If counting PCUs powering Elevator, Ailerons, and all Spoilers, how many PCUs power these control surfaces in total?

If counting PCUs powering Elevator, Ailerons, and all Spoilers, how many PCUs power these control surfaces in total?

• A. 12 PCUs
• B. 16 PCUs
• C. 18 PCUs
• D. 20 PCUs

Answer: (C)

Power Control Units (PCUs) power the hydraulic actuators that move flight control surfaces. To get the total, add up the PCUs dedicated to each surface across the aircraft. For the CRJ-550, the elevator is powered by four PCUs, the ailerons by two PCUs, and the spoilers by twelve PCUs (six on each wing). Adding these gives 18 PCUs in total. This arrangement provides the necessary redundancy so that a failure in one PCU doesn’t render a surface inoperable.

Power Control Units (PCUs) power the hydraulic actuators that move flight control surfaces. To get the total, add up the PCUs dedicated to each surface across the aircraft.

For the CRJ-550, the elevator is powered by four PCUs, the ailerons by two PCUs, and the spoilers by twelve PCUs (six on each wing). Adding these gives 18 PCUs in total. This arrangement provides the necessary redundancy so that a failure in one PCU doesn’t render a surface inoperable.