What is the term used for the downward air flow created by the rotor?

The term "downwash" specifically refers to the downward airflow generated by a rotor, such as that of a helicopter or a rotorcraft. This phenomenon occurs as the rotor blades spin and create lift, pushing air downward. The intensity and characteristics of this downwash are significant for understanding the performance and behavior of the aircraft. Downwash can impact the aircraft's flight dynamics and also influences the environment around the rotorcraft, such as affecting nearby objects or terrain, and is crucial for pilot awareness, particularly in takeoff or landing scenarios.

In contrast, other terms like backflow, airstream, and rotor slip describe different aerodynamic concepts but do not accurately capture the specific action of the rotor generating downward airflow. Backflow often relates to movements of air that can affect system performance but isn't limited to the downward movement caused by rotors. Airstream generally refers to the flow of air in any direction created by various forces, while rotor slip is a term associated with the efficiency of the rotor and its ability to convert rotational motion into lift. Thus, understanding "downwash" is key in the context of rotorcraft dynamics.