How does increasing airspeed impact induced drag on the rotor blades?

Increasing airspeed generally decreases induced drag on the rotor blades up to a certain point. Induced drag is a component of drag that is created as a byproduct of lift generation. It's caused by the vortices that form at the tips of the rotor blades as high-pressure air from below the blade flows around to the low-pressure area above the blade. These vortices create a downward airflow (induced flow) that reduces the effective angle of attack and increases drag. As the helicopter gains airspeed, the rotor system becomes more efficient at generating lift, and the induced flow is reduced. This leads to a decrease in induced drag. However, at very high airspeeds, profile drag (the drag caused by the friction of the air moving over the blade surface) becomes the dominant form of drag, and the total drag on the rotor blades begins to increase again.