Which term explains the lift imbalance across the rotor disk due to different air velocities on the advancing and retreating halves?

Which term explains the lift imbalance across the rotor disk due to different air velocities on the advancing and retreating halves?

• A. Dissymmetry of Lift
• B. Drag
• C. Feedback
• D. Feathering

Answer: (A)

Dissymmetry of lift describes the lift imbalance across the rotor disk in forward flight. Here, the advancing blade moves into air that’s flowing faster relative to the blade than the retreating blade does, so the advancing side generates more lift than the retreating side. If uncorrected, this would tilt the rotor disk and upset stability. The rotor system compensates through blade flapping and cyclic pitch adjustments: the advancing blade flaps up and reduces lift, while the retreating blade flaps down and increases lift, bringing the disk back toward level flight. The other terms don’t capture this specific aerodynamic effect—drag is a resistance force, feathering is about blade angle to minimize drag or for autorotation, and feedback isn’t the technical term for this phenomenon.

Dissymmetry of lift describes the lift imbalance across the rotor disk in forward flight. Here, the advancing blade moves into air that’s flowing faster relative to the blade than the retreating blade does, so the advancing side generates more lift than the retreating side. If uncorrected, this would tilt the rotor disk and upset stability. The rotor system compensates through blade flapping and cyclic pitch adjustments: the advancing blade flaps up and reduces lift, while the retreating blade flaps down and increases lift, bringing the disk back toward level flight. The other terms don’t capture this specific aerodynamic effect—drag is a resistance force, feathering is about blade angle to minimize drag or for autorotation, and feedback isn’t the technical term for this phenomenon.