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Thread: Wing Struts

  1. #1

    Wing Struts

    I have a 1946 Commonwealth Skyranger with steel wing struts. What is the best way to check the inside of them for corrosion? The outside of them have been stripped and look perfect. I have done a "TAP " test and the sound is constant. I have tilted them and do not hear anything rolling around. I have access at the base where the adjustment screws in and nothing falls out. I can use an automotive boroscope but it only goes in about 18". Any more ideas ? Thanks

  2. #2

    Join Date
    Oct 2011
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    Merkel, Tx
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    Skyranger, I have a 57 Pacer that I used to have to do a punch test on the struts periodically. Seems like we used a fabric tester and overlaid the bottom of the strut with 1/4" grid paper. Then we punched each square to the limit of the tester and looked for any deformation. This test was done only at the lower foot or so of the strut. I wound up fixing mine by replacing my old struts with new sealed struts. The thinking is that if internal corrosion is taking place, it will be at the bottom where water will collect.

    Like you I would be more comfortable if I could see the entire inside of the strut. Some of those borscopes do have extensions that you can buy. I know when I bought mine 10 years ago or so, extensions were available.

    If nothing else, you could punch test the entire strut.

    Best of luck,

    Tim

  3. #3
    FlyingRon's Avatar
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    The older piper struts are punch tested with the maule fabric tester (which by the way is useless for testing most fabrics these days, the polyester fabrics and their allowable finishes are done based on appearance rather than punching).

    You may get some information here: http://www.rearwin.com/index.asp

  4. #4

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    Quote Originally Posted by skyranger View Post
    What is the best way to check the inside of them for corrosion?
    I'd send it out for ultrasonic NDT. And I'd send the attach hardware and bolts (even if they are brand new) as well. An ultrasonic NDT test facility can provide you with a map showing the thickness of the metal. It's not that expensive, maybe ~$200 for all the struts. Of course, it's best to find something close by so there's no shipping involved. Alternatively, you can probably find an A&P school or other non-aviation NDT facility that can do ultrasonic testing.

    Testing with a Maule fabric tester won't provide any valid data.

  5. #5

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    X-Ray will give you by far the best indication of whether your struts are cracked or corroded. Several of us owners put together (and received approval for) an AMOC (Alternate Method of Compliance) for an AD that came out against the Taylorcraft strut. The original AD specified ultrasound, and SEVERAL trained, experienced aero engineers expressed their opinion that ultrasound was not the best... ultrasound might give you a measurement of metal thickness, but only X-Ray will give you an immediate "life-or-death" indication of the presence of corrosion or dangerous cracks. The X-ray gives you an immediate, intuitive, visual "look-see" into the strut metal. Definitely go with X-Ray!
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