To: 212 Man
The problem does not manifest itself until the helicopter comes up to speed. In a hover assuming a still wind day the rotor speed generates the relative wind passing over the blades (disc). However, when the helicopter comes up to speed the relative wind is now equal to the forward speed plus the rotational velocity of the advancing blade and minus the rotational velocity of the retreating blade. That’s how you get into retreating blade stall. With the helicopter moving forward at 100-120 Knots the blades as they become aligned with the longitudinal axis have a constant rotational velocity but the airflow over the centralized blades have an airflow component of 100-120 knots flowing down the blade spanwise. This has to have some effect on blade lift.
------------------
The Cat