Ktulu2, thanks for the quick response. I've read over the thread quickly. I see one of the comment also indicated problem at high altitude. In my case, the game set the starting speed around 300knot, i push to afterburner to gain speed before merge, but at that altitude, I didn't get much. I put nose down, pull the stick to turn; if I pull more than 3g, it will easily get into "departure"; I will have to reduce throttle, release the stick to get the control back. At one time I couldn't get out of the flat spin. Does this sound expected behavior?
Next time I will watch my AOA.