Gatt,
This is caused because at about D1.5 to 1000 AHII pulls up the more detailed texture of the plane. If you haven't been near this particular plane and the particular skin already in this session, your system searches your hard drive for the data and pulls it up.
Try these steps, after each one fly a bit before going to the next one:
1) Be sure you have textures pre-loading in system memory.
2) Set Max texture size down one notch from whatever you have it at now. Default is 512, if you've changed it to 1024, this will cause the stutter as the hard drive searches for the large data set for that plane.
3) Disable custom skins. That way your system only has to pull up the default ones.
4) With my old system I used to log on, then got to a busy airfield and sit in the field ack next to the runway for 15 minutes (I would just go get a cup of coffee in no enemy planes around). As your country's planes take off the skins will load into memory. This will pre-load most of the popular skins in your memory.
5) Download SIS Sandra, it's free. Run the storage test to make sure your HD is transfering data at the correct rate to the CPU/VPU. if not, you probably have an incorrect IDE or RAID setting.
