During autorotation flare, which result correctly describes rotor RPM?

During autorotation flare, which result correctly describes rotor RPM?

• A. Rotor RPM remains constant
• B. Rotor RPM decreases
• C. Rotor RPM increases
• D. Rotor RPM is unaffected by flare

Answer: (C)

During autorotation the rotor is driven by the upward air through the rotor, not by the engine. When you perform a flare, you raise the blade pitch (increase collective), which loads the rotor more and causes it to extract more energy from that upward airflow. That additional energy shows up as a rise in rotor angular velocity, so rotor RPM climbs toward the upper end of the operating range. This stored energy helps cushion the landing. After the flare, RPM is managed to stay in a safe range as you transition to touchdown.

During autorotation the rotor is driven by the upward air through the rotor, not by the engine. When you perform a flare, you raise the blade pitch (increase collective), which loads the rotor more and causes it to extract more energy from that upward airflow. That additional energy shows up as a rise in rotor angular velocity, so rotor RPM climbs toward the upper end of the operating range. This stored energy helps cushion the landing. After the flare, RPM is managed to stay in a safe range as you transition to touchdown.