When the pilot moves the control wheel or rudder pedals, what makes the respective lift control move?

• A. Electric motors
• B. Hydraulic power control units (PCUs) with redundant supply from two or three of the hydraulic systems
• C. Mechanical linkages
• D. Pneumatic actuators

Answer: (B)

Moving the control wheel or pedals sends a cockpit command to a hydraulic power control unit. The PCU, fed by hydraulic pressure from two or three independent systems, converts that command into movement of a hydraulic actuator attached to the corresponding lifting surface. The redundancy ensures the surface can still move even if one hydraulic system fails, and the PCU precisely positions the surface by modulating pressure with feedback. Electric motors or mechanical linkages wouldn’t provide the same reliable force and control for primary flight surfaces, and pneumatic actuators aren’t typically used for the high-force, precise actuation required in lift control.