What is your take on the internal audit requirements for AS9100D and even ISO 9001 2015; do the entire QMS once a year OR 3-5 years cycle?"
The internal audit process is an important tool that is used to take a close look at how your processes are working, even if you are using key performance indicators for the process to know how it is working. The internal audit takes a closer look at the details of the processes to ensure that they are adhered too, and to ensure that any corrective actions or improvement activities taken for the process are effective. So, while it is not specified in either AS9100 Rev D or ISO 9001:2015 at what frequency to perform internal audits (such as annually) it does mention that you need to plan your internal audits frequency by taking into consideration the importance of the processes, changes in the organisation and results of previous audits.
So, that being said, I would never recommend a 3 - 5 year cycle for internal audits. If you are not looking at a process for 3 yea rs how do you know if any corrective actions or improvements are effective or that changes to other parts of the organisation have not affected the process. If you found a problem in one audit how effective would it be to wait 3 years to look at that process again? Even the certification bodies have a schedule of three years where the do the entire QMS the first year, audit main processes (internal audit, management review, corrective action, etc) and some of the QMS the second year, audit the main processes and the remainder of the QMS the third year and then perform a complete QMS audit for the re-certification the following year (and starting the cycle over).
So, I am a big believer that having an annual audit schedule that includes all QMS processes, and important or problematic processes more than once if needed, so that you can gain the benefits of the audits. I also believe that this schedule needs to be maintained, meaning having an update to add a process that has changes or experienced problems. Having a cycle of 3 - 5 years before you re-audit a certain process in the QMS could lead to problems, and you will not get the biggest benefit from your internal audits.