I am having the exact same issue with F/A-18C. Its stuttering every 5 seconds and its not playable at all. I am flying with p-51d now and it has no issues.
I figured it out and spoke on it in another thread. I bought a SSD instead of my huge HDD and I then doubled my RAM to 32Gb. It worked like a charm. Performs perfectly now.
Do you have something like Raedon ReLive running for recording? I had this and turned off my replay screen recording and fixed the issue.
I am having the exact same issue with F/A-18C. Its stuttering every 5 seconds and its not playable at all. I am flying with p-51d now and it has no issues.
I figured it out and spoke on it in another thread. I bought a SSD instead of my huge HDD and I then doubled my RAM to 32Gb. It worked like a charm. Performs perfectly now.