Which flight control changes the angle of incidence differentially around the rotor system?

• A. Cyclic
• B. Collective
• C. Pedals
• D. Trim

Answer: (A)

Differentially changing the angle of incidence around the rotor is done with cyclic control. Cyclic adjusts the pitch of each rotor blade as it travels around the circle, so the angle of attack (and thus lift) varies with azimuth. This creates more lift on one side of the disk and less on the opposite side, tilting the thrust vector and rotating the rotor plane to point the helicopter in the desired direction. Collective would raise or lower pitch equally on all blades, changing total lift but not the disk tilt. Pedals mainly control yaw by adjusting tail rotor thrust, not the differential lift across the rotor disk. Trim helps maintain a steady condition without creating the required differential around the disk.