HYD 3 is typically used for on the A321?

• A. Secondary flight controls and certain actuators such as spoilers and gear
• B. Primary flight controls
• C. Landing gear
• D. Brakes only

Answer: (A)

On the A321, hydraulic systems are分配 to protect the primary flight controls and to keep essential functions available even if other systems are affected. HYD 3 is set aside for secondary flight controls and specific actuators, such as the spoilers and landing gear.

Spoilers provide speed control and assist in roll control, while the landing gear requires hydraulic power to extend and retract. By dedicating HYD 3 to these components, the aircraft ensures that, even if the primary flight-control hydraulics are troubled, the aircraft can still deploy the spoilers for deceleration and extend/retract the gear for a safe approach and landing. This is why HYD 3 is typically used for secondary flight controls and gear-related actuators.