Class I vs. Class II changes
Class I vs. Class II changes
(OP)
Does anyone know of a specification or standard that has a definitive explanation of the difference between a Class I and a Class II change?
--Scott
http://wertel.eng.pro





RE: Class I vs. Class II changes
Sorry, circular argument, I know.
I think it was the old MIL-STD-100 (now ASTM Y14.100?) that defines drawings, said spec. refers to Configuration Management standard MIL-STD-973 which probably addresses change classifications.
RE: Class I vs. Class II changes
The ASME specs (Y14.100 and Y14.35) don't give a definitive description. There is about a 1-line comment in there stating that Class I and Class II is determined based on the extent of change. Or something like that.
Or maybe it was MIL-STD-31000 that I read that line.
Either way, not definitive enough and I'm hoping that some specification or standard defines "extensive."
Thanks for the help, trueblood. I'll keep digging.
--Scott
http://wertel.eng.pro
RE: Class I vs. Class II changes
As a guess I'd say that good old "form, fit, function, or interchangeability" is the dividing line.
RE: Class I vs. Class II changes
As others say really you need to look at the relevant spec, as long and dull as that may be.
The issue of 'new part number or revision' is covered by ASME Y14.100
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Class I vs. Class II changes
Yet...
I am specifically looking at revision and change control. A typical revision has to be classified as Class I or Class II. In experience, a Class I is a typo or "insignificant" drafting change. A Class II change is something that requires requalification or revalidation of the system in which the change occurs. It therefore affects what parties get to have a say regarding the change because of the cost and schedule impact to incorporate the change.
Some say only typos are Class I.
Some say typos can be corrected as an administration "revision" and the drawing not rolled to the next rev.
Some say tolerance changes are Class I, others say Class II.
Some say dimensional changes are Class I, others Class II.
Then there are alternate materials, finishes, processing requirements, etc. etc.
And then there is the definition of why classification of change matters. Is a business process supposed to be different for a Class I change compared to a Class II change? Or is it just a check box on the ECO form reminiscent of procedures developed before computerized drafting and design?
--Scott
http://wertel.eng.pro
RE: Class I vs. Class II changes
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Class I vs. Class II changes
--Scott
http://wertel.eng.pro
RE: Class I vs. Class II changes
"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"
Mike