What term describes the differential lift between the advancing and retreating halves of the rotor disk due to different wind velocity across each half?

• A. Dissymmetry of Lift
• B. Translational Lift
• C. Induced Drag
• D. Autorotation

Answer: (A)

Dissymmetry of lift describes the differential lift across the rotor disk caused by the different wind speeds each half experiences during forward flight. When the helicopter moves forward, the advancing blade meets the air with higher relative velocity and produces more lift, while the retreating blade encounters lower relative velocity and produces less lift. If not balanced, this creates a rolling tendency, which pilots counteract with cyclic control to even out lift across the disk. Translational lift refers to the overall lift gained from moving into undisturbed air, induced drag is the drag produced by lift, and autorotation is rotor motion driven by upward air flow when the engine isn’t providing power.