When blades are said to feather, what does this indicate?

When blades are said to feather, this indicates that they are adjusting their pitch. Feathering refers to the ability of the rotor blades to change their angle of attack relative to the oncoming wind or airflow. By altering the pitch, the blades can optimize lift and drag characteristics according to flight conditions and power requirements.

This adjustment plays a crucial role in the performance of the helicopter, especially during different phases of flight, such as takeoff, hovering, and landing. Feathering is particularly important in managing rotor efficiency and response during maneuvers, allowing for better control and performance.

In contrast, the other options describe different states or actions of the rotor blades but do not capture the fundamental aspect of feathering. Static blades do not adjust pitch; moving downward describes the action of the blades during certain flight maneuvers but does not pertain to feathering; and increasing RPM relates to engine output rather than the pitch control of the rotor blades.