Contaminated rotor blades (by ice, snow or dust) can also have significant issues on helicopter’s performance, because:

• The All Up Mass increases, thus increasing the power required.
• The shape of the rotor blade section is distorted, reducing its aerodynamic efficiency encountering more air resistance and friction (thus, decreasing the lift production and increasing the drag) and, as a result, reducing the power available and increasing the power required.

On the other hand, when blades are clean, they encounter less air resistance and friction, allowing them to cut through the air more effectively. It means that the rotor disc needs to exert less energy to maintain its performance, thereby requiring less power.