cable which Steve found with broken strands was being bent over too small a diameter pully for the diameter of the wire. That pully should not be installed in that location with that diameter pully. CC should have their hands slapped for using that pully with that cable. The FAA says any change in direction of less than 3 degrees can be over a fairlead. Over 3 degrees, a pully of the proper diameter must must be used. The width of the groove is also important. Wider is better than too narrow.
    Last edited by skywagon8a; 10-29-2022 at 05:35 AM.
    N1PA

  30. #30
    frequent_flyer's Avatar
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    Interesting thread and I'll pay closer attention to cable condition at my next FX-3 inspection.

    I wonder how much pilot technique contributes to premature cable damage. Some pilots simply can't stop stirring the stick. Others won't move it at all in the same air conditions. The Garmin autopilot in my FX-3 is a horrible stick stirrer in anything but smooth air.

  31. #31

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    Most airplane’s have the cables to tight wears everything out and is like flying a truck

  32. #32
    skywagon8a's Avatar
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    Quote Originally Posted by dirthog4 View Post
    Most airplane’s have the cables to tight wears everything out and is like flying a truck
    Replace the sleeve bearing pulleys with ball bearing pulleys to reduce the wear while still tight enough to get proper tight control motion.
    N1PA
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  33. #33

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    Interesting- the willow mountain baggage mod uses very small pulleys for the elevator cables; probably the same as these in the pic. Will be keeping an even closer eye on them...
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  34. #34
    Gordon Misch's Avatar
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    The angle of wrap does indeed matter. The greater the angle the greater the length differential between inner and outer strands. Consider an extreme case, pully just barely touching the cable - angle of wrap nearly zero and length difference between inner and outer strands also nearly zero. Of course the fact that the strands are twisted complicates the situation for larger wrap angles. So 43.13 and Sky's table rule.
    Last edited by Gordon Misch; 10-30-2022 at 01:32 AM.
    Gordon

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  35. #35
    BC12D-4-85's Avatar
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    Lube the cables. Like elevators do.

    Gary

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