What does Hydraulic System 1 (HS1) provide and in what role?

• A. Provides hydraulic fluid pressure to non-flight control systems as a backup source.
• B. Provides hydraulic fluid pressure to non-flight control systems as a primary source.
• C. Provides hydraulic fluid pressure to the primary flight controls either as a backup or a backup source.
• D. Provides hydraulic fluid pressure to the primary flight controls either as a primary or backup source.

Answer: (D)

Hydraulic systems deliver pressurized fluid to move control surfaces, and the primary flight controls rely on this hydraulic power. Hydraulic System 1 is dedicated to supplying the primary flight controls, and it’s designed to function in two modes: as the main source of hydraulic pressure, or as a backup if the other sources aren’t available. This redundancy ensures the pilot can retain control of the aircraft even if one hydraulic system is degraded.

The other choices aren’t correct because HS1 is not primarily for non-flight-control systems, and it isn’t limited to just a backup role—the intended arrangement is to power the primary flight controls and provide redundancy by allowing either system to serve as the primary or the backup as needed.