Which system is primarily responsible for emergency hydraulic pressure supply?

The blue hydraulic system is primarily responsible for supplying emergency hydraulic pressure on the A320. This system is equipped with an electric hydraulic pump that can be activated to provide hydraulic pressure when other systems are unavailable, particularly during emergencies when the engine-driven pumps may not be operational.

The blue system is critical in situations where immediate hydraulic assistance is necessary, such as during a failure of the main hydraulic systems. Its ability to function independently ensures that essential flight controls and systems can still operate, enhancing safety during adverse conditions.

In contrast, the green system typically handles the primary flight control surfaces and is generally relied upon for normal operations. The red system is not a standard designation in this context, and the yellow system mainly supports the landing gear and additional systems. Therefore, the blue system’s role as an emergency hydraulic pressure source stands out as a vital feature for aircraft safety and control.