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Thread: Jc5a

  1. #1
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    Question Jc5a

    I've just been handed a copy some information being disemminated to the MOD supply lines concerning JC5a and corrosion problems associated with it.Apparently there is to be an embargo on the use of this product (Titanine and Desoto manufactured) throughout the MOD aviation world, specifically Nimrods. From my Google search, it seems to have its roots in a Boeing AD dated 2002 concerning corrosion in undercarriages and their attachments. There is no mention of JC5a batch numbers or even anything to do with investigation into Boeing production methods. (Heat treatments or cleanliness etc) So, how can it be that a product which has been in service for so long is suddenly a pariah? Anybody care to comment if there has been a subsequent rumble throughout the CAA world which may have fizzled out?

  2. #2
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    Default

    Not heard a sausage, use it all the time and it seems to work fine for me !
    Success is the ability to go from one failure to another with no loss of enthusiasm

  3. #3
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    Remember someone mentioning to me last year about Mastinox (civvi version of JC5A as far as I know) being a no-no because it held water that ingressed into joints. Seemed a bit daft to me, as it is a jointing compound after all and alot of helicopters (esp. new eurocopter) are held together with the stuff! Maybe he was referring to a particular batch or type. Who knows? It was just a passing comment in conversation. Haven't seen anything official to verify it though and mastinox is still being happily slapped on aircraft as far as I'm aware.

  4. #4
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    JC5A and Mastinox are both jointing compounds, but they are definately not joint sealants. It apparently has been proven (not sure where I heard it) that Eurocopter found this,through corrosion in pitch links and control rods, although they had been wet assembled with JC5A/Mastinox, there is still a requirement to seal the bearing/thread ends with PRC or similar, as mastinox will not prevent theingress of moisture.

  5. #5
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    As far as I know JC5A isn't approved by Boeing. Some component suppliers still use it as an alternative to its nasty brother, mastinox 6856K (BMS3-27), which is still approved for use.

  6. #6
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    "JC5A, in the presence of moisture, would decompose and produce decomposition by-products. These in turn would attack the primer first, and then the cadmium plating underneath, resulting in the accelerated corrosion rates of the base metal substate. "

  7. #7
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    Remeseal has this anything to do with Africa, 155's and pitch links? It is true that I have met people under the impression it can be used as a wipe on Proseal, but I assumed they were just stupid and only a select few would think it would be an effective sealant. Maybe I was wrong...
    Success is the ability to go from one failure to another with no loss of enthusiasm

  8. #8
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    Smile

    Thanks for all your comments gentlemen. The blurb I have doesn't mention sealant and I've never thought that JC5 was ever to be used in this context.
    I'll feel safe now in telling my Chief that the UK fleet of homebuilt aeroplanes won't be corroding and dropping out of the sky just yet (especially the wooden ones) Merry Christmas

  9. #9
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    I was of the impression that JC5A and Mastinox were, although both jointing compounds different, Mastinox being approved on some types and JC5A on others.
    It came off in me hand guv honest !!

  10. #10
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    Default mastinox on 155s

    Fenestron, no it wasn't. That's a new one on me?? This came out in conversation about floor panel corrosion. Bearings protected with grease 5/ or proseal but funnily enough, Eurocopter recommend that mastinox is used in copious amounts on control rod eye-end threads to prevent water ingress and corrosion inside control rods. Figure that one out??

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