What's minor wear?
What's minor wear?
I've struggled with (and asked a couple related questions about) this for my entire time designing repairs for aircraft. There is an allowable damage limit for one area of a part. But for everywhere else it says "No damage". But at some point minor, but measurable, damage becomes non-relevant. There are occasionally references for sheet metal parts that permit 10% or even 20% wear and give instructions for blending. In the attached figure the wear limits indicated are permitting the removal of ~.015" from the original V-blade profile (this is on a V2500 TR) which is much less than 10%, but this is a structurally more significant part than most sheet metal details.
However if I have .002" wear on a surface away from the "repairable zone" am I stuck? How do I justify accepting this wear as is and moving on. At what point can I call it negligible damage and move on without further analysis?
I was looking at justifying it by noting the part looks to have an anodize coating and since this is for a wear surface I would expect it hard anodized similar to MIL-A-8625 which could have a coating thickness of up to .0045. I also thought I could justify it by noting the wear damage was less than any expected measurement tolerance the part is being held to. I know that's an assumption since I don't have the drawing, but I would be surprised to find an extrusion with a thickness tolerance tighter than ±.010". I'm also assuming the part wasn't fabricated at the minimum material condition and my additional .002" might push it beyond that.
Is there an FAA or SRM (Goodrich or Airbus A320 in this case) reference for "below this call it negligible." that I'm missing?
Are there other, better justifications for blending minor wear that I could use?
Are the justifications I've listed reasonable or bogus?
What have you done when faced with similar minor issues you need to put your engineering stamp of approval on?
Thanks for expanding my knowledge when I'm in a dilemma and stumped.
Remember, first define the problem, then solve it.