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Roger Lee

Brake caliper and inspection fail

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Here are a couple of pictures from a recent job where a mechanic didn't do a good job during an annual inspection. It came to me 3-4 days after the inspection. This Matco brake caliper has been milled out by what I suspect was a loose disc screw. This disc had allen head screws and at the time I saw this had safety wire on all of the disc screws. Matco doesn't use allen head screws any more. They use Nordloc washers and a flat head screw.

This aircraft also didn't have hardly any brakes. Someone mixed Dot 5.0 and 5.1 brake fluid and it ate the MC seals and caliper seals.

 

The point of the post is don't forget to look under the lowest spot and don't assume it's okay. If your not sure about brake fluid type grab the phone and make a call.

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I hate the allen screws. They are always stripping out. Did they JUST switch to flat heads? I remember calling them up and complaining, and I had stocked up on 20 or so of those allens because I'm replacing them all the freaking time!

 

Also, for the nordlocks: they do wear out! If the ramps are rounded off, it's time to replace! It usually takes only about 3 or 4 times taking the screws out and those nordlocks are hosed. I keep a generous stock of those. I'll have to see if I have examples.

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Hi Corey,

 

The screws themselves have an allen opening and flat and these aren't the old tall allen socket head type screws. They are the ones you have been working with the last few years. This plane was a little older. If I have a stripped allen head screw I just use my handy dandy trusty Dremel tool with a cut off blade and put a groove in it and then just use a flathead screwdriver. Hasn't failed me yet.

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I've removed the nordlocks many times on my wheels, and they still hold the screws tight. I'm careful to align the teeth before tightening, I think that keeps wear down.

 

Mine probably should be replaced, does anybody have a good source for the right sized ones?

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It's when you take them off that they round off. They are literally locking teeth that you're breaking loose.

 

For the disc screws: http://www.matcomfg.com/WASHERNORDLOCSETNL14ZINCPLATE025-idv-3702-35.html

 

For the bolts that go through the liners: http://www.matcomfg.com/WASHERNORDLOCSETNL8ZINCPLATE0316-idv-3718-35.html

 

Drawings for parts reference are found in the manual. Here's the one for CTs: http://static.veracart.com/matco/item_pdfs/3671/document1.pdf

 

Matco's part naming scheme is a bit of a pain. Here's guidance on how it works for the technically curious: http://matcomfg.com/HowtoReadMFGPartNumbers-tp2-17-partnumbers.html

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I just had an A&P remove some screws with these. He thought someone accidentally applied two washers. he had no clue as to what they were. When I removed the screws they only had half the Nordloc washer. These were on Matco brakes.

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For those of you who might go thru these frequently and need a supply, you might find this company offers the Nordlocks for a better price.  I've ordered from Maryland Metrics but don't recall what I paid for a few of them for my brakes.  Matco is probably cheaper when buying just a few.

https://mdmetric.com/nordlock/Nord-Lock%20-%20Stainless%20steel%20washers.htm

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