Which hydraulic system is used for the parking brake?

The parking brake on the A320 is operated using the yellow hydraulic system. This system is chosen specifically to ensure that the parking brake remains functional even if other hydraulic systems are compromised. The yellow hydraulic system is associated with several critical aircraft functions, such as the nose landing gear retraction and extension, making it a robust choice for control systems that require reliability.

By utilizing the yellow hydraulic system, the A320 design compensates for any potential failure in the green or blue hydraulic systems, allowing pilots to secure the aircraft on the ground confidently. This design consideration underscores the importance of having a dedicated hydraulic system for essential functions like the parking brake, ensuring safety and operational integrity during all phases of flight operations.