One of my favorite FSX payware aircraft (and the one I would have IRL if $$ were not an issue) is the Pilatus PC12 (Flight1). No matter which spin_prop.bmp type texture I swap out the motion of the prop inside and out is such that instead of a steady rate of spin in one direction it kind of rocks and jerks back the other direction once or twice a revolution. Spoils an otherwise good experience. Is there a tweak in the [propeller] section in the air.cfg to fix/adjust this or is it in the model and can't be changed?