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What is process validation in AS9100 Rev D?

One concept that seems to confuse people when implementing AS9100 Rev D is how process validation fits into the aerospace Quality Management System (QMS). What is process validation? When is process validation required? What specific aerospace requirements exist for process validation? What documented information do you need? Find out below.

What is process validation?

Part of the confusion with process validation is due to a lack of understanding of the differences between verification and validation in the design process, and what these mean in the standard. In short, verification is a paper exercise when you compare the plans for the design (design outputs) against the requirements for the design (design inputs) and ensure that everything is covered (e.g., you have all the tests in your test plan that are required by the customer requirements). The validation of the design is done when you actually build a product or service and ensure that the resulting testing of the product or service actually meets the requirements.

Likewise, process validation is when you use a controlled process and ensure that it is actually giving you the output that the process is required to produce. For instance, you can have a welding process that is designed to weld together two pieces of steel; however, when it actually comes to performing this process, the results can be poor if you are using stainless steel, and you may find that the process needs to be modified. The only way to really perform a process validation is to perform the process, check that the parameters of the process can be met during that trial through the use of measurement, and then perform a full check on the products or services that come out of the process against the requirements (which might entail damaging or destroying the products made).

To learn more about the difference between verification and validation, see this article on Design verification vs. design validation in AS9100 Rev D.

When is process validation required?

The requirements of the AS9100 Rev D standard do not state that every process needs to be validated, only those processes where the resulting output cannot be verified by subsequent monitoring and measurement – processes that are commonly called “special processes” in the aerospace industry. This means that if you do not have a way to check if the product or service is compliant with the input requirements of the process, then the process needs to be validated. Some common examples of these processes are soldering and welding, where you are unable to check the strength of every joint during regular production without destroying or damaging the parts.

So, not every process is required to be validated per the AS9100 Rev D standard; however, you may choose to validate other processes at your discretion (for instance, to reduce a costly or complex inspection of a product or service in production by using a validated process).

What are the aerospace-specific requirements of process validation?

The AS9100 Rev D standard has an aerospace-specific section regarding the validation and control of special processes (clause This section includes six requirements on what the organization needs to do for a special process:

  1. Define criteria – In particular, this means defining the criteria for the process to be reviewed and approved. You need to define what is needed to perform the process validation and verify that the process meets the requirements. How many parts will you make? How will you test the parts?
  2. Conditions to maintain approval – How do you know the process still meets approval? Do you need to validate on a routine basis (e.g., yearly)? If the process is moved in your facility, do you need to revalidate? How about if you change facilities?
  3. Facility and equipment approval – Is your process dependent on the facilities and equipment that are involved (such as a particular machine)? This may affect your decisions on conditions to maintain approval if you have approved the machine as part of the process validation, and you end up replacing the machine.
  4. Qualified operators – Some special processes rely on operators being qualified to perform the process, such as welding or soldering. Does your special process need this?
  5. Specific methods – Does your process need specific methods or procedures in order for it to be implemented and monitored? For instance, is there a complicated monitoring process that you need to use to ensure the outputs will be correct?
  6. Documented information – What documented information is required for the validation and maintenance of the process? This needs to be defined by you, and we will talk more about this in the next section.

What documented information do you need?

As the AS9100 Rev D standard does not specify what information needs to be documented for process validation, you will need to follow the other rules of documented information in the standard, which are discussed in clause 4.4.2. First, what documented information do you need to support the operation of the process, such as documenting the information above (e.g., the conditions to maintain approval), which could cause a non-conformity in the process if they are not written down? Secondly, what documented information do you need to have confidence that the processes are carried out as planned, such as records to demonstrate that the process is adequately validated (e.g., reports of the testing). The last things to remember are the requirements for records of competence from clause 7.2, so if qualified personnel are required, how do you show this competence?

Process validation: Important for your business

While process validation is complex, it can save you time and money by making sure that your processes are more reliable, and this means you can be less reliant on post-production verifications, like product inspections. If you know your process will successfully produce the outputs that are required, you will have fewer problems with nonconforming products to control in your facilities, or worse, nonconforming products that escape to your customers.

To get a better understanding of what needs to be documented in order to validate AS9100 Rev D processes, download this free white paper: AS9100D List of mandatory documents.

Advisera Mark Hammar
Mark Hammar
Mark Hammar is a Certified Manager of Quality / Organizational Excellence through the American Society for Quality and has been a Quality Professional since 1994. Mark has experience in auditing, improving processes, and writing procedures for Quality, Environmental, and Occupational Health & Safety Management Systems, and is certified as a Lead Auditor for ISO 9001, AS9100, and ISO 14001.