What is that one guy talking about? Our center of rotation is wrong?
Rotor planes in Flightgear are in fact rotating around the center point of the rotor plane. The cell hangs under the center point of rotation of the rotor plane. Based on weight balance, its center of gravity is placed somewhere inside the cell. Perfect placement of course is directly underneath the center of rotation of the rotor plane. Based on the center of gravity the cell is rotating around it as soon as forces are acting on the cell due to the lift creation by the rotor plane on different axies. This behavior is simulated in FG and utilized in the helicopter models as well.