In what scenario would you typically find a helicopter in an auto-rotation state?

A helicopter enters an auto-rotation state typically during an emergency descent. This situation occurs when the helicopter experiences a loss of engine power or a significant failure, requiring the pilot to manage the descent without engine thrust. In an auto-rotation, the pilot allows the rotor blades to continue spinning by descending rapidly, which creates a downward airflow through the rotor system, enabling the blades to produce lift as they rotate.

This technique is crucial for controlling the helicopter's descent rate and ensuring a safe landing, even without engine power. Pilots are trained to become proficient in executing auto-rotations during their training to prepare for such emergencies. The other scenarios listed do not accurately depict conditions under which a helicopter would typically be in an auto-rotation state, as they either imply normal operating conditions or controlled landing scenarios where engine power is still available.