I have been going up and down for a while; especially noticing fluctuations when I look down in the cockpit. The final mistake I was making is that I had "vertical synch" enabled in Nhancer and frame rates locked in X-plane. I changed the X-plane setting to "do not lock". Now I get a rock solid 37 FPS in just about any aircraft including the BK117. The most intense aircraft I have is the Falcon 7X for 9.31; that takes me down to 25 FPS in VFR conditions. In that aircraft my frame rate improves drastically in IFR conditions- Why can't Mr. Gates do that? and I have every weather option enabled; volumetric fog, cumulus, particle clouds etc... My frames are plentiful now and they are extremely consistent throughout a flight. Donald Traill