 For instance, hovering sideways, or hovering stationary in a crosswind, the clean portion of the disk would be to the side, rather than the front of the rotor disk.Depending on the main-rotor rotation direction this might be seen as a nose pitch up or nose pitch down, a roll, or something in between.While a helicopter accelerates into a higher airspeed, more and more of the rotor disk will be in clean air and the lift differential will decrease.