Which term refers to the unequal lift across the rotor disc caused by differing air speeds on the advancing and retreating halves?

Which term refers to the unequal lift across the rotor disc caused by differing air speeds on the advancing and retreating halves?

• A. Dissymmetry of Lift
• B. Drag
• C. Dynamic Rollover
• D. Dual Rotor

Answer: (A)

In forward flight, the rotor disk doesn't experience the same airspeed across its span. The advancing half moves into the air at a higher speed, producing more lift, while the retreating half encounters slower air and generates less lift. This unequal lift across the rotor disk is called dissymmetry of lift. If not corrected, it would cause the rotor system to tilt and the helicopter to roll toward the retreating side. The controls and rotor design compensate by redistributing lift—through blade flapping and cyclic pitch adjustments—to balance the lift across the entire disk. The other terms describe different ideas: drag is resistive force, dynamic rollover is a dangerous stability issue, and dual rotor refers to a two-rotor configuration, not the unequal lift across a single rotor disk.

In forward flight, the rotor disk doesn't experience the same airspeed across its span. The advancing half moves into the air at a higher speed, producing more lift, while the retreating half encounters slower air and generates less lift. This unequal lift across the rotor disk is called dissymmetry of lift. If not corrected, it would cause the rotor system to tilt and the helicopter to roll toward the retreating side. The controls and rotor design compensate by redistributing lift—through blade flapping and cyclic pitch adjustments—to balance the lift across the entire disk. The other terms describe different ideas: drag is resistive force, dynamic rollover is a dangerous stability issue, and dual rotor refers to a two-rotor configuration, not the unequal lift across a single rotor disk.