How many hydraulic systems are standard on a narrowbody and what are their general responsibilities?

• A. Two independent hydraulic systems (System 1 and System 2) supply most primary flight controls, landing gear, brakes, and flaps/slats, with separate pumps and reservoirs for redundancy.
• B. Three hydraulic systems.
• C. One hydraulic system with dual pumps.
• D. Two hydraulic systems, both sharing a reservoir and not providing redundancy.

Answer: (A)

Two independent hydraulic systems are standard on a narrowbody. Each system has its own pump and reservoir and powers most primary flight controls, the landing gear, brakes, and flaps/slats. This arrangement provides redundancy: if one system loses pressure or fails, the other can still operate the primary controls and essential systems, helping to maintain safe flight and landing. The separate reservoirs also prevent cross-contamination and allow maintenance to isolate a failed system.

Three hydraulic systems would exceed what's typical for a narrowbody and isn’t necessary for standard redundancy. A single hydraulic system with dual pumps would not give the required level of safety through redundancy. Two systems sharing a reservoir would compromise independence and safety, since a fault in the reservoir could affect both systems.