Three independent hydraulic systems are present in an aircraft. Regarding flight controls, which statement best describes their operation?

• A. All 3 systems work simultaneously
• B. Only one system operates at a time
• C. Two systems operate in tandem with the third standby
• D. Hydraulic systems do not affect flight controls

Answer: (A)

When flight controls are powered by three independent hydraulic systems, the design relies on all three contributing to actuation in normal flight. Each system provides pressure to the flight-control actuators, so surfaces like the ailerons, elevator, and rudder can be moved by more than one source. This arrangement gives maximum control authority and, crucially, redundancy: if one system loses pressure, the remaining two can still move the controls. Some surfaces may have actuators fed by multiple systems, reinforcing this reliability. The idea that only one system operates at a time or that hydraulics don’t affect flight controls isn’t correct.