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Engineering Changes--Class I vs. Class II Changes

Engineering Changes--Class I vs. Class II Changes

Engineering Changes--Class I vs. Class II Changes

Most companies employ change classes on their engineering change documents to indicate whether the changes are major (affecting form, fit, or function) or minor (eg, typos).  My experience is that Class I indicates major changes and Class II, minor.  However, I don't know of a reference that defines this common practice.  I've checked MIL-STD-100 and ASME Y14.100, but I didn't see it defined in either.  Is there such a reference?

RE: Engineering Changes--Class I vs. Class II Changes

Not sure about most companies, perhaps some.

The thing is, if the modified part/assy is no longer fully interchangeable with older revisions then per Y14.100-2004 6.8 & D-13 it should normally be a new part number.

So in essence a class 1 change as you've defined it means new part number chased up through the assy levels until interchangeability is restored.

Class II is a true drawing revision.

Maybe look in ASME Y14.35M-1997 but I don't see it.

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RE: Engineering Changes--Class I vs. Class II Changes

Where I have been employed the last few years (Aerospace) each companies definition as been 'approximately' as follows.

"Class I changes affect an item's fit, form or function. These are changes that affect an item's specifications, weight, interchangeability, interfacing, reliability, safety, schedule, cost, etc. Class II changes are changes to correct documentation or changes to hardware not otherwise defined as a Class I change."

Interchangeability has its own set of requirements as well. Where I currently work our documentation is a plagiarized version of MIL-I-8500D "Interchangeability and Replaceability of Component Parts for Aerospace Vehicles"


RE: Engineering Changes--Class I vs. Class II Changes

Hi All,

Thanks for your inputs...very helpful  Mike, you're reference led me to MIL-STD-480, Sections 5.1 and 5.2, which define Class I and Class II changes...just what I was looking for.

Thanks again!

RE: Engineering Changes--Class I vs. Class II Changes

You are Welcome my friend.


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