What is the purpose of hydraulic systems on a commercial jet?

• A. To generate electrical power
• B. To power control surfaces, landing gear, flaps, and other systems requiring movement
• C. To provide cabin pressurization
• D. To cool the engines

Answer: (B)

Hydraulic systems are used because they can convert fluid pressure into large, precise motions with high power density. This makes them ideal for moving big, aerodynamic surfaces and other heavy components smoothly and reliably. On a commercial jet, the hydraulics power the control surfaces (ailerons, elevators, rudder) to steer the aircraft, as well as landing gear, flaps, and other systems that require controlled movement.

Electrical power generation, cabin pressurization, and engine cooling use different systems: generators provide electricity, environmental control systems handle pressurization, and dedicated cooling loops manage engine temperatures. So the hydraulic system’s main role is to furnish the movement needed for flight controls and other heavy actuated parts.