The PTU is automatically activated when there is a differential pressure of ___ PSI between the green and yellow systems.

The PTU, or Power Transfer Unit, is an essential component of the A320 aircraft’s hydraulic system. It is designed to assist in maintaining hydraulic pressure when there is a significant pressure difference between the green and yellow hydraulic systems. This differential pressure is indicative of an imbalance, which can occur if one system experiences a drop in pressure, thus necessitating the assistance of the PTU.

The correct activation threshold for the PTU is when there is a differential pressure of 700 PSI between the green and yellow hydraulic systems. At this point, the PTU engages automatically, allowing for power to be transferred from the green system to the yellow system (or vice versa), helping to normalize hydraulic pressure and ensure the reliable operation of hydraulic systems crucial for flight control and landing gear deployment.

Understanding this pressure threshold is critical for pilots and maintenance personnel, as it highlights the operational capabilities of the hydraulic system and ensures readiness in case of system discrepancies.

Other answer choices reflect lower activation thresholds, which do not align with the design and operational specifications of the A320's hydraulic systems, thus clarifying that 700 PSI is the standard for automatic PTU activation.