I don't have any experience with the F-15 yet, but some good general advice with DCS is, "Track or it didn't happen." The next time it happens, save the replay and attach it to your post. That makes it much easier for people to help. They should get saved to: C:\Users\UserName\Saved Games\DCS\Tracks
Even if you forget to save it, you can still find the most recent flight saved there, so you can copy and rename that.
Also, since this is about the F-15, it should probably go in this section: http://forums.eagle.ru/forumdisplay.php?f=321 Try to make your thread title more descriptive in the future too.